Phylogenetic analysis of Theileria equi and Babesia caballi sequences from thoroughbred mares and foals in Trinidad

The agents of equine piroplasmosis, Theileria equi and Babesia caballi, are endemic in Trinidad, West Indies. While transmission is mainly by ixodid ticks, transplacental transmission of T. equi has also been reported. This disease has contributed to foetal losses as well as morbidity and mortality of neonatal foals and adult horses. Previous 18S rRNA–based phylogenetic studies indicated a noticeable degree of variation within and among B. caballi and T. equi isolates from different geographical regions. The objective of this study was to evaluate the diversity of T. equi and B. caballi obtained from horses in Trinidad by amplifying a region of the 18S rRNA gene. The phylogenetic trees for T. equi sequences obtained from horses in 2006 and 2011–2013 revealed that Trinidad sequences were of genotype A. Additionally, all of the B. caballi sequences from Trinidad were grouped together with other B. caballi sequences of genotype A. However, T. equi sequences from horses in Saint Kitts and Nevis clustered with sequences of genotype C. This study also identified two genotypes of T. equi in the equine population of Brazil. All of the T. equi and B. caballi sequences obtained from horses in Trinidad belong to genotype A and were similar to T. equi and B. caballi sequences of the same genotype that were submitted to GenBank™ databases. Countries in close proximity to Trinidad have T. equi sequences belonging to genotype C; therefore, movement of horses between these countries can introduce a new genotype of T. equi into the equid population of Trinidad.