Health management of poultry
TC Tolenkhomba and Prava Mayengbam
Contd from prev issue
Marek’s Disease: Marek’s disease is a type of avian cancer. Tumours in nerves cause lameness and paralysis. Tumours can occur in the eyes and cause irregularly shaped pupils and blindness.
Tumours of the liver, kidney, spleen, gonads, pancreas, proventriculus, lungs, muscles, and skin can cause incoordination, unthriftiness, paleness, weak labored breathing, and enlarged feather follicles. In terminal stages, the birds are emaciated with pale, scaly combs and greenish diarrhoea. Marek’s disease is very similar to Lymphoid Leukosis, but Marek’s usually occurs in chickens 12 to 25 weeks of age and Lymphoid Leukosis usually starts at 16 weeks of age.
Prevention:Chicks can be vaccinated at the hatchery. While the vaccination prevents tumour formation, it does not prevent infection by the virus.
Lymphoid Leukosis: 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 diarrhoea develops in terminal stages.
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.
Infectious Bursal Disease: : In affected chickens greater than 3 weeks of age, there is usually a rapid onset of the disease with a sudden drop in feed and water consumption, watery droppings leading to soiling of feathers around the vent, and vent pecking. Feathers appear ruffled. Chicks are listless and sit in a hunched position. Chickens infected when less than 3 weeks of age do not develop clinical disease, but become severely and permanently immunosuppressed.
Treatment: There is no specific treatment. Vitamin-electrolyte therapy is helpful. High levels of tetracyclines are contraindicated because they tie up calcium, thereby producing rickets. Prevention: Vaccine is commercially available.
To be contd