Molecular identification of Trypanosomae evansi, species diversity and phenology of biting insects as potential vectors of surra in camels, Cholistan desert, Punjab, Pakistan

Surra is a vector borne disease of animals with a worldwide distribution. Trypanosoma evansi, the causative agent, is principally transmitted by hematophagous flies. It is associated with great economic losses, in link with working capacity and productivity of livestock. Cases of surra in camels of Cholistan deserts, recently reported by our laboratory, suggested the need to investigate on vectors in selected areas. In the current study, field collection of vectors was done jointly with camel herds investigated for surra. The collection was done twice a month from January 2012 to December 2013. Flies were identified morphologically by using taxonomic keys for Tabanidae and Stomoxyine flies. Random samples (n=100) of flies per species, collected from the field, where camels were diagnosed for surra, were examined and selected for the signs of blood engorgements. Molecular identification of T. evansi was carried out on whole flies and fly body parts (mid-guts and mouthparts) using TBR1/2 PCR and RoTat 1.2 PCR. A total of 4517 flies (tabanids and Stomoxys) were collected during the study period comprising Tabanus rubidus (18.6%), Tabanus striatus (37.8%) and Stomoxys calcitrans (43.6%). The total fly catch of each species was non- significantly different from each other (p 0.05) while 100% collected population of T. rubidus and T. striatus comprised of females only. Seasonal variations in the abundance was variable from a species to another. The apparent and relative abundance of T. rubidus, T. striatus and S. calcitrans on camels is suggestive of their role as mechanical vectors of surra in Punjab, Pakistan. The current study is a first and novel work related with recently reported study in our laboratory on the prevalence of Surra in camels of Cholistan desert, Pakistan