Transmission risk assessment of Aedes-borne arboviral diseases in Accra, Ghana

Abstract

Background: Dengue, Zika and Chikungunya are Aedes-borne viral diseases that have risen to become great global health concerns in the past years. Several countries in Africa have reported outbreaks of these diseases and despite Ghana sharing borders with some of such countries, it remains free of these outbreaks. Recent studies in Ghana have revealed that there are antibodies and viral RNA of the Dengue virus serotype-2 among individuals in some localities in the Greater Accra Region. This is an indication of a possible silent transmission ongoing in the population, hence the need to assess the risk of transmission of these viruses within the country. This cross-sectional study, therefore, assessed the risk of transmission of Dengue, Zika and Chikungunya viruses in a domestic/peri-domestic (Madina) and a forest (Achimota Forest) population in the Greater Accra Region, Ghana. Methodology/Findings: All stages of the Aedes mosquito (egg, larvae, pupae and adults) were collected around homes and in the forest area for estimation of risk indices. All eggs and immature stages were reared to adults and morphologically identified. The predominant species of Aedes mosquitoes identified from both sites were Aedes aegypti (98% in Madina and 98.1% in Achimota forest). Aedes albopictus, an important arbovirus vector, was identified only in Madina at a prevalence of 1.5% but Achimota forest had the higher species diversity. Both study sites recorded high risk indices; Madina: Positive Ovitrap Index = 26.6%, Container Index = 36.8%, House Index = 19.8%, Breteau Index = 70.4%; Achimota: Positive Ovitrap Index = 34.2% and Container Index = 67.9%. RT-PCR to detect the presence of Dengue, Chikungunya and Zika viruses was negative for all pools tested. Conclusion: All entomological risk indicators estimated showed that both sites had a high potential of an outbreak of arboviral diseases following the introduction of these viruses.