Studies on biting density and biting cycle of Culex quinquefasciatus, say in Khon Kaen City, Thailand.

ABSTRACT

Biting density and biting cycle of Culex quinquefasciatus in Khon Kaen City were examined during November 1994 to October 1995. Biting activity of the mosquito was assessed by using the indoor human bait method. Trapped mosquitos were identified and carefully dissected to determine their parities. Climatory data ie temperature, relative humidity and rainfall were also recorded during the study. The densities of mosquito ranged from 1.6/man/hour in December to 9.2/man/hours in March with the average of 5.0/man/hours. The lowest biting density was observed in winter and higher densities were in summer and rainy seasons. The temperature was the most important variable that influenced the biting density in each month of the year (p<0.05). The biting cycle showed that the mosquito active throughout the night, with peak activity at 22.00-23.00 hours. Parous rate of the mosquito ranged from 33.3% in February to 71.9% in November with the average of 47.3%. The biting proportion of parous mosquitos was high during the early hours of the night and gradually decreased until 06.00 hours, whereas that of the nulliparous mosquitos showed an increasing trend from 18.00 to 06.00 hours. The biting cycle of the parous mosquito reached the peak activity at 21.00-22.00 hours, 1 hour ahead of the peak for nulliparous mosquito. These findings suggested that Cx. quinquefasciatus in Khon Kaen City may be able to transmit bancroftian filariasis if they were exposed to microfilaria carrier individuals.