Estimation of gonotrophic cycle lengths and survival rates for vector mosquitoes of Japanese encephalitis in the suburbs of Bangkok, Thailand

Frequencies of blood meals and survival rates of vector mosquitoes are important parameters influencing transmission efficiency of pathogens. We applied the time series analysis proposed by Holmes and Birley (1987) for estimation of gonotrophic cycle lengths and survival rates of Culex tritaeniorhynchus and Cx. gelidus, Japanese encephalitis (JE) vectors in Thailand. Females of these species were collected at a buffalo shed and a pigsty in a suburban area near Bangkok during 30 and 24 consecutive nights, respectively. Specimens were dissected daily to determine the parity status by tracheation of ovaries. In total, 17,482 Cx. tritaeniorhynchus and 13,011 Cx. gelidus females were caught, including 15 and 19% of parous individuals, respectively. The time series analysis for the data set collected at the buffalo shed yielded a gonotrophic cycle length of 5 days and a survival rate per cycle of 20% for Cx. tritaeniorhynchus and 8 days and 16% for Cx. gelidus. From these estimates, daily survival rates were calculated as 72% and 80% for Cx. tritaeniorhynchus and Cx. gelidus, respectively. However, the data set collected at the pigsty did not yield significant results. Holmes and Birley's (1987) method could be an effective tool in epidemiological studies for Japanese encephalitis vectors, but its applicability is influenced by conditions at collection sites.