AVIAN PARASITES PART III: ARTHROPODS

By David Hannon, DVM

Arthropod parasites are differentiated from other parasites by the presence of a chitinous exoskeleton, and they typically have jointed appendages as well. These parasites usually infest the external areas of birds (called ectoparasites), but some can exist inside a bird's body. Most of these parasites can be prevented with good sanitation and hygiene, and by limiting contact with wild birds, or birds from questionable backgrounds. If you think your bird has an ectoparasite problem, the best course of action would be to contact your avian veterinarian, and act upon his recommendation. Most of the products sold over-the-counter for parasite control (sprays, powders, pest strips, etc.) are ineffective at best, or potentially dangerous at worst. Mite protectors, small perforated metal cans of insecticide that are hung on the cage, have no effect on common external avian parasites, and may even cause liver disease.

ARACHNIDS

A. Mites

1. Skin Mites - These mites infest a bird's skin or feather follicles, causing damage to these structures and secondary bacterial infection. The most common type of skin mite, Knemidokoptes, also known as scaly leg or face mites, infest the featherless areas, typically around the face and legs, burrowing into the skin. They are most commonly seen in budgerigars, but can infest almost any bird, including psittacines, passerines, poultry, raptors, and pigeons. Clinical symptoms include proliferative growths in the infested areas (it has been called "tassel-foot" in canaries), raised scales, swelling and inflammation, and feather loss in surrounding areas. Other species of mites that infest feather follicles (a disease informally known as "mange") cause feather loss and secondary bacterial infection (called folliculitis), and chronic long-term mite infestations can lead to follicular damage severe enough to prevent feather regrowth once the mites are gone. Most of these mites can be diagnosed fairly readily, and treated easily with systemic or topical medicines. The best prevention is good sanitation, and limiting contact with wild birds.

2. Feather Mites - Over 25 different feather mite families have been described, infesting almost all species of birds, with the exception of penguins, cassowaries, and rheas. These parasites are very species-specific, and typically do not cause pathological problems in their normal host species, except in cases of severely heavy infestation. If they infest a bird that is not their normal host species, clinical symptoms may be noted. These typically manifest as feather abnormalities or damage, but in severe cases, bacterial skin infections may occur. The highest populations tend to be on the ventral wing feathers, but the preferred location depends on the stage of the mite's life cycle, and the species. They are easily diagnosed and readily treatable, and preventable with good hygiene.

3. Quill Mites - These mites actually get inside the shaft of the feather, and live on the secretions and other material found there. They have specialized mouth parts that allow them to cut the quill to enter it, as well as make holes in the feather shaft below the level of the follicle to get at tissue fluid in those areas. These mites are fairly species-specific, and most birds are susceptible to at least one genus of mite. Clinical symptoms include discolored feather quills, altered feather growth, and feather loss due to either follicle damage or manual removal by the bird to relieve irritation. These parasites are spread by direct contact, so good sanitation is important for prevention, and currently there is no effective treatment.

4. Nest/Aviary Mites - These are mites that externally parasitize birds, but do not actually live on the bird. Instead, they live in the environment. Red mites (Dermanyssus) are the most common type encountered. They live in cracks and crevices, and come out at night to feed on the blood of the sleeping birds. This lifestyle obviously makes diagnosis difficult, but it emphasizes the importance of good environmental sanitation. Another type of environmental mite, called Trombiculidae, has larval stages called "chiggers", which will attach to a bird's skin and feed for three days, causing itching and irritation, and then fall off. The nymph and adult stages of this mite live in the soil and litter. Birds that are infested by these types of mites typically have an unthrifty appearance, and can exhibit weight loss, anemia, and dermatitis.

5. Subcutaneous Mites - These mites are fairly uncommon. They burrow under the skin and reside in cysts in the neck, breast, flanks, groin, and thighs. They are found in many different species of birds, and cause focal irritation and secondary infection, and can sometimes burrow into the underlying muscles or organs. Diagnosis and treatment are difficult.

6. Respiratory Mites - There are several different species of mites that infest the respiratory tract of birds. Most of these mites live in the upper respiratory, infesting the nasal cavities and feeding on blood, secretions, and desquamated tissue. Other than upper respiratory infections and discharges, these mites typically do not clinical problems. However, the canary lung mite (Sternostoma tracheacolum) and mites from the family Cytoditidae, also called air sac mites, can infest the trachea, lungs, and air sacs. Clinical symptoms include respiratory distress, coughing, sneezing, respiratory "clicks", and excessive mucus production. Often times, secondary bronchopneumonia and air sacculitis occur, and severe infestations can lead to respiratory obstruction and asphyxiation. They are readily treated with systemic and nebulized medicines.

B. Ticks - Ticks are much more common in wild birds than domestic, but they do occur. Just one or two will cause nothing more than just focal irritation, but severe infestations can lead to anemia. They also act as carriers for many infectious diseases, and there is a clinical syndrome, formerly only seen in mammals, but recently described in birds, called tick paralysis, whereas the tick secretes an unknown substance that causes a neurological paralysis. If the tick is removed early enough, these animals quickly recover, but since this has only been seen in wild birds thus far, the mortality rate is quite high.

INSECTS

A. Lice - These parasites are most commonly found in wild or poorly kept birds, or in poultry. They are fairly species-specific, and chew on feathers or skin at the base of feathers, thus causing irritation and secondary bacterial infections. Often times the eggs, or "nits", can be seen adhered to a birds feathers. Some species of lice can transmit certain species of filariid worms, discussed in Part II. They are spread by direct contact, and easily prevented with good husbandry practices.

B. Fleas - Fleas are occasionally noted in companion and aviary birds, but are more often found in wild birds or poultry. They are spread by direct contact, and can cause itching, anemia, and poor feather condition. The sticktight flea of poultry will adhere to the bird's head, and remain attached for days to weeks. The are easily diagnosed and treated, and preventable with good husbandry. Although some avian fleas can infest mammals, the fleas that your dog or cat have will not infest your bird.

C. Mosquitos - Mosquitos attack birds just like they attack other animals, and act as a carrier for many diseases, such as Plasmodium (avian malaria), Trypanosoma, and filariid worms. Control is best done with screens or mosquito netting, and by removing standing water from the area.

D. Flies and Gnats

1. Louse Flies - Also known as Hippoboscid flies, these little insects will infest wild birds most often, but can affect domestic birds, especially if the bird is in poor condition. Grossly, they look like houseflies, but actually they spend little time flying, and most of the time running in and out of a birds feathers, when they are not feeding on blood. Most healthy birds will preen them off, but sick or injured birds will not. These flies also act as carriers for Haemoproteus and Trypanosoma, both of which were discussed in Part I. They are easily preventable and treatable.

2. Black Flies - Simulium sp., also known as buffalo or turkey gnats, occur more commonly in temperate or subarctic areas. They fly from animal to animal feeding on blood, and attacks by swarms can cause anemia and death. They transmit the protozoan Leucocytozoan, which was discussed in Part I. Control is the same as for mosquitos.

3. Biting Midges - Formerly known as Culicoides, this is another species of small biting fly that feeds on blood. They act as carriers for Haemoproteus, Leucocytozoan, and some filariid worms. Control is the same as for mosquitos.