The Chook Shed - Diseases of chooks

Diseases of chooks

Chooks can catch a number of serious and less serious diseases.

It is therefore important that your birds are kept in clean, draft-free accommodation, fed a balanced diet and not kept in overcrowded conditions. Furthermore, when introducing new stock into your yards it is vitally important to quarantine such birds for at least two weeks to ensure they are healthy and will not infect your own birds with some hitherto unknown disease. Below is a list and descriptions of the more serious chook diseases.

Bacterial Diseases:

Pullorum is an acute infectious disease which once ran rampant. It affects young chicks and can result in 100% mortality. It is caused by a strain of salmonella. Strangely, it seems to affect heavy breed fowls more than light breeds. Pullorum is spread in a wide variety of ways. Feather dander, flies, cohabitation with infected chicks, on clothing and shoes and even infection passed through the ovary and into the egg, where the chick is infected before birth. This makes the disease very serious, particularly on commercial poultry farms. Infected chicks often die without any prior warning, but some may have white, pasty droppings which stick to the vent and which the chicks strain to pass. Others may gasp as if suffocating. Chicks which survive fail to thrive and are not generally useful. Another strain affects older birds which causes eggs to be infected in the ovaries. Such birds are useless as breeders. The disease can be treated by the use of certain antibiotics given in the feed. In Australia, this disease is notifiable, but does not have the same impact on poultry as it once did, due to vigorous testing and veterinary intervention.

Chronic Respiratory Disease (CRD) shows as flu-like symptoms and is often caused by a number of different bacteria. It is found where birds are overcrowded in cold, drafty conditions. Antibiotics are used to clear up this problem.

Coryza is another respiratory disease. Symptoms are swollen eyes, runny nostrils and eyes, with a particularly foul smell. Birds often show stained wings where they repeatedly wipe their eyes. This disease usually occurs when there is cold weather, (change of seasons is a high risk time) dusty conditions and in high pollen seasons. Antibiotics are used to cure this disease, however recovered birds remain carriers and will become continually reinfected. Some breeds and strains of chickens seem to be more susceptible than others.

In summary, these are just the more important and common fowl diseases. There are others which may strike your birds. Many display similar symptoms to more serious diseases and are therefore hard to accurately diagnose. Remember that good husbandry is the best defence against disease in your flock but should an outbreak occur, swift and decisive intervention is required to minimise the ill effects.

Viral Diseases:

Newcastle Disease is an extremely virulent disease which causes high mortality in flocks. Spread primarily on chicken carcases and chicken meat products, it can also be carried on clothing, by wild birds and be wind-borne. Affected birds tend to gape and salivate heavily, but without apparent respiratory distress. They usually have a yellowish-white, stinking diarrhea that is sometimes tinged with blood. Other symptoms are twisted necks, paralysis, loss of balance and circling movements of the head. Vaccines are available, however many countries insist upon a complete slaughter of birds in affected yards to control any further outbreak. Newcastle Disease is particularly dangerous as it can affect nearly all kinds of birds. A specific form of the disease occurs in Australia which does not affect Australian poultry, however the overseas strains of Isa Browns and other commercial hybrids are detrimentally affected.

Mareks Disease is a nasty disease that affects young birds between the ages of 9 to 16 weeks. It is caused by a strain of herpes virus. Birds develop drooping wings, lameness and paralysis, particularly of the legs. Another strain of the virus causes internal cancerous growths resulting in quick death, often with no prior warning signs. Mortality in both strains is very high. Birds are usually infected at day old, the virus being transmitted on feather dander (dust), often from the broody hen. Birds which survive the disease become carriers and once Mareks has appeared in your flock, it becomes virtually useless to hatch chicks under hens, an incubator being the only safe way to avoid chick losses. There is no cure for Mareks Disease however day old chicks can be vaccinated. Some fanciers claim to have bred resistance to Mareks into their flocks and it does appear that this can be done over time.

Fowl Pox is usually transmitted by mosquitoes. There are two main strains of the disease, the first appearing as greyish warty scabs on the comb, wattles and faces of the birds. These can result in serious disfigurement making such birds useless for showing. The second strain is more serious, causing cheesy substances to form in the respiratory passages, particularly the throat, which often causes death by asphyxiation. Birds that recover from Fowl Pox can remain carriers. There is no sure cure, other than treating the scabs with iodine and scraping the muck out of the birds' throats and painting with iodine. A vaccine is available which is applied with a two prong needle into the flap of skin on the wing. Unlike Mareks Disease where the vaccine must be given at day old, Fowl Pox vaccine can be given to birds of all ages.

Infectious Laryngo-Tracheitis (ILT) is a serious respiratory disease. It shows as an acute inflammation of the trachea. Affected birds cough and throw their heads back as if trying to clear their throats. If left to their own devices, death of the affected birds often results. While this disease appears to be viral, some types of antibiotics have been found to help the birds recover more or less with no further recurrence (however this may be due to misdiagnosis).

Infectious Bronchitis (IB) is another respiratory disease which tends to affect younger birds. Vaccination by eyedrop is recommended for both ILT and IB. Hens which recover often lay misshapen eggs for the rest of their lives.