I’ve just been told by my vet that one of my birds (now destroyed) had avian leukemia. Can anyone tell me if my other six birds are likely to contract this? I’ve just purchased three new birds, a Buff Orpington, a Cream Crested Legbar and a Rhode Island Red. The other three remaining birds are hybrids which I’ve had for two years. Any advice would be most welcome.Jill Jones,via email

Avian leukosis isn’t very contagious.  In the light of a query about avian leukosis, Victoria Roberts re-visits non-Marek’s disease tumours Control of tumours  in chickensCauseOther tumours in poultry (not Marek’s disease caused by herpesvirus) are caused by retroviruses and these include the avian leukosis/sarcoma viruses. Life cycleThere are two types of mechanism: lymphoid leukosis virus (most common) slowly transforms cells into neoplastic ones and the acutely transforming viruses do the damage faster, all of them using and damaging genes and causing tumours which can include:fibrosarcoma, chondroma, endothelioma, haemangioma, nephroblastoma, and hepatocarcinomaTumours can occur almost anywhere in the chicken as lymphoid tissue is spread throughout the bird (unlike mammals which have lymph nodes).

ProgressionLymphoid leukosis: incubation period from infection to the developed disease and death is about four months. Losses occur from 5-9 months of age in egg-laying and breeding stock. Other leukosis viruses affect adults sporadically.

SymptomsAny or all of the following:  poor appetite, weakness and emaciation, diarrhoea, pale wattles, enlarged liver.InfectionThe virus is ubiquitous in poultry worldwide and is passed down through the egg and also transmitted by direct or indirect contact. Virus survival outside the body is only hours, so the disease is not very contagious.

Lymphoid leukosis (most common): enlarged liver, spleen, bursa, kidneys, ovary.

Erythroid leukosis (rare): moderately enlarged liver and spleen, leukaemia, liquid cherry red bone marrow.

Myeloid leukosis (sporadic): enlarged liver, spleen, kidneys, ovary, yellowish grey bone marrow.Osteopetrosis (rare): thickening of long bones in legs and wings.

PreventionSome breeds are resistant to tumour development. Good husbandry, minimal stress are important.

Treatment (control)No treatment or vaccines are available. Control is based on high standards of hygiene and selection for resistance to the viruses by culling affected birds.

DiagnosisVirological testing, postmortem lesions and tumours.

Victoria Roberts BVSC MRCVSEmail the Vet’s forum at: vetsforum.csh@archant.co.uk

Disclaimer: The information and advice in this column is given in good faith. However, as the animals in question have not been examined by the author, no liability in respect of diagnosis or application of any treatments is accepted either by the author or by Country Smallholding

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