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The acute febrile illness comprises the majority of the disease burden to most populations in sub-saharan Africa. Studies suggest that malaria may be over-diagnosed, that may lead to a significant proportion of febrile diseases to be caused by pathogens not frequently considered in most settings in sub-saharan Africa. Climate change, increasing globalization and ease of travel could favor the continuing spread of mosquito to non indigenous habitats, expanding the number of regions in the world where local transmission of the vector-borne disease could occur. The major vectors of human arboviruses are Aedes species mosquito, belonging to the Stegomyia subgenus. These vectors cause outbreaks of chikungunya and dengue fever.
This study aimed at determining the distribution and the general biology of Aedes species of medical importance in Moshi, Northern Tanzania. The specific objectives were; to determine the distribution of Aedes species in different environments, to determine the feeding patterns of mosquito, to determine the susceptibility status of Ae. aegypti to insecticides and to determine arbovirus infectivity rates in Aedes aegypti.
The study was conducted in Moshi Urban and Rural districts, northern Tanzania during dry and early rainy seasons from December, 2011 to April 2012. The average mean temperature was 270C while mean annual rainfall was 170mm. Global Positioning System data was collected from study sites. Mosquito collections were done by using old tyres for larvae and pupae and MM trap for adults. Human landing catches were done to study mosquito feeding behaviour. Adult Aedes mosquitoes from field collections and insectary strain were tested for susceptibility to Permethrin (0.75%) and DDT (4.0%). Adult Ae. aegypti were preserved in -800C and shipped to Singapore for virus infectivity.
On the basis of elevation and geographical differences, urban upland sites had the highest larvae mean catch (247.0) per visit and 2228 adult collections of Ae. aegypti. Feeding patterns observed from urban upland and rural lowland showed that Ae. aegypti were most active during early and late hours of the day.
Ae. aegypti were mostly found in urban upland areas. Low numbers of Aedes species were observed in rural lowland (B) despite presence of large banana plantations whose leaf axils can serve water receptacles for breeding of the mosquitoes. Ae. aegypti were susceptible to both Permethrin (0.75%) and DDT (4.0%).
In this study Ae. aegypti was found to be abundant in rural upland areas due to miscellaneous disposal of containers such as old tyres and tins. Outdoor biting of Ae. aegypti was active during the early and late hours of the day, when temperatures were low and relative humidity was high and also when human hosts were most active outdoors.
Due to increase and spread of chikungunya and dengue infections in Tanzania, there is urgent need to conduct large scale epidemiological studies in several parts of the country and plan strategic control measures for Ae. aegypti, probably by applying insecticides and repellents. |
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