Spatiotemporal distribution and insecticide resistance status of Aedes aegypti in Ghana

Abstract

Background Vector control is the main intervention used to control arboviral diseases transmitted by Aedes mosquitoes because there are no effective vaccines or treatments for most of them. Control of Aedes mosquitoes relies heavily on the use of insecticides, the effectiveness of which may be impacted by resistance. In addition, rational insecticide application requires detailed knowledge of vector distribution, dynamics, resting, and feeding behaviours, which are poorly understood for Aedes mosquitoes in Africa. This study investigated the spatiotemporal distribution and insecticide resistance status of Aedes aegypti across ecological extremes of Ghana. Methods Immature mosquitoes were sampled from containers in and around human dwellings at seven study sites in urban, suburban, and rural areas of Ghana. Adult Aedes mosquitoes were sampled indoors and outdoors using Biogents BG-Sentinel 2 mosquito traps, human landing catches, and Prokopack aspiration. Distributions of immature and adult Aedes mosquitoes were determined indoors and outdoors during dry and rainy seasons at all sites. The phenotypic resistance status of Aedes mosquitoes to insecticides was determined using World Health Organization susceptibility bioassays. The host blood meal source was determined by polymerase chain reaction. Results A total of 16,711 immature Aedes were sampled, with over 70% found in car tyres. Significantly more breeding containers had Aedes immatures during the rainy season (11,856; 70.95%) compared to the dry season (4855; 29.05%). A total of 1895 adult Aedes mosquitos were collected, including Aedes aegypti (97.8%), Aedes africanus (2.1%) and Aedesluteocephalus (0.1%). Indoor sampling of adult Aedes yielded a total of 381 (20.1%) and outdoor sampling a total of 1514 (79.9%) mosquitoes (z = − 5.427, P = 0.0000) over the entire sampling period. Aedes aegypti populations were resistant to dichlorodiphenyltrichloroethane at all study sites. Vectors showed suspected resistance to bendiocarb (96–97%), permethrin (90–96%) and deltamethrin (91–96%), and were susceptible to the organophosphate for all study sites. Blood meal analysis showed that the Aedes mosquitoes were mostly anthropophilic, with a human blood index of 0.9 (i.e. humans, 90%; human and dog, 5%; dog and cow, 5%). Conclusions Aedes mosquitoes were found at high densities in all ecological zones of Ghana. Resistance of Aedes spp. to pyrethroids and carbamates may limit the efficacy of vector control programmes and thus requires careful monitoring. Graphical abstract

Insecticide resistance status of Aedes aegypti in southern and northern Ghana

“…Resistance of Aedes mosquitoes to insecticides has been reported in several West African countries including Burkina Faso, Cameroon, Senegal and Ghana [ 20 – 22 ]. In Ghana, resistance of Aedes aegypti to three of the classes of insecticides [pyrethroids, the organochlorine (DDT) and carbamates] recommended by WHO for vector control has been reported [ 23 – 25 ]. Mechanisms of resistance implicated in Aedes worldwide usually involve target-site mutations and metabolic detoxification [ 26 ].…”

Insecticide resistance status of Aedes aegypti in Southern and Northern Ghana

“…Other studies in Ghana and West Africa have reported susceptibility of Ae. aegypti populations to organophosphate insecticides [25,41,51]. However, our ndings and that of other studies from Cote d'Ivoire and Senegal with recent evidence shows that organophosphate resistance is also increasing [22,33].…”

“…Evidence of pyrethroid resistance in Ae. aegypti was also established in other previous studies from Ghana [23][24][25] and other African countries [20,21,28]. However, what is driving insecticide resistance in these populations is uncertain.…”

“…These ndings are similar to that of another study in Ghana, where the most predominant species in urban and suburban sites was Ae. aegypti [25] and generally are more likely to be found in urban and suburban areas [1,49]. Aedes aegypti was the most common species across six regions in Ghana based on surveillance data obtained from 2015 to 2016 by Amoa-Bosompem et al [50].…”

“…Resistance of Aedes mosquitoes to insecticides has been reported in several West African countries including Burkina Faso, Cameroon, Senegal and Ghana [20][21][22]. In Ghana, resistance of Aedes aegypti to three of the classes of insecticides (pyrethroids, the organochlorine (DDT) and carbamates) recommended by WHO for vector control has been reported [23][24][25]. Mechanisms of resistance implicated in Aedes worldwide most commonly involve target-site mutations and metabolic detoxi cation [26].…”