Impact of irrigated urban agriculture on malaria transmission in two cities in Ghana

Klinkenberg, Eveline. (2006) Impact of irrigated urban agriculture on malaria transmission in two cities in Ghana. PhD thesis, University of Liverpool.

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Abstract

In rapidly expanding cities worldwide, urban agriculture is being promoted to increase food security, improve nutritional status and contribute to poverty alleviation. However, there is a concern that urban agriculture, especially when irrigated, could increase urban malaria transmission by providing breeding places for Anopheles. To investigate tIus, epidemiological and socio-economic baseline surveys were carried out in tIle two main cities in Ghana, Accra and Kumasi, where communities close to (VA) and far from agriculture (U) were selected. A total of3525 children (1744 in Accra and 1781 in Kumasi) were enrolled in a house to house survey for malaria parasitaemia, Hb concentration and socio-economic factors. Although overall malaria prevalence was higher in Accra than Kumasi (14.8%, 95% CI 13.1-16.5% and 8.6%, 950/oCl 7.3- 9.9%, P=0.001), in bOtIl cities, malaria prevalence was heterogeneous, ranging from 3-35% between conmmnities. Factors associated witIl malaria prevalence were low socio-economic status, higher age and anaenua. In Accra, but not in Kumasi, conmmnities near urban agriculture had significantly lligher malaria prevalence (OR 1.53, 950/oCl 1.10-2.14, P=0.008) and some, but not all, cOimnunities showed a significant inverse link between malaria prevalence and distance from agriculture. A second survey in Accra two years later indicated important inter annual variation in malaria prevalence and importance of risk factors. Travel was an independent risk factor likely due to tIle low malaria prevalence. Entomological indices were measured by human bait catches (HBC), pyretIlfUm knockdown catches (PKD) and larval surveys. In Accra man biting rates by HBC were higher in UA tllan U communities for both Anopheles (8.4 in UA and 2.8 in U) and Culex (171.4 in UA and 41.7 in U). The annual entomological inoculation rate (EIR) was 19.9 in UA and 6.6 in U cOimnunities. Sporozoite infection rate was 0.65% (1111672) indicating local transmission. UrbanA. gambiae s.s. were found breeding in water at broken pipes, construction sites and poorly maintained drains. In the urban agricultural sites irrigation wells were the most common breeding sites, altIlOugh only 6% of wells hosted Anopheles. In a multivariate analysis, agriculture explained only a small proportion of parasitaenua prevalence and it was concluded tllat vector control nught best be directed at adults rather tIlan at breeding sites. In an insecticide-treated bednet trial, a cohort of approximately 250 cluldren in intervention and control areas was followed up at 0, 3 and 6 months after net distribution. After 6 montllS, there were fewer new cases of malaria and significantIy higher scores for nutritional indicators in children under 5 years in tIle intervention area, tIlan in tIle control area. Cluldren in tlle control area living witllin 300m of households that received nets had significantly lligher Hb concentrations and half the cllance of being anaemic compared to tIle children living more tI1an 300m away, suggesting a protective cOimnunity effect. Epidcnuology of urban malaria is complex and lughly heterogenous and as the majority of the African population is moving into tIle city better insight in risk factors and best options for malaria control is urgently needed.

Item Type:	Thesis (PhD)
Depositing User:	Symplectic Admin
Date Deposited:	20 Oct 2023 14:39
Last Modified:	20 Oct 2023 14:39
DOI:	10.17638/03175000
Copyright Statement:	Copyright © and Moral Rights for this thesis and any accompanying data (where applicable) are retained by the author and/or other copyright owners. A copy can be downloaded for personal non-commercial research or study, without prior permission or charge.
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3175000