Common Diseases of Backyard Poultry

The keeping of backyard poultry gives great enjoyment to many people. The production of fresh eggs and meat for human consumption, plus the enjoyment they give as pets or show birds, makes poultry valuable members of many families. Poultry may become ill from many causes. There are a few major categories of diseases that commonly occur in small poultry flocks. External parasites   Poultry can carry a large variety of parasites on their bodies. They should be examined regularly, and treated for external parasites every two to three months. These parasites range in size from large, blood sucking ticks up to 1 cm in size, down to the microscopic scaly face mite that is less than 0.5 mm in size. Other external parasites that are commonly encountered are the flea and lice.     External parasites generally cause mild clinical signs such as feather damage, anaemia and irritation. Internal parasites  Backyard poultry also carry a wide range of internal parasites. Internal parasites attack the lining of the intestine, and absorb nutrients from the bird’s gut for maintenance of its own body and multiply for production of eggs. Clinical signs of internal parasitism may include weight loss, pale combs or diarrhea. Large round worms can be visible with the naked eye.  They are transmitted by the ingestion of eggs from the faces of infected birds. Regular removal and cleaning of faces from the bird's enclosure will result in less worm eggs in the environment, and less chance of worms spreading from bird to bird. Intracelluler parasites can only visible under a microscope - Eimeria and Giardia         Marek's disease Marek's disease is a viral infection that only affects poultry. The virus is spread from bird to bird in feather dander and dust. It lives in the environment for long periods, and can spread between properties on people's clothes and on shared equipment. Birds are usually infected at a young age, but may not show signs of disease until some months later. The virus that causes Marek's disease attacks the white blood cells of the bird, and results in cancer. These cancers most commonly affect the nerves and cause paralysis. Usually, the legs are affected, but the tumors may also affect the nerves in the wings and neck. Birds may also develop tumors in the body. As they grow, these tumors may cause a number of signs including weight loss, diarrhea, ill thrift, and difficulty breathing. A vaccine should be given to birds at one day of age. It is recommended that all birds be vaccinated, even though the vaccine is not as effective as it used to be. This is due to the virus that causes the disease mutating slightly over time. Most large hatcheries vaccinate their chicks, so birds purchased from them should be protected, and vaccine is available at a reasonable cost for birds hatched privately. Leucosis Avian leucosis is also a viral disease affecting chickens which causes tumors or cancers. These tumors occur in older birds than those affected by Marek's disease, usually more than 6 months old. It causes listlessness and loss of weight and the bird eventually dies. The viruses affect the white cells and tumors usually appear in the liver and spleen but also in other sites. Sometimes the tumor appears as white lumps, at other times the liver and spleen appear larger than normal. The viruses are transmitted through the egg and commercial producers attempt to eliminate it from their strains of birds. There is very little that a poultry owner can do except keep the bird comfortable and destroy it when life becomes unpleasant for it. Respiratory disease There are many causes of respiratory disease in poultry. Respiratory signs such as coughing, sneezing and discharge from the eyes and nostrils can be caused by parasites (gapeworm - Syngamus trachea), dust, high ammonia levels, or a variety of bacteria or viruses. In all cases, a veterinarian with experience in poultry disease must diagnose the exact cause, particularly if mortalities occur. Some of the respiratory viruses such as Infectious Laryngotracheitis Virus (ILT), Newcastle Disease and Avian Influenza are notifiable or exotic diseases, and must be reported to a Government Veterinarian if they are suspected. Treatment will depend on the cause of the respiratory signs. For some viral causes such as ILT, vaccination is recommended. Fowl pox Another viral infection of birds is fowl pox. This disease is spread by biting insects and sometimes by fighting. The virus enters the body through a scratch or scrape, and raised scabs form on the scratch and surrounding areas. Scabs can also form in the mouth and throat. Most cases improve without treatment, although some birds become ill from secondary infection. Birds that recover are immune for life. Prevention is only by vaccination, this may need to be done every few years to give complete protection. Nutritional deficiencies Many small flocks of birds are fed only table scraps. This diet is not sufficient to meet the nutritional demands of growing birds or layers. Common deficiencies include calcium (resulting in poor bone growth and rickets), energy (poor growth, weight loss, poor egg production), and vitamin A (poor skin and feathering). Formulated diets are available for all stages of a hen's life, (starter, grower and layer) and these should be fed in conjunction with table scraps, fruit and vegetables to form a balanced diet.   Reproductive problems Commercial birds are bred to lay for only one, or two laying seasons. If they are then sold to backyard producers for extended laying, they are prone to reproductive problems. This includes egg binding (where the egg is unable to be passed out of the bird), metritis (inflammation of the oviduct and shell gland), and yolk peritonitis (free yolk in the abdominal cavity, leading to infection). Affected birds stop laying eggs, are depressed, stop eating and eventually die. They often develop a swollen abdomen, and may have respiratory difficulties. Surgery by a veterinarian is possible to resolve these conditions, however, the surgery results in the bird being unable to lay eggs. Hence, it is reserved only for pet birds. Exotic disease Newcastle Disease and Avian Influenza are the major exotic diseases small poultry keepers need to be aware of. Signs of Newcastle Disease range from mild respiratory signs to very severe depression drop in egg production, diarrhoea, collapse and nervous system signs. Death rates can be up to 100%. Avian Influenza often appears suddenly, and birds die quickly. Diarrhoea, depression, decreased egg production, swollen and discolored wattles and respiratory signs may all be observed. You can prevent your birds becoming infected with these diseases by limiting their exposure to migrating waterfowl and wild birds that can carry these viruses. Preventing overseas visitors who may be inadvertently carrying the virus, from accessing your birds and refusing to accept birds or eggs that may have been imported will also decrease the chances of your birds becoming infected.