Lymphoid Leukosis Synonyms:
visceral leukosis, leukosis, big liver, LL Species affected: Although primarily a disease of chickens, lymphoid leukosis can infect turkeys, guinea fowl, pheasants, and doves, but not on a large scale.
Clinical signs:
The virus involved has a long incubation period (4 months or longer). As a result, clinical signs are not noticeable until the birds are 16 weeks or older. Affected birds become progressively weaker and emaciated. There is regression of the comb. The abdomen becomes enlarged. Greenish diarrhea develops in terminal stages (see Table 2).
Transmission:
The virus is transmitted through the egg to offspring. Within a flock, it is spread by bird- to-bird contact and by contact with contaminated environments. The virus is not spread by air. Infected chicken are carriers for life.
Treatment: none
Prevention:
The virus is present in the yolk and egg white of eggs from infected hens. Most national and international layer breeders have eradicated lymphoid leukosis from their flocks. Most commercial chicks are lymphoid-leukosis negative because they are hatched from LL-free breeders. The disease is still common in broiler breeder flocks.