Mosquito Biting Behavior: Statistical Power and Sources of Variation in Toxicity and Repellent Bioassays

Abstract

Compounds thought to be effective against mosquitoes as either 'insecticides' or 'repellents' have recently been shown to contain properties of both, or possess other behavior-modifying actions. Prompted in part by these reports, we conducted posterior analyses of our data to examine some interrelated statistical issues inherent in our bioassay system. Using a modified K&D module, the responses of over 25,000 adult Aedes aegypti (L.) females exposed to either alphacypermethrin or DEET were compared with the responses of mosquitoes exposed to untreated controls for toxicity and biting (alphacypermethrin) or biting alone (DEET). Our analyses indicated that; (1) our bioassay system has more statistical power to determine a compound's toxicity than its repellent qualities, (2) day-to-day variability is large and needs to be accommodated in analyses; there are other, potentially even larger sources of variability (e.g., mosquito heterogeneity) which invalidate statistical tests that are based on the assumption of binomially or multinomially distributed data (e.g., chi2 tests), and (3) unlike biting mosquitoes exposed to DEET, the proportions of biting mosquitoes exposed to alphacypermethrin are unrelated to the proportions of concurrently tested biting controls, even after adjusting for daily variation in toxicity. Thus, there is a clear behavioral indicator in this bioassay system that the 'repellency' of DEET (a presumed repellent) differs in a fundamental way from that of alphacypermethrin (a presumed toxicant), which may allow the differentiation between classes of compounds based on biting behavior alone.

Protective efficacy of menthol propylene glycol carbonate compared to N, N-diethyl-methylbenzamide against mosquito bites in Northern Tanzania

“…gambiae s.l. In both laboratory and field evaluation of various repellent dosages, protection was found to be dosage dependent as found elsewhere [30,31] while with blends, the synergistic effect was dosage mixture dependent [11,32]. The strategy of using repellents in combination (Blends) conferred a better protection with little amount of repellent used (Blend 2 and Blend 3) compared to DEET and MR08 30% alone.…”

Host feeding responses of Aedes aegypti (L.) exposed to deltamethrin

“…In addition to sample size limitations, we could not control for all sources of potential variation, including inherent mosquito behavioral heterogeneity in response to external cues and chemicals, therefore some inference testing (distribution-free nonparametric methods, e.g., log-rank) used in this study was less powerful statistically compared to parametric approaches (e.g., GLM). Nevertheless, we assume samples were randomly drawn from a binomial distribution, that individual responses (means) were within normal approximations, and that all trials were mutually independent, which may not have been the case in all instances (Kramer et al 2010). Although potential test-to-test variability (outside of sampling error) is of concern (e.g., day-to-day variation in response), the statistical options used to compare mixed If a column of the model matrix corresponding to a parameter is found to be linearly dependent, or aliased, with columns corresponding to parameters preceding it in the model, PROC GENMOD assigns it zero degrees of freedom and displays a value of zero for both the parameter estimate and its standard error.…”

DEET (N,N‐Diethyl‐meta‐toluamide) Induced Delay of Blowfly Landing and Oviposition Rates on Treated Pig Carrion (Sus scrofaL.)

“…The strength of these hypotheses faded following the discovery of DEET-sensitive olfactory receptor neurons that directly detect DEET and ultimately elicit avoidance behavior in mosquitoes (21). DEET also affects mosquito behavior in fundamentally different ways from toxicants that cause it to be classified as a ''repellent'' (22). If this repellency hypothesis prevails, the behavior of carrion-feeding flies, such as Calliphoridae and Sarcophagidae, should also be influenced by DEET.…”