Study shows paradoxical relationship between dengue hemorrhagic fever and its carrier mosquitoes

[Sally Furniss]

Study shows paradoxical relationship between dengue hemorrhagic fever and its carrier mosquitoes

A study by researchers in Thailand, Japan, and the UK has shown a negative correlation between dengue hemorrhagic fever (DHF) and the density of the Aedes mosquitoes that transmit the virus. The study, published July 16th in the open-access journal PLoS Neglected Tropical Diseases, explains how current efforts to reduce the mosquitoes may actually increase the incidence of the potentially fatal viral disease.
At least tens of millions of people are infected by dengue virus every year. Therefore, health authorities in tropical countries and the World Health Organization, have organized tremendous efforts towards the reduction of Aedes mosquitoes. However, the number of DHF patients continues to increase. To find an answer to this paradox, the researchers tested the hypothesis that more people with a mosquito-borne illness exist where there are more mosquitoes.
The researchers organized community volunteers who visited one million houses in Thailand and surveyed local densities of Aedes mosquitoes. They then compared this data to the number of people with DHF from each of 1,000 districts visited. The researchers found the incidence of DHF in areas of moderate mosquito density to be 40% higher than in areas of the highest mosquito density.
The researchers hypothesized that this paradoxical relationship is due to the peculiar fact that DHF develops most frequently when the patient is infected with dengue a second time. The results of this study imply that the current strategy of dengue control ? reducing Aedes mosquitoes ? may not necessarily be beneficial.
Additionally, the researchers developed computer simulation software based upon their hypothesis. The simulation predicted that epidemiological studies should be continued for a very long duration, preferably over a decade, to clearly detect such a paradoxical relationship between Aedes abundance and incidence of DHF. Such long-term studies are necessary, especially because tremendous efforts and resources have been (and perhaps will be) spent on combating Aedes.

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PLEASE ADD THIS LINK TO THE PUBLISHED ARTICLE IN ONLINE VERSIONS OF YOUR REPORT: http://www.plosntds.org/doi/pntd.0000263 (link will go live on Wednesday, July 16)
CITATION: Thammapalo S, Nagao Y, Sakamoto W, Saengtharatip S, Tsujitani M, et al. (2008) Relationship between Transmission Intensity and Incidence of Dengue Hemorrhagic Fever in Thailand. PLoS Negl Trop Dis 2(7): e263. doi:10.1371/journal.pntd.0000263
CONTACT:
Dr. Yoshiro Nagao
Osaka University Graduate School of Medicine
2-2 Yamadaoka, Suita, 565-0871, Japan
Email: nagaoy@anes.med.osaka-u.ac.jp


http://www.eurekalert.org/pub_releases/2008-07/plos-ssp070908.php

 

[tropical]

Re: Study shows paradoxical relationship between dengue hemorrhagic fever and its carrier mosquitoes

"The researchers found the incidence of DHF in areas of moderate mosquito density to be 40% higher than in areas of the highest mosquito density.
The researchers hypothesized that this paradoxical relationship is due to the peculiar fact that DHF develops most frequently when the patient is infected with dengue a second time. The results of this study imply that the current strategy of dengue control — reducing Aedes mosquitoes — may not necessarily be beneficial."

A classical un-logic study-type outcome.

Maybe to refine the study.
Obviously the populations of historical endemic area with highest mosquito density have more resistance, like for other gastro/... illness.
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I must than leave more open water containers to increase the mosquito number - that will shield me better from the illness than their extermination ...