First Report of Trypanosoma theileri in Equine Host and Tabanus sp. in Malaysia.
Authors: Tan Li Peng, Mohd Rajdi Nur Zul Izzati, Mohamad Mimi Armiladiana, Mohamed Maizan, Hamdan Ruhil Hayati, Goriman Khan Mohd Azam Khan, Ahmad Syazwan Samsuddin, Seng Hua Lee
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: *Trypanosoma theileri* Infection in Malaysian Equines *Trypanosoma theileri*, a protozoan parasite traditionally considered cattle-specific and transmitted by tabanid flies, has been documented across Southeast Asia and beyond, yet remained unreported in Malaysia until now. During investigation of a *T. evansi* outbreak in Kelantan state, researchers identified *T. theileri* in blood samples from an infected horse and in *Tabanus* sp. flies through PCR and DNA sequencing analysis, marking both the first detection of the parasite in Malaysia and its first documented infection in an equid host. Phylogenetic clustering revealed the Malaysian isolates grouped with previously described lineages from Japan, Chad and Brazil, though clinical signs attributable specifically to *T. theileri* infection remained uncertain in the affected horse. The discovery challenges the accepted host-specificity of this species—whilst other regional isolates appear restricted to ruminants, this equine case suggests broader susceptibility, with molecular evidence indicating at least two distinct *T. theileri* genotypes circulating across Kelantan districts. Given the expanding ruminant and equine industries in Malaysia and the potential for *Tabanus* populations to maintain transmission cycles, practitioners should consider *T. theileri* in the differential diagnosis for affected horses in affected regions, particularly those showing clinical signs consistent with haemoprotozoal infection, whilst further multi-region genetic characterisation and epidemiological surveillance will clarify the strains' pathogenic significance and industry implications.
Read the full abstract on PubMed
Practical Takeaways
- •Equine practitioners in Malaysia should be aware that T. theileri can infect horses and should consider this parasite in differential diagnoses for blood protozoal infections, despite previous assumptions of ruminant-only host specificity
- •Tabanid fly control measures may help reduce transmission risk, as Tabanus sp. has been confirmed as a vector for T. theileri in equine populations
- •Further molecular characterization of T. theileri strains in Malaysia is needed to understand prevalence and potential impact on equine and cattle industries
Key Findings
- •First report of Trypanosoma theileri in an equine host in Malaysia, previously considered host-specific to ruminants
- •T. theileri detected in both horse blood and Tabanus sp. fly vector via PCR and DNA sequencing
- •T. theileri isolates clustered with phylogenetic lineages from Japan, Chad, and Brazil cattle
- •Evidence suggests at least two genotypes of T. theileri circulating in two districts of Kelantan, Malaysia