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Background: Aedes aegypti (Diptera: Culicidae) is the main vector of the dengue virus globally. Dengue vector control is
mainly based on reducing the vector population through interventions, which target potential breeding sites. However,
in Tanzania, little is known about this vector’s habitat productivity and insecticide susceptibility status to support
evidence-based implementation of control measures. The present study aimed at assessing the productivity and
susceptibility status of A. aegypti mosquitoes to pyrethroid-based insecticides in Dar es Salaam, Tanzania.
Methods: An entomological assessment was conducted between January and July 2015 in six randomly selected
wards in Dar es Salaam, Tanzania. Habitat productivity was determined by the number of female adult A. aegypti
mosquitoes emerged per square metre. The susceptibility status of adult A. aegypti females after exposure to
0.05% deltamethrin, 0.75% permethrin and 0.05% lambda-cyhalothrin was evaluated using the standard WHO
protocols. Mortality rates were recorded after 24 h exposure and the knockdown effect was recorded at the
time points of 10, 15, 20, 30, 40, 50 and 60 min to calculate the median knockdown times (KDT50 and KDT95).
Results: The results suggest that disposed tyres had the highest productivity, while water storage tanks had
the lowest productivity among the breeding habitats Of A. aegypti mosquitoes. All sites demonstrated reduced
susceptibility to deltamethrin (0.05%) within 24 h post exposure, with mortalities ranging from 86.3 ± 1.9 (mean
± SD) to 96.8 ± 0.9 (mean ± SD). The lowest and highest susceptibilities were recorded in Mikocheni and Sinza
wards, respectively. Similarly, all sites demonstrated reduced susceptibility permethrin (0.75%) ranging from
83.1 ± 2.1% (mean ± SD) to 96.2 ± 0.9% (mean ± SD), in Kipawa and Sinza, respectively. Relatively low mortality
rates were observed in relation to lambda-cyhalothrin (0.05%) at all sites, ranging from 83.1 ± 0.7 (mean ± SD)
to 86.3 ± 1.4 (mean ± SD). The median KDT50 for deltamethrin, permethrin and lambda-cyhalothrin were 24.9–30.
3 min, 24.3–34.4 min and 26.7–32.8 min, respectively. The KDT95 were 55.2–90.9 min for deltamethrin, 54.3–94.
6 min for permethrin and 64.5–69.2 min for lambda-cyhalothrin.
Conclusions: The productive habitats for A. aegypti mosquitoes found in Dar es Salaam were water storage
containers, discarded tins and tyres. There was a reduced susceptibility of A. aegypti to and emergence of
resistance against pyrethroid-based insecticides. The documented differences in the resistance profiles of A.
aegypti mosquitoes warrants regular monitoring the pattern concerning resistance against pyrethroid-based
insecticides and define dengue vector control strategies |
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| dc.subject |
Culicidae, Aedes aegypti, Abundance, Productivity, Pyrethroid, Knockdown effect, Dar es Salaam, Tanzania |
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