Fighting mosquito resistance to insecticides

Controlling mosquitoes that carry human diseases is a global health challenge as their ability to resist insecticides now threatens efforts to prevent epidemics. Scientists from the CNRS, IRD, Université Claude Bernard Lyon 1, Université Joseph Fourier in Grenoble and Institut Pasteur in French Guiana have identified new genetic markers for mosquito resistance to insecticides, which could improve its detection in the field. This work was published in Genome Research on 23 July 2015.

The ability of mosquitoes to resist insecticides represents a serious threat to the prevention of diseases such as malaria, dengue and Chikungunya. The detection and monitoring of the resistances developed by natural mosquito populations will be essential to enabling their management in the field for as long as there are no alternatives to the use of insecticides.

Repeat infection with malaria parasites might make mosquitoes more dangerous

In malaria-endemic regions, humans are often infected repeatedly with the Plasmodium parasite, and the consequences of such multiple infections are under intense study. In contrast, little is known about possible co-infection and its consequences in the Anopheles mosquitoes that transmit the disease. A study published on July 16th in PLOS Pathogens reports that not only can individual mosquitoes accumulate infections from multiple blood feeds, but also that an existing malaria infection makes mosquitoes more susceptible to a second infection, and that infections reach higher densities when another strain is already present.

Interested in interactions between malaria parasites and their insect hosts, Laura Pollitt, from the University of Edinburgh, UK, and colleagues in the US, asked whether and how mosquitoes can be infected with different Plasmodium strains, how such heterogeneous parasites interact in the insects, and whether such interactions affect transmission of malaria to vertebrate hosts.

The researchers set up cages of female Anopheles mosquitoes and allowed them at defined times to feed on mice infected with two different Plasmodium strains. This study design allowed them to examine how the presence of a co-infecting strain affects parasites that enter the vector first and second, and to test whether co-infection impacts mosquito survival.

The mosquito smells, before it sees, a bloody feast

The itchy marks left by the punctured bite of a mosquito are more than pesky, unwelcomed mementos of a day at the lake.

These aggravating bites can also be conduits for hitchhiking pathogens to worm their way into our bodies. Mosquitoes spread malaria, dengue, yellow fever and West Nile virus, among others. As the bloodsucking insects evolve to resist our best pesticides, mosquito control may shift more to understanding how the mosquitoes find a tasty -- and unsuspecting -- human host.

A team of biologists from the University of Washington and the California Institute of Technology has cracked the cues mosquitoes use to find us. As they report in a paper published July 16 in Current Biology, the minute insects employ a razor-sharp sense of smell to tip them off that a warm-blooded meal is nearby, and then use vision and other senses to home in on the feast.

"Very little was known about what a host looks like to the mosquito and how a mosquito decides where to land and begin to feed," said UW biologist Jeff Riffell, co-author on the paper and one of three professors collaborating on these efforts.