Phylogenetic analysis and geographical distribution of Theileria equi and Babesia caballi sequences from horses residing in Spain.

The study investigates the type and distribution of two parasites, namely Theileria equi and Babesia caballi, which cause equine piroplasmosis, a significant equine tick-borne disease in Spain. The research reveals a variation in these parasites across Spain that have implications for monitoring and control of the disease.

Objective of the Study

• The research intends to determine the genetic diversity and the distribution of Theileria equi and Babesia caballi, parasites responsible for equine piroplasmosis, across Spain. Since previous studies were limited in geographical scope, this study aims to present a nationwide assessment.

Methods Used

• Researchers collected 100 blood samples from horses confirmed with equine piroplasmosis.
• They carried out a PCR protocol to amplify a certain gene named 18S small subunit rRNA from the parasites in the blood samples.
• They then sequenced these amplified genes for further analysis.

Results and Findings

• Out of the 100 samples, they were successfully able to sequence 77 samples from Theileria equi and 6 from Babesia caballi.
• Phylogenetic analysis of the sequences revealed that the Theileria equi parasites fall into three main groups or clades – A, D, and E while Babesia caballi parasites fall into clades A and B.
• The distribution of these clades was previously unknown in Spain. Particularly, parasites from Theileria equi clade D and Babesia caballi clade B were never reported before.
• The researchers detected more diversity (97.3-98.3% variation) within Theileria equi clade E samples compared to those in clade A (99.7-100% similarity).
• Using a multivariable logistic regression model, the study found that horses in the northern regions of Spain were more likely to be infected with Theileria equi clade E type.

Conclusion and Considerations

• The study concludes that there is a significant genetic variation in the Theileria equi and Babesia caballi parasites across Spain. This has implications for monitoring and controlling equine piroplasmosis.
• Because of the diverse parasite strains identified, the study suggests that increased controls on horse movements between Spain and other countries with equine piroplasmosis might help prevent disease spread.