Occurrence and Genetic Diversity of Babesia caballi and Theileria equi in Chilean Thoroughbred Racing Horses

Abstract

This study aimed to serologically and molecularly survey Babesia caballi and Theileria equi in thoroughbred horses from racecourses in Chile. Additionally, the genetic diversity of the positive samples was assessed. A total of 286 thoroughbred horses from the Santiago and Valparaíso racecourses had their serum samples submitted to an ELISA for B. caballi and T. equi, and 457 samples (from the Santiago, Valparaíso, and Concepción racecourses) were tested with nested PCRs for the B. caballi 48 KDa rhoptry protein (RAP-1) and T. equi 18S rRNA genes. Selected RAP-1 and 18S positive products were sequenced to perform phylogenetic and haplotype analyses. An overall seroprevalence of 35.6% was observed for these Chilean racecourses: 23.7% for T. equi, 8.4% for B. caballi, and 3.5% for both agents. Overall, a 53.6% occurrence by nPCR was detected for the three Chilean racecourses: 44.2% for T. equi, 5.4% for B. caballi, and 3.9% for both agents. Phylogenetic analysis of T. equi and B. caballi showed genetic proximity with sequences previously detected in other countries. Haplotype analysis revealed a low diversity among the Chilean sequences, which may have originated from those reported in Brazil, Israel, or Cuba. Babesia caballi and T. equi were detected for the first time in Chilean thoroughbred horses.

Diagnostic Performance of Competitive ELISA and Western Blot Methods for the Detection of Antibodies against Theileria equi and Babesia caballi

“…A successful vaccine against EP has yet to be developed, and the significant genetic diversity within T. equi and B. caballi clades complicates vaccine development efforts. The economic impact of this disease and the restrictions on the trade of infected animals have led the WOAH Animal Health Code to categorize EP as a notifiable disease [ 26 ]. This highlights the need for robust and effective measures of control against the disease in countries where it is endemic, and for combined high-sensitivity serological techniques to enhance the detection of the disease in animals exposed to the parasites that cause EP.…”

Seroprevalence of Anti-Theileria equi Antibodies in Horses from Three Geographically Distinct Areas of Romania

“…A number of studies concerning the seroprevalence of T. equi and B. caballi have been conducted in different countries outside Europe [15,30,[39][40][41][42][43][44][45][46][47][48]]. The highest rates of infection were predominantly reported in subtropical and tropical areas (in Brazil, between 80% and 90% for both parasite species) [39,40].…”

“…The highest rates of infection were predominantly reported in subtropical and tropical areas (in Brazil, between 80% and 90% for both parasite species) [39,40]. Mongolia, northern China, the United States [41,42], Mexico [43], Egypt [30,44,47], Chile [15] and Nigeria [45,46] have all reported cases of T. equi infection.…”

“…Due to the non-specific clinical manifestation, unnoticeable symptoms, as well as the frequent asymptomatic evolution, the disease can pass unnoticed in most animals. From a clinical point of view, the disease may range from an asymptomatic form to a super-acute form, with clinical signs associated with severe intravascular haemolysis [9,10,15]. The obvious clinical form might be a combination of factors that can be influenced by the pathogenicity of the parasite, the animal's nutritional and immune status, the density of the infected ticks, and the infectious dose [10].…”

“…Serological techniques are used to identify the chronic carriers by testing their serum for the presence of specific antibodies. Molecular techniques for the detection of T. equi and B. caballi based on species-specific polymerase chain reaction (PCR) assays, targeting the specific genes, have been developed and continue to expand [15].…”