Host landing and diel activity of potent vectors of bluetongue disease, Culicoides oxystoma and Culicoides peregrinus

Abstract

Background The spread of bluetongue virus (BTV) depends on the vectorial ability of Culicoides affecting the susceptible host. Animal farms in West Bengal have reported prevalence of potent vectors of BTV (C. oxystoma, C. peregrinus and C. fulvus). Additionally, high seroprevalence of BTV was also reported from this cattle dense region. To minimize the risk of disease outbreak a strategy to reduce the exposure of cattle to midges bite is necessary. Therefore host-seeking activity of two important potent vectors, C. oxystoma and C. peregrinus on cattle were studied in two farm sites of West Bengal, India. Methods The study was done in 2018-19 comprising 297 hours of collection over 27 nights. A comparison was made between the catches obtained by mouth aspirator and light trap. Hourly collections of Culicoides were taken directly from cattle (oral aspirator) as well as light trap was operated in close vicinity of cattle at a different shed. Results A total of 15,456 Culicoides belonging to C. oxystoma, C. peregrinus and C. fulvus were collected in light trap and aspirator during the study. 8,758 midges were collected by aspirator, whereas 6,698 individuals were collected in light trap. The following species were aspirated: C. peregrinus and C. oxystoma; while the light trap catches consisted of C. fulvus, C. oxystoma and C. peregrinus. Light trap collection exhibited crepuscular activity whereas aspirator collection was maximum between 4:00 hr and 5:00 hr. Maximum landing of midges was observed in the neck and hump region of the cattle. Conclusion It was observed that the preferred time of feeding of C. peregrinus and C. oxystoma on cattle were early morning hours though midges were ubiquitous from dusk to dawn. Surprisingly the preferential landing of the two vectors were mostly restricted to the neck and hump region of the cattle. The results obtained during the study warrants further insight into the factors influencing the landing site by the vectors which may be useful biological data in disease management and draw effective deterrent strategies.