Disease: Atoxoplasmosis

This page provides general information about this condition; reveal the text by clicking on the green headers. Press releases, results from DWHC investigations as well as other useful documents and relevant literature can be found at the bottom of the page.


Atoxoplasmosis refers to an infection with the protozoan parasite Atoxoplasma that has recently been classified as a member of the coccidian genus Isospora. Several species of atoxoplasma have been identified and these generally show host-species specificity i.e. the species that infects canaries differs to the species that causes disease in sparrows. These single-celled parasites have a direct life cycle meaning that all stages of reproduction and development occur within a single host.

Susceptible species

Passerines (songbirds) appear to be particularly susceptible to infection with atoxoplasma spp. and it is thought that atoxoplasmosis is endemic in many wild passerine species.

Due to the feco-oral nature of transmission, a high rate of disease is often seen in captive birds such as in zoo collections, conservation projects and private aviaries where infection pressure may be particularly high due to high stocking densities and, accordingly, high concentrations of feces containing oocysts (infectious stages of the parasite).

In recent years there has been increasing interest in ascertaining the level of infection in wild passerine species: For example, the prevalence in house sparrows in Israel was reported at 70%; in tree sparrows in Sweden the prevalence was 57% and infection was associated with reduced survival and lower mating success.

Gill H, Paperna I. Proliferative visceral Isospora (atoxoplasmosis) with morbid impact on the Israeli sparrow Passer domesticus. Parasitology research. 2008 Aug;103(3):493-9.
Halvarsson, P. 2016. Host-Parasite Interactions in Natural Populations. Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 1395. 43 pp. Uppsala: Acta Universitatis Upsaliensis. ISBN 978-91-554-9633-3.

Signs in animals

Signs of infection in wild birds are not well documented but reports of atoxoplasmosis in captive birds typically describe disease occurring in fledglings (young birds) in which diarrhoea and liver enlargement are typical, and in stressed birds in which apathy, loss of appetite and weight loss may be noted.

Infection of animals

Atoxoplasma undergoes the sexual phase of its life cycle in the avian host’s intestines and this results in infectious oocysts being excreted in the feces. Ingestion of food or water contaminated with oocyst-containing feces is the usual source of infection in birds. The parasite undergoes various stages of development in the white blood cells circulating round the body before entering the cells lining the intestines where oocysts are formed, completing the cycle.

Preventative measures

Several hygiene measures are recommended to minimise the risk of spread of this disease; these are particularly relevant to people involved in the management of captive passerine species: As the oocysts can survive for months in feces, aviaries should be cleaned and disinfected regularly. Efforts should be made to minimise the chance of fecal contamination of food and water sources. As it is probable that captive birds are infected by wild birds, outdoor enclosures should be designed to minimise contact.



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