Theileria equi in the horses of Iran: Molecular detection, genetic diversity, and hematological findings.

This research aimed to analyze and identify the prevalence and genetic diversity of parasites causing the disease, equine piroplasmosis, in horses from the Fars province of Iran. The study found that the infection rate in the region is higher than the national average. All detected strain sequences demonstrated a common ancestry. Differences in gene sequences suggest that vaccine efficacy may be a concern.

Objective of the Study

• The main objective of this research was to understand the prevalence and genetic diversity of piroplasma parasites – specifically, Theileria equi and Babesia caballi – within the horse population in the Fars province of Iran. These parasites cause equine piroplasmosis, a disease that significantly impacts the equine industry worldwide.

Methods and Findings

• The researchers analyzed the blood samples of 133 horses and found that 40 of those samples were infected, resulting in a positive prevalence rate of 30.07% for Theileria equi in the province. This is higher than the national average prevalence rate of 24.11%.
• The prevalence of the other parasite, Babesia caballi, was found to be zero in the study area, which is less than the average prevalence detected in previous studies across Iran (5.47%).
• Horses which tested positive for the parasites exhibited certain hematological alterations such as anemia, thrombocytopenia, leukocytosis with a left shift of neutrophilia, and monocytosis commonly associated with equine piroplasmosis.

Genetic Diversity

• Further, PCR products of 18S rDNA and EMA-1 genes of Theileria equi were sequenced, all resulting 18S rDNA sequences displayed 100% similarity, indicating a common ancestry.
• The phylogenetic tree analysis using the 18S rDNA gene showed that the Iranian T. equi is closely related to strains from Cuba and the USA.
• However, a phylogenetic tree based on the EMA-1 gene demonstrated significant genetic diversity among these parasites and identified 10 different genotypes in the Fars province. EMA-1 is an important immunogenic antigen in these parasites, thus, the observed genetic variability could potentially impact the effectiveness of vaccines currently in use.

Conclusions and Recommendations

• The study recommends further research in the southern region of Iran to provide a clearer picture of the prevalence and diversity of equine piroplasmosis agents and to contribute to the development of more effective solutions and preventative measures.