Zoonotic Diseases: Giardia and Avian Influenza

Zoonotic diseases are diseases that are transmissable from animals to humans. Young children, elderly adults and individuals with poorly functioning immune systems are at the greatest risk of being infected by a zoonotic disease.

While there are a number of diseases which can be transmitted by companion birds, many are more likely to be transmitted by poultry or wild birds. If your bird has been examined by an avian veterinarian and is considered healthy, the risks of infection are significantly reduced.

The following diseases in birds which are of reasonable significance include: Chlamydiosis (Psittacosis), Salmonellosis, Campylobacteriosis, New Castles Disease, Allergic Alveolitus, Mycobacteriosis (tuberculosis), Influenza, Giardia, and Cryptosporidiosis.

Chlamydiosis (Psittacosis or Parrot Fever) and Salmonellosis were discussed in Zoonotic Diseases – Part I. Allergic Alveolitus, Campylobacteriosis and New Castles Disease were addresssed in Zoonotic Diseases – Part II and Avian Tuberculosis was described in Zoonotic Diseases – Part III. Part IV addresses Giardia and Avian Influenza.


Giardia is an intestinal protozoan that is found in the small intestine of infected birds, dogs, cats, humans and other mammals. The motile form, the trophozoite, attaches to the villi (fingerlike projections) of the small intestine by means of a sucking disk. The cyst form is passed in the feces (as well as the trophozoite) and is able to survivie in the environment.

People, birds and other animals become infected when they ingest contaminated food and water. Giardia cysts are not destroyed by standard chlorination. Boiling will destroy them, however.

The most frequently infected companion birds include budgies, cockatiels, lovebirds and grey cheeked parakeets. This may be the result of the way these birds are raised – in very densely populated environments. Other species may also be infected.

Infected adult budgies and cockatiels (as well as other species) often appear clinically normal, but shed the infective cysts intermittently in their feces. Certain stresses, such as reproduction, molting or other diseases, may cause clinical signs such as the passing of voluminous, foul smelling, watery droppings, passing whole seeds in the droppings, ruffled feathers and death. The highest mortality is in nestlings and birds weakened by other illness. Some birds, especially budgies and cockatiels, are thought to become itchy as a result of a toxin secreted by the parasite. These birds tear out their feathers, frequently screaming as they do. People can develop severe cramping and diarrhea from Giardia.

Giardia appears to be limited in host range. The giardia infecting budgies is Giardia psittcai. It is unknown if these species can infect other types of birds. Giardia from mammals may infect humans, but the zoonotic potential for avian giardiasis is believed to be low, since it is not thought that avian giardia can infect mammals.

Diagnosis of giardia in live birds can be difficult. Feces must be fresh – examined within ten minutes – in order to find the motile trophozite. If the feces cannot be examined immediately, it may be placed in polyvinyl alcohol and later trichrome stained for cysts. Multiple specimens may need to be examined because the parasite is shed intermittently.

Infected birds may be treated with metronidazole. Unfortunately, not all birds may be cleared and reinfection from the environment is common. Multiple courses of treatment are often necessary.

Quarantine, avoidance of overcrowding, and treatment of birds showing clinical signs will decrease the incidence of Giardia in a collection.

Avian Influenza

Influenza is caused by an enveloped RNA virus. It is an infectious disease of birds, swine, humans and other animals. Three types of Influenza viruses exist – types A, B, and C. Influenza A viruses infect birds and other animals, while B and C infect people.

Hundreds of subtypes of Influenza A viruses have been isolated from birds and other mammals. Influenza viruses are continuously undergoing change, resulting in new serotypes. Migratory birds, especially waterfowl are believed to be reservoirs for Influenza A virus. The infection often causes an inapparent intestinal disease in waterfowl. These infected waterfowl don’t show signs of disease unless severely stressed by other diseases or transport. These inapparently infected birds shed the virus from their respiratory tract, conjunctiva (lining of the eyes) and in their feces – serving as a source of infection for other birds. Incubation may be as short as a few hours.

The signs of illness depend upon the species infected, the age, environmental factors, and virulence of the viral strain. Birds may die suddenly without showing signs of illness or develop depression, appetite loss, coughing, sneezing and decreased egg production.

Influenza A has been isotated from captive birds, including psittacines (parrots) and passerines (canaries, finches, sparrow, starlings, etc). Psittacines my demonstrate loss of balance, torticollis (twisted neck) and may die.

The virus may be isolated from swabs of the cloaca and upper respiratory tract in the live bird. It may be isolated from the lungs, liver, spleen and brain at postmortem.

A companion bird could serve as a source of virus exposure for humans, but it is more likely that humans could serve as a source of virus exposure for susceptible companion birds. If a human has clinical signs of the “flu”, he should avoid contact with his bird.

Wild migratory birds should not be allowed contact with companion birds, chickens and turkeys – as they may serve as a means of spreading Influenza.

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