Spatial risk assessment of Rift Valley Fever potential outbreaks using a vector surveillance system in Kenya

Nanyingi M , Ogola E,  Olang G, Otiang E,  Munyua P,  Thumbi S, Bett B, Muchemi G, Kiama S and Njenga K

Rift Valley fever (RVF) is a vector-borne, viral, zoonotic disease that threatens human and animal health. In Kenya the geographical distribution is determined by spread of competent transmission vectors. Existing RVF predictive risk maps are devoid of vectors interactions with eco-climatic parameters in emergence of disease. We envisage to develop a vector surveillance system (VSS) by mapping the distribution of potential RVF competent vectors in Kenya; To evaluate the correlation between mosquito distribution and environmental-climatic attributes favoring emergence of RVF and investigate by modeling the climatic, ecological and environmental drivers of RVF outbreaks anddevelop a risk map for spatial prediction of RVF outbreaks in Kenya.

Using a cross-sectional design we classified Kenya into 30 spatial units/districts (15 case, 15 control for RVF) based on historical RVF outbreaks weighted probability indices for endemicity. Entomological and ecological surveillance using GPS mapping and monthly (May 2013- February 2014) trapping of mosquitoes is alternatively done in case and control areas. 2500 mosquitoes have been collected in 15 districts (50% geographical target for each for case and control). Species identified as (Culicines-86%, Anophelines-9.7%, Aedes- 2.6%) with over 65% distribution in RVF endemic areas. We demonstrate the applications of spatial epidemiology using GIS to illustrate RVF risk distribution and propose utilizing a Maximum Entropy (MaxEnt) approach to develop Ecological Niche Models (ENM) for prediction of competent RVF vector distributions in un-sampled areas. Targeting RVF hotspots can minimize the costs of large-scale vector surveillance hence enhancing vaccination and vector control strategies. A replicable VSS database and methods can be used for risk analysis of other vector-borne diseases.

The Socio-Economics and Burden Impact of Rift Valley Fever in Garissa, Kenya

Nanyingi, M. O.,^1,3,5* Thumbi, S M.,^5,6 Muchemi, G. M. 1., Bett, B.,⁴ Kiama, S. G.² and Njenga, K.⁵

 

1 Department of Public Health, Pharmacology and Toxicology, University of Nairobi PO BOX 29053S0065 Nairobi, Kenya.

2 Wangari Maathai Institute for Environmental Studies and Peace, University of Nairobi PO. BOX. 30197 Nairobi, Kenya.

3 Colorado State University, Feed The Future Programme, CO 80523S1644, USA.

4International Livestock Research Institute (ILRI), P.O. Box 30709 Nairobi 00100, Kenya.

5Kenya Medical Research Institute, US Centres for Disease Control and Prevention, Kenya.

6Paul G Allen Global Animal Health, PO Box 647090, Washington State University, Pullman WA, USA.

Rift Valley fever (RVF) is a viral, vector borne zoonosis that has significant threat to livestock health and production and public health in Africa. Recent outbreaks have led to high livestock mortalities and human morbidity and socio economic impacts in Garissa. To assess the level of knowledge of pastoralists to causation and transmission risk factors and describe their attitude and practices in response to RVF outbreaks and management in the context of climate change shocks. To estimate the livelihood losses and burden impacts in Garissa. A population based cross sectional household survey was conducted in March 2012 and March 2013 in four hotspots. A multistage purposive sampling was used to identify 250 participants who included pastoralists, veterinary and medical personnel and livestock traders. KAP evaluation was by questionnaires in depth key informant interviews and focus group discussions. Participatory rural appraisal tools were used to assess the economic significance of the RVF outbreaks, risk factors and management costs. 185 respondents (74%) had good knowledge of RVF (symptoms scored >50%) and risk factor analysis indicated > 150 (60%) understood the consumption of meat of dead or infected animal, milk, touching aborted foetuses caused disease. Estimated lost revenue due to closure of livestock markets and bans was over Ksh.3 billion. Intervention costs and burden of the outbreaks is discussed. There is good knowledge and attitude on RVF risk, transmission and control. It re-emergence is associated with negative impacts on livelihoods and economic endpoints in Garissa.

Keywords: Rift Valley Fever, Knowledge, Attitudes and Practices, Socioeconomics,

Garissa