Seasonal population dynamics and a role as natural vector of Leucocytozoon of black fly, Simulium chumpornense Takaoka & Kuvangkadilok

The black fly, Simulium chumpornense Takaoka & Kuvangkadilok, is suspected to be a natural vector of Leucocytozoon. In this study, seasonal variation in abundance of the adult fly and molecular detection of Leucocytozoon in S. chumpornense and in domestic chicken was investigated in northeastern Thailand. A total of 10,416 female adults were obtained by monthly collection for one year at six sampling sites. There was a peak of abundance in the dry season (March - May) when more than 74% of the specimens were collected. An increased number of suitable habitats for immature stages during the dry season is potentially a factor driving dry season abundance. Molecular genetic investigations revealed that S. chumpornense harbored the infectious stage of Leucocytozoon sp. indicating that it is a natural vector of this parasite. Blood smear screening for the parasite in domestic chickens found a considerable prevalence (52%) of Leucocytozoon spp. infections. The cytochrome b sequences of this parasite in domestic chickens comprised two lineages. One lineage was closely related to Leucocytozoon sp. found in S. chumpornense and another matched with L. schoutedeni. Therefore, S. chumpornense is a vector of Leucocytozoon sp. while L. schoutedeni is possibly transmitted by other ornithophilic black fly species.