Search

Babesia caballi is an intra-erythrocytic parasite causing equine piroplasmosis. Three B. caballi genotypes (A, B, and C) have been identified based on the 18 S rRNA and rhoptry-associated protein (rap-1) gene sequences. These variant parasite genotypes compromise the diagnostic utility of the WOAH-recommended serological assays in declaring horses free of equine piroplasmosis. Although a gene encoding a spherical body protein 4 (sbp4) has recently been identified as a potential antigen for the serological detection of B. caballi, the ability of this antigen to detect the different geographical strains has not been determined. The molecular distinction between variant B. caballi genotypes is limited and therefore we developed molecular typing assays for the rapid detection and quantification of distinct parasite genotypes. Field samples were screened for the presence of B. caballi using an established multiplex equine piroplasmosis qPCR assay. In this study, B. caballi genotype A was not detected in any field samples screened. However, phylogenetic analysis of the amplified sbp4 and 18 S rRNA genes confirmed the phylogenetic groupings of the South African isolates into either B. caballi genotypes B or C. A multiple sequence alignment of the sbp4 gene sequences obtained in this study together with the published sbp4 sequences representing B. caballi genotype A, were used to identify conserved regions within the gene to design three primer pairs and three genotype-specific TaqMan minor-groove binder (MGB™) probes. The qPCR assays were shown to be specific and efficient in the detection and differentiation between B. caballi genotypes A, B, and C and could be used as a diagnostic assay to prevent the unintentional spread of variant B. caballi genotypes globally., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Raksha Vasantrai Bhoora reports financial support was provided by National Research Foundation. Alicia Venter reports financial support was provided by AgriSETA. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Ehrlichiosis is a potentially fatal zoonotic tick-borne disease, caused by a pleomorphic Gram-negative bacterium. It occurs worldwide and affects humans, domestic and wild animals. Dogs infected with Ehrlichia canis develop canine monocytic ehrlichiosis (CME), a significant infectious disease of canines. TaqMan® based real-time PCR assays to detect Ehrlichia spp. affecting dogs were developed and a real-time PCR assay specific for E. canis validated. The efficiency of the assay was 93% and the 95% limit of detection was 33 E. canis plasmid copies/µl of blood (95% confidence interval: 23 - 58). The assay was specific for E. canis when tested against other haemoparasites. Consistent repeatability was observed, with an inter-run standard deviation (SD) range between 0.33 and 1.29 and an intra-run SD range between 0.04 and 1.14. Field samples were tested in parallel by both the E. canis real-time PCR assay and a reverse line blot hybridization assay. The results were in agreement for the two assays, with an exception of two out of 121 samples. Bayesian latent class analysis was used to calculate a diagnostic sensitivity of the E. canis real-time PCR assay of 90% and a specificity of 92%. This assay is a sensitive and reliable molecular detection method for E. canis and will be a useful tool for early diagnosis and timely treatment for this haemoparasite., Competing Interests: Declaration of Competing Interest No potential conflict of interest was reported by the authors., (Copyright © 2022. Published by Elsevier GmbH.)