Beyond the entomological inoculation rate: characterizing multiple blood feeding behavior and Plasmodium falciparum multiplicity of infection in Anopheles mosquitoes in northern Zambia. Issue 1 (December 2017)

• Record Type: Journal Article
• Authors: Das, Smita; Muleba, Mbanga; Stevenson, Jennifer; Pringle, Julia; Norris, Douglas
• Is Part Of: Parasites & vectors. Volume 10:Issue 1(2017)
• Page Start: 1
• Page End: 13
• Publication Date: 2017-12
• Subjects: Malaria -- Anopheles mosquitoes -- Entomological inoculation rate -- Multiplicity of infection -- Zambia -- ICEMR; Parasitism -- Periodicals; Parasites -- Periodicals; Vector-pathogen relationships -- Periodicals; Animals as carriers of disease -- Periodicals; Insects as carriers of disease -- Periodicals; 616.96
• DOI: 10.1186/s13071-017-1993-z
• Languages: English
• ISSNs: 1756-3305

Abstract

Abstract Background A commonly used measure of malaria transmission intensity is the entomological inoculation rate (EIR), defined as the product of the human biting rate (HBR) and sporozoite infection rate (SIR). The EIR excludes molecular parameters that may influence vector control and surveillance strategies. The purpose of this study was to investigateAnopheles multiple blood feeding behavior (MBF) andPlasmodium falciparum multiplicity of infection (MOI) within the mosquito host in Nchelenge District, northern Zambia. Mosquitoes were collected from light traps and pyrethroid spray catch in Nchelenge in the 2013 wet season. All anophelines were tested for blood meal host, P. falciparum, and MOI using PCR. Circumsporozoite (CSP) ELISA and microsatellite analysis were performed to detect parasites in the mosquito and MBF, respectively. Statistical analyses used regression models to assess MBF and MOI and exact binomial test for human sex bias. Both MBF and MOI can enhance our understanding of malaria transmission dynamics beyond what is currently understood through conventional EIR estimates alone. Results The dominant malaria vectors collected in Nchelenge wereAnopheles funestus (sensu stricto ) andAn. gambiae (s.s. ) The EIRs ofAn. funestus (s.s. ) andAn. gambiae (s.s. ) were 39.6 infectious bites/person/6 months (ib/p/6mo) and 5.9 ib/p/6mo, respectively, and took multiple human blood meals at high rates, 23.2 and 25.7% respectively. There was no bias in human host sex preference in the blood meals. The SIR was further characterized for parasite genetic diversity. The overallP. falciparum MOI was 6.4 in infected vectors, exceeding previously reported average MOIs in humans in Africa. Conclusions BothAnopheles MBF rates andP. falciparum MOI in Nchelenge were among some of the highest reported in sub-Saharan Africa. The results suggest an underestimation of the EIR and large numbers of circulating parasite clones. Together, the results describe important molecular aspects of transmission excluded from the traditional EIR measurement. These elements may provide more sensitive measures with which to assess changes in transmission intensity and risk in vector and parasite surveillance programs.