Five-month old Australorp suddenly lame. Update: Now another pullet going lame!

[LaFleche]

Without your loving care and devotion they would have been long gone. But Marek's will still progress.

I have been through this ordeal some 10 years ago when buying some hatching eggs that obviously brought the virus.

Everything I tried (even Vit. B12 injections etc.) seemed to help for some days or weeks, just to have them relapse and getting worse and worse until I could not account for them to keep on suffering any longer and culled them all.
I sent some in for necropsy to our state poultry lab and the results were all for Marek's with some additional opportunistic bacterial infections.

The breeder I had bought the eggs from later confirmed that his own hatchlings and then youngsters were weak and all died within a few weeks. His birds seemingly had contracted the virus while on a regional poultry show.

To me it seems that your pullets all came already infected with the virus from the same hatchery and must have been exposed there. There might even be some genetic susceptibility as well.

I am very sorry that your beloved pullets relapsed and all your attempts to save them was in vain.

 

[KaseySnow]

I'm so sorry to hear it, that is heartbreaking.
Is it possible that she has recently contracted Mareks instead of whatever it was that they have been battling? Or are you now thinking that it has been Mareks all along? I guess there really will be no way to know for sure without a necropsy. I'm so sorry.

 

[azygous]

I've always suspected Marek's, but it didn't seem possible. I practice bio-security due to my flock carrying the leucosis virus. On the rare occasion I have a visitor that keeps chickens, I make them bring other footwear to wear inside my run that has been santitized and they santiize again when they get home so my LL doesn't get into their flock. I don't see how Marek's could infect these chickens.

None of my other chicks have had these symptoms. The hatchery they came from has such strict biosecurity they forbid visitors or on-site sales. It's a huge, huge operation.

While the leucosis virus is transmitted vertically, hen to egg, Marek's is not. So it can't hide in hatching eggs.

I'm giving these two a few more days to see if the recent round of medication is going to have any effect, then I will consider. euthanasia.

 

[HiEverybirdy]

Wondering if fluctuating spring hormones are causing flares of whatever this is. Sorry you're on such a roller coaster.

 

[azygous]

Hormones do seem a possibility. It's definitely coincidental with these two both coming into lay and then within days, this relapse. I've been supplementing calcium, but it obviously hasn't helped.

 

[LaFleche]

While the leucosis virus is transmitted vertically, hen to egg, Marek's is not. So it can't hide in hatching eggs.

This might be true for hatcheries that are known to disinfect the hatching eggs in a formaldehyde dip or bath and thus kill all the viruses and germs that might adhere on the eggshells (think bloom or dirty foot prints) prior to loading their incubators.

But I did not disinfect the eggs prior to breeding them. So in my case it did come with the eggs or rather adhered to the not so clean outside of the eggshells from this breeder, who later confirmed that he as well had the same problem and sent some of his chicks and pullets to necropsy and they came back with diagnosed Marek's.

Luckily, I hatched these eggs in an incubator (always disinfected carefully before and after breeding) and raised them separately in a different area of our property without a broody hen. All my other chicks hatched that same month from my own eggs and raised by my own broodies were not affected.

I then kept a closed flock for several years and never before and never since then had Marek's in my flock.

As I practise very strict biosecurity regulations to protect my rare species birds, no visitors will ever get into my coops or chicken runs and all other have to get their shoes sprayed with disinfectant and to put on and wear these plastic thingies over their shoes right at the gate to our property. And keep them on until they leave.

I don't show my birds at expositions or fairs and I do not go there myself, as these places are well known among poultry breeders to serve as hotspots for contracting deadly poultry viruses and bacteria.
Fellow breeders went home from these shows with their highly priced birds and brought back also deadly disease that killed their whole breeding stock within a few weeks. Some of them do not bring their show birds back home anymore for this reason, but sell them then and there right after the exposition or even cull, if they don't find buyers fast enough. Decades worth of breeding work just gone and lots of heartache.

Another thought: do they vaccinate for Marek's at buyers request at your hatchery?

In case they do: Unless they disinfect and completely change their clothing, headgear etc. after having tended to the vaccinated, they might have transferred the virus unknowingly. Think leaky vaccines.

 

[RoostersAreAwesome]

In case they do: Unless they disinfect and completely change their clothing, headgear etc. after having tended to the vaccinated, they might have transferred the virus unknowingly. Think leaky vaccines.

The Marek’s vaccine can’t give chickens Marek’s. However, vaccinated chickens that are exposed to the virus are still carriers of it despite not showing symptoms.

 

[LaFleche]

The Marek’s vaccine can’t give chickens Marek’s. However, vaccinated chickens that are exposed to the virus are still carriers of it despite not showing symptoms.

"Here we show experimentally that immunization of chickens against Marek's disease virus enhances the fitness of more virulent strains, making it possible for hyperpathogenic strains to transmit. Immunity elicited by direct vaccination or by maternal vaccination prolongs host survival but does not prevent infection, viral replication or transmission, thus extending the infectious periods of strains otherwise too lethal to persist. Our data show that anti-disease vaccines that do not prevent transmission can create conditions that promote the emergence of pathogen strains that cause more severe disease in unvaccinated hosts."
Source: https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.1002198
https://pubmed.ncbi.nlm.nih.gov/26214839/

 

[RoostersAreAwesome]

"Here we show experimentally that immunization of chickens against Marek's disease virus enhances the fitness of more virulent strains, making it possible for hyperpathogenic strains to transmit. Immunity elicited by direct vaccination or by maternal vaccination prolongs host survival but does not prevent infection, viral replication or transmission, thus extending the infectious periods of strains otherwise too lethal to persist. Our data show that anti-disease vaccines that do not prevent transmission can create conditions that promote the emergence of pathogen strains that cause more severe disease in unvaccinated hosts."
Source: https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.1002198
https://pubmed.ncbi.nlm.nih.gov/26214839/

As I understand it, that doesn’t mean the vaccine is leaky, it means that extremely deadly strains of Marek’s that normally wouldn’t be able to spread (due to killing all or most of the birds that are exposed) are able to spread through vaccinated birds who get infected by those strains.

 

[LaFleche]

“In our tests of the leaky Marek’s-disease virus in groups of vaccinated and unvaccinated chickens, the unvaccinated died while those that were vaccinated survived and transmitted the virus to other birds left in contact with them,” Nair says. “Our research demonstrates that the use of leaky vaccines can promote the evolution of nastier ‘hot’ viral strains that put unvaccinated individuals at greater risk.”

Source: https://www.futurity.org/viruses-leaky-vaccines-968692/