Ecology, Distribution And Risk Of Transmission Of Viral Haemorrhagic Fevers By Aedes Mosquitoes Around The Port Areas Of Tema, Southern Ghana

ABSTRACT The genus Aedes (Diptera: Culicidae) consists of mosquitoes that are of medical and veterinary importance. They are known to serve as vectors for several arboviruses that cause diseases such as yellow fever, dengue, chikungunya and zika. These arboviruses initially circulate among wild animals with transmission to humans and agriculturally important domestic animals made possible through vectors such as mosquitoes. This therefore prompts the importance and necessity for species identification which is considered pivotal for a successful control strategy. Since the only current information on Aedes species composition in Ghana is however lacking especially when the only comprehensive study on Aedes mosquitoes in the country dates back to 1971. This study was therefore aimed at generating baseline ecological and entomological information on the different species of Aedes mosquitoes in the Port areas of Tema which consist of Golden Jubilee Terminal area of Tema Port, Tema Community One and Tema New Town, especially to delineate the extent of distribution of the invasive species Aedes albopictus which is currently being introduced into various countries through importation of used tyres. The mosquitoes from this study were collected using human landing catches, ovitraps and larval collections for a period of six months. A total of four hundred and four (404) households were surveyed for larval collections using a simple random sampling method throughout the period of survey which covered rainy and dry seasons. Mosquito larval survey was carried out using pipette, scooper or ladle depending on the container type. Ovitraps were set around the three study sites to obtain Aedes mosquito eggs. A total of 1,092 containers were inspected in both seasons and of these, 237 (21.7 %) were positive for mosquito larvae or pupae in the rainy season while 181 (16.6 %) were positive in the dry season. A total of 6,498 mosquitoes were collected and identified morphologically using taxonomic keys. Of these, 6,038 (92.9 %) were Aedes aegypti, 337 (5.2 %) were Culex spp and 123 (1.9 %) were Anopheles gambiae. The total number of mosquitoes obtained per area included 3,053 (47 %) from Tema Community One, 3,057 (47 %) from Tema New Town and 388 (6 %) from Golden Jubilee Terminal area. The Ae. aegypti larvae were found in a number of water holding containers which included disposed plastic containers, earthenware pots, car tyres, plastic barrels, plastic basins, buckets, metal drums, jerrycans and polytanks. The species was prevalent in plastic basins (36.9 %), plastic barrels (21.5 %) and car tyres (13.4 %). A high proportion of Ae. aegypti (72.1 %) eggs were found in the ovitraps during the rainy season compared to 24.9 % during the dry season. Most of the mosquito breeding occurred in the rainy season and there was a significant association between species and breeding sites (χ2 = 461.154, df = 16, P < 0.001) during both xv seasons. Ae. aegypti was the most common mosquitoes biting mostly outdoors (65.6 %) with more bites occurring in the rainy season (63.6 %) in the two residential sites (Tema Community One and Tema New Town). The risk of transmission of viral haemorrhagic fever in the study sites were assessed using House Index, Container Index, Breteau Index and were respectively as follows: Tema Community One (34.2 %, 39.4 % and 108.3 % for rainy and 23.3 %, 31.7 % and 82.5 % for dry season), Tema New Town (41.3 %, 44.9 % and 134.7 % for rainy and 28 %, 40.6 % and 109.3 % for dry season) and Golden Jubilee Terminal (14.3 %, 28.6 % and 85.7 % for rainy and 0 % for all in dry season). The man-vector contact rates for the two residential sites were 1.5 and 0.8 bites per man hour in the rainy and dry seasons respectively for Tema Community One and 1.3 and 0.8 bites per man hour in the rainy and dry seasons for Tema New Town. These observations indicate that the risk of transmission of viral haemorrhagic fevers in the study sites is highly probable.