Molecular detection of Theileria species and Babesia caballi from horses in Nigeria

Authors: PHILIP, MSHELIA - Ahmadu Bello University; Kappmeyer, Lowell; Johnson, Wendell; KUDI, CALEB - Ahmadu Bello University; OLUYINKA, OKUBANJO - Ahmadu Bello University; BALOGUN, EMMANUEL - Ahmadu Bello University; RICHARD, EDEH - University Of Jos; ONOJA, EMMANUEL - Ahmadu Bello University; SEARS, KELLY - Washington State University; Ueti, Massaro

Submitted to: Parasitology Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/2/2020
Publication Date: 7/10/2020
Citation: Philip, M.W., Kappmeyer, L.S., Johnson, W.C., Kudi, C.A., Oluyinka, O.O., Balogun, E.O., Richard, E.E., Onoja, E., Sears, K.P., Ueti, M.W. 2020. Molecular detection of Theileria species and Babesia caballi from horses in Nigeria. Parasitology Research. 119:2955-2963. https://doi.org/10.1007/s00436-020-06797-y.
DOI: https://doi.org/10.1007/s00436-020-06797-y

Interpretive Summary: The single-celled parasites Theileria equi, Theileria haneyi and Babesia caballi infect the red blood cells of horses following the bite of ticks carrying the parasites. Infection of the red blood cells results in loss of performance, illness and even death in horses, causing economic losses for the horse industry. Nigeria has a large horse population, however, a survey for these parasites using sensitive molecular-based tools has not been conducted. Two kinds of polymerase chain reaction (PCR) amplification of parasite DNA were used in this study. The first PCR kind targeted the specific parasite species to reveal the percentages of horses infected by each type of parasite. The second PCR kind targeted any parasite in the broader group of parasites to uncover infections from undiscovered parasites or infections by parasites previously undescribed in horses. The results show that out of 300 Nigerian horses tested, 13% have Theileria equi DNA, 3.3% have Babesia caballi DNA, and 2.7% have Theileria haneyi DNA. No novel infections of undiscovered parasites were found. While percentages of infections may seem relatively low, these may still play a significant role in the dissemination of the disease within Nigeria and to other countries. Countries such as the United States restrict importation of horses pending testing for these parasites to protect its horse population.

Technical Abstract: Equine piroplasmosis (EP) is an infectious, tick-borne disease caused by the hemoprotozoan parasites, Theileria equi, Babesia caballi, and a recently reported new species, T. haneyi. Infections by these apicomplexan parasites limit performance and cause economic losses for the horse industry. Equine piroplasmosis is widespread in northern regions of Nigeria, where an increasing portion of the animal population is composed of horses. Equine piroplasmosis has remained an epidemiologically challenging disease, especially as the movement of horse’s increases within and across Nigeria. In this study, 300 horse blood samples were collected in three states from northwestern Nigeria. The presence of piroplasms was analyzed with a nested PCR targeting species-specific genes including ema1 (T.equi), rap1 (B. caballi) and a novel gene (T. haneyi). Nested PCR results demonstrated that the prevalence of T. equi was 13.0% (39/300), B. caballi was 3.3% (10/300) and T. haneyi was 2.7% (8/300). Mixed infection with T. equi and B. caballi was 2.7% (8/300) while T. equi, B. caballi and T. haneyi multiple infection prevalence was 0.6% (2/300). This study revealed that horses in Nigeria are infected predominantly with T. equi. We demonstrated parasite genetic diversity by sequencing the 18S rRNA gene. The phylogenetic analysis showed that among T. equi-like parasites, 28 samples were clade A, 13 samples were found to be clade C and 16 were clade D. Infections of imported and resident horses play a significant role in the epidemiology of EP in Nigeria which highlights the importance of restricting the movement of infected horses to prevent the spread of these tick-borne protozoan pathogens.