Prevalence and genetic diversity of equine piroplasms in Tov province, Mongolia

Abstract

Equine piroplasmosis represents a serious problem in horse industry. Although, researchers suggested the possible use of sub-unit vaccines to control equine piroplasmosis, the genetic diversity of vaccine candidate antigens was not properly investigated. In the present study, we screened 250 horses reared in three different districts of Tov province, Mongolia, for Babesia caballi and Theileria equi using ELISA and nested PCR (nPCR) assays. Among these animals, piroplasms were detected in 128 (51.2%) horses by nPCR assays (B. caballi, 42.4%; T. equi, 6.4%; and mixed infections, 2.4%), while 204 (81.6%) were positive by ELISA (B. caballi, 51.6%; T. equi, 19.6%; and mixed infections, 10.4%). Male and middle-aged horses showed higher positive rates than female and younger or older horses. The findings also suggested that a combination of nPCR and ELISA techniques might be useful to detect horses that were chronically or subclinically infected with piroplasms. B. caballi-BC48 and T. equi-EMA-1 gene sequences, in addition to 18S rRNA, were subjected to phylogenetic analyses, and the findings suggested the presence of genetically diverse populations of equine piroplasms in Mongolia. BC48 sequences were separated into four clades in phylogram, and all the Mongolian sequences determined in the present study were found in a single clade. However, a single BC48 sequence previously isolated from a tick in Mongolia formed a separate branch. Similarly, EMA-1 sequences formed four clades, and Mongolian sequences were observed in two different clades, one of which was formed only of Mongolian sequences and is suggested as a new clade. This is the first report that describes the genotypes of equine piroplasms in Mongolia. The findings also emphasized the need for further investigations to study the effect of genetic diversity observed among BC48 as well as EMA-1 sequences on host's immune responses.