Insecticide resistance testing in malaria vectors in Tanzania: Challenges in mosquito sampling and rearing under field conditions

Abstract

Background: The National Institute for Medical Research, Amani centre, in collaboration with National Malaria Control Programme, has been conducting annual insecticide resistance surveillance since 1999, aimed at early detection of resistance to insecticides used for malaria control in Tanzania. The Standard WHO method for larvae collection and rearing were used but challenges and limitations were encountered. For example rearing the larvae and adult mosquitoes using the Standard WHO method experienced 100% mortality for larvae; and adults in three days. The researchers therefore made modifications to the Standard WHO method to create suitable tools for the field environment. Methods: A ladle was created from an empty water bottle in which an oval hole longitudinally cut halfway from the bottom. Instead of using TetraMin as mosquito larval food, green algae were collected from mosquito breeding sites and used as larval food. Improvised heater of charcoal stoves and humidifier of wet fabric such as "Kanga" and "Kitenge" were also used. Results and conclusion: There was 90% larval survival, adult mosquito survived much better and the scientists had a total of 467 mosquitoes to run the insecticide susceptibility tests. Innovative ways are necessary under field conditions for mosquito breeding in susceptibility studies.

Effect of physicochemical parameters on Anopheles and Culex mosquito larvae abundance in different breeding sites in a rural setting of Muheza, Tanzania

“…To obtain adult mosquitoes for morphological identification, larvae were sampled using a standard dipping technique from various breeding sites in each village using two types of dipper. One was the standard dipper described by WHO [ 7 ] and the other was an improvised dipper described by Emidi et al [ 25 ] which is suitable for small breeding sites such as animal hoof prints. A total of 50 to 100 mosquito larvae were collected per village and reared at the insectary for morphological identification of emerging adults.…”