Aedes albopictus mosquito during the bite at the skin. Courtesy of IRD/Philippe BOUSSES
How many mosquitoes live in your neighborhood? How many mosquito bites have you and your neighbors gotten this week? Answering these questions--and gauging how mosquito populations change over time or after a control strategy is implemented--has historically been difficult. Now, researchers reporting in PLOS Neglected Tropical Diseases have described a blood test that can be used to assess human exposure to Aedes mosquitos. The test, which measures antibodies to an Aedes salivary peptide, showed decreased human exposure to mosquito bites after a vector control program.
Various species of Aedes mosquitoes can carry dengue fever, chikungunya virus, Zika fever, and yellow fever, among other pathogens. To slow the spread of these diseases, efforts have been made to control Aedes populations. But determining whether control efforts are working has typically required time and labor-intensive monitoring of larval habitats and mosquito traps. Recently, researchers developed tests that determine whether someone has been bitten by a specific Aedes species by measuring whether their blood has antibodies that react to that species' saliva, but working with the whole saliva required is challenging.
In the new work, author Franck Remoue, of the MIVEGEC unit of the Institut de Recherche pour le Developpement (IRD) France, and colleagues tested whether antibodies against one individual peptide from Aedes aegypti saliva could be indicative of exposure to other Aedes species. The team collected four sequential blood samples--before, during, and after a mosquito control intervention--from 102 adults in Saint-Denis, a city on the Indian Ocean island La Reunion where Aedes albopictus, but not Aedes aegypti, are endemic. Mosquitos were also tallied using traditional mosquito trap and larval counting methods during the intervention, which involved spraying insecticide and physical elimination of mosquito breeding sites.
Despite being exposed only to Aedes albopictus mosquitos, 88 percent of people in the study had a positive antibody reaction to the Aedes aegypti salivary peptide, before vector control. 30 days after the control strategy was implemented, that number felt to 68 percent, a trend that was also seen in the manual tallying of larva and adult mosquitos. Moreover, on an individual basis, the level of the antibody immune response decreased significantly between the time points after vector control. Future studies will be needed to validate the tests in children and determine the ideal timing of testing to gauge the effectiveness of mosquito control strategies.
"These results validate the usefulness of the antibody response to one salivary antigen for evaluating human exposure to Aedes bites and for monitoring vector control strategies against arboviral diseases," the researchers conclude.
Reference: Elanga Ndille E, Doucoure S, Poinsignon A, Mouchet F, Cornelie S, D'Ortenzio E, et al. (2016) Human IgG Antibody Response to Aedes Nterm-34kDa Salivary Peptide, an Epidemiological Tool to Assess Vector Control in Chikungunya and Dengue Transmission Area. PLoS Negl Trop Dis 10 (11): e0005109. doi:10.1371/journal.pntd.0005109