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

Reinaldo Torres,Carla Freschi,Victoria Valente Califre De Mello,Ananda Müller,Claudio Hurtado,Sandra Pérez-Macchi,Rosangela Zacarias Machado,Marcos Rogério André,Pedro Bittencourt

doi:10.3390/pathogens10060714

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.

Highlights

Together known as equine piroplasmosis (EP), are two tick-borne diseases caused by the protozoans Babesia caballi and Theileria equi (Apicomplexa: Piroplasmida) [1], which belong to the Babesiidae and Theileriidae families, respectively [2]
According to the enzyme linked immunosorbent assays (ELISA) results, 102 out of 286 (35.6% [95% CI: 30.6–40.6%]) horses from Chilean racecourses were seropositive
In Santiago and Valparaíso, 19 out of 150 (12.6% [95% CI: 7.8–19%]) and 5 out of 136 (3.6%, 95% [CI: 1.2–8.3%]) of the horses were seropositive for B. caballi, and 63 out of 150 (42%, 95% [CI: 34–50%]) and 5 out of 136 (3.6%, 95% [CI: 1.2–8.3%]) for T. equi, respectively (Table 1)

Summary

Introduction

Together known as equine piroplasmosis (EP), are two tick-borne diseases caused by the protozoans Babesia caballi and Theileria equi (Apicomplexa: Piroplasmida) [1], which belong to the Babesiidae and Theileriidae families, respectively [2]. Babesia caballi and T. equi are transmitted by ticks (biological vectors), and frequently co-infect horses [4,5,6,7]. B. caballi and T. equi can be transmitted mechanically or iatrogenically via contaminated needles and syringes, blood transfusions, and surgical instruments [9]. Both B. caballi and T. equi infections can be subclinical to severe acute diseases, and symptoms are often variable and non-specific in horses [5,12]. Infection with T. equi causes a more severe clinical disease than infection with B. caballi [13]. With a lower packed cell volume (PCV), hemoglobin and erythrocytes counts [5,6,7,12,17]

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Conclusion