Equivalent susceptibility of Anopheles gambiae M and S molecular forms and Anopheles arabiensis to Plasmodium falciparum infection in Burkina Faso

Abstract

BackgroundThe Anopheles gambiae sensu lato (s.l.) species complex in Burkina Faso consists of Anopheles arabiensis, and molecular forms M and S of Anopheles gambiae sensu stricto (s.s.). Previous studies comparing the M and S forms for level of infection with Plasmodium falciparum have yielded conflicting results.MethodsMosquito larvae were sampled from natural pools, reared to adulthood under controlled conditions, and challenged with natural P. falciparum by experimental feeding with blood from gametocyte carriers. Oocyst infection prevalence and intensity was determined one week after infection. DNA from carcasses was genotyped to identify species and molecular form.ResultsIn total, 7,400 adult mosquitoes grown from wild-caught larvae were challenged with gametocytes in 29 experimental infections spanning four transmission seasons. The overall infection prevalence averaged 40.7% for A. gambiae M form, 41.4% for A. gambiae S form, and 40.1% for A. arabiensis. There was no significant difference in infection prevalence or intensity between the three population groups. Notably, infection experiments in which the population groups were challenged in parallel on the same infective blood displayed less infection difference between population groups, while infections with less balanced composition of population groups had lower statistical power and displayed apparent differences that fluctuated more often from the null average.ConclusionThe study clearly establishes that, at the study site in Burkina Faso, there is no difference in genetic susceptibility to P. falciparum infection between three sympatric population groups of the A. gambiae s.l. complex. Feeding the mosquito groups on the same infective blood meal greatly increases statistical power. Conversely, comparison of the different mosquito groups between, rather than within, infections yields larger apparent difference between mosquito groups, resulting from lower statistical power and greater noise, and could lead to false-positive results. In making infection comparisons between population groups, it is more accurate to compare the different groups after feeding simultaneously upon the same infective blood.

<span>Sporozoite Infection Rate and Identification of the Infective and Refractory Species of <i>Anopheles gambiae</i> (Giles) Complex</span>

“…This suggests a geographic scale of adaptation and sympatric association between the parasite and the vector. Similar reports of geographic scale of adaptation (Haris et al, 2012) and sympatric association (Gnémé et al, 2013) have been posited. This is also in agreement with the reports of Collins et al (1986), Molina-Cruz et al, (2012) that showed the survival of P. falciparum in A. gambiae mosquitoes seemed to correlate with their geographical origin.…”

“…For the infection experiment, the female mosquitoes were starved for 18 to 20 hours prior to feeding them with the infectious blood meal (Gnémé et al, 2013). On the 5 th day of emergence, the identified A. gambiae females were infected by allowing them to feed on an individual who had been diagnosed positive for infection by P. Falciparum, following the regulations of Department of Health and Human Services (HHS, 2009).…”

The kdr-bearing haplotype and susceptibility to Plasmodium falciparum in Anopheles gambiae: genetic correlation and functional testing

“…In order to collect a random sample of essentially unrelated individuals, fewer than ten larvae were collected from any one larval site and a single collection comprised larvae from >50 larval sites. Collections were done in the Sudan Savanna region of Burkina Faso in the village of Goundry (12°30′N, 1°20′W), 30 km N of the capital city, Ouagadougou, across months of the malaria transmission season of 2007 and 2008 [ 29 ]. Larvae were raised in Centre National de Recherche et de Formation sur le Paludisme (CNRFP) insectaries in Ouagadougou to adulthood under standard insectary conditions [ 29 ].…”

“…Collections were done in the Sudan Savanna region of Burkina Faso in the village of Goundry (12°30′N, 1°20′W), 30 km N of the capital city, Ouagadougou, across months of the malaria transmission season of 2007 and 2008 [ 29 ]. Larvae were raised in Centre National de Recherche et de Formation sur le Paludisme (CNRFP) insectaries in Ouagadougou to adulthood under standard insectary conditions [ 29 ]. Following emergence, 3-day old adults were challenged with wild P. falciparum by experimental infection.…”

Reticulate Speciation and Barriers to Introgression in theAnopheles gambiaeSpecies Complex

“…Prior to the 1940s, A. gambiae was considered a single biologically variable species, but crossing studies and genetic analysis led to the naming of nine morphologically similar species that vary in their geographic distribution, geographic overlap with other complex members, and ecology (reviewed in Coetzee et al 2013). It is becoming increasingly appreciated from ecological distinctions and recent discoveries of additional genetic substructure that, even within species, Anopheles species frequently form partially reproductively isolated and differentiated subpopulations (Costantini et al 2009; Gnémé et al 2013; Lee et al 2013). As an example of this dynamic, a new subgroup of A. gambiae s.l.…”