Influence of Sugar Availability and Indoor Microclimate on Survival ofAnopheles gambiae(Diptera: Culicidae) Under Semifield Conditions in Western Kenya

Abstract

The influence of indoor microclimate on survival of female Anopheles gambiae sensu stricto Giles (Diptera: culicidae) mosquitoes fed on different nutrition sources was evaluated in a semifield experimental hut exposed to ambient climate in western Kenya. Cages of mosquitoes (n approximately 50 per cage) were placed in nine positions within the hut combining three different sides and three different heights. At each height and side, mosquitoes were offered either human blood (once every 2 d), glucose (6% wt:vol) or a combination of the two diets over three experiments so that each cage position received one diet source. The effect of diet on survival was significant with mean survival times of 14 d for mosquitoes fed blood alone, 29 d for sugar alone and 33 d for blood plus sugar. Sugar availability decreased the odds of mortality approximately 85% compared with the blood group. Micro heterogeneities of temperature but not relative humidity also influenced survival although to a much lesser extent. The side but not height within the hut at which mosquitoes were placed, influenced survival but could not be explained by either temperature or relative humidity differences. The potential influence of seemingly minor heterogeneities of indoor microclimate upon vector longevity and vectorial capacity may merit further investigation. Also, the availability of sugar was shown to be a potentially crucial determinant of vectorial capacity. Compared with blood alone, the availability of sugar served to increase survival potential of vectors beyond ages at which they are old enough to transmit malaria.

Influence of soil quality in the larval habitat on development of Anopheles gambiae Giles

“…Three to four days after soil flooding, 450-500 eggs from an Anopheles gambiae Giles sensu stricto (Mbita strain) rearing (hatching rate 90-100%) were dispensed into each of the troughs (on the assumption that the different treatments had no effect on hatching rate). Larvae in the control troughs were fed with defined quantities of Tetramin® fish food every day for optimal development, following a rearing protocol (Okech et al 2003). The water level was checked each day and filtered lake water was added if necessary to all troughs.…”

Infection of Anopheles gambiae mosquitoes with entomopathogenic fungi: effect of host age and blood-feeding status

“…Mosquito populations are known to experience senescence (Harrington et al 2001; Okech et al 2003; Styer et al 2007). As mosquitoes age, adverse changes to major life-history parameters have been recorded, including differences in mortality, flight capacity, immune function, salivary gland function, and cuticular hydrocarbon composition (Rowley and Graham 1968; Nayar and Sauerman 1973; Beckett 1990; Chen et al 1990; Brei et al 2004; Hugo et al 2006).…”

“…Various studies have recorded contradicting effects of blood feeding on mosquito longevity. One hypothesis is that mosquitoes which are fed on blood alone, without access to sugar, will have lower survival, possibly because nutrients are diverted for egg production (Okech et al 2003). Alternately, other experiments have recorded that blood feeding can actually increase mosquito survival when compared with mosquitoes fed only on sugar (Scott et al 1993; Scott et al 1997).…”

Calibration and evaluation of field cage for oviposition study with Aedes (Stegomyia) aegypti female (L.) (Diptera: Culicidae)

“…Okech et al (2003) compared the temperature and relative humidity of the air in semi-fi eld conditions with those obtained in natural environment. They did not notice any signifi cant difference between the average values obtained in both environments and the A. gambiae behavioral responses.…”

“…In these studies it was possible to study the biological cycle , determinants of mating and the reproductive success of the genetically modifi ed mosquitoes (Okanda et al 2002), trap evaluation and development , Njiru et al 2006, infl uence of sugar availability and indoor microclimate on survival (Okech et al 2003), and feeding and survival in the absence of blood meals (Impoinvil et al 2004). However, before using the semi-fi eld in oviposition studies, it is necessary to identify/ establish the variables which can infl uence the response of the evaluated insects.…”