Twenty years of equine piroplasmosis research: global distribution, molecular diagnosis, and phylogeny

Authors: TIROSH-LEVY, SHARON - Hebrew University Of Jerusalem; GOTTLIEB, YUVAL - Hebrew University Of Jerusalem; Fry, Lindsay; KNOWLES, DONALD - Washington State University; STEINMAN, AMIR - Hebrew University Of Jerusalem

Submitted to: Pathogens
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/4/2020
Publication Date: 11/8/2020
Publication URL: https://handle.nal.usda.gov/10113/7190165
Citation: Tirosh-Levy, S., Gottlieb, Y., Fry, L.M., Knowles, D.P., Steinman, A. 2020. Twenty years of equine piroplasmosis research: global distribution, molecular diagnosis, and phylogeny. Pathogens. 9(11). Article 926. https://doi.org/10.3390/pathogens9110926.
DOI: https://doi.org/10.3390/pathogens9110926

Interpretive Summary: Equine piroplasmosis is caused by a group of protozoan parasites in the Theileria and Babesia genera. Globally, these tick-transmitted parasites are endemic in tropical and sub-tropical regions, and sporadic, isolated outbreaks have occurred in multiple locations in the southern United States. Equine piroplasmosis causes significant economic losses due to: 1. Restrictions placed on international movement of infected horses; and 2. Morbidity and mortality of infected animals and resultant reduced ability of horses to work (e.g. traction, riding, sporting, etc.), medical costs, and loss of valuable animals. Currently, non-endemic countries, including the United States, screen horses for equine piroplasmosis prior to entry. Apart from stringent testing efforts, prevention of equine piroplasmosis is largely based on tick control measures and anti-protozoal drug treatment, as there are not yet vaccines available to prevent infection or clinical disease. This article reviews recent literature on equine piroplasmosis, and summarizes a meta-analysis of serological and molecular epidemiologic reports on equine theileriosis and equine babesiosis. The results of the meta-analysis provide further evidence that equine piroplasmosis is spreading into more temperate regions of the world, and emphasizes the importance of continued sequencing and genotyping of these parasites to better monitor spread and predict virulence in horses.

Technical Abstract: Equine piroplasmosis (EP), caused by the hemoparasites Theileria equi, Theileria haneyi, and Babesia caballi, is an important tick-borne disease of equines, which is prevalent in most parts of the world. Infection may affect animal welfare and has economic impact related to limitations on horse transport between endemic and non-endemic regions, reduced performance of sport horses and treatment costs. This manuscript provides a brief literature review of EP and a meta-analysis of its molecular epidemiology. The global seroprevalence and molecular prevalence of these parasites were evaluated by analyzing the epidemiological data published in the last 20 years. Genotyping of T. equi based on its 18S rRNA, ema-1 and ema-2 genes and of B. caballi based on its 18S rRNA and rap-1 genes was preformed using all sequences submitted to the GenBank database. The results of this analysis revealed that EP is endemic in most parts of the world, and that it is spreading into more temperate climates. The use of DNA sequencing and genotyping is important to monitor the spread of parasites, and future research is warranted to provide improved genotypic characterization of newly recognized parasite species and strains, and to extract potential links to virulence.