Molecular identification of Anopheles gambiae sensu stricto Giles (formerly Anopheles gambiae Savannah Form) in Kamuli District, Uganda

Abstract

Anopheles gambiae sensu stricto Giles (formerly A. gambiae S molecular form), the largely anthropophilic species, is reportedly the most important malaria vector in Uganda among the A. gambiae complex species. Indoor and outdoor human-biting mosquitoes were caught for four consecutive nights in each of 48 households in Kamuli district using human-baited bed net traps for subsequent identification of the principal Anopheles sibling species responsible for transmitting malaria. Sibling species under the A. gambiae complex were characterized by polymerase chain reaction using species specific single nucleotide polymorphism (SNPs) in the intergenic spacer region (IGS) with primers specific for A. gambiae s.s., Anopheles arabiensis, Anopheles melas, Anopheles merus and Anopheles quadriannulatus. Molecular forms of the A. gambiae s.s. were further discriminated using primers specific for Mopti and Savannah forms. Out of 300 A. gambiae s.l. amplified, 98% (n= 294) were A. gambiae s.s. Out of 142 A. gambiae s.s. samples analyzed for molecular forms, 78.9% (n=112) were identified as A. gambiae s.s. Giles (A. gambiae Savannah (S) form, while the other 21.1% were not identifiable. the presence of A. gambiae s.s. Giles in Kamuli was also reported. Considering the anthropophilic, endophagic and endophilic behavior of A. gambiae s.s. (and of the molecularly similar A. gambiae s.s. Giles), the combined use of insecticide-treated nets (ITNs), indoor residual spraying, larval source management and improved house design in the context of integrated vector management, may be the appropriate vector control strategies in the area. There is also need for regular monitoring of the vector species composition, distribution and behavior for proper planning of appropriate vector control interventions in the future.

Sibling Species Composition and Susceptibility Status of Anopheles gambiae s.l. to Insecticides Used for Indoor Residual Spraying in Eastern Uganda

“…revealed that the predominant sibling malaria vector species in the study area is A. arabiensis (95.5%). Studies in other parts of the country, for example, Tororo [ 16 ], Kamuli [ 39 ], Jinja [ 18 ], have documented sympatric existence of A. arabiensis with A. gambiae s.s. and A. funestus [ 20 ]. These three species have also been reported as the main vectors of Plasmodium falciparum malaria in Sub-Saharan Africa [ 8 , 25 , 40 ].…”

Bio-Efficacy of Insecticides Used for Vector Control in Busia and Tororo Districts, Eastern Uganda

“…Emerged adults from the reared larvae were morphologically identified using simplified standard morphological keys adopted from Gillies & Coetzee (1987) to deduce the species present (Kabbale et al, 2016). Whilst to check and to improve on the precision of the morphological identification, emerged adult mosquitoes were observed under a dissecting microscope and identified using standardized morphological keys as by Coetzee (2020).…”

“…However, this could not rule out the fact that there could be other prevailing ecological or human factors in Busia district responsible for their proliferation such as increased permanent breeding sites. The A. funestus that dominated in Busia district is known to breed all year round and prefer permanent, stagnant water bodies, while Anopheles gambiae sensu lato breed in temporary human created water bodies including rice paddies, pools, puddles, construction sites and hoof prints which were more prevalent in Tororo than Busia district [2,5,28].…”

“…High malaria transmission rates in Sub-Saharan Africa (SSA) are attributed to the continuous presence of effective and competent Plasmodium vectors, Anopheles gambiae complex and the Anopheles funestus group which play a key role in transmitting the most dangerous malaria parasite species Plasmodium falciparum The core essentials that make these species highly effective Plasmodium vectors are their preference for humans as a source of blood combined with indoor resting habits and exploitation of breeding habitats created by human activities. Information of these vector innate feeding preferences and resting habits when combined with data on host accessibility, precisely forecasts the intensity of Plas-modium transmission Plasmodium transmission in Uganda is perennial with two peaks in March to May and September to December consistent to the rainfall seasons, favoring mosquitoes to breed and also during which the vector biting density increases [1][2][3][4][5][6][7][8].…”

Species Composition and Distribution of Anopheles Mosquito Vectors in Kontagora, Niger State, Nigeria

“…The multiplex PCR technique was used for molecular characterization of members of the An. gambiae complex as described by Okwa et al (2007), Brogdon and Chan (2010) and Kabbale et al (2016). Direct method was used where legs and (or) wings of each morphologically identified member of An.…”