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Open Access Research

Differential Plasmodium falciparum infection of Anopheles gambiae s.s. molecular and chromosomal forms in Mali

Rebecca T Trout Fryxell1*, Catelyn C Nieman2, Abdrahamane Fofana3, Yoosook Lee2, Sekou F Traoré3, Anthony J Cornel4, Shirley Luckhart5 and Gregory C Lanzaro2

Author Affiliations

1 Department of Entomology and Plant Pathology, University of Tennessee, Knoxville, TN, 37996, USA

2 Vector Genetics Laboratory, Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California – Davis, Davis, CA, 95616, USA

3 Malaria Research and Training Center, University of Bamako, Bamako, Mali

4 Department of Entomology, Mosquito Control Research Laboratory, University of California – Davis, Davis, CA, 95616, USA

5 Department of Medical Microbiology and Immunology, School of Medicine, University of California – Davis, Davis, CA, 95616, USA

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Malaria Journal 2012, 11:133  doi:10.1186/1475-2875-11-133

Published: 27 April 2012

Abstract

Background

Anopheles gambiae sensu stricto (s.s.) is a primary vector of Plasmodium falciparum in sub-Saharan Africa. Although some physiological differences among molecular and chromosomal forms of this species have been demonstrated, the relative susceptibility to malaria parasite infection among them has not been unequivocally shown. The objective of this study was to investigate P. falciparum circumsporozoite protein infection (CSP) positivity among An. gambiae s.s. chromosomal and molecular forms.

Methods

Wild An. gambiae from two sites Kela (n = 464) and Sidarebougou (n = 266) in Mali were screened for the presence of P. falciparum CSP using an enzyme-linked immunosorbent assay (ELISA). Samples were then identified to molecular form using multiple PCR diagnostics (n = 713) and chromosomal form using chromosomal karyotyping (n = 419).

Results

Of 730 An. gambiae sensu lato (s.l.) mosquitoes, 89 (12.2%) were CSP ELISA positive. The percentage of positive mosquitoes varied by site: 52 (11.2%) in Kela and 37 (13.9%) in Sidarebougou. Eighty-seven of the positive mosquitoes were identified to molecular form and they consisted of nine Anopheles arabiensis (21.4%), 46 S (10.9%), 31 M (12.8%), and one MS hybrid (14.3%). Sixty of the positive mosquitoes were identified to chromosomal form and they consisted of five An. arabiensis (20.0%), 21 Savanna (15.1%), 21 Mopti (30.4%), 11 Bamako (9.2%), and two hybrids (20.0%).

Discussion

In this collection, the prevalence of P. falciparum infection in the M form was equivalent to infection in the S form (no molecular form differential infection). There was a significant differential infection by chromosomal form such that, P. falciparum infection was more prevalent in the Mopti chromosomal forms than in the Bamako or Savanna forms; the Mopti form was also the most underrepresented in the collection. Continued research on the differential P. falciparum infection of An. gambiae s.s. chromosomal and molecular forms may suggest that Plasmodium – An. gambiae interactions play a role in malaria transmission.

Keywords:
Anopheles gambiae; Mali; Malaria; Plasmodium falciparum; Molecular form; Chromosomal form