Measuring the Host-Seeking Ability of Aedes aegypti Destined for Field Release

Abstract

Host seeking is an essential process in mosquito reproduction. Field releases of modified mosquitoes for population replacement rely on successful host seeking by female mosquitoes, but host-seeking ability is rarely tested in a realistic context. We tested the host-seeking ability of female Aedes aegypti mosquitoes using a semi-field system. Females with different Wolbachia infection types (wMel-, wAlbB-infected, and uninfected) or from different origins (laboratory and field) were released at one end of a semi-field cage and recaptured as they landed on human experimenters 15 m away. Mosquitoes from each population were then identified with molecular tools or through minimal dusting with fluorescent powder. Wolbachia-infected and uninfected populations had similar average durations to landing and overall recapture proportions, as did laboratory and field-sourced Ae. aegypti. These results indicate that the host-seeking ability of mosquitoes is not negatively affected by Wolbachia infection or long-term laboratory maintenance. This method provides an approach to study the host-seeking ability of mosquitoes in a realistic setting, which will be useful when evaluating strains of mosquitoes that are planned for releases into the field to suppress arbovirus transmission.

Wolbachia’s Deleterious Impact on Aedes aegypti Egg Development: The Potential Role of Nutritional Parasitism

“…aegypti, decreasing adult female lifespan as well as blood-feeding success, fecundity, fertility and viability of eggs over time [13,32,[48][49][50]. [32,33,40,47] No negative impact [32] No negative impact [15,33] No negative impact [51] Decreased [15,47,51] or no negative impact [33] wAlbB No negative impact [33,46,47] No negative impact [46] Minor or no negative impact [33,46,47] No negative impact [51] Decreased [33,46,47] or no negative impact [33] wMelPop-CLA Decreased (age associated) [32,49,50] Survival not impacted. Delay in male pupation and female 4th instar larval development [49] Decreased [13,50] Decreased [48], exacerbated with age [49] Decreased [32,49,50] Field releases of Ae.…”

“…If energy stores are depleted, a blood-meal is not sufficient to initiate egg development [107]. Wolbachia is not likely to be impacting iron or sucrose availability to its host as only the most virulent Wolbachia strain, wMelPop-CLA, is consistently linked to disruption in fecundity [32,49] and adult longevity [13,50] (Table 1), and Wolbachia infection has not been shown to negatively impact attraction to a blood-meal [51]. Overall, while it is important to understand the role of all nutrients, it is evident that deficiencies of protein and lipids are the most significant causes of disruptions in egg production.…”

A diagnostic primer pair to distinguish between wMel and wAlbB Wolbachia infection - A simplified real-time PCR approach for use in field collected Aedes aegypti in dengue reduction trials

“…In previous work, we have used a Wolbachia-specific primer pair, w1 [7], which targets a conserved locus VNTR-141 containing tandem repeats [11]. This pair of primers works efficiently in amplifying wMel and wMelPop infections in a real-time PCR and HRM assay, but achieves only poor amplification of wAlbB [10]. As well as being used for Wolbachia detection, primers are needed for quantification of Wolbachia density in mosquitoes.…”

“…There are various Wolbachia specific primers for wMel, wAlbB or wMelPop [9,[12][13][14], but currently there is no standardised assay for Wolbachia screening that is comparable between strains and that can be used to compare results between laboratories. Although cross-laboratory comparability may not be a realistic aim when using a SYBR® equivalent/non-probe-based assay, the use of extra internal controls can make these assays robust for relative density estimates, improving consistency within laboratory experiments [7,10].…”

“…However, difficulties can arise in using these assays when there is a need to detect Wolbachia and distinguish between multiple Wolbachia strains. In experiments where superinfected lines are used [9], or where mosquitoes carrying different single infections need to be distinguished for experiments or in field collected samples [10], different assays are currently required. Given that both wMel and wAlbB strains are now actively being used in field releases and that each strain may have advantages in particular situations, the requirement for multiple strain identification is likely to increase in the foreseeable future.…”