Gene interplay aids spread of dengue

AFP-JIJI

Complex genetic interactions between mosquitoes and the dengue fever virus spread the dangerous disease, a study by French and Thai scientists says.

The mosquito-borne disease has traditionally been a problem of the tropics, but globalization, climate change and jet travel are helping it move into temperate zones. There is no vaccine or cure.

In a study published in the journal PLoS Genetics, a team found that some mosquitoes are able to pass on the virus after sucking blood from an infected human, but others do not. The answer lies in a genetic pairing between insect and virus, according to the paper by the French Pasteur Institute and the Thai Armed Forces Research Institute of Medical Sciences.

To infect humans, the mosquito first has to be colonized by the virus. After the mosquito feeds on an infected individual, the virus becomes established in the midgut cells, then disseminates throughout the rest of body. The mosquito becomes infectious once the virus reaches the salivary glands and is released into its saliva.

But the infection occurs only when the right strain of mosquito meets the right strain of dengue, according to the paper, which tested wild insects on the four viral types. A mosquito may be resistant to one type of virus but vulnerable to another.

The finding has implications for plans to control dengue by releasing genetically engineered virus-resistant mosquitoes.

The World Health Organization estimates that there may be 50 million to 100 million dengue infections worldwide every year, and 2.5 billion people are at risk from the disease.