Browsing by Author "Philbert, Anitha"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Insecticide resistance in malaria vectors: seasonal susceptibility, mechanisms and relationships to agricultural practices, in Magu and Sengerema agro-ecosystem zone
    (2016) Philbert, Anitha
    Malaria is a major public health challenge, globally and in Tanzania. The main method to reduce malaria transmission is through vector control using insecticides, mainly the Pyrethroids. Pyrethroids are also widely used in agriculture, thus exerting more selection pressure among malaria vectors breeding in agricultural areas. The aim of the present study therefore, was to investigate the role of agro-chemical use, on the selection for resistance to insecticides among malaria vectors. Mosquito larvae were collected from the rice, cotton and tomato farms and reared to obtain adults for susceptibility testing. The susceptibility status of An. gambiae s.l. was assessed using WHO bioassay tests to the 5 Pyrethroids [Permethrin (0.75%), Deltamethrin (0.05%), Lambdacyhalothrin (0.05%), Etofenprox (0.5%), Cyfluthrin (0.15%)] and DDT (4%). The survivors were screened for knockdown resistance (kdr) both western (L1014F) and eastern (L1014S) variants. Questionnaires and field observations were used to assess the Knowledge, Attitude and Practices (KAP) of Farmers regarding pesticide usage and management. Pesticide residues levels in soil and sediments from the mosquitoes’ breeding habitats were determined by Gas Chromatography Mass Spectrophotometer (GS-MS. Anopheles arabiensis constitute over 90% of the natural population of An. gambiae s.l. in the studied area. Anopheles gambiae s.l. was resistant to all the insecticides tested. The East African kdr (L1014S) allele was found in 13 out of 535 specimens, (435 that survived insecticide exposures and 100 that following exposures) , the allele frequency ranged from 0.9% to 50%. Pyrethroids constitute 50% of all pesticides used against crop and livestock pests. The majority of farmers (80%) applied pesticides in mixed form and up to 15 times per cropping season. Furthermore, DDT and its metabolites (DDE & DDD) residues were found in the soil and sediment samples, the concentration ranged from undetectable amounts – 9.90 ng/g (dry weight). Vector control interventions
  • No Thumbnail Available
    Item
    Studies on the ecological adaptation of the mosquito aedes aegypti (diptera-culicidae) to urbanization, Dar es salaam
    (University of Dar es Salaam, 2011) Philbert, Anitha
    A twelve-month seasonal abundance pattern of the mosquito Aedes aegypti (Diptera-Culicidae) was studied using larvitraps (old tyres, vegetations, outdoor water storage containers and flower pots) in the four sampling sites namely, Vingunguti, Julius Nyerere International Airport (JNIA), Mbagala and Mkuranga (Vikindu). The aim was to investigate the ecological adaptation of the mosquito Ae. aegypti in response to increased urbanization in and around Dar es Salaam. Results from this study are compared to those from previous studies carried out in the same sites from 1968 to 1970s under the auspices of the East Africa Aedes Research Unit (EAARU). Human population size and buildings per unit area were used to quantify the level of urbanization between sites. Aedes aegypti mosquitoes were active during both dry and rainy seasons. Pearson’s correlation coefficient between the amount of rainfall and the abundance of Ae. aegypti mosquitoes for each site and for a particular breeding habitat revealed no significant correlation. There was no significant difference in the Abundance of Ae. aegypti between the rainy and dry season, (F= 0.08, P=0.92). Five genera of mosquitoes, Aedes, Culex, Mansonia, Anopheles, and Toxorhynchites were collected. Aedes aegypti was the dominant species (F=23.07, P<0.001) being abundant in old tyres ovi-traps (P=0.0045, t=2.878,) in both seasons than in other larvi-traps. There was a significant difference in the Ae. aegypti mosquito abundance in the four sites studied (F=3.804, P=0.005) indicative of the species’ adaptive capacity to breed in the constantly changing environment. Currently, in Dar es Salaam, the habitats have been altered into buildings and other developmental projects due to increase in urbanization level, these favour the breeding and proliferation of Ae. aegypti mosquitoes.