Clinical and molecular study of Babesia caballi in racing horses in Baghdad

Abstract

The objective of this study was to investigate Babesia caballi in horses at three main gatherings of racehorses located in the Baghdad Governorate through clinical examinations, microscopy, and conventional polymerase chain reaction (PCR) assays. The 18S rRNA gene of B. caballi was PCR amplified, sequenced, and phylogenetically examined between January and December of 2021. One hundred sixty blood samples were taken from horses of different ages, breeds, and sexes. Prevalence and risk variables for babesiosis were analyzed using chi-square tests and odds ratios. 3 ml of blood was taken from the jugular vein in test tubes containing anticoagulant to detect Babesia caballi in blood smears and molecular technology. The outcomes showed that the clinical manifestations of babesiosis comprised pale to icterus, mucus membranes, emaciation, anorexia, and leg swelling—a slight increase in body temperature, heart rate, and respiratory rate. Microscopic observation revealed the presence of Babesia caballi in 49 out of 160 (30.625%) horse blood smears. These smears exhibited various morphological stages of B. caballi within the red blood cells. The confirmation process of 160 blood samples by PCR to detect 18Sr RNA demonstrated that 91 samples (56.87%) yielded positive findings for the desired product size of 540 base pairs (bp). There was no significant variation in the percentage of infection with B. caballi between stallions and mares. Additionally, it is worth noting that no age group exhibited a significant prevalence of infection. However, it is essential to highlight that Arabian horse breeds showed a greater susceptibility to infection at a rate of 63.34%; however, this difference was not statistically significant when compared to Thoroughbred and crossbred horses. This study identified a new genotype of Babesia caballi based on phylogenetic analysis of our samples and comparison with data from the International Gene Bank. This genotype, called Clade C, is characterized by a high infection rate and low illness severity.

Keywords

• clinical
• molecular
• babesiosis
• horses
• baghdad