Home HOMEPAGE   Wed, 05/22/2019 GMT + 7
    Q & A   Site map Forum   Site map Sitemap   E-mali Contact   Vietnamese Vietnamese
IMPE-QN
Web Sites & Commerce News - Events
Web Sites & Commerce Introduction
Web Sites & Commerce Collaborative activities
Web Sites & Commerce Training
Finance & Retail Specific research studies
Epidemiology
Entomology
Malariology
Malaria parasitology
Intestinal parasitology
Molecular - biology
Web Sites & Commerce Publications
Web Sites & Commerce Mass organization activities
Web Sites & Commerce Legal documents
Web Sites & Commerce Statistical data
Web Sites & Commerce Work safety
Web Sites & Commerce Vietnam`s Physicians
Web Sites & Commerce Malariology
Web Sites & Commerce Helminthology
Web Sites & Commerce Other vector-borne diseases

SEARCH

LOGIN
Username
Password

WEBLINKS
Other links

Visiting users: 271
3 7 1 4 6 8 6 9
Online
2 7 1
 Specific research studies Entomology
Mutant mosquitoes make insecticide-resistance monitoring key to controlling Zika

One of the most common insecticides used in the battle against theAedes aegypti mosquito has no measurable impact when applied in communities where the mosquito has built up resistance to it, a study led by Emory University finds.

 

The study is the first to show how vital insecticide-resistance monitoring is to control the Aedes mosquito -- which carries the viruses that cause Zika, dengue fever and yellow fever.

The journal PLoS Neglected Tropical Diseases published the research.

"The results are striking," says Gonzalo Vazquez-Prokopec, a disease ecologist at Emory and first author of the study. "If you use the insecticide deltamethrin in an area with high-deltamethrin resistance, it's the same as if you didn't spray at all. It does not kill the Aedes aegypti mosquitoes. The efficacy is not different to a control."

The results of the randomized, controlled trial are important because some public health departments in places where Zika and dengue viruses are endemic do not necessarily monitor for insecticide resistance.

"The recent epidemic of the Zika virus has raised awareness that we need to focus o­n what really works when it comes to mosquito control," Vazquez-Prokopec says. "The data from our study makes a bold statement: Any mosquito-control program involving spraying insecticides needs to be based o­n knowledge of the current levels of insecticide-resistance of the local mosquitoes."

It is not difficult to determine levels of insecticide resistance, he adds. Public health workers can use standardized bioassays to coat a bottle with an insecticide in a specific dose. They can then introduce mosquitoes from the area to be monitored into the bottles and observe the number of them killed after 24 hours.

The current study -- conducted in three neighborhoods of Merida, Mexico -- measured the efficacy of indoor residual spraying against adult Aedes aegypti mosquitoes in houses treated with either deltamethrin (to which the local mosquitoes expressed a high degree of resistance) or bendiocarb (another insecticide to which the mosquitoes were fully susceptible), as compared to untreated control houses.

The bediocarb-treated areas showed a 60-percent kill rate for Aedes aegypti mosquitoes during a three-month period, while the deltamethrin-treated areas and the control areas showed no detectable impact o­n the mosquitoes.

It's a natural biological process for mosquitoes to mutate in response to insecticide exposure, Vazquez-Prokopec says. These mutations can occur at the molecular level, preventing the insecticide from binding to an enzymatic target site. They can also happen at the metabolic level -- when a mosquito's metabolism "up regulates" the production of enzymes that can neutralize the toxic effects of an insecticide.

"Both mechanisms can occur in the same mosquito," Vazquez-Prokopec says, "making insecticide resistance a challenging and fascinating problem."

Even more worrying are so-called "super bug" mosquitoes, that show resistance to more than o­ne insecticide.

"You can't stop evolution," Vazquez-Prokopec says. "That's why it's important for countries to have resistance-monitoring systems at both local and national levels to help manage the use of insecticides more efficiently and effectively."

For the past 20 years, there has been a rise in resistance to insecticides in mosquitoes, particularly in the Anopheles genus, some of which transmit the malaria parasite. Anopheles mosquitoes o­nly bite between dusk and dawn, so the use of bed nets in areas where malaria is endemic have long been a method to reduce the opportunity for mosquitoes to transmit malaria.

More than a decade ago, bed nets treated with pyretheroids -- a class of pesticides that includes deltamethrin -- were rolled out in Africa in a big way to fight malaria. Pyretheroids are commonly used because they are odorless, cheap, long-lasting and have low mammalian toxicity.

The widespread use of insecticide-treated bed nets eventually led to a rise in resistance to pyretheroids by the Anopheles mosquito. The nets, however, still provide a physical barrier between people and mosquitoes so they retain some benefit.

A similar rise in resistance is being seen in the Aedes mosquito in some areas. But the Aedes mosquitoes bite during the day, making bed nets ineffective and insecticide spraying campaigns more critical to their control.

Previous research led by Vazquez-Prokopec showed that contact tracing of human cases of dengue fever, combined with indoor residual spraying for Aedes mosquitoes in homes, provided a significant reduction in the transmission of dengue during an outbreak.

The insecticide-resistance study adds to the growing body of knowledge of what works -- and what doesn't -- to control the Aedes mosquito in order to lessen the impact of a mosquito-borne disease outbreak, or to prevent o­ne altogether.

"We're always going to be chasing the problem of insecticide resistance in mosquitoes, but the more data that we have -- and the more tools we have in our arsenal -- the more time we can buy," Vazquez-Prokopec says.


Journal Reference:

1.Gonzalo M. Vazquez-Prokopec, Anuar Medina-Barreiro, Azael Che-Mendoza, Felipe Dzul-Manzanilla, Fabian Correa-Morales, Guillermo Guillermo-May, Wilbert Bibiano-Marn, Valentn Uc-Puc, Eduardo Geded-Moreno, Jos Vadillo-Snchez, Jorge Palacio-Vargas, Scott A. Ritchie, Audrey Lenhart, Pablo Manrique-Saide.Deltamethrin resistance in Aedes aegypti results in treatment failure in Merida, Mexico.PLOS Neglected Tropical Diseases, 2017; 11 (6): e0005656 DOI:10.1371/journal.pntd.0005656

07/07/2017
(Source: www.sciencedaily.com)  

Announcement

LIBRARY
Book
Magazine
Document
Photos
Thesis
Documentary form
Research studies
PROFFESSIONAL SOFTWARE
Malaria forecast & management
Document management
Personel management
LEGAL DOCUMENTS
Law
Decision
Decree
Instruction
Circular
Official document
Reports
Others
SPECIFIED IMFORMATION
Malaria facts
Malaria epidemic
Petechial fever
HEALTH SERVICES
Hospital & medical centre
Drugstore
Surgery
Your doctor

Institue of Malariology Parastology and Entomology Quy Nhon
Address: 611B Nguyen Thai Hoc Str,. Quy Nhon City
Tel: (84) 056 846571 Fax: (84) 056 846755
• Designed by Quang Ich JSC