Also see Bloodborne Organisms et seq.
Parasites of the Circulatory System
Also see Bloodborne Organisms.
Haemoproteus was previously documented with great frequency in imported Cacatua sp. Leucocytozoon, Plasmodium, and Atoxoplasma spp are all seen occasionally in various species, most commonly in raptors, canaries, and Columbiformes, and are currently not of major significance in psittacines. Atoxoplasmosis is still diagnosed in canaries.
Parasites of the Gastrointestinal System
This intestinal protozoal disease is seen most often in cockatiels. Adult birds may be latent carriers. Transmission is presumably direct (ingestion of infective cysts). Affected cockatiels occasionally exhibit feather pulling in the axillary and inner thigh regions, along with vocalization. A true causal relationship between giardiasis and these clinical signs has not been proved. Droppings of affected cockatiels may be voluminous and aerated (a “popcorn” appearance).
Microscopic examination of a warm saline mount of fresh feces may reveal motile trophozoites. Because the presence of cysts is variable, serial tests are advised. The accuracy of the Giardia SNAP test designed for human medicine is unknown. Many veterinary diagnostic labs offer tests for fecal giardiasis.
Metronidazole (50 mg/kg, sid for 5–7 days) is the recommended treatment. In cockatiels, treatment of giardiasis with fenbendazole at dosages extrapolated from dogs has been anecdotally reported to cause death.
Trichomonas gallinae (called frounce in birds of prey and canker in Columbiformes) is occasionally seen in pet birds, notably budgerigars. Whitish yellow, caseous lesions adherent to the mucosa of the oropharynx, crop, and esophagus may occur in raptors and Columbiformes. Budgerigars generally do not have grossly visible oral lesions but do have increased salivation and regurgitation. Transmission is by direct (parents feeding young) or indirect (ingestion of contaminated food and water) contact; raptors may become infected by ingesting infected pigeons or doves. Microscopic examination of a warm saline mount of material from the oral cavity may reveal the flagellated organism.
Treatment protocols include carnidazole (20 mg/kg, PO, once), ronidazole (5 mg/kg, sid for 14 days), or metronidazole (40–60 mg/kg, PO, sid for 5 days).
Other Protozoal Diseases
Other protozoan parasites such as coccidia are much more common in gallinaceous or Columbiforme birds, although coccidial oocysts are seen occasionally in psittacines and passerines. Cryptosporidiosis has been seen in a variety of psittacine birds and Gouldian finches, but is thought to be a secondary rather than a primary pathogen. Atoxoplasmosis is a highly pathogenic protozoal disease that causes hepatomegaly and splenomegaly in canaries, with coccidia-like oocysts shed in the feces.
Various genera and species occur in caged birds, and wild birds may transmit certain nematodes to captive parrots housed outdoors. Transmission is direct, via ingestion of embryonated ova. Clinical findings include loss of condition, weakness, emaciation, and death; intestinal obstruction is common in heavy infections. Diagnosis of intestinal nematode infection is by fecal flotation, although shedding of ova may be intermittent. Pyrantel pamoate (20–50 mg/kg, PO) or fenbendazole (20–50 mg/kg, PO) are generally effective. In warm climates where exposure via outdoor aviaries is likely, routine deworming with one of these anthelmintics is often performed.
Cestodes have become uncommon following the shift from imported to domestically bred birds. Intermediate hosts are most likely insects and arachnids of various types, earthworms, and slugs. Praziquantel (8 mg/kg, PO or IM) is the recommended treatment. Recurrence is rare in the majority of cases in which the intermediate host is not indigenous to the area where the bird is housed.
Parasites of the Integumentary System
Scaly Face (Leg) Mite
Cnemidocoptes pilae is common in budgerigars and rare in all other psittacines. In budgerigars, white, porous, proliferative encrustations involving the corners of the mouth, cere, beak, and occasionally the periorbital area, legs, or vent are typical. Passerines can also be parasitized but have different clinical signs. In passerine birds (particularly the canary and the European goldfinch), crusts form on the legs and surfaces of the digits (“tassel foot”). Immunocompromise plays a role in the expression of these mites in both psittacines and passerines; individuals that are immunocompetent are generally not affected.
The mites can be recovered from facial scrapings of budgerigars, although the clinical appearance is generally pathognomonic. In passerines affected with Cnemidocoptes, skin scrapings of the legs often result in hemorrhage and are generally not recommended. Ivermectin at 200–400 μg/kg, PO or by injection, is generally effective. The treatment is usually repeated in 2 wk.
Psittacines are seldom affected by any type of feather mite. Occasionally, infestation with the red mite (Dermanyssus gallinae) may be found in outdoor aviaries, especially in nest boxes. A causative relationship between mites and feather picking is often assumed by owners of feather-picking birds, although this is rarely the case. More commonly, behavioral, husbandry, and/or systemic factors are linked to feather loss (see Feather Destructive Behavior).
Mite-infested birds may be treated with pyrethrin sprays, 5% carbaryl powder, or ivermectin. Nest box treatment includes mixing 5% carbaryl powder into the nest box substrate. Cages should be cleaned thoroughly, and wooden nest boxes should be discarded and replaced.
Parasites of the Respiratory System
Air Sac Mites
Sternostoma tracheacolum parasitizes the entire respiratory tract, most frequently of canaries and Gouldian finches. All stages of the mite are found within the respiratory tissues. The life cycle is poorly understood.
In mild infections, birds are usually asymptomatic; in heavy infections, audible dyspnea (high-pitched noises and clicking), sneezing, tail bobbing, and open-mouthed breathing are noted. Copious amounts of saliva are seen in the oropharynx, and ptyalism may be present. Signs are exacerbated by handling, exercise, and other stresses. Mortality can be high. Transillumination of the trachea in a darkened room occasionally reveals the mite. Response to treatment can assist in reaching a diagnosis.
When the recovery of an individual bird is paramount, treatment should be administered quickly and with minimal handling. Ivermectin (200–400 μg/kg) may be administered, and the dose repeated in ∼2 wk.
Sarcocystosis is a major cause of mortality in parrots housed outdoors in the southern USA. In severely affected areas, even indoor birds can be infected via contaminated food. The oocysts of this protozoan parasite are passed from infected opossum feces by insects (eg, cockroaches) or rats into the feed cups of birds. The feces of these transport hosts are then consumed by the birds, and a rapidly fatal disease can develop. Old World species are immunologically naive to this disease, and a high mortality rate is observed in untreated birds such as cockatoos, African Greys, and Eclectus parrots. Cockatiels are also susceptible, and renal as well as pneumonic lesions are often noted at necropsy in this species. Although not directly contagious, birds in communal aviaries are often affected simultaneously, and large die-offs have been documented.
Clinical signs include lethargy, passive regurgitation of water, and anemia. Protracted treatment with trimethoprim/sulfa (25 mg/kg, sid-bid) and pyrimethamine (0.5 mg/kg, PO, sid) is often effective. No specific diagnostic test is available, although certain plasma electrophoresis results may be indicative, and an antibody test has been developed. Muscle biopsies may be conclusive for the encysted stages but are not commonly performed. Response to treatment is generally monitored by serial PCV sampling. Newer drugs used to treat infection by the related protozoa, Sarcocystis neurona, that affects horses have not yet been evaluated for treatment in birds.
Gross necropsy signs include increased lung density and hemorrhage and renal pathology. Clinical signs may also reflect CNS involvement. Histopathology samples should include lung, kidney, muscle, and CNS tissue if neurologic signs were apparent.
Last full review/revision July 2011 by Teresa L. Lightfoot, DVM, DABVP (Avian)