Survey of infection and determination of the transmission vector of Onchocerca fasciata in camels ( Camelus bactrianus ) in Inner Mongolia, China

Onchocerciasis in camels is caused by adult Onchocerca spp. and results in great economic losses to the camel industry. However, only a few studies on Onchocerca have been conducted, especially regarding the intermediate host and vector(s). In the present study, 192 camels were examined from December and January during 2013 and 2016, and the filarial larvae suspected to be Onchocerca spp. were further identified. Furthermore, aquatic dipteran insects in the living environment of camels were collected from May to September between 2013 and 2017 and dissected. Eventually, onchocercal lesions were observed in 95 of 192 (49%) camels and the captured insects were classified into 49 species from 42 genera in 21 families, among which 18 species were newly recorded in Inner Mongolia and 14 were haematophagous species. The filarial larvae were found in Culicoides puncticollis and identified as Onchocerca fasciata, indicating that C. puncticollis is the vector of O. fasciata in Inner Mongolia. These findings provide an estimate of onchocerciasis infection in camels and an alternative method of identifying insects and screening vectors using molecular methods. Important data are also provided for the diagnosis and control of onchocerciasis, thereby further filling the gap in knowledge regarding transmission vectors in China.