Coccidia are a diverse group of parasitic protozoan that have been found to be endemic in wild species of birds. Most often coccidia do not cause clinical signs in wild populations, but disseminated disease has been seen in birds including sandhill cranes (Grus canadensis), lesser scaup (Aythya affins), and Bali mynah (Leucopsar rothschildi).1,2,4 It is suspected that each species of bird has a unique coccidian parasite, but there is concern for interspecies transmission.3 This study speciated coccidian parasites noted in a house sparrow (Passer domesticus) population within the Fort Wayne Children’s Zoo to document suspected normal pathogens of this species and to develop risk assessments for collection birds. Forty-four individuals were trapped from an off-exhibit enclosure with the use of mist nets. The birds were anesthetized for blood collection followed by humane euthanasia for collection of additional samples, including liver tissue and feces. Stool analysis was performed by centrifugation and direct microscopic examination to identify the presence of coccidia. Liver touch preps were prepared for cytologic examination and tissue was frozen for future polymerase chain reaction (PCR) testing. Blood was used to make buffy coat smears and frozen for future use. Nineteen of the forty-four (43%) birds were positive on at least one of the surveillance tests. Twelve positive samples were selected for PCR testing including seven fecal samples, four liver samples, and one whole blood sample. Nine of these samples were positive for a coccidian species. PCR isolated a Northern house sparrow Isospora through speciation as the most abundant amongst the submitted samples, but percent homologous varied between 72%, 94%, and 99% homologous based on GenBank AY331573. PCR also identified an isolate from a Southern Cape Sparrow with 90% homologous (GenBank AY331572) and Eimeria species with an 88% homology over a 435 base pair region to Eimeria reichenowi. A single sample had mixed species present with an Isospora species being dominant. This study showed the capability of disseminated or systemic coccidia without clinical disease in house sparrows with positive PCR samples from liver and whole blood from apparently healthy birds as well as the demonstrated possibility of multiple species of coccidia in a single species of bird. The different percentages of homology represent similarities in evolutionary or ancestral background. The differences in homology seen in this study are suggestive of new subspecies or species based on the percent homology. The isolates with lower percent homology to those that they were compared could be a new undescribed species; whereas the isolates that 99% similar are most likely representative of the species it is being compared to. Further studies are needed, not only in house sparrows, but in all birds to fully classify coccidia species and begin building databases of individual species that cause systemic diseases or can be spread between species.
The authors would like to thank the Fort Wayne Children’s Zoo for approval of the project as well as the veterinary technicians for assistance processing samples.
1. Novilla MN, Carpenter JW. Pathology and pathogenesis of disseminated visceral coccidiosis in Cranes. Avian Pathol. 2004;33(3):275–280.
2. Partington, CJ, Gardiner CH, Fritz D, Phillips LG, Montali RJ. Atoxoplasmosis in Bali mynahs (Leucopsar rothschildi). J. Zoo Wildl. Med. 1989;20:328–335.
3. Schrenzel MD, Mallouf GA, Gaffney PM, Tokarz D, Keener LL, McClure D, Griffey S, McAloose D, Rideout BA. Molecular Characterization of Isosporoid Coccidia (Isopora and Atoxoplasma Spp.) in Passerine Birds. J Parasitol. 2005;91(3):635–647.
4. U.S. Department of the Interior and U.S. Geological Survey. Field Manual of Wildlife Diseases: General Field Procedures and Diseases of Birds. Washington (DC): Biological Resources Division; 1999. p. 207–218.