Comparing the risk of mosquito-borne infections in humans in irrigated and non-irrigated sites in Kenya
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Comparing the risk of mosquito-borne infections in humans in irrigated and non-irrigated sites in Kenya

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Presentation by Bernard Bett, Rosemary Sang, Cristobal Verdugo, Salome Bukachi, Salome Wanyoike, Mohammed Said, Enoch Ontiri, Shem Kifugo, Tom Fredrick Otieno, Ian Njeru, Joan Karanja, Johanna......

Presentation by Bernard Bett, Rosemary Sang, Cristobal Verdugo, Salome Bukachi, Salome Wanyoike, Mohammed Said, Enoch Ontiri, Shem Kifugo, Tom Fredrick Otieno, Ian Njeru, Joan Karanja, Johanna Lindahl and Delia Grace at the EcoHealth 2014 conference, Montreal, Canada, 11-15 August 2014.

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  • 1. Comparing the risk of mosquito-borne infections in humans in irrigated and non-irrigated sites in Kenya Bernard Bett1, Rosemary Sang2, Cristobal Verdugo, Salome Bukachi3, Salome Wanyoike4, Mohammed Said1, Enoch Ontiri1, Shem Kifugo1, Tom Fredrick Otieno1, Ian Njeru5, Joan Karanja5, Johanna Lindahl1, Delia Grace1 1. International Livestock Research Institute 2. Kenya Medical Research Institute 3. University of Nairobi 4. Department of Veterinary Services 5. Ministry of Health EcoHealth 2014 conference Montreal, Canada 11-15 August 2014
  • 2. Introduction •More and more range lands in Africa are being converted to crop lands through irrigation to alleviate food insecurity •These land use changes are mostly associated with: Increasing human population – traditional sources of food no longer adequate Climate change – decline in land productivity, reduction in rain-fed agriculture
  • 3. Introduction •Results: major trade-offs in ecosystem services More food produced (provisioning services) at the expense of biodiversity and regulatory services (disease, flooding, erosion) More effects of climate change – due to deforestation, use of fertilizers – hence, shift in vegetation communities, biome and biodiversity
  • 4. Introduction •This study: –investigates whether the development of irrigation schemes in an arid and semi- arid area in Kenya increases the risk of mosquito-borne infections [Rift Valley fever, West Nile virus, Dengue fever] Study site with stagnant water in irrigation canals – source of water for the locals but also breeding grounds for mosquitoes
  • 5. Introduction •Hypotheses –The creation of permanent water masses through irrigation alters vector biodiversity and abundance, populations of livestock and humans at risk and the nature and frequency interactions between hosts and vectors –The occurrence of relatively intensive systems has impacts on health, wellbeing and economy that differ quantitatively and qualitatively from impacts in minimally altered ecosystems. Pastoralists in the study site
  • 6. Methodology •The study site: – Tana River and Garissa counties, northeastern Kenya •Study design – Cross sectional surveys – Power sample size estimation techniques – this suggested that we needed 220 households and 550 subjects !. !. Bura Hola 0 5 10 20 30 40 Kilometers ´ Legend Settlements Irrigation Schemes permanent mixed temporary !. Towns Study Block Tana River County Tana River Other Rivers Riverrine Forests
  • 7. Methodology Data collection –Collation of secondary data from the local health centres –Entomological surveys conducted using CDC miniature light traps –Blood sampling – people above 5 years of age –Laboratory screening of sera using ELISA –Ethical approvals – African Medical Research Foundation (AMREF)
  • 8. Results Mosquitoes trapped – relative abundance and species distribution
  • 9. Results 0.00 0.10 0.20 0.30 0.40 RVF WNV Dengue Irrigateed area Non-irrigated area Disease Seroprevalence Samples screened –481 samples have been screened so far –Questionnaires administered to 430 households Serological tests –WNV and Dengue sero- prevalence apparently higher than that for RVF though confirmatory are yet to be done Relative seroprevalence of RVF, WNV and Dengue
  • 10. Risk factor analysis Model – 2 Logistic regression models Outcomes –RVF –Combined WNV and Dengue outcomes Predictors –Subject-level variables –Household-level variables –Area/village-level variables
  • 11. Risk factor analysis - findings For WNV and Dengue model I. Males have a higher risk of exposure than females II. Farmers have a higher risk compared to pastoralists For RVF model I Males have a higher risk of exposure than females
  • 12. •Create awareness among the local communities on infectious diseases associated with irrigation •Build capacity on differential diagnosis of febrile illnesses in the local health centres. Currently, most cases are treated as: –Malaria –Brucellosis –Typhoid Intervention points 0 0.1 0.2 0.3 0.4 0.5 0.6 Proportion Communities’ perceptions on diseases that manifest similar signs as malaria – limited knowledge on arboviruses
  • 13. •Sensitize policymakers and health service providers to make health services more accessible to the locals – at present, less than 30% of the people utilize these services 0.00 0.10 0.20 0.30 0.40 Use herbal concotions Do nothing Self medication Visit local hospitals Health-seeking behaviour Proportion Ways in which the local communities respond to febrile illnesses such as malaria
  • 14. In conclusion •Arboviral infections are common •Different risk factors, such as age and occupation, are important •Need capacity building
  • 15. Acknowledgements This work falls under the project ‘Dynamic Drivers of Disease in Africa: Ecosystems, livestock/wildlife, health and wellbeing: REF:NE/J001422/1” partly funded with support from the Ecosystem Services for Poverty Alleviation Programme (ESPA). The ESPA program is funded by the Department for International Development (DFID), the Economic and Social Research Council (ESRC) and the Natural Environment Research Council (NERC). Other funding was provided by CGIAR Research Program Agriculture for Nutrition and Health