Anopheles gambiae and Anopheles arabiensis population densities and infectivity in Kopere village, Western Kenya

  • Andrew Ambogo Obala School of Medicine, Moi University, PO Box 4606-30100, Eldoret, Kenya
  • Helen L Kutima Jomo Kenyatta University of Agriculture and Technology (JKUAT), PO Box 62000-00200, Nairobi, Kenya
  • Henry D.N. Nyamogoba School of Medicine, Moi University, PO Box 4606-30100, Eldoret, Kenya
  • Anne W Mwangi USAID-Academic Model Providing Access to Healthcare, IU-Kenya Partnership, Eldoret, Kenya
  • Chrispinus J Simiyu USAID-Academic Model Providing Access to Healthcare, IU-Kenya Partnership, Eldoret, Kenya
  • Gideon N Magak School of Medicine, Moi University, Eldoret, Kenya
  • Barasa O Khwa-Otsyula School of Medicine, Moi University, Eldoret, Kenya
  • John H Ouma Institute of Tropical Medicine and Infectious Diseases, JKUAT, Nairobi, Kenya
Keywords: malaria, anopheles, climate, infectivity, transmission

Abstract

Introduction: This study was conducted in a sugar belt region of western Kenya interfacing epidemic and endemic malaria transmission. We investigated Anopheles gambiae sensu stricto (ss) and Anopheles arabiensis species compositions and densities, human host choice, and infectivity.

Methodology: Mosquitoes were captured using pyrethrum spray catch technique and first identified based on morphology; species were confirmed by PCR. Blood meal preference and sporozoite rates were determined by ELISA. Parity rates and entomological inoculation rates (EIR) were determined. Seasonal densities were compared against environmental temperatures, relative humidity and rainfall.

Results: In total 2,426 An. gambiae were collected.  Out of 1,687 female blood-fed mosquitoes, 272 were randomly selected for entomological tests. An. gambiae ss and An. arabiensis comprised 75% (205/272) and 25% (68/272) of the selection, respectively. An. gambiae ss had higher preference for human blood (97%; n=263/272) compared with An. arabiensis, which mostly fed on bovines (88%; n=239/272).  The sporozoite and parity rates were 6% (16/272) and 66% (179/272) for An. gambiae ss and 2% (4/272) and 53% (144/272) for An. arabiensis respectively, while EIR was 0.78 infective bites/person/night.  Climate (ANOVA; F=14.2; DF=23) and temperature alone (r=0.626; t=3.75; p=0.001) were significantly correlated with vector densities.

Conclusion: An. gambiae ss are the most efficient malaria vector mosquito species in Kopere village. Because An. gambiae ss largely rests and feeds indoors, use of indoor residual spray and insecticide-treated nets is likely the most suitable approach to malaria vector control in Kopere village and other parts of Kenya where this species is abundant. 

Author Biography

Andrew Ambogo Obala, School of Medicine, Moi University, PO Box 4606-30100, Eldoret, Kenya

Dr. Andrew A Obala

Lecturer

Medical Parasitology and Entomology

Department of Medical Microbiology and Parasitology

Moi University, School of Medicine

PO Box 4606, ELDORET, Kenya.

Published
2012-08-21
How to Cite
1.
Obala AA, Kutima HL, Nyamogoba HD, Mwangi AW, Simiyu CJ, Magak GN, Khwa-Otsyula BO, Ouma JH (2012) Anopheles gambiae and Anopheles arabiensis population densities and infectivity in Kopere village, Western Kenya. J Infect Dev Ctries 6:637-643. doi: 10.3855/jidc.1979
Section
Original Articles