Species composition and risk of transmission of Aedes-borne arboviruses around some Yellow hotspot areas in Northern Ghana

Abstract

Aedes-borne viral diseases mainly Yellow Fever (YF), Dengue (DEN), Zika (ZIK) and Chikungunya (CHK) have contributed to many deaths in the world especially in Africa. There have been major outbreaks of these diseases in West Africa. YF outbreaks have occurred in Ghana. Although Ghana has not recorded any outbreak of DEN, ZIK and CHK, the risk is high due to its proximity to West African countries where outbreaks have been recently been recorded. This study assessed the risk of transmission of Yellow fever (YFV), Dengue (DENV), Chikungunya (CHKV) and Zika (ZIKV) viruses in Larabanga and Mole Game Reserve areas in Northern Ghana. The immature and adult stages of Aedes mosquitoes were collected from Larabanga and Mole Game Reserve area. There was a significant (P>0.001) number of mosquitoes collected during the rainy season than the dry season. A total of 1,930 Aedes mosquitoes were collected during the rainy season and morphologically identified. Of these, 1,915 (99.22%) were Aedes aegypti and 15 (0.22%) were Aedes vittatus. During the dry season, 27 Aedes aegypti mosquitoes were collected. A total of 415 Ae. aegypti mosquitoes were molecularly identified to subspecies level of which Aedes (Ae) aegypti aegypti was the predominant subspecies. Both Ae. aegypti aegypti and Ae aegypti formosus exist in sympatry in the area. All Aedes pools (75) were negative for DENV, ZIKV and CHKV when examined by RT-PCR. Three Larval indices namely House Index, HI (percentage of houses positive for Aedes larvae or pupae), Container Index, CI (the percentage of containers positive for Aedes larvae or pupae) and Breteau Index, BI (the number of positive containers (with larvae and/or pupae per 100 inspected houses) were assessed as a measure for risk of transmission. The HI, CI and BI for both sites were as follows; Mole game reserve (HI, 42.1%, CI, 23.5% and BI, 100 for rainy season and 0 for all indices for dry season) and Larabanga (39%, 15.5% and 61 for rainy season and 2.3%, 1.3% and 2.3 for dry season). The spatial distribution of Aedes breeding sites in both areas indicated that Aedes larvae were breeding in areas with close proximity to humans. Lorry tires were the main source of Aedes larvae in all the study areas. Information about the species composition and the potential role of Aedes mosquitoes in future outbreaks of the diseases that they transmit is needed to design efficient surveillance and vector control tools.