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

Abstract

The ability of Anopheles gambiae complex mosquitoes to transmit Plasmodium infection is known to be variable within sibling species of the complex with strains that cannot transmit the parasite. High sporozoite infection rate recorded showed that A. gambiae mosquitoes are potent malaria vectors in southwestern Nigeria. The aim of this study was to identify the infective and refractory strains of A. gambiae mosquitoes and to determine the sporozoite infection rate in this area. The infective strains were A. gambiae (sensu stricto) and A. arabiensis, while the refractory strains were A. gambiae (sensu stricto). However, ovarian polytene chromosome banding patterns could not be used to distinguish between the infective and refractory strains of A. gambiae (sensu stricto). This study showed that the refractory strains of Anopheles gambiae complex are present, but in low frequencies, in southwestern Nigeria, and that the sibling species of Anopheles gambiae (A. gambiae s.s. and A. arabiensis) are potent malaria vectors.

A Simple Key for Identifying the Sibling Species of the Malaria Vector Anopheles gambiae (Giles) Complex by Polytene Chromosome Cytogenetics

“…However, the fact the parasite was not successful in reaching the salivary glands of some of the mosquito's supports the reports by Julián (2010) and Chris et al (2011) that the mosquito inherent defence system is capable of terminating the development of all the parasites before they reach the salivary glands leading to total refractoriness. It also confirms the report by Obembe and Awopetu (2014) that refractory strains of A. gambiae are present in South-Western Nigeria, though at a very low frequency.…”

“…In a similar research by Obembe and Awopetu (2014) in the study area, virtually, the same results were obtained. Similar reports were also recorded by Collins et al (1986) and Alvaro et al (2012).…”

“…However, Obembe and Awopetu (2014) has reported similarly high P. falciparum sporozoite rates in the study areas. Okwa et al (2006) also reported a high sporozoite rate (62.9%) for A. gambiae in Badagry area of Lagos, Nigeria.…”

“…There is insufficient information on the identification of the sibling species of malaria vectors and their infective and refractory strains in south-western Nigeria (Obembe and Awopetu, 2014), perhaps, due to lack of facilities and funding for carrying out the molecular, PCR-based assay, method of identification. Hence, the current study was designed to promote malaria vector research, not only in Nigeria, but also in other less developed countries of the world, particularly in sub-Saharan Africa.…”

“…comorensis Brunhes, le Goff and Geoffroy (Gillies and DeMeillon, 1968;White, 1974 and1985;Hunt et al, 1998;Harbach, 2003;Coetzee et al, 2013). Amongst these sibling species, A. gambiae and A. Arabiensis are the two major malaria vectors in Africa (Gillies and De Meillon 1968), particularly in Nigeria (Boreham et al, 1979;Onyabe and Conn, 2001;Obembe and Awopetu, 2014). There are strains of A. gambiae complex sibling species in which the parasite cannot complete its life cycle; such strains are said to be refractory (Collins et al, 1986;Chris et al, 2011;Obembe and Awopetu, 2014).…”