Spatio-Temporal Distribution And Insecticide Resistance Status Of Aedes Mosquitoes In Ghana

ABSTRACT

Background: The Aedes mosquito is an important vector of arboviruses, which include the Yellow fever virus (YFV), Dengue virus (DENV), and Chikungunya virus (CHIKV). Spatial distribution by their shared vectors is grounded on environmental and demographic factors. Currently, vector control is still the main instrument to reduce or eradicate incidence of arboviruses since there are no effective vaccines for a number of public health important arboviruses. With an upsurge in insecticide resistance, surveillance of the target population for ideal choice of insecticides is of great significance. The feeding habits of Aedes mosquitoes is more likely anthropophilic, exophagic and endophilic. For such reason, they can serve as vectors for numerous pathogens responsible for both human and animal diseases.

Aim of Study: This study investigated the spatio-temporal distribution and insecticide resistance status of Aedes mosquitoes in Ghana.

Method: The study was a cross-sectional study. Mosquito samples were collected from seven study sites in three ecological zones of Ghana. Indoor and outdoor sampling was done with Biogent sentinel-2 mosquito traps (BG traps), human landing catch (HLC) and prokopack aspirator (PPK). The mosquito vectors were sorted into species morphologically. Their spatial and temporal distribution was determined seasonally, indoor and outdoor for all site. Phenotypic resistance status of Aedes mosquitoes to insecticides was determined using the WHO susceptibility bioassay. Host blood meal sources was determined by PCR.

Results: A total of 2193 adult Aedes mosquitos were collected in this study; Aedes aegypti (97.3%), Aedes africanus (2.2%) and Aedes luteocephalus (0.05%). The human landing catch method recorded the highest densities of 210.9 (77%) followed by PPK 74 (17.8%) and BG trap 15.5 (5.2%). The dry and wet seasons recoded 73.5 (42.1%) and 103.95 (57.9%) respectively.

A total of 390 resting female adult Aedes mosquito were collected using the PPK method: The gonotrophic status of the Aedes collected using the Prokopack were 68.9 % (269/390) unfed, 11.3% (44/390) blood-fed, 17.9% (70/390) half-gravid and 1.8% (7/390) gravid. The test results showed that Aedes mosquito populations from all study sites were resistant to DDT (0 - 84%) mortality. Vectors showed resistance to deltamethrin in Tema (68%) and patchy resistance in the other sites. Vectors showed resistance to permethrin in Accra (40.0%) and Larabanga (88.8%), patchy resistance in Dwease (90%), Navrongo (90%) and Paga (96%). Aedes mosquitoes showed resistance to bendiocarb in Larabanga, susceptibility in Ada foah and Accra, patchy resistance in Tema (95.0%), Accra (97.5%), Dwease (96.3%), Navrongo (96%) and Paga (97%). Aedes mosquitoes were susceptible to organophosphates in all the sites. Blood meal analysis showed that the Aedes mosquitoes were mostly anthropophilic with HBI of 0.9 i.e. [(human = 90%), (human and dog = 5%), (dog and cow = 5%)].

Conclusion: Aedes mosquitoes are found in all the ecological zones of Ghana and have the potential to contribute actively to arboviral transmission. The development of resistance to pyrethroids and carbamates by these mosquitoes may have an operational impact on the efficacy of insecticide on vector control interventions.