Infectious Diseases

By Edward T. Mallinson.

Infectious diseases ordinarily are produced by protozoa, bacteria, viruses, parasites, or fungi. Their accurate diagnosis frequently requires expert laboratory analysis.

Protozoan diseases are produced by single-celled animals that can be seen as small and usually rounded creatures when magnified 40 times their size in a common light microscope. They frequently attack the digestive tract of most types of poultry and pet birds. They are involved also in producing malaria-like infections of the blood of pigeons, cockatoos, and other pet birds.

Digestive protozoan infections such as coccidiosis, trichomoniasis, histomoniasis, hexamitiasis, and giardiasis ordinarily are prevented by keeping poultry or birds off the ground and on dry deep fresh litter or in cages where exposure to droppings is almost totally prevented.

Keeping waterers clean and as free of fecal droppings as possible is another important step in preventing digestive protozoan infections.

Protozoan infections of the blood stream such as plasmodium, leucocytozoan and hemaproteus infections generally are prevented by confinement to prevent exposure to bloodsucking insects. Numerous species of mosquitoes, blackflies, biting midges, and certain flies transmit these infections.

When it is impossible to confine your flock or collection to preclude exposure to these flying insects, they must be controlled with insecticide sprays and by the removal, at a distance as large as you can, of weeds and trash from the perimeter around your operation.

Preventing digestive diseases and maintaining healthy birds is easier when you keep them caged off the ground, because they are less likely to come in contact with fecal droppings.

Mowing May Help

High insect populations are fostered by any place where water can accumulate, from ditches to streams or lakes, especially when bordered by heavy vegetation. Such border areas sometimes can be improved by mowing.

Specific protozoan infections of chickens, turkeys, and other birds will be discussed separately in the special diseases chapters of this section.

Preventive and outbreak treatments are included in the preventive medicine tables in this chapter.

Bacteria Infections.

Bacteria are very small forms of life visible only as small dots or short rods when magnified 1,000 times their size in a microscope. In bacterial infections the causative bacteria travel to various locations of the body via the bloodstream. Chronic infections occur when the bacteria localize in one or more organs or tissues.

Disease-producing bacteria generally are capable of not only invading many different parts of the body, but also many different species of birds and animals.

Disease Features

The following outlines some of the more distinguishing features of these infectious agents that not uncommonly are found in both backyard poultry and a variety of other birds.

Chlamydiosis.

Infections with the causative bacteria, Chlamydia psittaci, in man and birds are called psittacosis. In poultry and other avian types, such as turkeys, the disease is called ornithosis.

Chronic lung infections and persistent intestinal infection and diarrhea are the main effects. They may be severe, mild or almost undetectable. In pigeons, the eyelids may become crusty and swollen.

This disease is detailed further in the Special Diseases of Pet Birds chapter.

Colibacillosis.

Caused by Escherichia coli, this bacteria may act as a primary invader or secondary infection following another disease.

The young are more frequently affected, particularly when sanitation is below standard.

Air Sac Disease

A major problem can be encountered when the infection produces severe, cheesy-like inflammations over the heart, liver and air sacs of growing birds. This form of colibacillosis is often called "air sac disease." It is a common complication of chilling or poor ventilation combined with acute viral and mycoplasma infections.

Colibacillosis of the navel or omphalitis, which produces reddening, swelling, mushiness or wetness around a poorly healing navel, can result in the loss of many hatchlings during the first 7 to 10 days of life. Shipment of day-old stock over long distances tends to increase these losses, which usually have their origin at the hatchery or breeder flock level.

Chronic infections of the oviduct (salpingitis), the liver (coligranuloma), and leg or wing joints also occur.

Erysipelas infections are especially destructive to turkeys. They may be found also in chickens, game birds, and waterfowl. Wild birds may be infected along with swine, sheep, and humans. The infection in birds usually starts from breaks in the skin due to fighting or cannibalism.

People handling poultry or birds sick with this disease can develop painful infections of the hand or fingers. Professional medical assistance should be obtained immediately to prevent deeper, more serious infection.

Fortunately, prompt administration of penicillin or other antibiotics is highly effective in controlling this disease. The causative bacteria tends to resist disinfectants and survives well in alkaline soils for months to years.

Hemophilus Infection.

Infections produced by Hemophilus gallinarum typically produce "colds" where discharges from the eyes and nose and swelling of the face are prominent symptoms. The disease is discussed in further detail under fowl coryza in the chapter on Special Poultry Diseases. Pheasants and guineas also may be infected, and possibly other avian species.

Mycoplasmosis.

An assortment of small, relatively delicate bacterial agents called mycoplasma afflict the respiratory and reproductive organs of many avian species.

The list of affected types now includes chickens, turkeys, partridges, pheasants, peafowl, quail, guineas, ducks, and pigeons. As research in pet bird diseases expands, the list will lengthen.

Prolonged Course

Mycoplasma infections have a prolonged course in a flock or colony, frequently setting the stage for more serious respiratory disease should shipping stress or ventilation problems develop.

Mycoplasma characteristically worsen and extend the effects of virus or other bacterial infections. They often are "behind the scenes" in outbreaks of fowl coryza and air sac disease, and in lowered egg production.

These infections may also occur in joint tissues, producing swelling and lameness (synovitis).

Fowl Cholera Pasteurellosis.

Under the right conditions, poultry, game birds, waterfowl, wild birds, and many pet birds can suffer heavy losses following acute infections with Pasteurella multocida.

Chronic infections subsequent to an acute outbreak may result in joint, wattle, sinus, nasal, and middle ear or skull bone infections. The latter often results in twisting of the neck similar to that in Newcastle disease.

The disease is not egg-transmitted. It is, however, readily spread by recovered wild or domesticated carrier birds or animals and contaminated crates, feedbags, shoes, and equipment.

Salmonellosis.

There are more than 2,200 different species of Salmonella (S.) bacteria. Most are capable of infecting many different types of pets, poultry and livestock. Some, like pullorum disease (S. pullorum) and fowl typhoid (S. gallinarum) are particularly infectious to poultry. They are discussed at the beginning of the poultry disease chapter. Both readily spread to day-old stock by infected breeders via the hatching egg.