Sequence heterogeneity in the 18S rRNA gene in Theileria equi from horses presented in Switzerland.

The article describes a study focusing on the detection of Theileria equi, a parasite in horses, in Switzerland. Using a particular assay method and blood samples from 100 horses, the study found evidence of the parasite’s presence. Notably, certain probes failed to identify specific genotypes, highlighting a need for better detection methods. The study also observed a significant sequence variation within the parasite gene, prompting further investigation.

Methodology and Findings

• To ascertain the occurrence of piroplasms in horses within Switzerland, researchers employed a reverse line blot (RLB) hybridization assay method. A batch of 100 equine blood samples, accumulated from the University of Zurich’s animal hospital, served as the study’s data pool.
• Through a polymerase chain reaction (PCR), the V4 hypervariable region of the 18S rRNA gene – found within the Theileria equi – was amplified for clear detection. RLB assay then allowed for detailed analysis.
• From the total number of examined samples, seven horses’ blood demonstrated hybridization to Theileria/Babesia genus-specific and Theileria genus-specific probe. A distinctive finding was that two blood samples hybridized with the Theileria equi-specific probe suggesting confirmed infection.
• The remaining five positively-tested samples didn’t blend with any species-specific probes, leading to the consideration of unidentified Theileria variants or genotypes presence.

Gene Sequencing and Analysis

• For a more comprehensive identification, researchers sequenced the 18S rRNA gene of the five samples that didn’t hybridize with species-specific probes. They found these sequences to bear close resemblance with Theileria equi isolated from horses in Spain and China, displaying an identity match of at least 98.4%.
• Considering the travel history of four out of the seven positive-tested horses – to countries like France, Italy, Spain or current residence in Hungary – the study provides an insight into the possible spread and diversity of Theileria equi.

Implications of the Study

• The undertaken study expands knowledge on the presence and sequence heterogeneity of T. equi in Switzerland. It suggests an urgent need to design species-specific probes targeting gene regions unique to T. equi.
• Interestingly, none of the seven horses that tested positive for Theileria equi showed suspected signs of Theileria infection, indicating that the parasite can be present without obvious symptoms.
• This suggests the need for clinicians to consider possible equine piroplasma infections even in areas not traditionally considered endemic or in horses devoid of piroplasmosis signs.