Abstract
To assess the risk of transmission of viral haemorrhagic fevers in northern Ghana. A two-year cross-sectional entomological study was carried out in four communities in the northern part of Ghana. Standard WHO methods were used to collect adult and larvae of Aedes mosquitoes to estimate man-vector contact rates and larval indices. A total of 2804 households were surveyed to estimate larval indices and man-vector contacts of potential vectors of viral haemorrhagic fevers such as Yellow fever and Dengue. Over 56% households in each study site were positive for Aedes larvae. Relatively higher Breteaux index (BI) and Container index (CI) were estimated in Damongo (BI: 180 and CI: 44.8) and Jirapa (BI: 149.7 and CI: 41.5) compared to Tumu (BI: 76.1 and CI: 19.5) and Bolgatanga (BI: 72.4 and CI: 20.6). Man-biting rates of 9.8 and 18.5 bites /man/hour were estimated for Damongo and Jirapa respectively whilst Bolgatanga recorded 10 B/M/H. Generally, man-vector contact rates in all the study sites were higher during the dry season than the wet season. Larval indices showed seasonal variations and the dry season was identified as the high-risk period for transmission of viral haemorrhagic fevers and possible disease outbreaks. No flavivirus was detected in the 2034 Aedes mosquitoes from the study sites by RT-PCR. Aedes mosquito larval densities and adult biting rates, in all the study areas were sufficient to promote outbreaks of viral haemorrhagic fevers.
Highlights
Epidemics of viral haemorrhagic fevers including Yellow fever (YF), Dengue haemorrhagic fever (DHF) and Dengue (DEN) transmitted mainly by mosquitoes pose significant public health problems in the tropics[1, 2]
This paper reports on the entomological assessment of risk of transmission of viral haemorrhagic fevers (YF and DEN) in some communities in the northern regions of the country
More than 56% households at each study site were positive for Aedes larvae, and Damongo and Jirapa recorded the highest larval indices (Table 1)
Summary
Epidemics of viral haemorrhagic fevers including Yellow fever (YF), Dengue haemorrhagic fever (DHF) and Dengue (DEN) transmitted mainly by mosquitoes pose significant public health problems in the tropics[1, 2]. Yellow fever outbreaks are known to recur every ten to twelve years in the southern sector of Ghana.[4] In a recent study of a suspected yellow fever epidemic in northern Ghana, only two of 96 blood samples of patients suspected to have haemorrhagic fever were yellow fever positive; the identity of the rest could not be established using conventional methods (Osei-Kwasi, personal Communication, 2004.). This suggests that other viruses or perhaps yellow fever virus presenting different epitopes may have been involved. Vectors of both YF and DEN, have been implicated in some of the YF outbreaks in Ghana[3,4,5]
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