Aim: To describe the pathology of coccidiosis in hihi and to provide preliminary data on the taxonomy of the coccidia involved using molecular methods.
Methods: In an initial study from 1994 to 1997, gross and histopathological examinations were performed on 12 dead juvenile hihi from the National Wildlife Centre (NWC) at Mt. Bruce. In a second study during 2008-2010 DNA from sporulated oocysts and liver tissue was used for PCR analysis and sequencing. Faecal samples were also obtained from infected hihi from the NWC and examined for coccidial oocysts, which were then sporulated in the laboratory in 1994-1997 and 2007-2009. In addition, a post mortem was performed on a dead adult hihi from the NWC in 2008, and 18 archived hihi tissues from 11 individual birds stored at the Institute of Veterinary, Animal and Biomedical Sciences (IVABS) were used for DNA extraction.
Results: Severe gross and histopathological changes in the intestine and occasionally in the liver were found in the 12 dead birds examined. The morphological characteristics of the sporulated oocysts suggested that two types of coccidia were present. PCR analysis and sequencing of extracted DNA supported the existence of at least two different coccidia species in hihi. These were genetically more closely related to the genus Eimeria than to the morphologically similar genus Cystisospora (formerly Isospora) of mammals. In addition, one liver tissue sample that was examined post mortem was positive for at least two different coccidia species of the family Eimeriidae according to sequencing results, and the presence of extraintestinal coccidian stages was confirmed.
Conclusions: Preliminary morphological and sequencing results suggest that two types of eimeriid coccidia are present and at least one of these commonly has extraintestinal stages.
Clinical relevance: Coccidiosis in hihi is a serious disease capable of causing mortalities in juvenile and adult birds in captive situations. Treatment and control of the disease will be difficult as the extraintestinal stages of the organism are likely to be refractile to oral treatment.