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Industry: Email Alert RSS FeedDengue emergence and adaptation to peridomestic mosquitoes
Emerging Infectious Diseases, Oct, 2004 by Abelardo C. Moncayo, Zoraida Fernandez, Diana Ortiz, Mawlouth Diallo, Amadou Sall, Sammie Hartman, C. Todd Davis, Lark Coffey, Christian C. Mathiot, Robert B. Tesh, Scott C. Weaver
Ae. aegypti from Mae Sed, Tak, Thailand, were also less susceptible than the Galveston population to DENV-2 strains used in this study, with the exception of endemic DENV-2 strain 1349 from Burkina Faso (infection and dissemination rates were 94.3% and 80%, respectively, with this strain) (Table 4). Like the Galveston and Bolivian populations, the Thai population exhibited consistent differences in susceptibility to endemic versus sylvatic strains (33.0%-94.3% infection with the endemic strains vs. 0%-13% for sylvatic strains; 84.8%-90.9% dissemination rate for endemic strains vs. 0%-50% for sylvatic strains). Infection rates for both endemic strains were higher than for the pooled sylvatic rates (p < 0.001), while dissemination rates were not significantly different (p > 0.1).
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Ae. albopictus Susceptibility
Like Ae. aegypti, Ae. albopictus from Galveston, Texas, exhibited greater susceptibility to endemic than sylvatic DENV strains. After ingesting blood meals containing 6.5-8.0 [log.sub.10] TCI[D.sub.50]/mL of endemic strains, 92.3%-100% of mosquitoes became infected, with high rates of dissemination (Table 5). In contrast, only 11.1% of mosquitoes became infected after ingesting 8.0 [log.sub.10] TCI[D.sub.50]/mL of the sylvatic strain. The infection rates for endemic strains were higher than for sylvatic strains (p < 0.0001), but the difference in dissemination was not significant (p = 1.000; only one infected mosquito with a sylvatic strain was tested and exhibited dissemination).
Ae. albopictus from two different locations in Brazil were also tested. One location was urban, Pindamonhangaba, while the other, Pedrinhas, was rural. Again, a significant difference in susceptibility was observed between endemic (strain New Guinea C) and sylvatic (strain 33974) infections with F1 mosquitoes of both geographic locations (Pindamonhangaba, p < 0.001, Pedrinhas, p < 0.001). However, no significant differences were detected in dissemination rates for either F1 mosquito population (p > 0.1). For the Pedrinhas mosquito population, F2 mosquitoes were tested with additional endemic and sylvatic strains. Again, the endemic strains infected at a higher rate (p < 0.001) than sylvatic strains, even when blood meal titers were lower (Table 6). Dissemination rates were also markedly different (p = 0.004).
Geographic Variation in Susceptibility among Mosquito Populations
Geographic variation for DENV susceptibility has been reported previously for both Ae. aegypti and Ae. albopictus (18,19). We found geographic variation among populations of both species. In general, Ae. aegypti from Galveston, Texas, were more susceptible than those from Bolivia (p < 0.001) but not those from Thailand (p > 0.1). Ae. albopictus from Galveston were also more susceptible to DENV-2 infection than those collected in Brazil (p = 0.009).
Overall Trends
In general, in the 701 peridomestic mosquitoes from four localities used in this study, we found high susceptibility to endemic DENV-2 isolates but much less susceptibility to sylvatic strains. These differences were detected despite the blood meal titers of sylvatic strains being equal to or greater than those of endemic strains. Dissemination rates within infected mosquitoes generally showed no significant difference between endemic and sylvatic strains. Our data also indicated that Ae. albopictus was more susceptible to endemic DENV-2 strains than Ae. aegypti (overall 94% vs. 69% infection rates). Comparing Ae. aegypti and Ae. albopictus from one geographic location, Galveston, we did not find a difference between mosquito species when we compared infection with endemic strains 1349 (p > 0.1) or the New Guinea C strain (p > 0.1). However, Galveston Ae. aegypti were more susceptible to sylvatic strain 33974 than were Ae. albopictus from Galveston (p = 0.026).
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