Mosquito control programs aimed at reducing the rate of transmission of dengue in Thailand, has actually had the opposite effect, according to a new study published online Monday in the Proceedings of the National Academy of Sciences.Researchers at Duke University in Durham, NC, and the Osaka University Graduate School of Medicine, Japan indicate that despite efforts to reduce the number of dengue - 1981, cases of the disease in the most serious form , dengue haemorrhagic fever, have increased dramatically.
Dengue hemorrhagic fever kills about 10 percent of those infected in Thailand. In its mild form, the disease results in a fever, which in some cases takes only a few days.
In Thailand, according to researchers, from 200000 to 500000 cases of dengue fever are reported each year. The World Health Organization estimates that over 50 million cases of dengue worldwide every year.
The researchers say that programmes for the eradication of mosquitoes have meant people are less exposed to all four strains of dengue virus, and thus have reduced immunity.
Dengue infection peaked in Thailand in 2001, according to the authors, when there were more than half a million cases. By comparison, in 1995 there were fewer than 50000 cases.
"We are certainly at a point where we would actually see a decrease in the infection rate, which is substantial enough to reduce the overall number of cases of hemorrhagic fever dengue," said Katia Koelle, assistant professor of biology at the Duke University, in a news release.
