The sugar substitute erythritol shortens the lifespan of Aedes aegypti potentially by N-linked protein glycosylation.

Adult male and female mosquitoes consume sugar as floral and extrafloral nectar. Earlier work demonstrated that mosquito populations and their vector potential are dependent upon the availability of sugar sources. Thus, a novel method of vector control may involve targeting sugar-feeding mosquitoes. Multiple human-safe sugar substitutes are already approved by the U.S. Food and Drug Administration and are readily available. However, plant-based sugar substitutes such as stevia (erythritol) have been shown to affect lifespan in other flies. Therefore, the current study was carried out to test the potential of commercially available sugar substitutes to adversely affect the survival, fecundity, and metabolism of adult Aedes aegypti mosquitoes. Of the four sugar substitutes tested, erythritol (Stevia), sucralose (Splenda), aspartame (Equal), and saccharin (Sweet'N Low), only erythritol negatively affected mosquito longevity and fecundity. The effect on fecundity was probably due in part to a corresponding decrease in glycogen and lipid levels over time in mosquitoes fed on erythritol. Comparative mosquito head transcriptomes indicated upregulation of a gene in the mannose biosynthesis pathway in females fed on erythritol, suggesting that N-linked glycosylation might be responsible for the negative impact of erythritol feeding in mosquitoes. Mosquitoes preferred sucrose when a choice was given but were not averse to erythritol. Our results suggest the possibility of using erythritol alone or in combination with sucrose as a component of attractive toxic sugar baits for a human-safe approach for mosquito control.

Blood Digestion by Trypsin-Like Serine Proteases in the Replete Lyme Disease Vector Tick, Ixodes scapularis.

Ixodes scapularis is the major vector of Lyme disease in the Eastern United States. Each active life stage (larva, nymph, and adult) takes a blood meal either for developing and molting to the next stage (larvae and nymphs) or for oviposition (adult females). This protein-rich blood meal is the only food taken by Ixodes ticks and therefore efficient blood digestion is critical for survival. Studies in partially engorged ticks have shown that the initial stages of digestion are carried out by cathepsin proteases within acidic digestive cells. In this study, we investigated the potential role of serine proteases in blood digestion in replete ticks. RNA interference was used for functional analysis and a trypsin-benzoyl-D, L-arginine 4-nitoanilide assay was used to measure active trypsin levels. Hemoglobinolytic activity was determined in vitro, with or without a serine protease inhibitor. Our data suggest that trypsin levels increase significantly after repletion. Knockdown of serine proteases negatively impacted blood feeding, survival, fecundity, levels of active trypsin in the midgut, and resulted in lower hemoglobin degradation. Incubation of midgut extract with a trypsin inhibitor resulted in 65% lower hemoglobin degradation. We provide evidence of the serine proteases as digestive enzymes in fully engorged, replete females. Understanding the digestive profile of trypsin during blood meal digestion in I. scapularis improves our understanding of the basic biology of ticks and may lead to new methods for tick control.