Predicting air-borne droplet drift from agricultural areas

Non-Peer Reviewe

Prioritizing Replenishments of the Forward Reserve

Having sufficient inventories in the piece-picking area of a warehouse is an essential condition for warehouse operations. This requires a timely replenishment of the products from a reserve area in case they could run out of stock. In this paper we develop analytical models to arrive at priority rules for these replenishments in case replenishments and order picking are done simultaneously because of time pressure. This problem was observed in a warehouse of a large cosmetics firm. The priority rules are compared by means of simulation and regression. Finally we present the results o

A novel method for standardized application of fungal spore coatings for mosquito exposure bioassays

<p>Abstract</p> <p>Background</p> <p>Interest in the use of fungal entomopathogens against malaria vectors is growing. Fungal spores infect insects via the cuticle and can be applied directly on the insect to evaluate infectivity. For flying insects such as mosquitoes, however, application of fungal suspensions on resting surfaces is more realistic and representative of field settings. For this type of exposure, it is essential to apply specific amounts of fungal spores homogeneously over a surface for testing the effects of fungal dose and exposure time. Contemporary methods such as spraying or brushing spore suspensions onto substrates do not produce the uniformity and consistency that standardized laboratory assays require. Two novel fungus application methods using equipment developed in the paint industry are presented and compared.</p> <p>Methods</p> <p>Wired, stainless steel K-bars were tested and optimized for coating fungal spore suspensions onto paper substrates. Different solvents and substrates were evaluated. Two types of coating techniques were compared, i.e. manual and automated coating. A standardized bioassay set-up was designed for testing coated spores against malaria mosquitoes.</p> <p>Results</p> <p>K-bar coating provided consistent applications of spore layers onto paper substrates. Viscous Ondina oil formulations were not suitable and significantly reduced spore infectivity. Evaporative Shellsol T solvent dried quickly and resulted in high spore infectivity to mosquitoes. Smooth proofing papers were the most effective substrate and showed higher infectivity than cardboard substrates. Manually and mechanically applied spore coatings showed similar and reproducible effects on mosquito survival. The standardized mosquito exposure bioassay was effective and consistent in measuring effects of fungal dose and exposure time.</p> <p>Conclusions</p> <p>K-bar coating is a simple and consistent method for applying fungal spore suspensions onto paper substrates and can produce coating layers with accurate effective spore concentrations. The mosquito bioassay was suitable for evaluating fungal infectivity and virulence, allowing optimizations of spore dose and exposure time. Use of this standardized application method will help achieve reliable results that are exchangeable between different laboratories.</p

Synergy in Efficacy of Fungal Entomopathogens and Permethrin against West African Insecticide-Resistant Anopheles gambiae Mosquitoes

Background Increasing incidences of insecticide resistance in malaria vectors are threatening the sustainable use of contemporary chemical vector control measures. Fungal entomopathogens provide a possible additional tool for the control of insecticide-resistant malaria mosquitoes. This study investigated the compatibility of the pyrethroid insecticide permethrin and two mosquito-pathogenic fungi, Beauveria bassiana and Metarhizium anisopliae, against a laboratory colony and field population of West African insecticide-resistant Anopheles gambiae s.s. mosquitoes. Methodology/Findings A range of fungus-insecticide combinations was used to test effects of timing and sequence of exposure. Both the laboratory-reared and field-collected mosquitoes were highly resistant to permethrin but susceptible to B. bassiana and M. anisopliae infection, inducing 100% mortality within nine days. Combinations of insecticide and fungus showed synergistic effects on mosquito survival. Fungal infection increased permethrin-induced mortality rates in wild An. gambiae s.s. mosquitoes and reciprocally, exposure to permethrin increased subsequent fungal-induced mortality rates in both colonies. Simultaneous co-exposure induced the highest mortality; up to 70.3±2% for a combined Beauveria and permethrin exposure within a time range of one gonotrophic cycle (4 days). Conclusions/Significance Combining fungi and permethrin induced a higher impact on mosquito survival than the use of these control agents alone. The observed synergism in efficacy shows the potential for integrated fungus-insecticide control measures to dramatically reduce malaria transmission and enable control at more moderate levels of coverage even in areas where insecticide resistance has rendered pyrethroids essentially ineffective

Tools for delivering entomopathogenic fungi to malaria mosquitoes: effects of delivery surfaces on fungal efficacy and persistence.

BACKGROUND\ud \ud Entomopathogenic fungi infection on malaria vectors increases daily mortality rates and thus represents a control measure that could be used in integrated programmes alongside insecticide-treated bed nets (ITNs) and indoor residual spraying (IRS). Before entomopathogenic fungi can be integrated into control programmes, an effective delivery system must be developed.\ud \ud METHODS\ud \ud The efficacy of Metarhizium anisopliae ICIPE-30 and Beauveria bassiana I93-825 (IMI 391510) (2 × 10(10) conidia m(-2)) applied on mud panels (simulating walls of traditional Tanzanian houses), black cotton cloth and polyester netting was evaluated against adult Anopheles gambiae sensu stricto. Mosquitoes were exposed to the treated surfaces 2, 14 and 28 d after conidia were applied. Survival of mosquitoes was monitored daily.\ud \ud RESULTS\ud \ud All fungal treatments caused a significantly increased mortality in the exposed mosquitoes, descending with time since fungal application. Mosquitoes exposed to M. anisopliae conidia on mud panels had a greater daily risk of dying compared to those exposed to conidia on either netting or cotton cloth (p < 0.001). Mosquitoes exposed to B. bassiana conidia on mud panels or cotton cloth had similar daily risk of death (p = 0.14), and a higher risk than those exposed to treated polyester netting (p < 0.001). Residual activity of fungi declined over time; however, conidia remained pathogenic at 28 d post application, and were able to infect and kill 73 - 82% of mosquitoes within 14 d.\ud \ud CONCLUSION\ud \ud Both fungal isolates reduced mosquito survival on immediate exposure and up to 28 d after application. Conidia were more effective when applied on mud panels and cotton cloth compared with polyester netting. Cotton cloth and mud, therefore, represent potential substrates for delivering fungi to mosquitoes in the field

Midgut microbiota of the malaria mosquito vector Anopheles gambiae and Interactions with plasmodium falciparum Infection

The susceptibility of Anopheles mosquitoes to Plasmodium infections relies on complex interactions between the insect vector and the malaria parasite. A number of studies have shown that the mosquito innate immune responses play an important role in controlling the malaria infection and that the strength of parasite clearance is under genetic control, but little is known about the influence of environmental factors on the transmission success. We present here evidence that the composition of the vector gut microbiota is one of the major components that determine the outcome of mosquito infections. A. gambiae mosquitoes collected in natural breeding sites from Cameroon were experimentally challenged with a wild P. falciparum isolate, and their gut bacterial content was submitted for pyrosequencing analysis. The meta-taxogenomic approach revealed a broader richness of the midgut bacterial flora than previously described. Unexpectedly, the majority of bacterial species were found in only a small proportion of mosquitoes, and only 20 genera were shared by 80% of individuals. We show that observed differences in gut bacterial flora of adult mosquitoes is a result of breeding in distinct sites, suggesting that the native aquatic source where larvae were grown determines the composition of the midgut microbiota. Importantly, the abundance of Enterobacteriaceae in the mosquito midgut correlates significantly with the Plasmodium infection status. This striking relationship highlights the role of natural gut environment in parasite transmission. Deciphering microbe-pathogen interactions offers new perspectives to control disease transmission.Institut de Recherche pour le Developpement (IRD); French Agence Nationale pour la Recherche [ANR-11-BSV7-009-01]; European Community [242095, 223601]info:eu-repo/semantics/publishedVersio

Eave tubes for malaria control in Africa : Initial development and semi-field evaluations in Tanzania Lucy Tusting, Jo Lines

Background: Presented here are a series of preliminary experiments evaluating "eave tubes" - a technology that combines house screening with a novel method of delivering insecticides for control of malaria mosquitoes. Methods: Eave tubes were first evaluated with overnight release and recapture of mosquitoes in a screened compartment containing a hut and human sleeper. Recapture numbers were used as a proxy for overnight survival. These trials tested physical characteristics of the eave tubes (height, diameter, angle), and different active ingredients (bendiocarb, LLIN material, fungus). Eave tubes in a hut with closed eaves were also compared to an LLIN protecting a sleeper in a hut with open eaves. Eave tubes were then evaluated in a larger compartment containing a self-replicating mosquito population, vegetation, and multiple houses and cattle sheds. In this "model village", LLINs were introduced first, followed by eave tubes and associated house modifications. Results: Initial testing suggested that tubes placed horizontally and at eave height had the biggest impact on mosquito recapture relative to respective controls. Comparison of active ingredients suggested roughly equivalent effects from bendiocarb, LLIN material, and fungal spores (although speed of kill was slower for fungus). The impact of treated netting on recapture rates ranged from 50 to 70 % reduction relative to controls. In subsequent experiments comparing bendiocarb-treated netting in eave tubes against a standard LLIN, the effect size was smaller but the eave tubes with closed eaves performed at least as well as the LLIN with open eaves. In the model village, introducing LLINs led to an approximate 60 % reduction in larval densities and 85 % reduction in indoor catches of host-seeking mosquitoes relative to pre-intervention values. Installing eave tubes and screening further reduced larval density (93 % relative to pre intervention values) and virtually eliminated indoor host-seeking mosquitoes. When the eave tubes and screening were removed, larval and adult catches recovered to pre-eave tube levels. Conclusions: These trials suggest that the "eave tube" package can impact overnight survival of host-seeking mosquitoes and can suppress mosquito populations, even in a complex environment. Further testing is now required to evaluate the robustness of these findings and demonstrate impact under field conditions