This is not to spit on: Scientists say they may be able to track diseases transmitted by mosquitoes fatal studying saliva insects leave behind when they feed sweet bait.
diseases transmitted by mosquitoes are a major health hazard worldwide. Some, such as malaria, chronically afflict certain regions. But others, such as dengue fever, West Nile virus and chikungunya, can rapidly emerge in new places or reappear in areas where they have gone dormant. This means that those responsible for public health should keep a constant eye on the movement of diseases.
The usual methods for the detection of virus by mosquitoes all have a weakness: Based on clinical diagnoses means a disease has already happened in the population; keep '' sentinel 'animals is expensive, and the animals themselves provide a food source for mosquitoes; and capturing thousands of mosquitoes and analyzing their RNA is expensive and labor intensive.
Now, Andrew van den Hurk, a virologist with Queensland Health Forensic and Scientific Services in Coopers Plains, Australia, and colleagues found a way to monitor diseases transmitted by mosquitoes that may be simpler than the current and suitable methods for use over large geographical areas. For their new study, the researchers took advantage of the fact that mosquitoes are sloppy eaters: When they feed on a sugar source, the insects leave behind a slobbery mess. And van den Hurk and colleagues have discovered that they can detect the virus in the mosquito residue spit, as they report online today in Proceedings of the National Academy of Sciences .
To prove this, the scientists created box traps that attract mosquitoes with gas, carbon dioxide Äîmosquitoes are attracted to things, because it indicates the presence of an animal breathing and therefore a meal , Äîand then suck them inside a fan. Once in the trap, the mosquitoes feed on filter paper soaked in honey, Äîdyed blue for the color rubbed off on mosquitoes that take the bait. Researchers have traps in Bunbury in Western Australia near Cairns, in northeastern Australia, Äîtwo historical warm beds virus Ross River and Barmah Forest mosquitoes. Over 11 weeks, the scientists returned to the traps weekly to collect the filter paper and the trapped mosquitoes and send to the laboratory for analysis.
Whenever the filter paper returned positive for viral RNA, laboratories also found the virus in mosquitoes they had captured, which means the filter paper accurately reflects the presence of carrying mosquitoes virus. Scientists suggest that the technique could be able to be modified to detect other diseases like malaria and the virus of bluetongue.
Honey is antibacterial, so it's a great way to protect the viral RNA from bacteria until the researchers return to collect. Traps can be left out for more than a week, allowing them to set traps on a relatively large geographical area and check the traps intermittently, the researchers say. Another advantage is speed. Laboratories can analyze the filter paper using a RNA technology known as identifying the reaction reverse transcription polymerase chain reaction, indicating that the diseases are almost instantaneously present. However, sorting, storage and transportation of mosquitoes trapped for analysis of RNA is a process much longer and more arduous. The current method also requires keeping the samples cold mosquitoes Äîsomething it is not always possible in warm, tropical environments.
Jonathan Day, an entomologist at the University of Medical Entomology Laboratory in Vero Beach Florida, said that compared to analyze the trapped mosquitoes or finding the infection in sentinel animals, essentially new technique could halve the time required to detect and respond to an outbreak in a new area. But he said it remains to be seen whether the technique will be profitable enough to justify switching to researchers it. '' It is certainly intelligent, '' Day said, '' but the cost is the critical factor. '' Day also highlights that the technique lets you know if the disease is present and can not tell the researchers the extent of the infection from a mosquito population in the area.
Rory McAbee, biologist at Fresno Mosquito and Vector Control District in California, acknowledges that the method could be a time saver for researchers, but warns that traps only work for the mosquitoes that are attracted to the dioxide atoms. '' All species will not enter the trap, '' she said. '' This should be assessed for each species and viruses. ''
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