Field #assessment of #insecticide #dusting and #bait station #treatment impact against #rodent #flea and house flea species in the #Madagascar #plague context (PLoS Negl Trop Dis., abstract)

[Source: PLoS Neglected Tropical Diseases, full page: (LINK). Abstract, edited.]

OPEN ACCESS /  PEER-REVIEWED / RESEARCH ARTICLE

Field assessment of insecticide dusting and bait station treatment impact against rodent flea and house flea species in the Madagascar plague context

Adélaïde Miarinjara  , Soanandrasana Rahelinirina , Nadia Lova Razafimahatratra, Romain Girod, Minoarisoa Rajerison , Sebastien Boyer

Published: August 6, 2019 / DOI: https://doi.org/10.1371/journal.pntd.0007604 / This is an uncorrected proof.

 

Abstract

Bubonic is the most prevalent plague form in Madagascar. Indoor ground application of insecticide dust is the conventional method used to control potentially infected rodent fleas that transmit the plague bacterium from rodents to humans. The use of bait stations is an alternative approach for vector control during plague epidemics, as well as a preventive control method during non-epidemic seasons. Bait stations have many advantages, principally by reducing the amount of insecticide used, lowering the cost of the treatment and minimizing insecticide exposure in the environment. A previous study reported promising results on controlling simultaneously the reservoir and vectors, when slow-acting rodenticide was incorporated in bait stations called “Boîtes de Kartman”. However, little evidence of an effective control of the fleas prior to the elimination of rodents was found. In this study, we evaluated bait stations containing insecticide powder and non-toxic attractive rodent bait for their potential to control rat fleas. Its efficacy was compared to the standard method. The impact of both methods on indoor and outdoor rodent fleas, as well as the human household flea Pulex irritans were analyzed at different time points after treatments. Bait stations did not cause any significant immediate or delayed reduction of rat fleas and increasing the number of operational bait stations per household did not significantly improve their efficacy. Insecticide ground dusting appeared to be the most efficient method to control indoor rat fleas. Both methods appeared to have little impact on the density of outdoor rat fleas and human fleas. These results demonstrate limited effectiveness for bait stations and encourage the maintenance of insecticide dusting as a first-line control strategy in case of epidemic emergence of plague, when immediate effect on rodent fleas is needed. Recommendations are given to improve the efficacy of the bait station method.

 

Author summary

Insecticide ground dusting inside houses is the recommended measure to control rat fleas responsible for bubonic plague transmission. The main inconvenience of this method is the direct contact of houseowners to the toxic insecticide dust and spillage in environment. A bait station approach, where the insecticide is confined in a box or tunnel containing rodent attractant, seems to be a valuable complementary or alternative vector control tool. However currently, little is known about its real efficacy on reducing or eliminating fleas harbored by rats. Guidelines regarding its implementation (density and duration of use) as vector control tool are lacking. Those questions were addressed during a field trial study, where bait stations were deployed at different densities per household and followed up at different time points. The efficacy of bait station was compared to the standard method. The present study allowed to demonstrate that bait station approach requires more improvements to be efficient. Meanwhile, insecticide ground dusting is still recommended for to control rat fleas during epidemics.

___

Citation: Miarinjara A, Rahelinirina S, Razafimahatratra NL, Girod R, Rajerison M, Boyer S (2019) Field assessment of insecticide dusting and bait station treatment impact against rodent flea and house flea species in the Madagascar plague context. PLoS Negl Trop Dis 13(8): e0007604. https://doi.org/10.1371/journal.pntd.0007604

Editor: José Reck Jr., Instituto de Pesquisas Veterinarias Desiderio Finamor, BRAZIL

Received: February 5, 2019; Accepted: July 4, 2019; Published: August 6, 2019

Copyright: © 2019 Miarinjara et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: All relevant data are within the manuscript and its Supporting Information files.

Funding: This work was supported and funded by Institut Pasteur de Madagascar. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Competing interests: The authors have declared that no competing interests exist.

Keywords: Plague; Bubonic plague; Fleas; Rodents; Insecticides; Madagascar.

——-

Advertisements

The ability of #Anopheles gambiaemosquitoes to #bite through a #permethrin-treated #net and the consequences for their fitness (Sci Rep., abstract)

[Source: Scientific Reports, full page: (LINK). Abstract, edited.]

Article | OPEN | Published: 31 May 2019

The ability of Anopheles gambiaemosquitoes to bite through a permethrin-treated net and the consequences for their fitness

Gaël Hauser, Kevin Thiévent & Jacob C. Koella

Scientific Reports 9, Article number: 8141 (2019)

 

Abstract

Insecticide-treated bed-nets (ITNs) control malaria by keeping mosquitoes from reaching people sleeping under a net and by killing mosquitoes. Most tests of ITNs consider their overall epidemiological outcome without considering the different behaviors underlying their effects. Here we consider one of these behaviors: that mosquitoes can bite through the net if its user is touching it. We assayed the ability of an insecticide-sensitive strain of the mosquito Anopheles gambiae to bite through a permethrin-treated or an untreated net, and their subsequent survival and fecundity. Despite the irritancy of permethrin, 71% of the mosquitoes took blood through the ITN (vs. 99% through the untreated net). The ITN reduced the time spent biting, the blood-meal size and the fecundity, and it killed about 15% of the mosquitoes within 24 hours of feeding (vs. 5% on the untreated net). However, the mosquito’s survival was much higher than what we found in WHO cone assays, suggesting that the bloodmeal increased the mosquito’s resistance to the insecticide. Thus, our results suggest that the irritancy and the toxicity of ITNs are reduced when mosquitoes contact and feed on their host, which will affect our understanding of the personal and community protection offered by the ITNs.

Keywords: Mosquitoes; Anopheles spp.; Insecticides.

——

RNAi-based #bioinsecticide for #Aedes #mosquito #control (Sci Rep., abstract)

[Source: US National Library of Medicine, full page: (LINK). Abstract, edited.]

Sci Rep. 2019 Mar 11;9(1):4038. doi: 10.1038/s41598-019-39666-5.

RNAi-based bioinsecticide for Aedes mosquito control.

Lopez SBG1, Guimarães-Ribeiro V1, Rodriguez JVG1, Dorand FAPS1, Salles TS1, Sá-Guimarães TE1, Alvarenga ESL1, Melo ACA1,2, Almeida RV1, Moreira MF3,4.

Author information: 1 Universidade Federal do Rio de Janeiro, Departamento de Bioquímica, Instituto de Química, 21941-909, Rio de Janeiro, RJ, Brazil. 2 Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular, Rio de Janeiro, RJ, Brazil. 3 Universidade Federal do Rio de Janeiro, Departamento de Bioquímica, Instituto de Química, 21941-909, Rio de Janeiro, RJ, Brazil. monica@iq.ufrj.br. 4 Instituto Nacional de Ciência e Tecnologia em Entomologia Molecular, Rio de Janeiro, RJ, Brazil. monica@iq.ufrj.br.

 

Abstract

Zika virus infection and dengue and chikungunya fevers are emerging viral diseases that have become public health threats. Their aetiologic agents are transmitted by the bite of genus Aedes mosquitoes. Without effective therapies or vaccines, vector control is the main strategy for preventing the spread of these diseases. Increased insecticide resistance calls for biorational actions focused on control of the target vector population. The chitin required for larval survival structures is a good target for biorational control. Chitin synthases A and B (CHS) are enzymes in the chitin synthesis pathway. Double-stranded RNA (dsRNA)-mediated gene silencing (RNAi) achieves specific knockdown of target proteins. Our goal in this work, a new proposed RNAi-based bioinsecticide, was developed as a potential strategy for mosquito population control. DsRNA molecules that target five different regions in the CHSA and B transcript sequences were produced in vitro and in vivo through expression in E. coli HT115 and tested by direct addition to larval breeding water. Mature and immature larvae treated with dsRNA targeting CHS catalytic sites showed significantly decreased viability associated with a reduction in CHS transcript levels. The few larval and adult survivors displayed an altered morphology and chitin content. In association with diflubenzuron, this bioinsecticide exhibited insecticidal adjuvant properties.

PMID: 30858430 DOI: 10.1038/s41598-019-39666-5

Keywords: Arbovirus; Mosquitoes; Aedes spp.; Insecticides.

—–

Effects of #Deltamethrin #Treatment on Small #Mammal and #Ectoparasite Population Dynamics and #Plague Prevalence in a North American Mixed-Grass Prairie System (Vector Borne Zoo Dis., abstract)

[Source: Vector Borne and Zoonotic Diseases, full page: (LINK). Abstract, edited.]

Effects of Deltamethrin Treatment on Small Mammal and Ectoparasite Population Dynamics and Plague Prevalence in a North American Mixed-Grass Prairie System

Lauren P. Maestas  and Hugh B. Britten

Published Online: 22 Jan 2019

 

Abstract

Sylvatic plague affects many species in North American prairie ecosystems. Deltamethrin is commonly used to manage fleas in potential outbreak areas. Understanding the role of small mammals and their ectoparasites in sylvatic plague maintenance is pertinent to understanding the ecology of plague and its persistence in nature. This study examined the effects of plague management using deltamethrin on communities of small mammals, their flea faunas, and Yersinia pestis prevalence. We trapped small mammals from 2014 to 2016 on the Lower Brule Indian Reservation (LOBR), South Dakota, and analyzed the effects of deltamethrin treatment on small mammal populations, flea loads, and Y. pestis prevalence. We collected higher flea loads from small mammals on sites not treated with deltamethrin (1.10 fleas per animal) than from deltamethrin-treated sites (1.03 fleas per animal). We observed significant negative trends in mean flea load per animal between pre- and post-treatment collections. We detected no significant effects of deltamethrin treatment on animal captures pre- and post-treatment, but observed significant differences in animal captures by experimental unit. We detected no serological evidence for the presence of Y. pestis antibodies in small mammals and 1.2% Y. pestis prevalence across all sampled fleas. Although there is little overlap in the species of fleas infesting small mammals and prairie dogs, the occurrence of flea spillover has been documented. In our study, treatment with deltamethrin reduced flea loads on small mammals by up to 49%. Our data suggest that although the efficacy of deltamethrin on the LOBR—a mixed-grass system—may not be as high as that found in a comparable study in a short-grass system, deltamethrin is still a useful tool in the management of plague.

Keywords: Insecticides; Plague; Yersinia pestis; Wildlife; North America Region; Deltamethrin.

—–

#Insecticide #resistance genes affect #Culex quinquefasciatus #vector competence for #WNV (Proc Roy Soc B., abstract)

[Source: Proceedings of the Royal Society Biological Sciences, full page: (LINK). Abstract, edited.]

Insecticide resistance genes affect Culex quinquefasciatus vector competence for West Nile virus

Célestine M. Atyame, Haoues Alout, Laurence Mousson, Marie Vazeille, Mawlouth Diallo, Mylène Weill and Anna-Bella Failloux

Published: 16 January 2019 / DOI: https://doi.org/10.1098/rspb.2018.2273

 

Abstract

Insecticide resistance has been reported to impact the interactions between mosquitoes and the pathogens they transmit. However, the effect on vector competence for arboviruses still remained to be investigated. We examined the influence of two insecticide resistance mechanisms on vector competence of the mosquito Culex quinquefasciatus for two arboviruses, Rift Valley Fever virus (RVFV) and West Nile virus (WNV). Three Cx. quinquefasciatus lines sharing a common genetic background were used: two insecticide-resistant lines, one homozygous for amplification of the Ester2locus (SA2), the other homozygous for the acetylcholinesterase ace-1 G119S mutation (SR) and the insecticide-susceptible reference line Slab. Statistical analyses revealed no significant effect of insecticide-resistant mechanisms on vector competence for RVFV. However, both insecticide resistance mechanisms significantly influenced the outcome of WNV infections by increasing the dissemination of WNV in the mosquito body, therefore leading to an increase in transmission efficiency by resistant mosquitoes. These results showed that insecticide resistance mechanisms enhanced vector competence for WNV and may have a significant impact on transmission dynamics of arboviruses. Our findings highlight the importance of understanding the impacts of insecticide resistance on the vectorial capacity parameters to assess the overall consequence on transmission.

Keywords: Arbovirus; Rift Valley Fever virus; West Nile Virus; Mosquitoes; Insecticides; Culex quinquefasciatus.

——

Increased #risk of #CNS #tumours with #carbamate #insecticide use in the prospective cohort #AGRICAN (Int J Epidemiol., abstract)

[Source: International Journal of Epidemiology, full page: (LINK). Abstract, edited.]

Increased risk of central nervous system tumours with carbamate insecticide use in the prospective cohort AGRICAN

Clément Piel,  Camille Pouchieu, Lucile Migault, Béatrix Béziat, Mathilde Boulanger, Mathilde Bureau, Camille Carles, Anne Grüber, Yannick Lecluse, Virginie Rondeau, Xavier Schwall, Séverine Tual, Pierre Lebailly, Isabelle Baldi, AGRICAN group

International Journal of Epidemiology, dyy246, https://doi.org/10.1093/ije/dyy246

Published:23 November 2018

Citation: Clément Piel, Camille Pouchieu, Lucile Migault, Béatrix Béziat, Mathilde Boulanger, Mathilde Bureau, Camille Carles, Anne Grüber, Yannick Lecluse, Virginie Rondeau, Xavier Schwall, Séverine Tual, Pierre Lebailly, Isabelle Baldi, AGRICAN group; Increased risk of central nervous system tumours with carbamate insecticide use in the prospective cohort AGRICAN, International Journal of Epidemiology, , dyy246, https://doi.org/10.1093/ije/dyy246

© 2018 Oxford University Press

 

Abstract

Background

Pesticide exposures are suspected to be implicated in the excess of central nervous system (CNS) tumours observed in farmers, but evidence concerning individual pesticides remains limited. Carbamate insecticides, used on a wide range of crops, have shown evidence of carcinogenicity in some experimental studies. In the cohort AGRICAN (AGRIculture & CANcer), we assessed the associations between potential exposures to carbamate insecticides and the incidence of CNS tumours, overall and by histological subtype.

Methods

AGRICAN enrolled 181 842 participants involved in agriculture. Incident CNS tumours were identified by linkage with cancer registries from enrolment (2005–07) until 2013. Carbamate exposure was assessed by combining information on lifetime periods of pesticide use on crop or livestock and the French crop-exposure matrix PESTIMAT, individually for each of the 19 carbamate insecticides registered in France since 1950. Associations were estimated using proportional hazards models with age as the underlying time scale, adjusting for gender, educational level and smoking.

Results

During a 6.9-year average follow-up, 381 incident cases of CNS tumours occurred, including 164 gliomas and 134 meningiomas. Analyses showed increased risks of CNS tumours with overall exposure to carbamate insecticides and linear trends with duration of use of each carbamate. Considering tumour subtypes, hazard ratios for gliomas ranged from 1.18 for thiofanox to 4.60 for formetanate, and for meningiomas from 1.51 for carbaryl to 3.67 for thiofanox.

Conclusions

Findings reinforce carcinogenicity evidence for already suspected active ingredients and draw attention to additional active ingredients, notably used on fruit trees, vineyards, potatoes and beets.

Carbamates, insecticides, CNS tumours, occupational exposure, risk factors, cohort studies, agriculture, pesticides, cancer, farmers

Topic: cancer – central nervous system neoplasms – exposure – agriculture – carbamates – carbaryl – avian crop – follow-up – glioma – insecticides – carbamate insecticide – meningioma – pesticides – gender – farm animals

Issue Section: Original Article

© The Author(s) 2018; all rights reserved. Published by Oxford University Press on behalf of the International Epidemiological Association

This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model)

Keywords: Cancer; Toxic chemicals; Carbamates; Insecticides; Pesticides.

——

#Autism and #DDT: What one million #pregnancies can — and can’t — reveal (Nature, excerpt)

[Source: Nature, full page: (LINK). Excerpt, edited.]

NEWS  / 16 AUGUST 2018

Autism and DDT: What one million pregnancies can — and can’t — reveal

by Sara Reardon

Mothers with high levels of the pesticide DDT in their blood during pregnancy are more likely to bear children who develop autism, according to a study of blood samples from more than one million pregnant women in Finland.

(…)

Keywords: Insecticides; Toxic Chemicals; DDT; Autism; Pregnancy; Psychiatry; Neurology.

——