Genetic diversity of Theileria equi and Babesia caballi infecting horses of Central-Southern Italy and preliminary results of its correlation with clinical and serological status.

The research article centres on the genetic diversity of Theileria equi and Babesia caballi in horses from Central-Southern Italy. It links this diversity to the clinical and serological status of the horses and explores possible methods of disease detection.

Research Context

• Babesia caballi and Theileria equi are pathogens transmitted by ticks that cause equine piroplasmosis, an infection that affects the Equidae family, including horses. This disease invokes substantial health issues and economic losses.
• Equine piroplasmosis is considered a notifiable disease by the World Animal Health Organization due to possible movement restrictions for positive horses. Consequently, it is crucial to develop reliable detection methods.

Methodology and Sample

• The study utilized 39 EDTA and whole-blood samples from both symptomatic and asymptomatic horses in Central-Southern Italy, collected between 2013 and 2014.
• These samples were chosen due to their high positive results in Real-Time PCRs that target the 18S rRNA gene specific for each piroplasm or due to discordant results in their serological ELISA/18S rRNA RT-PCR analysis.
• A nested PCR scoured the hypervariable V4 region of the 18S rRNA gene of both piroplasms present in all samples. Further, a PCR also targeted the equi merozoite antigen 1-gene (EMA-1) in T. equi positive samples.

Results and Genetic Analysis

• Thirty-sequences were obtained for T. equi, comprised of twenty-five for the V4 region of the 18S rRNA gene and thirteen for the EMA-1 gene. Furthermore, eight samples tested positive for both targets.
• For B. caballi, only six 18S rRNA gene sequences were extracted.
• The phylogenetic analysis grouped T. equi sequences of the 18S rRNA gene into three categories – A (15), B (9), and C (1), and those of B. caballi into A (1), B1 (3), and B2 (2) groups.
• This analysis implies a genetic heterogeneity in both T. equi and B. caballi sequences independent of their geographical location, consistent with findings from other studies.

Statistical Associations

• A statistical association was evaluated between the phylogenetic groups of the T. equi 18S rRNA gene and clinical signs, serological discordant results, and T. equi EMA-1 negativity. The results indicated these groups to be statistically related to the presence of clinical signs and ELISA negativity/18S rRNA RT-PCR positivity.
• Babesia caballi sequences were not statistically analysed due to the insufficient number of samples.
• The EMA -1 sequences, which mostly grouped in the same cluster, were also not statistically analysed.
• The results provide critical information which can help in refining serological and molecular diagnostic methods.