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. 2021 Jun 7;10(6):714.
doi: 10.3390/pathogens10060714.

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

Reinaldo Torres  1 , Claudio Hurtado  1 , Sandra Pérez-Macchi  2 , Pedro Bittencourt  3 , Carla Freschi  4 , Victoria Valente Califre de Mello  5 , Rosangela Zacarias Machado  5 , Marcos Rogério André  5 , Ananda Müller  1   3
Affiliations

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

Reinaldo Torres et al. Pathogens. .

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.

Keywords: ELISA; babesiosis; equine piroplasmosis; nested PCR; theileriosis.

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Phylogenetic tree of Theileria equi 18S rRNA (1600 bp) sequences. The analysis was performed using the maximum likelihood method with the TPM3uf+I substitution model. Numbers in the branches correspond to bootstrap values after 1000 repetitions. 18S rRNA sequences of T. sergenti and T. bufelli were used as outgroups. Red branches identify the sequences from this study.
Figure 2
Figure 2
Phylogenetic tree of B. caballi 48 KDa rhoptry protein (430 bp) sequences. The analysis was performed using the Bayesian method with a TPM2uf substitution model. Numbers in the branches correspond to bootstrap values after 1000 repetitions. The 48 KDa rhoptry protein gene sequence of B. microti was used as an outgroup. The red branch indicates the sequence from this study.
Figure 3
Figure 3
Haplotype TCS network [39] for Theileria equi 18S rRNA sequences (1600 bp) detected in blood samples from Chilean thoroughbred horses and others in GenBank. Each small dash indicates a mutational event. Black circles represent median vectors.
Figure 4
Figure 4
Haplotype TCS network [39] for B. caballi 48 KDa rhoptry protein sequences (430 bp) detected in blood samples from Chilean thoroughbred horses and others in GenBank. Each small dash indicates a mutational event. Black circles represent median vectors.
Figure 5
Figure 5
The political division of Chile, showing administrative regions where the horses were sampled.
See this image and copyright information in PMC

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