Lymphoid Leukosis

Lymphoid Leukosis,  also called lymphoid Leucosis, Liver cancer, Liver disease or LL is a tragic disease that affects a chicken’s liver and can cause a painful death. Because of that, humane euthanasia is usually recommended to ease the suffering of poor birds that contract this illness and to help prevent the spread of the disease to other members of the flock. You’ll definitely want to consult with a veterinarian if you suspect a member of your flock has this disease. Read on to find out more:




General signs –

Fatigue, weakness, ruffled feathers, depression, lethargy, loss of appetite, drop in laying, shrivelled comb, loose poo, and finally death

Cardinal or diagnostic signs –

Post mortem signs may be diagnostic: tumours in liver or other organs, swollen joints




Yes — spreads through contact, droppings, blood (for example mosquitoes), or from hen to chick through the egg. Late-feathering birds are thought to be more susceptible to the virus.

Communicability to humans


Incubation period

14 weeks, onset usually occurs around laying age.


Yes, especially if the virus was passed in ovo from its mother.



Home treatment and/or prevention

Prevention: Practice good biosecurity. Unfortunately, this disease is difficult to prevent, even with good management practices. Purchase poultry from reputable, NPIP (National Poultry Improvement Plan) sources that closely monitor their flocks’ health.

Treatment: None. This usually leads to a painful death, although some birds can survive to be carriers and infect others. Consult your vet to be sure, but generally, this is one of those tragic illnesses where it’s advisable to humanely euthanize affected birds so they don’t infect others. Sanitize the coop and run, and be sure to also sanitize the brooder and/or incubator.

Veterinary care

None. Your vet can humanely euthanize suffering birds, and may have good advice for sanitizing the coop/run/brooder.


No, however some birds can survive to shed the virus.

Other conditions, illnesses and/or diseases with similar signs:
Marek’s disease, pullorum.

Characteristically, lymphoid leukosis is a disease of adult chickens; however, the disease appears to be increasing in importance for turkeys and game birds. Although the virus of lymphoid leukosis can produce various responses (blood, bone, lymph), the lymphoid tumour response is the most common.

The disease is transmitted in a variety of ways. The causative viral agent is passed out of the body of infected birds via eggs and faeces. The virus may be transmitted mechanically from infected birds to susceptibles by blood-sucking parasites or by man in such procedures as fowl pox vaccination.

Lymphoid leukosis characteristically produces lymphoid tumours, particularly in the liver and spleen. The tumours may also affect other visceral organs such as the ovary and lungs. Affected birds may die without preliminary symptoms, but the disease usually is chronic in nature and affected birds show loss of appetite, progressive emaciation and diarrhoea. Clinically affected birds invariably die. Losses due to the disease are most severe shortly after the onset of egg production, but losses will continue for as long as the flock is retained. Total loss may approach twenty per cent during the life of a flock.

Clinical diagnosis of lymphoid leukosis is based upon flock history and disease manifestations. The lymphoid disease cannot be readily distinguished from the visceral response to Marek’s disease; however, there are some features that aid in the differential diagnosis.

There is no treatment for lymphoid leukosis. Although the disease cannot be prevented completely, there are certain steps that can be taken to help control the level of infection within a flock. Some steps are:

Buy resistant strains of birds since genetic resistance is a deterrent,
Brood in isolation and do not mix birds of different ages, especially through six weeks of age,
Keep the incubator clean and disinfected,
Control blood-sucking parasites,
Good care, limiting stress, and adequate ration will be of benefit.