Seasonal abundance, blood meal sources and insecticide susceptibility in major anopheline malaria vectors from southern Mauritania

Abstract

BackgroundMalaria is endemic in the southernmost Sahelian zone of Mauritania where the major known mosquito vector is Anopheles arabiensis. Understanding seasonal population dynamics, feeding preferences and insecticide resistance status of these vectors in the area is essential to improve vector control measures implemented at a local scale. Here, malaria vector populations’ bionomics is described in two sentinel sites located in the Sahelian zone of Mauritania.MethodsBetween September 2014 and December 2016, longitudinal entomological surveys were conducted in Kobeni (15°49'N, 09°24'W) and Rosso (16°30'N; 15°48'W), two localities in the southern Sahelian zone of Mauritania. Adult mosquitoes were collected using indoor pyrethrum spray catch (PSC). Morphological and PCR-based methods were used to identify the species, detect Plasmodium parasites and analyze blood meals in individual mosquitoes. WHO insecticide susceptibility tests were performed with malathion (5%), bendiocarb (0.1%), permethrin (0.75%) and deltamethrin (0.05%) using female An. gambiae (s.l.) reared from larval and pupal collections from natural breeding sites.ResultsA total of 2702 Anopheles mosquitoes were collected by PSC during the study period comprising 2291 Anopheles gambiae (s.l.), 376 Anopheles rufipes and 35 Anopheles pharoensis. In Rosso, all mosquitoes from the An. gambiae (s.l.) complex were molecularly identified as An. arabiensis (n = 455/455, 100%). Anopheles pharoensis represented 2.5% (n = 35/1420) of the specimens collected by PSC in Rosso. In Kobeni, An. arabiensis was dominant (n = 278/301, 92.3%) and occurred together with Anopheles coluzzii (n = 18/301, 6%) and An. gambiae (s.s.) (n = 3/301, 1%). Two An. coluzzii × An. arabiensis hybrids were also detected (0.7%) in Kobeni, and An. rufipes was the only other Anopheles species found resting indoors (n = 376/1277, 29.4%). There was an average of 5.6 and 3.6 indoor resting female An. gambiae (s.l.) per room in Kobeni and Rosso, respectively. Indoor resting female An. gambiae (s.l.) mosquitoes in both sites fed most frequently on bovine blood (35.5% in Rosso and 37% in Kobeni). The proportion of An. gambiae (s.l.) mosquitoes that took human blood was significantly higher in Kobeni (HBI = 37%) than in Rosso (HBI = 5.6%) and 32% of An. gambiae (s.l.) mosquitoes contained blood from more than one host species. None of the 1414 tested mosquitoes in both sites were found positive for Plasmodium spp. sporozoites. WHO insecticide resistance tests revealed resistance to permethrin in the An. arabiensis population from Rosso (mortality = 64%) as well as reduced mortality to deltamethrin (mortality = 97%).ConclusionThis study provides updated information on the composition and dynamics of the malaria vector system in southern Mauritania where malaria is endemic. Such data are a necessary prerequisite to devise and implement tailored malaria elimination strategies in areas of low residual transmission.

Malaria epidemiology in Kobeni department, southeastern Mauritania from 2015 to 2017

“…Kobeni is the only sentinel site in Mauritania where studies on malaria epidemiology have been conducted regularly by several research teams over the past 20 years [2,7,9,[24][25][26][27][28][29][30][31][32][33]. Kobeni is situated within the 'heart' of area of seasonal but intense malaria transmission in Mauritania.…”

“…For instance, in our study population, the majority of febrile subjects attributed the usefulness of a bed net to the reduction of nuisance caused by mosquitoes rather than its capacity to prevent the bites of infective mosquitoes, to kill mosquitoes when it is insecticide impregnated, and as a consequence, to prevent from being infected by malaria parasites. Moreover, the level of insecticide resistance in Anopheles arabiensis is still very low (deltamethrin, 100% mortality; permethrin, 98.6% mortality) in Kobeni [9]. Therefore, there is a need to sensitize households on the sustained use of LLINs in order to optimize their role as an effective malaria control tool.…”

“…is the main malaria vector in the country [5][6][7]. Pyrethroid resistance in Anopheles arabiensis has recently been reported in the Saharan and sahelian zones [8,9].…”

Low Malaria Transmission in Rosso, an Irrigated Rice-Growing Area in Mauritania

“…The main findings of the present longitudinal study were that (i) malaria prevalence in Rosso is very low (2.2% based on RDT; 0.6% based on PCR) and (ii) high rates of mosquito net ownership and coverage (i.e., the number of ITNs per household) at the household level and high frequency of 'regular' use were observed among the study population with no variation in the seasonality of ITNs use (dry vs. wet season). Although the development and operation of water projects in this area resulted in the creation of new and highly productive mosquito larval habitats [23], these findings suggest that environmental changes had little impact on malaria transmission in Rosso.…”

First report of Anopheles (Cellia) multicolor during a study of tolerance to salinity of Anopheles arabiensis larvae in Nouakchott, Mauritania

“…melas [8]. Anopheles arabiensis is widely distributed in the Sahelian as well as the Saharan zone of the country [7,9,10]. Moreover, previous studies have shown that it is the only malaria vector encountered in Nouakchott [11,12].…”