Fitness, survival and resistance management of the yellow fever mosquito, Aedes aegypti (L.)

Recent data show that wild Aedes aegypti feed frequently and almost exclusively on humans without ingesting sugar for energy, and egg production is attributed to low concentrations of isoleucine in human blood. However, human blood is reportedly sub-optimal for Ae. aegypti compared with other types of blood. To understand why this species prefers to repeatedly feed on blood that is reproductively sub-optimal, groups of females were provided natural, low-isoleucine human blood, human blood supplemented with isoleucine and natural chick and rodent blood in a series of experiments. Egg production, energy reserves, feeding frequency and blood volume were compared. No differences in egg production were found among females offered low isoleucine blood compared with isoleucine-supplemented human blood, or among those offered chick and rodent blood, contradicting previous reports. When females were maintained on both sugar and blood (a common rearing practice, but unnatural wild behavior), rodent-fed females produced more eggs than human-fed females. Greater energy reserves were found in human-fed mosquitoes. Females ingested smaller meals from human hosts than rodents, yet fed with greater frequency on human blood. A life table study demonstrated greatest survival and fitness with females offered human blood alone. Field survival of Ae. aegypti was investigated. Two age cohorts (3 and 13 days) were released and recaptured in 3 experiments in Puerto Rico and Thailand. Regression analysis demonstrated a greater probability of daily survival for the older cohort. Greater survivorship among older females changes the current view of dengue transmission dynamics. Collapsible black fabric resting boxes were evaluated for surveillance of adult Ae. aegypti over a 10 month period in two regions of Thailand. Thirty percent of total females were collected from two resting boxes in each house. Resting boxes, as a surveillance tool, also decrease sampling time. Satisfactory control of Ae. aegypti was not achieved with deltamethrin impregnated resting boxes placed inside Thai houses. Females were susceptible to topical application, but contact irritancy with deltamethrin-treated fabric was observed. Lambdacyhalothrin treated boxes were more effective. Treated resting boxes place low resistance selection pressure on populations and may be an inexpensive and sustainable control method for Ae. aegypti