Mosquito biting and malaria situation in an urban setting in Zambia

Abstract

Unprecedented increased mosquito bites were observed in urban and peri-urban areas of Lusaka District and there was a perceived increase in malaria which necessitated a study in 2009 to determine the mosquito biting and malaria situation within urban and peri-urban settings. We analysed water bodies as sources of mosquito larvae (vegetable gardens, sewerage maturation ponds and foot paths) and, weather factors for possible effects on mosquito densities, species distribution and reviewed laboratory confirmed malaria cases and interventions implemented in the previous five years from 2009. We collected high densities of Culex quinquefasciatus mosquito larvae (mean; 250 per scoop) from sewerage maturation ponds overgrown with water hyacinth - an aquatic vegetation and collected large numbers of adult Cx. quinquefasciatus indoor (mean: 14.2, range: 2.8 to 34 per room) and up to 2,000 Cx. quinquefasciatus out-door in one open structure. However, we did not find adult Anopheles in any of these collections but we found Anopheles larvae along a footpath in one peri-urban location. There was no evidence of increased malaria cases despite reported increased mosquito biting but a district-wide and nationwide decline in malaria trends. A combination of factors; human and environmental, created suitable micro-habitats that increased densities of the Culex mosquito but not malaria vector species within urban and peri-urban settings. An intensified surveillance, monitoring and evaluation measure is vital to understanding malaria situation and delivering effective malaria interventions in different epidemiological settings.