Avian Leukosis

Whilst we are all very familiar with Marek’s disease, causing tumours in chicken flocks, Avian Leukosis disease is another tumour causing virus that can have equally devastating effects.

Avian leukosis virus belongs to a family of viruses called retroviruses. Included in this family are bovine leukosis (affecting cattle), feline leukosis (affecting cats) and HIV. Note that the virus cannot spread to humans or any other species.

Like all retroviruses, the virus is relatively weak and does not survive well outside of the birds. Hence it is only transmitted via mating, through the egg and through biting pests (such as red mites and biting flies).

Like Marek’s disease, Avian leukosis infects the white blood cells, causing two problems: firstly, the virus damages the infected white blood cells. The bird cannot fight off other diseases that an otherwise healthy bird would do.

This leads to the bird developing other infections such as respiratory disease and coccidiosis. When your vet treats these infections, the birds don’t recover as well as expected.

Secondly, the virus eventually forms tumours in the bird’s internal organs, such as the liver, spleen, kidneys, reproductive organs, and bones.

See the picture in the dropdown toggle below, hidden because Google sent us a warning saying it was objectionable content.

Spleen showing Avian Leukosis
Tumours in the Spleen from Avian Leukosis.

Initial observations

Initially, the birds may appear to have a minor respiratory infection or diarrhoea; however, even with treatment, the birds often fail to improve. The affected chickens often become dull and lose a lot of weight. Eventually, if not euthanized, these birds die. In some cases, Avian leukosis causes bone tumours to form in the legs, leading to thickened bowed legs. However, it is important to note that, unlike Marek’s disease, Avian leukosis never causes nervous signs as the virus does not cause tumours in the nervous system.

Diagnosing avian leukosis

The best way to diagnose leukosis is through a post mortem where the vet will look for tumours in the internal organs. Often it is difficult to distinguish between Marek’s and Avian leukosis on post mortem without histopathology (the tissue is cut into thin slices and examined through a microscope to look for the cancerous cells).

Again, there is a picture in the dropdown toggle below, hidden because Google says it’s objectionable content.

Lumen with Avian Leukosis
An area of the gut with tumours.

Treatment

There is no treatment for leukosis, and unfortunately, it is usually kinder to put any affected birds to sleep.

Prevention is based upon keeping a closed flock and only buying birds (and eggs, for that matter) from reputable suppliers. If you have had an affected bird, then any of its offspring are potentially infected, as are any birds it has mated with.

If you have had an outbreak, it is important to destroy all red mites. Biting flies can also carry the virus between birds.

One other problem with this virus is that infected birds often act as reservoirs for other diseases such as respiratory disease, which can infect birds that do not have avian leukosis.

If you suspect any of your birds have avian leukosis disease, then you must seek veterinary help immediately.

Related Posts:

Aspergillosis

Aspergillosis is an infectious fungal disease affecting poultry in which birds will usually be left gasping for breath. The disease is

Read More »
Gapeworm
Respiratory Problems
Gapeworm

Gapeworms (Syngamus trachea) are included under ‘respiratory system’ since the adult worms reside in the trachea (or windpipe) and often produce a

Read More »
Wrinkled Egg Shells Infectious Bronchitis
Respiratory Problems
Infectious Bronchitis

Infectious bronchitis (I.B) is the most contagious poultry disease. It has very similar symptoms to mycoplasma. The main difference is the

Read More »
Gapeworm

Gapeworms (Syngamus trachea) are included under ‘respiratory system’ since the adult worms reside in the trachea (or windpipe) and often produce a

Read More »

On this page:

You might also enjoy:

Chickens in Cold Weather

Keeping Chickens In Cold Weather

How cold can chickens tolerate? What should you feed chickens in winter? How do you stop water freezing? Here are my tips for the cold, winter weather.

family Guide

A Family Guide to Keeping Chickens Book Review

This practical, full colour book, is ideal for the complete beginner. Even someone who has never kept animals before should be able to follow the clear, detailed guidance that is given at every stage.

Double and Triple Yolk Eggs

Double Or Multi-Yolk Eggs

Double or multi yolk eggs, whilst very enjoyable, are actually a fault. They are common in young, laying hens, especially from hens that are from highly productive strains.

Call Ducks on Grass

Keeping Call Ducks

At one time Call Ducks were known as Decoys and were fed or tethered at the entrance to long traps.

A poultry orchard with geese

Creating an Orchard for Poultry

Traditionally, in Europe, people kept poultry in orchards. Chickens and waterfowl would eat insects and fallen fruit, and geese would keep the grass short. Droppings helped provide nutrients for the trees, and the trees provided shade, shelter and safety.