Epidemiological and molecular study of Theileria spp. in sheep and goats in Erbil, Iraq.

Abstract

Theileria spp. are a group of hemoprotozoal parasites pose a significant threat to small ruminants in tropical and subtropical regions of the world. Because of that and due to the limited data on the genetic diversity of Theileria species in Erbil Governorate, northern Iraq, this study was conducted to assess the prevalence of Theileria spp. in sheep and goats using both Giemsa-stained blood smears and PCR methods as a diagnostic criterion. The overall infection rate detected by blood smears was 26.2% in sheep and 18.3% in goats, while PCR showed higher infection rates, 47.7% in sheep and 38.3% in goats. PCR analysis identified various Theileria species, including T. ovis, T. lestoquardi, T. uilenbergi, and T. annulata, each displaying different prevalence rates. Significantly, T. lestoquardi had the highest rate of single infections, especially in goats, with an infection rate of 34.8%. Mixed infections were prevalent, occurring in 22.6% of sheep and 26.1% of goats, primarily involving T. ovis and T. lestoquardi. An assessment of factors influencing infection rates revealed that tick infestation and irregular use of acaricides were significant risk factors. Sheep with tick infestations exhibited a 59% infection rate, while goats had an infection rate of 44.25%. Regular use of acaricides was associated with a reduction in prevalence in both species. Additionally, animals with a history of tick infestations and those in communal grazing systems demonstrated higher infection rates. The sequence analysis of isolates from sheep and goats, based on the 18S rRNA gene, identified several species. The identified species have been deposited in the NCBI with the following accession numbers: T. ovis (PQ325696, PQ325698), T. lestoquardi (PQ325701, PQ325702), T. uilenbergi (PQ325706, PQ325707), and T. annulata (PQ325699, PQ325700). The findings from this investigation offer valuable insights into the genetic diversity and epidemiology of Theileria species in sheep and goats. It can be concluded that periodically controlling vector ticks and arthropods is an important factor in controlling and reducing the spread of theileriosis in targeted domestic animals.