Molecular detection of Trypanosoma evansi and Theileria/Babesia sp. in Tabanus spp. populations (Diptera: Tabanidae) from Nueva Ecija, Philippines

Abstract

Hematophagous flies of the family Tabanidae (Order Diptera) are important nuisance pests and vectors of several diseases in both animals and humans. In this study, the potential role of tabanids in the transmission of protozoans such as Babesia sp., Theileria sp. and Trypanosoma evansi was determined. Nzi traps were installed near backyard farms in Brgy. Catalanacan, Science City of Muñoz, Nueva Ecija, Philippines from May to June 2023 for the collection of tabanids. The species, relative abundance, and density of the collected tabanids were recorded. While the occurrence of Tr. evansi (n = 383) and Theileria/Babesia sp. (n = 382) in the dissected proboscis of tabanids were determined using polymerase chain reaction (PCR). The presence of human blood among the samples that were positive for Tr. evansi and Theileria/Babesia sp. was also determined as an indicator of potential human exposure to the protozoans. A total of 4,317 tabanids were collected belonging to Tabanus partitus (99.95 %, 4,315/4,317) and Ta. reducens (0.05 %, 2/4,317). Using conventional PCR, the occurrences for Tr. evansi and Theileria/Babesia sp. were 47.26 % (181/383) and 31.15 % (119/382) in Ta. partitus, respectively, while both were detected in 6.01 % (23/383) of the proboscis. Twelve samples that were positive for Theileria/Babesia sp. were subjected to sequencing and were found to belong to the genus Theileria. About 18.41 % (51/277) of the samples positive for either or both protozoans have detectable human blood, indicating that humans have been bitten by tabanids in the study area, thus demonstrating the risk of exposure to hemoprotozoan-carrying tabanids.