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Marek's Disease. Questions, Questions, Questions...HELP!
- Thread starter farm-gal91
- Start date
- Thread starter
- #32
- Sep 28, 2012
- 123
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Here is the full article. I will get more. I trust all of these. They are from a site called VIN and it is for vets and technicians. I will see what else I can find.
Abstract
Marek's disease, first described in 1907, has been extensively documented in poultry science literature. Vaccination programs, while not 100% effective, have kept commercial losses generally low. The backyard poultry raiser who does not have access to vaccines and the pet owner whose birds live past the expected protection of a single dose vaccine are at increased risk of this infection. Symptoms are diverse but fairly specific and can be helpful for antemortem diagnosis. Morbidity is variable but mortality is high. No treatment is currently available..
History
Marek's disease has a fascinating and well documented history.1 It is a herpesviral infection of chickens (Gallus gallus) and occasionally quail. The disease, first seen as a paresis in roosters, appears to have been originally documented by Marek in 1907. It was characterized by mononuclear infiltrations in peripheral and spinal nerve roots, but was soon shown to also involve the iris (frequently causing blindness) and the brain. Visceral lymphomas, especially involving the ovary, were next added to the list.
The 1920s and 1930s saw vigorous attempts to transmit the disease with variable success. Efforts in the 1930s worked at controlling losses genetically through selection of resistant breeding stock; a technique that is still used today.
Cancer research in the 1960s was given a huge boost when the causative agent of Marek's, a herpesvirus, was finally isolated, and shown to produce visceral tumors. Shortly thereafter, viral attenuation and the successful development of a vaccine brought the world the first effective cancer vaccine. The virus continues to be used as a model of oncogenic herpesvirus infections. Current research has, after finding apparent atherosclerotic lesions in chickens infected with the virus, used this as a model for similar human vascular conditions.
Marek's disease is effectively controlled in the United States commercial poultry industry with vaccination. However, vaccine failures and more virulent viral strains do occur sporadically and can cause significant losses. Small backyard flocks are rarely vaccinated and can thus be very susceptible. Chickens that are kept as pets, even if originally vaccinated, often outlive the vaccine's expected protective period and are then found to be susceptible. Antemortem diagnosis is challenging but possible. Most literature describes and generally depends on postmortem findings and pathology for confirmation. No treatment is available.
Diagnostics
Diagnosing Marek's can be challenging, as clinical symptoms are very diverse. The underlying pathology is a mononuclear infiltration of tissue. Depending on which tissues are involved, different clinical manifestations are possible. The 3 most common presentations will be discussed here.
This herpesvirus has an affinity for nervous tissue, especially peripheral nerves and spinal nerve roots and ganglia. While numerous plexuses are pathologically seen to be involved (celiac, brachial, and sciatic), clinical presentation most often involves progressive paresis of one or both legs. If owners are observant and manage their hens well, the birds are often still bright, alert, and in good feather and weight even when presenting fully recumbent. Neurological exam shows obvious weakness but variable response to sensory and deep pain stimuli. Physical palpation of the limbs is usually unremarkable unless pressure or rub sores have developed secondary to the ambulatory dysfunction. At this stage, renal inflammation or enlargement, or chronic egg laying problems, which may all irritate the sciatic plexus, must be included in the differential. Other affected nervous tissue problems may present as drooping wings, neck weakness, torticollis, as well as breathing and swallowing difficulties. Symptoms are usually progressive and unresponsive to treatment. Analgesics and anti-inflammatory medications have been tried.
Completely different symptoms arise when the viral infection results in visceral lymphomatosis. In the hen, the ovary and oviduct are usually involved. The abnormalities in the ovary disrupt normal ovulation functions and egg yolk peritonitis frequently results. Hens present with enlarged fluid-filled abdomens. Abdominal aspirates range from clear yellow to thick and cloudy as egg yolks may remain intact or have ruptured. Irritation and secondary infections take their toll and hens are usually anorexic, thin, and depressed. Exploratory laparotomies to clean out peritonitis usually reveal numerous large masses in the reproductive tract and often throughout the abdomen. Diagnosis can be confirmed with biopsy and histopathology. Ovariohysterectomy, while possibly life extending, is usually not successful as cancerous masses will continue to erupt on other viscera.
In a completely different presentation of Marek's, the iris is involved in the mononuclear infiltration. The iris changes color. The loss of pigmentation will cause the iris to be a light grey color, often with concurrent changes in the shape of the pupil. These birds often go blind and may not develop any others symptoms of the disease.
Other presentations of Marek's disease include skin leukosis, transient paralysis, and acute severe depression with high mortality and few clinical symptoms usually associated.
Vaccination
Vaccination is used by the commercial poultry industry as the foundation for controlling Marek's disease. Three serotypes of the virus are used. They are more effective when combined with a herpesvirus of turkeys (HVT). HVT in combination with serotypes 1 or 2 makes up the majority of the vaccines available on the commercial market. The HVT virus is in a cell-associated form, requires storage in liquid nitrogen, and is sold in 1000-dose aliquots. At thawing, all 1000 doses need to be administered within 1 hour. The vaccination protocol requires vaccination at 1 day of age. This is usually done subcutaneously between the shoulder blades, but the vaccine may also be given intramuscularly. Embryo vaccination, usually at 18 days incubation, has been effective and economical for broiler chicks. Three manufactures offer vaccines. They are Select Laboratories, Gainesville, GA, USA; Intervet, Inc, Millsboro, DE, USA; and Tri Bio Laboratories, Inc, State College, PA, USA.2
The pet chicken owner is strongly recommended to purchase chicks from sources that vaccinate at 1 day of age. Avoid introducing unvaccinated chicks or older hens into the flock. Small breeding flocks are more problematic. The vaccine is difficult to handle and not very cost effective for this situation. Of equal concern is the live virus form of these vaccines. In a large, all-in/all-out poultry facility, a live virus can be monitored and confined. The safe use of these vaccines in uncontrolled, outdoor situations needs to be questioned. Efficacy in older birds has not yet been determined.
The virus is shed in feather dandruff and can remain viable for years in the environment under optimal conditions. Apparently healthy birds may carry and shed the virus. Passive transfer via some insects is possible and may play some role in outdoor flocks. Small closed flocks, fresh air, good nutrition, and low stress all seem to factor together to lower morbidity rates. Owners need to be made aware of the risk of maintaining birds showing symptoms of Marek's disease within their flock.
References
1. Calnek BW, Witter RL. Marek's disease. In: Calnek BW, ed. Diseases of Poultry. 10th ed. Ames, IA: Iowa State University Press; 1997:369-413.
2. Bennett K. Compendium of Veterinary Products. 2nd ed. Port Huron, MI: North American Compendiums Inc; 1993.
Speaker Information
(click the speaker's name to view other papers and abstracts submitted by this speaker) Marli Lintner, DVM
Avian Medical Center
Lake Oswego, OR, USA
Abstract
Marek's disease, first described in 1907, has been extensively documented in poultry science literature. Vaccination programs, while not 100% effective, have kept commercial losses generally low. The backyard poultry raiser who does not have access to vaccines and the pet owner whose birds live past the expected protection of a single dose vaccine are at increased risk of this infection. Symptoms are diverse but fairly specific and can be helpful for antemortem diagnosis. Morbidity is variable but mortality is high. No treatment is currently available..
History
Marek's disease has a fascinating and well documented history.1 It is a herpesviral infection of chickens (Gallus gallus) and occasionally quail. The disease, first seen as a paresis in roosters, appears to have been originally documented by Marek in 1907. It was characterized by mononuclear infiltrations in peripheral and spinal nerve roots, but was soon shown to also involve the iris (frequently causing blindness) and the brain. Visceral lymphomas, especially involving the ovary, were next added to the list.
The 1920s and 1930s saw vigorous attempts to transmit the disease with variable success. Efforts in the 1930s worked at controlling losses genetically through selection of resistant breeding stock; a technique that is still used today.
Cancer research in the 1960s was given a huge boost when the causative agent of Marek's, a herpesvirus, was finally isolated, and shown to produce visceral tumors. Shortly thereafter, viral attenuation and the successful development of a vaccine brought the world the first effective cancer vaccine. The virus continues to be used as a model of oncogenic herpesvirus infections. Current research has, after finding apparent atherosclerotic lesions in chickens infected with the virus, used this as a model for similar human vascular conditions.
Marek's disease is effectively controlled in the United States commercial poultry industry with vaccination. However, vaccine failures and more virulent viral strains do occur sporadically and can cause significant losses. Small backyard flocks are rarely vaccinated and can thus be very susceptible. Chickens that are kept as pets, even if originally vaccinated, often outlive the vaccine's expected protective period and are then found to be susceptible. Antemortem diagnosis is challenging but possible. Most literature describes and generally depends on postmortem findings and pathology for confirmation. No treatment is available.
Diagnostics
Diagnosing Marek's can be challenging, as clinical symptoms are very diverse. The underlying pathology is a mononuclear infiltration of tissue. Depending on which tissues are involved, different clinical manifestations are possible. The 3 most common presentations will be discussed here.
This herpesvirus has an affinity for nervous tissue, especially peripheral nerves and spinal nerve roots and ganglia. While numerous plexuses are pathologically seen to be involved (celiac, brachial, and sciatic), clinical presentation most often involves progressive paresis of one or both legs. If owners are observant and manage their hens well, the birds are often still bright, alert, and in good feather and weight even when presenting fully recumbent. Neurological exam shows obvious weakness but variable response to sensory and deep pain stimuli. Physical palpation of the limbs is usually unremarkable unless pressure or rub sores have developed secondary to the ambulatory dysfunction. At this stage, renal inflammation or enlargement, or chronic egg laying problems, which may all irritate the sciatic plexus, must be included in the differential. Other affected nervous tissue problems may present as drooping wings, neck weakness, torticollis, as well as breathing and swallowing difficulties. Symptoms are usually progressive and unresponsive to treatment. Analgesics and anti-inflammatory medications have been tried.
Completely different symptoms arise when the viral infection results in visceral lymphomatosis. In the hen, the ovary and oviduct are usually involved. The abnormalities in the ovary disrupt normal ovulation functions and egg yolk peritonitis frequently results. Hens present with enlarged fluid-filled abdomens. Abdominal aspirates range from clear yellow to thick and cloudy as egg yolks may remain intact or have ruptured. Irritation and secondary infections take their toll and hens are usually anorexic, thin, and depressed. Exploratory laparotomies to clean out peritonitis usually reveal numerous large masses in the reproductive tract and often throughout the abdomen. Diagnosis can be confirmed with biopsy and histopathology. Ovariohysterectomy, while possibly life extending, is usually not successful as cancerous masses will continue to erupt on other viscera.
In a completely different presentation of Marek's, the iris is involved in the mononuclear infiltration. The iris changes color. The loss of pigmentation will cause the iris to be a light grey color, often with concurrent changes in the shape of the pupil. These birds often go blind and may not develop any others symptoms of the disease.
Other presentations of Marek's disease include skin leukosis, transient paralysis, and acute severe depression with high mortality and few clinical symptoms usually associated.
Vaccination
Vaccination is used by the commercial poultry industry as the foundation for controlling Marek's disease. Three serotypes of the virus are used. They are more effective when combined with a herpesvirus of turkeys (HVT). HVT in combination with serotypes 1 or 2 makes up the majority of the vaccines available on the commercial market. The HVT virus is in a cell-associated form, requires storage in liquid nitrogen, and is sold in 1000-dose aliquots. At thawing, all 1000 doses need to be administered within 1 hour. The vaccination protocol requires vaccination at 1 day of age. This is usually done subcutaneously between the shoulder blades, but the vaccine may also be given intramuscularly. Embryo vaccination, usually at 18 days incubation, has been effective and economical for broiler chicks. Three manufactures offer vaccines. They are Select Laboratories, Gainesville, GA, USA; Intervet, Inc, Millsboro, DE, USA; and Tri Bio Laboratories, Inc, State College, PA, USA.2
The pet chicken owner is strongly recommended to purchase chicks from sources that vaccinate at 1 day of age. Avoid introducing unvaccinated chicks or older hens into the flock. Small breeding flocks are more problematic. The vaccine is difficult to handle and not very cost effective for this situation. Of equal concern is the live virus form of these vaccines. In a large, all-in/all-out poultry facility, a live virus can be monitored and confined. The safe use of these vaccines in uncontrolled, outdoor situations needs to be questioned. Efficacy in older birds has not yet been determined.
The virus is shed in feather dandruff and can remain viable for years in the environment under optimal conditions. Apparently healthy birds may carry and shed the virus. Passive transfer via some insects is possible and may play some role in outdoor flocks. Small closed flocks, fresh air, good nutrition, and low stress all seem to factor together to lower morbidity rates. Owners need to be made aware of the risk of maintaining birds showing symptoms of Marek's disease within their flock.
References
1. Calnek BW, Witter RL. Marek's disease. In: Calnek BW, ed. Diseases of Poultry. 10th ed. Ames, IA: Iowa State University Press; 1997:369-413.
2. Bennett K. Compendium of Veterinary Products. 2nd ed. Port Huron, MI: North American Compendiums Inc; 1993.
Speaker Information
(click the speaker's name to view other papers and abstracts submitted by this speaker) Marli Lintner, DVM
Avian Medical Center
Lake Oswego, OR, USA
- Thread starter
- #33
- Sep 28, 2012
- 123
- 4
- 94
Here is the full article. I will get more. I trust all of these. They are from a site called VIN and it is for vets and technicians, no one else can login. I will see what else I can find.
Abstract
Marek's disease, first described in 1907, has been extensively documented in poultry science literature. Vaccination programs, while not 100% effective, have kept commercial losses generally low. The backyard poultry raiser who does not have access to vaccines and the pet owner whose birds live past the expected protection of a single dose vaccine are at increased risk of this infection. Symptoms are diverse but fairly specific and can be helpful for antemortem diagnosis. Morbidity is variable but mortality is high. No treatment is currently available..
History
Marek's disease has a fascinating and well documented history.1 It is a herpesviral infection of chickens (Gallus gallus) and occasionally quail. The disease, first seen as a paresis in roosters, appears to have been originally documented by Marek in 1907. It was characterized by mononuclear infiltrations in peripheral and spinal nerve roots, but was soon shown to also involve the iris (frequently causing blindness) and the brain. Visceral lymphomas, especially involving the ovary, were next added to the list.
The 1920s and 1930s saw vigorous attempts to transmit the disease with variable success. Efforts in the 1930s worked at controlling losses genetically through selection of resistant breeding stock; a technique that is still used today.
Cancer research in the 1960s was given a huge boost when the causative agent of Marek's, a herpesvirus, was finally isolated, and shown to produce visceral tumors. Shortly thereafter, viral attenuation and the successful development of a vaccine brought the world the first effective cancer vaccine. The virus continues to be used as a model of oncogenic herpesvirus infections. Current research has, after finding apparent atherosclerotic lesions in chickens infected with the virus, used this as a model for similar human vascular conditions.
Marek's disease is effectively controlled in the United States commercial poultry industry with vaccination. However, vaccine failures and more virulent viral strains do occur sporadically and can cause significant losses. Small backyard flocks are rarely vaccinated and can thus be very susceptible. Chickens that are kept as pets, even if originally vaccinated, often outlive the vaccine's expected protective period and are then found to be susceptible. Antemortem diagnosis is challenging but possible. Most literature describes and generally depends on postmortem findings and pathology for confirmation. No treatment is available.
Diagnostics
Diagnosing Marek's can be challenging, as clinical symptoms are very diverse. The underlying pathology is a mononuclear infiltration of tissue. Depending on which tissues are involved, different clinical manifestations are possible. The 3 most common presentations will be discussed here.
This herpesvirus has an affinity for nervous tissue, especially peripheral nerves and spinal nerve roots and ganglia. While numerous plexuses are pathologically seen to be involved (celiac, brachial, and sciatic), clinical presentation most often involves progressive paresis of one or both legs. If owners are observant and manage their hens well, the birds are often still bright, alert, and in good feather and weight even when presenting fully recumbent. Neurological exam shows obvious weakness but variable response to sensory and deep pain stimuli. Physical palpation of the limbs is usually unremarkable unless pressure or rub sores have developed secondary to the ambulatory dysfunction. At this stage, renal inflammation or enlargement, or chronic egg laying problems, which may all irritate the sciatic plexus, must be included in the differential. Other affected nervous tissue problems may present as drooping wings, neck weakness, torticollis, as well as breathing and swallowing difficulties. Symptoms are usually progressive and unresponsive to treatment. Analgesics and anti-inflammatory medications have been tried.
Completely different symptoms arise when the viral infection results in visceral lymphomatosis. In the hen, the ovary and oviduct are usually involved. The abnormalities in the ovary disrupt normal ovulation functions and egg yolk peritonitis frequently results. Hens present with enlarged fluid-filled abdomens. Abdominal aspirates range from clear yellow to thick and cloudy as egg yolks may remain intact or have ruptured. Irritation and secondary infections take their toll and hens are usually anorexic, thin, and depressed. Exploratory laparotomies to clean out peritonitis usually reveal numerous large masses in the reproductive tract and often throughout the abdomen. Diagnosis can be confirmed with biopsy and histopathology. Ovariohysterectomy, while possibly life extending, is usually not successful as cancerous masses will continue to erupt on other viscera.
In a completely different presentation of Marek's, the iris is involved in the mononuclear infiltration. The iris changes color. The loss of pigmentation will cause the iris to be a light grey color, often with concurrent changes in the shape of the pupil. These birds often go blind and may not develop any others symptoms of the disease.
Other presentations of Marek's disease include skin leukosis, transient paralysis, and acute severe depression with high mortality and few clinical symptoms usually associated.
Vaccination
Vaccination is used by the commercial poultry industry as the foundation for controlling Marek's disease. Three serotypes of the virus are used. They are more effective when combined with a herpesvirus of turkeys (HVT). HVT in combination with serotypes 1 or 2 makes up the majority of the vaccines available on the commercial market. The HVT virus is in a cell-associated form, requires storage in liquid nitrogen, and is sold in 1000-dose aliquots. At thawing, all 1000 doses need to be administered within 1 hour. The vaccination protocol requires vaccination at 1 day of age. This is usually done subcutaneously between the shoulder blades, but the vaccine may also be given intramuscularly. Embryo vaccination, usually at 18 days incubation, has been effective and economical for broiler chicks. Three manufactures offer vaccines. They are Select Laboratories, Gainesville, GA, USA; Intervet, Inc, Millsboro, DE, USA; and Tri Bio Laboratories, Inc, State College, PA, USA.2
The pet chicken owner is strongly recommended to purchase chicks from sources that vaccinate at 1 day of age. Avoid introducing unvaccinated chicks or older hens into the flock. Small breeding flocks are more problematic. The vaccine is difficult to handle and not very cost effective for this situation. Of equal concern is the live virus form of these vaccines. In a large, all-in/all-out poultry facility, a live virus can be monitored and confined. The safe use of these vaccines in uncontrolled, outdoor situations needs to be questioned. Efficacy in older birds has not yet been determined.
The virus is shed in feather dandruff and can remain viable for years in the environment under optimal conditions. Apparently healthy birds may carry and shed the virus. Passive transfer via some insects is possible and may play some role in outdoor flocks. Small closed flocks, fresh air, good nutrition, and low stress all seem to factor together to lower morbidity rates. Owners need to be made aware of the risk of maintaining birds showing symptoms of Marek's disease within their flock.
References
1. Calnek BW, Witter RL. Marek's disease. In: Calnek BW, ed. Diseases of Poultry. 10th ed. Ames, IA: Iowa State University Press; 1997:369-413.
2. Bennett K. Compendium of Veterinary Products. 2nd ed. Port Huron, MI: North American Compendiums Inc; 1993.
Speaker Information
(click the speaker's name to view other papers and abstracts submitted by this speaker) Marli Lintner, DVM
Avian Medical Center
Lake Oswego, OR, USA
Abstract
Marek's disease, first described in 1907, has been extensively documented in poultry science literature. Vaccination programs, while not 100% effective, have kept commercial losses generally low. The backyard poultry raiser who does not have access to vaccines and the pet owner whose birds live past the expected protection of a single dose vaccine are at increased risk of this infection. Symptoms are diverse but fairly specific and can be helpful for antemortem diagnosis. Morbidity is variable but mortality is high. No treatment is currently available..
History
Marek's disease has a fascinating and well documented history.1 It is a herpesviral infection of chickens (Gallus gallus) and occasionally quail. The disease, first seen as a paresis in roosters, appears to have been originally documented by Marek in 1907. It was characterized by mononuclear infiltrations in peripheral and spinal nerve roots, but was soon shown to also involve the iris (frequently causing blindness) and the brain. Visceral lymphomas, especially involving the ovary, were next added to the list.
The 1920s and 1930s saw vigorous attempts to transmit the disease with variable success. Efforts in the 1930s worked at controlling losses genetically through selection of resistant breeding stock; a technique that is still used today.
Cancer research in the 1960s was given a huge boost when the causative agent of Marek's, a herpesvirus, was finally isolated, and shown to produce visceral tumors. Shortly thereafter, viral attenuation and the successful development of a vaccine brought the world the first effective cancer vaccine. The virus continues to be used as a model of oncogenic herpesvirus infections. Current research has, after finding apparent atherosclerotic lesions in chickens infected with the virus, used this as a model for similar human vascular conditions.
Marek's disease is effectively controlled in the United States commercial poultry industry with vaccination. However, vaccine failures and more virulent viral strains do occur sporadically and can cause significant losses. Small backyard flocks are rarely vaccinated and can thus be very susceptible. Chickens that are kept as pets, even if originally vaccinated, often outlive the vaccine's expected protective period and are then found to be susceptible. Antemortem diagnosis is challenging but possible. Most literature describes and generally depends on postmortem findings and pathology for confirmation. No treatment is available.
Diagnostics
Diagnosing Marek's can be challenging, as clinical symptoms are very diverse. The underlying pathology is a mononuclear infiltration of tissue. Depending on which tissues are involved, different clinical manifestations are possible. The 3 most common presentations will be discussed here.
This herpesvirus has an affinity for nervous tissue, especially peripheral nerves and spinal nerve roots and ganglia. While numerous plexuses are pathologically seen to be involved (celiac, brachial, and sciatic), clinical presentation most often involves progressive paresis of one or both legs. If owners are observant and manage their hens well, the birds are often still bright, alert, and in good feather and weight even when presenting fully recumbent. Neurological exam shows obvious weakness but variable response to sensory and deep pain stimuli. Physical palpation of the limbs is usually unremarkable unless pressure or rub sores have developed secondary to the ambulatory dysfunction. At this stage, renal inflammation or enlargement, or chronic egg laying problems, which may all irritate the sciatic plexus, must be included in the differential. Other affected nervous tissue problems may present as drooping wings, neck weakness, torticollis, as well as breathing and swallowing difficulties. Symptoms are usually progressive and unresponsive to treatment. Analgesics and anti-inflammatory medications have been tried.
Completely different symptoms arise when the viral infection results in visceral lymphomatosis. In the hen, the ovary and oviduct are usually involved. The abnormalities in the ovary disrupt normal ovulation functions and egg yolk peritonitis frequently results. Hens present with enlarged fluid-filled abdomens. Abdominal aspirates range from clear yellow to thick and cloudy as egg yolks may remain intact or have ruptured. Irritation and secondary infections take their toll and hens are usually anorexic, thin, and depressed. Exploratory laparotomies to clean out peritonitis usually reveal numerous large masses in the reproductive tract and often throughout the abdomen. Diagnosis can be confirmed with biopsy and histopathology. Ovariohysterectomy, while possibly life extending, is usually not successful as cancerous masses will continue to erupt on other viscera.
In a completely different presentation of Marek's, the iris is involved in the mononuclear infiltration. The iris changes color. The loss of pigmentation will cause the iris to be a light grey color, often with concurrent changes in the shape of the pupil. These birds often go blind and may not develop any others symptoms of the disease.
Other presentations of Marek's disease include skin leukosis, transient paralysis, and acute severe depression with high mortality and few clinical symptoms usually associated.
Vaccination
Vaccination is used by the commercial poultry industry as the foundation for controlling Marek's disease. Three serotypes of the virus are used. They are more effective when combined with a herpesvirus of turkeys (HVT). HVT in combination with serotypes 1 or 2 makes up the majority of the vaccines available on the commercial market. The HVT virus is in a cell-associated form, requires storage in liquid nitrogen, and is sold in 1000-dose aliquots. At thawing, all 1000 doses need to be administered within 1 hour. The vaccination protocol requires vaccination at 1 day of age. This is usually done subcutaneously between the shoulder blades, but the vaccine may also be given intramuscularly. Embryo vaccination, usually at 18 days incubation, has been effective and economical for broiler chicks. Three manufactures offer vaccines. They are Select Laboratories, Gainesville, GA, USA; Intervet, Inc, Millsboro, DE, USA; and Tri Bio Laboratories, Inc, State College, PA, USA.2
The pet chicken owner is strongly recommended to purchase chicks from sources that vaccinate at 1 day of age. Avoid introducing unvaccinated chicks or older hens into the flock. Small breeding flocks are more problematic. The vaccine is difficult to handle and not very cost effective for this situation. Of equal concern is the live virus form of these vaccines. In a large, all-in/all-out poultry facility, a live virus can be monitored and confined. The safe use of these vaccines in uncontrolled, outdoor situations needs to be questioned. Efficacy in older birds has not yet been determined.
The virus is shed in feather dandruff and can remain viable for years in the environment under optimal conditions. Apparently healthy birds may carry and shed the virus. Passive transfer via some insects is possible and may play some role in outdoor flocks. Small closed flocks, fresh air, good nutrition, and low stress all seem to factor together to lower morbidity rates. Owners need to be made aware of the risk of maintaining birds showing symptoms of Marek's disease within their flock.
References
1. Calnek BW, Witter RL. Marek's disease. In: Calnek BW, ed. Diseases of Poultry. 10th ed. Ames, IA: Iowa State University Press; 1997:369-413.
2. Bennett K. Compendium of Veterinary Products. 2nd ed. Port Huron, MI: North American Compendiums Inc; 1993.
Speaker Information
(click the speaker's name to view other papers and abstracts submitted by this speaker) Marli Lintner, DVM
Avian Medical Center
Lake Oswego, OR, USA
- Thread starter
- #34
- Sep 28, 2012
- 123
- 4
- 94
Here is the full article. I will get more. I trust all of these. They are from a site called VIN and it is for vets and technicians, no one else can login. I will see what else I can find.
Abstract
Marek's disease, first described in 1907, has been extensively documented in poultry science literature. Vaccination programs, while not 100% effective, have kept commercial losses generally low. The backyard poultry raiser who does not have access to vaccines and the pet owner whose birds live past the expected protection of a single dose vaccine are at increased risk of this infection. Symptoms are diverse but fairly specific and can be helpful for antemortem diagnosis. Morbidity is variable but mortality is high. No treatment is currently available..
History
Marek's disease has a fascinating and well documented history.1 It is a herpesviral infection of chickens (Gallus gallus) and occasionally quail. The disease, first seen as a paresis in roosters, appears to have been originally documented by Marek in 1907. It was characterized by mononuclear infiltrations in peripheral and spinal nerve roots, but was soon shown to also involve the iris (frequently causing blindness) and the brain. Visceral lymphomas, especially involving the ovary, were next added to the list.
The 1920s and 1930s saw vigorous attempts to transmit the disease with variable success. Efforts in the 1930s worked at controlling losses genetically through selection of resistant breeding stock; a technique that is still used today.
Cancer research in the 1960s was given a huge boost when the causative agent of Marek's, a herpesvirus, was finally isolated, and shown to produce visceral tumors. Shortly thereafter, viral attenuation and the successful development of a vaccine brought the world the first effective cancer vaccine. The virus continues to be used as a model of oncogenic herpesvirus infections. Current research has, after finding apparent atherosclerotic lesions in chickens infected with the virus, used this as a model for similar human vascular conditions.
Marek's disease is effectively controlled in the United States commercial poultry industry with vaccination. However, vaccine failures and more virulent viral strains do occur sporadically and can cause significant losses. Small backyard flocks are rarely vaccinated and can thus be very susceptible. Chickens that are kept as pets, even if originally vaccinated, often outlive the vaccine's expected protective period and are then found to be susceptible. Antemortem diagnosis is challenging but possible. Most literature describes and generally depends on postmortem findings and pathology for confirmation. No treatment is available.
Diagnostics
Diagnosing Marek's can be challenging, as clinical symptoms are very diverse. The underlying pathology is a mononuclear infiltration of tissue. Depending on which tissues are involved, different clinical manifestations are possible. The 3 most common presentations will be discussed here.
This herpesvirus has an affinity for nervous tissue, especially peripheral nerves and spinal nerve roots and ganglia. While numerous plexuses are pathologically seen to be involved (celiac, brachial, and sciatic), clinical presentation most often involves progressive paresis of one or both legs. If owners are observant and manage their hens well, the birds are often still bright, alert, and in good feather and weight even when presenting fully recumbent. Neurological exam shows obvious weakness but variable response to sensory and deep pain stimuli. Physical palpation of the limbs is usually unremarkable unless pressure or rub sores have developed secondary to the ambulatory dysfunction. At this stage, renal inflammation or enlargement, or chronic egg laying problems, which may all irritate the sciatic plexus, must be included in the differential. Other affected nervous tissue problems may present as drooping wings, neck weakness, torticollis, as well as breathing and swallowing difficulties. Symptoms are usually progressive and unresponsive to treatment. Analgesics and anti-inflammatory medications have been tried.
Completely different symptoms arise when the viral infection results in visceral lymphomatosis. In the hen, the ovary and oviduct are usually involved. The abnormalities in the ovary disrupt normal ovulation functions and egg yolk peritonitis frequently results. Hens present with enlarged fluid-filled abdomens. Abdominal aspirates range from clear yellow to thick and cloudy as egg yolks may remain intact or have ruptured. Irritation and secondary infections take their toll and hens are usually anorexic, thin, and depressed. Exploratory laparotomies to clean out peritonitis usually reveal numerous large masses in the reproductive tract and often throughout the abdomen. Diagnosis can be confirmed with biopsy and histopathology. Ovariohysterectomy, while possibly life extending, is usually not successful as cancerous masses will continue to erupt on other viscera.
In a completely different presentation of Marek's, the iris is involved in the mononuclear infiltration. The iris changes color. The loss of pigmentation will cause the iris to be a light grey color, often with concurrent changes in the shape of the pupil. These birds often go blind and may not develop any others symptoms of the disease.
Other presentations of Marek's disease include skin leukosis, transient paralysis, and acute severe depression with high mortality and few clinical symptoms usually associated.
Vaccination
Vaccination is used by the commercial poultry industry as the foundation for controlling Marek's disease. Three serotypes of the virus are used. They are more effective when combined with a herpesvirus of turkeys (HVT). HVT in combination with serotypes 1 or 2 makes up the majority of the vaccines available on the commercial market. The HVT virus is in a cell-associated form, requires storage in liquid nitrogen, and is sold in 1000-dose aliquots. At thawing, all 1000 doses need to be administered within 1 hour. The vaccination protocol requires vaccination at 1 day of age. This is usually done subcutaneously between the shoulder blades, but the vaccine may also be given intramuscularly. Embryo vaccination, usually at 18 days incubation, has been effective and economical for broiler chicks. Three manufactures offer vaccines. They are Select Laboratories, Gainesville, GA, USA; Intervet, Inc, Millsboro, DE, USA; and Tri Bio Laboratories, Inc, State College, PA, USA.2
The pet chicken owner is strongly recommended to purchase chicks from sources that vaccinate at 1 day of age. Avoid introducing unvaccinated chicks or older hens into the flock. Small breeding flocks are more problematic. The vaccine is difficult to handle and not very cost effective for this situation. Of equal concern is the live virus form of these vaccines. In a large, all-in/all-out poultry facility, a live virus can be monitored and confined. The safe use of these vaccines in uncontrolled, outdoor situations needs to be questioned. Efficacy in older birds has not yet been determined.
The virus is shed in feather dandruff and can remain viable for years in the environment under optimal conditions. Apparently healthy birds may carry and shed the virus. Passive transfer via some insects is possible and may play some role in outdoor flocks. Small closed flocks, fresh air, good nutrition, and low stress all seem to factor together to lower morbidity rates. Owners need to be made aware of the risk of maintaining birds showing symptoms of Marek's disease within their flock.
References
1. Calnek BW, Witter RL. Marek's disease. In: Calnek BW, ed. Diseases of Poultry. 10th ed. Ames, IA: Iowa State University Press; 1997:369-413.
2. Bennett K. Compendium of Veterinary Products. 2nd ed. Port Huron, MI: North American Compendiums Inc; 1993.
Speaker Information
(click the speaker's name to view other papers and abstracts submitted by this speaker) Marli Lintner, DVM
Avian Medical Center
Lake Oswego, OR, USA
Abstract
Marek's disease, first described in 1907, has been extensively documented in poultry science literature. Vaccination programs, while not 100% effective, have kept commercial losses generally low. The backyard poultry raiser who does not have access to vaccines and the pet owner whose birds live past the expected protection of a single dose vaccine are at increased risk of this infection. Symptoms are diverse but fairly specific and can be helpful for antemortem diagnosis. Morbidity is variable but mortality is high. No treatment is currently available..
History
Marek's disease has a fascinating and well documented history.1 It is a herpesviral infection of chickens (Gallus gallus) and occasionally quail. The disease, first seen as a paresis in roosters, appears to have been originally documented by Marek in 1907. It was characterized by mononuclear infiltrations in peripheral and spinal nerve roots, but was soon shown to also involve the iris (frequently causing blindness) and the brain. Visceral lymphomas, especially involving the ovary, were next added to the list.
The 1920s and 1930s saw vigorous attempts to transmit the disease with variable success. Efforts in the 1930s worked at controlling losses genetically through selection of resistant breeding stock; a technique that is still used today.
Cancer research in the 1960s was given a huge boost when the causative agent of Marek's, a herpesvirus, was finally isolated, and shown to produce visceral tumors. Shortly thereafter, viral attenuation and the successful development of a vaccine brought the world the first effective cancer vaccine. The virus continues to be used as a model of oncogenic herpesvirus infections. Current research has, after finding apparent atherosclerotic lesions in chickens infected with the virus, used this as a model for similar human vascular conditions.
Marek's disease is effectively controlled in the United States commercial poultry industry with vaccination. However, vaccine failures and more virulent viral strains do occur sporadically and can cause significant losses. Small backyard flocks are rarely vaccinated and can thus be very susceptible. Chickens that are kept as pets, even if originally vaccinated, often outlive the vaccine's expected protective period and are then found to be susceptible. Antemortem diagnosis is challenging but possible. Most literature describes and generally depends on postmortem findings and pathology for confirmation. No treatment is available.
Diagnostics
Diagnosing Marek's can be challenging, as clinical symptoms are very diverse. The underlying pathology is a mononuclear infiltration of tissue. Depending on which tissues are involved, different clinical manifestations are possible. The 3 most common presentations will be discussed here.
This herpesvirus has an affinity for nervous tissue, especially peripheral nerves and spinal nerve roots and ganglia. While numerous plexuses are pathologically seen to be involved (celiac, brachial, and sciatic), clinical presentation most often involves progressive paresis of one or both legs. If owners are observant and manage their hens well, the birds are often still bright, alert, and in good feather and weight even when presenting fully recumbent. Neurological exam shows obvious weakness but variable response to sensory and deep pain stimuli. Physical palpation of the limbs is usually unremarkable unless pressure or rub sores have developed secondary to the ambulatory dysfunction. At this stage, renal inflammation or enlargement, or chronic egg laying problems, which may all irritate the sciatic plexus, must be included in the differential. Other affected nervous tissue problems may present as drooping wings, neck weakness, torticollis, as well as breathing and swallowing difficulties. Symptoms are usually progressive and unresponsive to treatment. Analgesics and anti-inflammatory medications have been tried.
Completely different symptoms arise when the viral infection results in visceral lymphomatosis. In the hen, the ovary and oviduct are usually involved. The abnormalities in the ovary disrupt normal ovulation functions and egg yolk peritonitis frequently results. Hens present with enlarged fluid-filled abdomens. Abdominal aspirates range from clear yellow to thick and cloudy as egg yolks may remain intact or have ruptured. Irritation and secondary infections take their toll and hens are usually anorexic, thin, and depressed. Exploratory laparotomies to clean out peritonitis usually reveal numerous large masses in the reproductive tract and often throughout the abdomen. Diagnosis can be confirmed with biopsy and histopathology. Ovariohysterectomy, while possibly life extending, is usually not successful as cancerous masses will continue to erupt on other viscera.
In a completely different presentation of Marek's, the iris is involved in the mononuclear infiltration. The iris changes color. The loss of pigmentation will cause the iris to be a light grey color, often with concurrent changes in the shape of the pupil. These birds often go blind and may not develop any others symptoms of the disease.
Other presentations of Marek's disease include skin leukosis, transient paralysis, and acute severe depression with high mortality and few clinical symptoms usually associated.
Vaccination
Vaccination is used by the commercial poultry industry as the foundation for controlling Marek's disease. Three serotypes of the virus are used. They are more effective when combined with a herpesvirus of turkeys (HVT). HVT in combination with serotypes 1 or 2 makes up the majority of the vaccines available on the commercial market. The HVT virus is in a cell-associated form, requires storage in liquid nitrogen, and is sold in 1000-dose aliquots. At thawing, all 1000 doses need to be administered within 1 hour. The vaccination protocol requires vaccination at 1 day of age. This is usually done subcutaneously between the shoulder blades, but the vaccine may also be given intramuscularly. Embryo vaccination, usually at 18 days incubation, has been effective and economical for broiler chicks. Three manufactures offer vaccines. They are Select Laboratories, Gainesville, GA, USA; Intervet, Inc, Millsboro, DE, USA; and Tri Bio Laboratories, Inc, State College, PA, USA.2
The pet chicken owner is strongly recommended to purchase chicks from sources that vaccinate at 1 day of age. Avoid introducing unvaccinated chicks or older hens into the flock. Small breeding flocks are more problematic. The vaccine is difficult to handle and not very cost effective for this situation. Of equal concern is the live virus form of these vaccines. In a large, all-in/all-out poultry facility, a live virus can be monitored and confined. The safe use of these vaccines in uncontrolled, outdoor situations needs to be questioned. Efficacy in older birds has not yet been determined.
The virus is shed in feather dandruff and can remain viable for years in the environment under optimal conditions. Apparently healthy birds may carry and shed the virus. Passive transfer via some insects is possible and may play some role in outdoor flocks. Small closed flocks, fresh air, good nutrition, and low stress all seem to factor together to lower morbidity rates. Owners need to be made aware of the risk of maintaining birds showing symptoms of Marek's disease within their flock.
References
1. Calnek BW, Witter RL. Marek's disease. In: Calnek BW, ed. Diseases of Poultry. 10th ed. Ames, IA: Iowa State University Press; 1997:369-413.
2. Bennett K. Compendium of Veterinary Products. 2nd ed. Port Huron, MI: North American Compendiums Inc; 1993.
Speaker Information
(click the speaker's name to view other papers and abstracts submitted by this speaker) Marli Lintner, DVM
Avian Medical Center
Lake Oswego, OR, USA
- Thread starter
- #35
- Sep 28, 2012
- 123
- 4
- 94
Here is the full article. I will get more. I trust all of these. They are from a site called VIN and it is for vets and technicians, no one else can login. I will see what else I can find.
Abstract
Marek's disease, first described in 1907, has been extensively documented in poultry science literature. Vaccination programs, while not 100% effective, have kept commercial losses generally low. The backyard poultry raiser who does not have access to vaccines and the pet owner whose birds live past the expected protection of a single dose vaccine are at increased risk of this infection. Symptoms are diverse but fairly specific and can be helpful for antemortem diagnosis. Morbidity is variable but mortality is high. No treatment is currently available..
History
Marek's disease has a fascinating and well documented history.1 It is a herpesviral infection of chickens (Gallus gallus) and occasionally quail. The disease, first seen as a paresis in roosters, appears to have been originally documented by Marek in 1907. It was characterized by mononuclear infiltrations in peripheral and spinal nerve roots, but was soon shown to also involve the iris (frequently causing blindness) and the brain. Visceral lymphomas, especially involving the ovary, were next added to the list.
The 1920s and 1930s saw vigorous attempts to transmit the disease with variable success. Efforts in the 1930s worked at controlling losses genetically through selection of resistant breeding stock; a technique that is still used today.
Cancer research in the 1960s was given a huge boost when the causative agent of Marek's, a herpesvirus, was finally isolated, and shown to produce visceral tumors. Shortly thereafter, viral attenuation and the successful development of a vaccine brought the world the first effective cancer vaccine. The virus continues to be used as a model of oncogenic herpesvirus infections. Current research has, after finding apparent atherosclerotic lesions in chickens infected with the virus, used this as a model for similar human vascular conditions.
Marek's disease is effectively controlled in the United States commercial poultry industry with vaccination. However, vaccine failures and more virulent viral strains do occur sporadically and can cause significant losses. Small backyard flocks are rarely vaccinated and can thus be very susceptible. Chickens that are kept as pets, even if originally vaccinated, often outlive the vaccine's expected protective period and are then found to be susceptible. Antemortem diagnosis is challenging but possible. Most literature describes and generally depends on postmortem findings and pathology for confirmation. No treatment is available.
Diagnostics
Diagnosing Marek's can be challenging, as clinical symptoms are very diverse. The underlying pathology is a mononuclear infiltration of tissue. Depending on which tissues are involved, different clinical manifestations are possible. The 3 most common presentations will be discussed here.
This herpesvirus has an affinity for nervous tissue, especially peripheral nerves and spinal nerve roots and ganglia. While numerous plexuses are pathologically seen to be involved (celiac, brachial, and sciatic), clinical presentation most often involves progressive paresis of one or both legs. If owners are observant and manage their hens well, the birds are often still bright, alert, and in good feather and weight even when presenting fully recumbent. Neurological exam shows obvious weakness but variable response to sensory and deep pain stimuli. Physical palpation of the limbs is usually unremarkable unless pressure or rub sores have developed secondary to the ambulatory dysfunction. At this stage, renal inflammation or enlargement, or chronic egg laying problems, which may all irritate the sciatic plexus, must be included in the differential. Other affected nervous tissue problems may present as drooping wings, neck weakness, torticollis, as well as breathing and swallowing difficulties. Symptoms are usually progressive and unresponsive to treatment. Analgesics and anti-inflammatory medications have been tried.
Completely different symptoms arise when the viral infection results in visceral lymphomatosis. In the hen, the ovary and oviduct are usually involved. The abnormalities in the ovary disrupt normal ovulation functions and egg yolk peritonitis frequently results. Hens present with enlarged fluid-filled abdomens. Abdominal aspirates range from clear yellow to thick and cloudy as egg yolks may remain intact or have ruptured. Irritation and secondary infections take their toll and hens are usually anorexic, thin, and depressed. Exploratory laparotomies to clean out peritonitis usually reveal numerous large masses in the reproductive tract and often throughout the abdomen. Diagnosis can be confirmed with biopsy and histopathology. Ovariohysterectomy, while possibly life extending, is usually not successful as cancerous masses will continue to erupt on other viscera.
In a completely different presentation of Marek's, the iris is involved in the mononuclear infiltration. The iris changes color. The loss of pigmentation will cause the iris to be a light grey color, often with concurrent changes in the shape of the pupil. These birds often go blind and may not develop any others symptoms of the disease.
Other presentations of Marek's disease include skin leukosis, transient paralysis, and acute severe depression with high mortality and few clinical symptoms usually associated.
Vaccination
Vaccination is used by the commercial poultry industry as the foundation for controlling Marek's disease. Three serotypes of the virus are used. They are more effective when combined with a herpesvirus of turkeys (HVT). HVT in combination with serotypes 1 or 2 makes up the majority of the vaccines available on the commercial market. The HVT virus is in a cell-associated form, requires storage in liquid nitrogen, and is sold in 1000-dose aliquots. At thawing, all 1000 doses need to be administered within 1 hour. The vaccination protocol requires vaccination at 1 day of age. This is usually done subcutaneously between the shoulder blades, but the vaccine may also be given intramuscularly. Embryo vaccination, usually at 18 days incubation, has been effective and economical for broiler chicks. Three manufactures offer vaccines. They are Select Laboratories, Gainesville, GA, USA; Intervet, Inc, Millsboro, DE, USA; and Tri Bio Laboratories, Inc, State College, PA, USA.2
The pet chicken owner is strongly recommended to purchase chicks from sources that vaccinate at 1 day of age. Avoid introducing unvaccinated chicks or older hens into the flock. Small breeding flocks are more problematic. The vaccine is difficult to handle and not very cost effective for this situation. Of equal concern is the live virus form of these vaccines. In a large, all-in/all-out poultry facility, a live virus can be monitored and confined. The safe use of these vaccines in uncontrolled, outdoor situations needs to be questioned. Efficacy in older birds has not yet been determined.
The virus is shed in feather dandruff and can remain viable for years in the environment under optimal conditions. Apparently healthy birds may carry and shed the virus. Passive transfer via some insects is possible and may play some role in outdoor flocks. Small closed flocks, fresh air, good nutrition, and low stress all seem to factor together to lower morbidity rates. Owners need to be made aware of the risk of maintaining birds showing symptoms of Marek's disease within their flock.
References
1. Calnek BW, Witter RL. Marek's disease. In: Calnek BW, ed. Diseases of Poultry. 10th ed. Ames, IA: Iowa State University Press; 1997:369-413.
2. Bennett K. Compendium of Veterinary Products. 2nd ed. Port Huron, MI: North American Compendiums Inc; 1993.
Speaker Information
(click the speaker's name to view other papers and abstracts submitted by this speaker) Marli Lintner, DVM
Avian Medical Center
Lake Oswego, OR, USA
Abstract
Marek's disease, first described in 1907, has been extensively documented in poultry science literature. Vaccination programs, while not 100% effective, have kept commercial losses generally low. The backyard poultry raiser who does not have access to vaccines and the pet owner whose birds live past the expected protection of a single dose vaccine are at increased risk of this infection. Symptoms are diverse but fairly specific and can be helpful for antemortem diagnosis. Morbidity is variable but mortality is high. No treatment is currently available..
History
Marek's disease has a fascinating and well documented history.1 It is a herpesviral infection of chickens (Gallus gallus) and occasionally quail. The disease, first seen as a paresis in roosters, appears to have been originally documented by Marek in 1907. It was characterized by mononuclear infiltrations in peripheral and spinal nerve roots, but was soon shown to also involve the iris (frequently causing blindness) and the brain. Visceral lymphomas, especially involving the ovary, were next added to the list.
The 1920s and 1930s saw vigorous attempts to transmit the disease with variable success. Efforts in the 1930s worked at controlling losses genetically through selection of resistant breeding stock; a technique that is still used today.
Cancer research in the 1960s was given a huge boost when the causative agent of Marek's, a herpesvirus, was finally isolated, and shown to produce visceral tumors. Shortly thereafter, viral attenuation and the successful development of a vaccine brought the world the first effective cancer vaccine. The virus continues to be used as a model of oncogenic herpesvirus infections. Current research has, after finding apparent atherosclerotic lesions in chickens infected with the virus, used this as a model for similar human vascular conditions.
Marek's disease is effectively controlled in the United States commercial poultry industry with vaccination. However, vaccine failures and more virulent viral strains do occur sporadically and can cause significant losses. Small backyard flocks are rarely vaccinated and can thus be very susceptible. Chickens that are kept as pets, even if originally vaccinated, often outlive the vaccine's expected protective period and are then found to be susceptible. Antemortem diagnosis is challenging but possible. Most literature describes and generally depends on postmortem findings and pathology for confirmation. No treatment is available.
Diagnostics
Diagnosing Marek's can be challenging, as clinical symptoms are very diverse. The underlying pathology is a mononuclear infiltration of tissue. Depending on which tissues are involved, different clinical manifestations are possible. The 3 most common presentations will be discussed here.
This herpesvirus has an affinity for nervous tissue, especially peripheral nerves and spinal nerve roots and ganglia. While numerous plexuses are pathologically seen to be involved (celiac, brachial, and sciatic), clinical presentation most often involves progressive paresis of one or both legs. If owners are observant and manage their hens well, the birds are often still bright, alert, and in good feather and weight even when presenting fully recumbent. Neurological exam shows obvious weakness but variable response to sensory and deep pain stimuli. Physical palpation of the limbs is usually unremarkable unless pressure or rub sores have developed secondary to the ambulatory dysfunction. At this stage, renal inflammation or enlargement, or chronic egg laying problems, which may all irritate the sciatic plexus, must be included in the differential. Other affected nervous tissue problems may present as drooping wings, neck weakness, torticollis, as well as breathing and swallowing difficulties. Symptoms are usually progressive and unresponsive to treatment. Analgesics and anti-inflammatory medications have been tried.
Completely different symptoms arise when the viral infection results in visceral lymphomatosis. In the hen, the ovary and oviduct are usually involved. The abnormalities in the ovary disrupt normal ovulation functions and egg yolk peritonitis frequently results. Hens present with enlarged fluid-filled abdomens. Abdominal aspirates range from clear yellow to thick and cloudy as egg yolks may remain intact or have ruptured. Irritation and secondary infections take their toll and hens are usually anorexic, thin, and depressed. Exploratory laparotomies to clean out peritonitis usually reveal numerous large masses in the reproductive tract and often throughout the abdomen. Diagnosis can be confirmed with biopsy and histopathology. Ovariohysterectomy, while possibly life extending, is usually not successful as cancerous masses will continue to erupt on other viscera.
In a completely different presentation of Marek's, the iris is involved in the mononuclear infiltration. The iris changes color. The loss of pigmentation will cause the iris to be a light grey color, often with concurrent changes in the shape of the pupil. These birds often go blind and may not develop any others symptoms of the disease.
Other presentations of Marek's disease include skin leukosis, transient paralysis, and acute severe depression with high mortality and few clinical symptoms usually associated.
Vaccination
Vaccination is used by the commercial poultry industry as the foundation for controlling Marek's disease. Three serotypes of the virus are used. They are more effective when combined with a herpesvirus of turkeys (HVT). HVT in combination with serotypes 1 or 2 makes up the majority of the vaccines available on the commercial market. The HVT virus is in a cell-associated form, requires storage in liquid nitrogen, and is sold in 1000-dose aliquots. At thawing, all 1000 doses need to be administered within 1 hour. The vaccination protocol requires vaccination at 1 day of age. This is usually done subcutaneously between the shoulder blades, but the vaccine may also be given intramuscularly. Embryo vaccination, usually at 18 days incubation, has been effective and economical for broiler chicks. Three manufactures offer vaccines. They are Select Laboratories, Gainesville, GA, USA; Intervet, Inc, Millsboro, DE, USA; and Tri Bio Laboratories, Inc, State College, PA, USA.2
The pet chicken owner is strongly recommended to purchase chicks from sources that vaccinate at 1 day of age. Avoid introducing unvaccinated chicks or older hens into the flock. Small breeding flocks are more problematic. The vaccine is difficult to handle and not very cost effective for this situation. Of equal concern is the live virus form of these vaccines. In a large, all-in/all-out poultry facility, a live virus can be monitored and confined. The safe use of these vaccines in uncontrolled, outdoor situations needs to be questioned. Efficacy in older birds has not yet been determined.
The virus is shed in feather dandruff and can remain viable for years in the environment under optimal conditions. Apparently healthy birds may carry and shed the virus. Passive transfer via some insects is possible and may play some role in outdoor flocks. Small closed flocks, fresh air, good nutrition, and low stress all seem to factor together to lower morbidity rates. Owners need to be made aware of the risk of maintaining birds showing symptoms of Marek's disease within their flock.
References
1. Calnek BW, Witter RL. Marek's disease. In: Calnek BW, ed. Diseases of Poultry. 10th ed. Ames, IA: Iowa State University Press; 1997:369-413.
2. Bennett K. Compendium of Veterinary Products. 2nd ed. Port Huron, MI: North American Compendiums Inc; 1993.
Speaker Information
(click the speaker's name to view other papers and abstracts submitted by this speaker) Marli Lintner, DVM
Avian Medical Center
Lake Oswego, OR, USA
- Thread starter
- #36
- Sep 28, 2012
- 123
- 4
- 94
Here is the full article. I will get more. I trust all of these. They are from a site called VIN and it is for vets and technicians, no one else can login. I will see what else I can find.
Abstract
Marek's disease, first described in 1907, has been extensively documented in poultry science literature. Vaccination programs, while not 100% effective, have kept commercial losses generally low. The backyard poultry raiser who does not have access to vaccines and the pet owner whose birds live past the expected protection of a single dose vaccine are at increased risk of this infection. Symptoms are diverse but fairly specific and can be helpful for antemortem diagnosis. Morbidity is variable but mortality is high. No treatment is currently available..
History
Marek's disease has a fascinating and well documented history.1 It is a herpesviral infection of chickens (Gallus gallus) and occasionally quail. The disease, first seen as a paresis in roosters, appears to have been originally documented by Marek in 1907. It was characterized by mononuclear infiltrations in peripheral and spinal nerve roots, but was soon shown to also involve the iris (frequently causing blindness) and the brain. Visceral lymphomas, especially involving the ovary, were next added to the list.
The 1920s and 1930s saw vigorous attempts to transmit the disease with variable success. Efforts in the 1930s worked at controlling losses genetically through selection of resistant breeding stock; a technique that is still used today.
Cancer research in the 1960s was given a huge boost when the causative agent of Marek's, a herpesvirus, was finally isolated, and shown to produce visceral tumors. Shortly thereafter, viral attenuation and the successful development of a vaccine brought the world the first effective cancer vaccine. The virus continues to be used as a model of oncogenic herpesvirus infections. Current research has, after finding apparent atherosclerotic lesions in chickens infected with the virus, used this as a model for similar human vascular conditions.
Marek's disease is effectively controlled in the United States commercial poultry industry with vaccination. However, vaccine failures and more virulent viral strains do occur sporadically and can cause significant losses. Small backyard flocks are rarely vaccinated and can thus be very susceptible. Chickens that are kept as pets, even if originally vaccinated, often outlive the vaccine's expected protective period and are then found to be susceptible. Antemortem diagnosis is challenging but possible. Most literature describes and generally depends on postmortem findings and pathology for confirmation. No treatment is available.
Diagnostics
Diagnosing Marek's can be challenging, as clinical symptoms are very diverse. The underlying pathology is a mononuclear infiltration of tissue. Depending on which tissues are involved, different clinical manifestations are possible. The 3 most common presentations will be discussed here.
This herpesvirus has an affinity for nervous tissue, especially peripheral nerves and spinal nerve roots and ganglia. While numerous plexuses are pathologically seen to be involved (celiac, brachial, and sciatic), clinical presentation most often involves progressive paresis of one or both legs. If owners are observant and manage their hens well, the birds are often still bright, alert, and in good feather and weight even when presenting fully recumbent. Neurological exam shows obvious weakness but variable response to sensory and deep pain stimuli. Physical palpation of the limbs is usually unremarkable unless pressure or rub sores have developed secondary to the ambulatory dysfunction. At this stage, renal inflammation or enlargement, or chronic egg laying problems, which may all irritate the sciatic plexus, must be included in the differential. Other affected nervous tissue problems may present as drooping wings, neck weakness, torticollis, as well as breathing and swallowing difficulties. Symptoms are usually progressive and unresponsive to treatment. Analgesics and anti-inflammatory medications have been tried.
Completely different symptoms arise when the viral infection results in visceral lymphomatosis. In the hen, the ovary and oviduct are usually involved. The abnormalities in the ovary disrupt normal ovulation functions and egg yolk peritonitis frequently results. Hens present with enlarged fluid-filled abdomens. Abdominal aspirates range from clear yellow to thick and cloudy as egg yolks may remain intact or have ruptured. Irritation and secondary infections take their toll and hens are usually anorexic, thin, and depressed. Exploratory laparotomies to clean out peritonitis usually reveal numerous large masses in the reproductive tract and often throughout the abdomen. Diagnosis can be confirmed with biopsy and histopathology. Ovariohysterectomy, while possibly life extending, is usually not successful as cancerous masses will continue to erupt on other viscera.
In a completely different presentation of Marek's, the iris is involved in the mononuclear infiltration. The iris changes color. The loss of pigmentation will cause the iris to be a light grey color, often with concurrent changes in the shape of the pupil. These birds often go blind and may not develop any others symptoms of the disease.
Other presentations of Marek's disease include skin leukosis, transient paralysis, and acute severe depression with high mortality and few clinical symptoms usually associated.
Vaccination
Vaccination is used by the commercial poultry industry as the foundation for controlling Marek's disease. Three serotypes of the virus are used. They are more effective when combined with a herpesvirus of turkeys (HVT). HVT in combination with serotypes 1 or 2 makes up the majority of the vaccines available on the commercial market. The HVT virus is in a cell-associated form, requires storage in liquid nitrogen, and is sold in 1000-dose aliquots. At thawing, all 1000 doses need to be administered within 1 hour. The vaccination protocol requires vaccination at 1 day of age. This is usually done subcutaneously between the shoulder blades, but the vaccine may also be given intramuscularly. Embryo vaccination, usually at 18 days incubation, has been effective and economical for broiler chicks. Three manufactures offer vaccines. They are Select Laboratories, Gainesville, GA, USA; Intervet, Inc, Millsboro, DE, USA; and Tri Bio Laboratories, Inc, State College, PA, USA.2
The pet chicken owner is strongly recommended to purchase chicks from sources that vaccinate at 1 day of age. Avoid introducing unvaccinated chicks or older hens into the flock. Small breeding flocks are more problematic. The vaccine is difficult to handle and not very cost effective for this situation. Of equal concern is the live virus form of these vaccines. In a large, all-in/all-out poultry facility, a live virus can be monitored and confined. The safe use of these vaccines in uncontrolled, outdoor situations needs to be questioned. Efficacy in older birds has not yet been determined.
The virus is shed in feather dandruff and can remain viable for years in the environment under optimal conditions. Apparently healthy birds may carry and shed the virus. Passive transfer via some insects is possible and may play some role in outdoor flocks. Small closed flocks, fresh air, good nutrition, and low stress all seem to factor together to lower morbidity rates. Owners need to be made aware of the risk of maintaining birds showing symptoms of Marek's disease within their flock.
References
1. Calnek BW, Witter RL. Marek's disease. In: Calnek BW, ed. Diseases of Poultry. 10th ed. Ames, IA: Iowa State University Press; 1997:369-413.
2. Bennett K. Compendium of Veterinary Products. 2nd ed. Port Huron, MI: North American Compendiums Inc; 1993.
Speaker Information
(click the speaker's name to view other papers and abstracts submitted by this speaker) Marli Lintner, DVM
Avian Medical Center
Lake Oswego, OR, USA
Abstract
Marek's disease, first described in 1907, has been extensively documented in poultry science literature. Vaccination programs, while not 100% effective, have kept commercial losses generally low. The backyard poultry raiser who does not have access to vaccines and the pet owner whose birds live past the expected protection of a single dose vaccine are at increased risk of this infection. Symptoms are diverse but fairly specific and can be helpful for antemortem diagnosis. Morbidity is variable but mortality is high. No treatment is currently available..
History
Marek's disease has a fascinating and well documented history.1 It is a herpesviral infection of chickens (Gallus gallus) and occasionally quail. The disease, first seen as a paresis in roosters, appears to have been originally documented by Marek in 1907. It was characterized by mononuclear infiltrations in peripheral and spinal nerve roots, but was soon shown to also involve the iris (frequently causing blindness) and the brain. Visceral lymphomas, especially involving the ovary, were next added to the list.
The 1920s and 1930s saw vigorous attempts to transmit the disease with variable success. Efforts in the 1930s worked at controlling losses genetically through selection of resistant breeding stock; a technique that is still used today.
Cancer research in the 1960s was given a huge boost when the causative agent of Marek's, a herpesvirus, was finally isolated, and shown to produce visceral tumors. Shortly thereafter, viral attenuation and the successful development of a vaccine brought the world the first effective cancer vaccine. The virus continues to be used as a model of oncogenic herpesvirus infections. Current research has, after finding apparent atherosclerotic lesions in chickens infected with the virus, used this as a model for similar human vascular conditions.
Marek's disease is effectively controlled in the United States commercial poultry industry with vaccination. However, vaccine failures and more virulent viral strains do occur sporadically and can cause significant losses. Small backyard flocks are rarely vaccinated and can thus be very susceptible. Chickens that are kept as pets, even if originally vaccinated, often outlive the vaccine's expected protective period and are then found to be susceptible. Antemortem diagnosis is challenging but possible. Most literature describes and generally depends on postmortem findings and pathology for confirmation. No treatment is available.
Diagnostics
Diagnosing Marek's can be challenging, as clinical symptoms are very diverse. The underlying pathology is a mononuclear infiltration of tissue. Depending on which tissues are involved, different clinical manifestations are possible. The 3 most common presentations will be discussed here.
This herpesvirus has an affinity for nervous tissue, especially peripheral nerves and spinal nerve roots and ganglia. While numerous plexuses are pathologically seen to be involved (celiac, brachial, and sciatic), clinical presentation most often involves progressive paresis of one or both legs. If owners are observant and manage their hens well, the birds are often still bright, alert, and in good feather and weight even when presenting fully recumbent. Neurological exam shows obvious weakness but variable response to sensory and deep pain stimuli. Physical palpation of the limbs is usually unremarkable unless pressure or rub sores have developed secondary to the ambulatory dysfunction. At this stage, renal inflammation or enlargement, or chronic egg laying problems, which may all irritate the sciatic plexus, must be included in the differential. Other affected nervous tissue problems may present as drooping wings, neck weakness, torticollis, as well as breathing and swallowing difficulties. Symptoms are usually progressive and unresponsive to treatment. Analgesics and anti-inflammatory medications have been tried.
Completely different symptoms arise when the viral infection results in visceral lymphomatosis. In the hen, the ovary and oviduct are usually involved. The abnormalities in the ovary disrupt normal ovulation functions and egg yolk peritonitis frequently results. Hens present with enlarged fluid-filled abdomens. Abdominal aspirates range from clear yellow to thick and cloudy as egg yolks may remain intact or have ruptured. Irritation and secondary infections take their toll and hens are usually anorexic, thin, and depressed. Exploratory laparotomies to clean out peritonitis usually reveal numerous large masses in the reproductive tract and often throughout the abdomen. Diagnosis can be confirmed with biopsy and histopathology. Ovariohysterectomy, while possibly life extending, is usually not successful as cancerous masses will continue to erupt on other viscera.
In a completely different presentation of Marek's, the iris is involved in the mononuclear infiltration. The iris changes color. The loss of pigmentation will cause the iris to be a light grey color, often with concurrent changes in the shape of the pupil. These birds often go blind and may not develop any others symptoms of the disease.
Other presentations of Marek's disease include skin leukosis, transient paralysis, and acute severe depression with high mortality and few clinical symptoms usually associated.
Vaccination
Vaccination is used by the commercial poultry industry as the foundation for controlling Marek's disease. Three serotypes of the virus are used. They are more effective when combined with a herpesvirus of turkeys (HVT). HVT in combination with serotypes 1 or 2 makes up the majority of the vaccines available on the commercial market. The HVT virus is in a cell-associated form, requires storage in liquid nitrogen, and is sold in 1000-dose aliquots. At thawing, all 1000 doses need to be administered within 1 hour. The vaccination protocol requires vaccination at 1 day of age. This is usually done subcutaneously between the shoulder blades, but the vaccine may also be given intramuscularly. Embryo vaccination, usually at 18 days incubation, has been effective and economical for broiler chicks. Three manufactures offer vaccines. They are Select Laboratories, Gainesville, GA, USA; Intervet, Inc, Millsboro, DE, USA; and Tri Bio Laboratories, Inc, State College, PA, USA.2
The pet chicken owner is strongly recommended to purchase chicks from sources that vaccinate at 1 day of age. Avoid introducing unvaccinated chicks or older hens into the flock. Small breeding flocks are more problematic. The vaccine is difficult to handle and not very cost effective for this situation. Of equal concern is the live virus form of these vaccines. In a large, all-in/all-out poultry facility, a live virus can be monitored and confined. The safe use of these vaccines in uncontrolled, outdoor situations needs to be questioned. Efficacy in older birds has not yet been determined.
The virus is shed in feather dandruff and can remain viable for years in the environment under optimal conditions. Apparently healthy birds may carry and shed the virus. Passive transfer via some insects is possible and may play some role in outdoor flocks. Small closed flocks, fresh air, good nutrition, and low stress all seem to factor together to lower morbidity rates. Owners need to be made aware of the risk of maintaining birds showing symptoms of Marek's disease within their flock.
References
1. Calnek BW, Witter RL. Marek's disease. In: Calnek BW, ed. Diseases of Poultry. 10th ed. Ames, IA: Iowa State University Press; 1997:369-413.
2. Bennett K. Compendium of Veterinary Products. 2nd ed. Port Huron, MI: North American Compendiums Inc; 1993.
Speaker Information
(click the speaker's name to view other papers and abstracts submitted by this speaker) Marli Lintner, DVM
Avian Medical Center
Lake Oswego, OR, USA
- Thread starter
- #37
- Sep 28, 2012
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I have no clue why it posted so many times, sorry.
No worries, lol. Thanks!
- Thread starter
- #39
- Sep 28, 2012
- 123
- 4
- 94
Just not good on the computer haha.
I can't help it but I'm still thinking about my chicken. Here's the last photo of her. She went peacefully.
I can't help it but I'm still thinking about my chicken. Here's the last photo of her. She went peacefully.
I feel for you, I do, but at least you have the resources for euthanasia.
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