Abstract:
Since 1931, Rift Valley fever (RVF) epidemics have recurred in Kenya at an average interepidemic period of up to 10 years. The most recent epidemic occurred in 2006/2007. It
resulted in losses. Estimated as KES 2.1 Billion. A post epidemic assessment recommended
adoption of One Health (OH) approach to RVF management as well as implementation of
livestock control strategies that offer highest benefits to both the livestock and public health
sectors. Evidence to guide such decisions was inadequate. Costs and benefits analysis (CBA)
of RVF control had not been conducted. This study provides the evidence in four sequential
steps of data collection and analysis, focusing on RVF high risk areas in Kenya. The steps
included, (i) a social network analysis at national and sub-national (Garissa County) levels
that identified RVF stakeholders and the extent to which they had institutionalised One
Health (OH) approach, (ii) delineation of eleven (1 baseline and 10 alternatives) livestock
RVF control strategies (that combined different levels of surveillance, vaccination, and
mosquito control) and estimation of the associated control costs for the period 2007-2014.
The impacts of the control measures on a hypothetical epidemic 2014/2015 were simulated in
a (iii) herd dynamics and RVF modelling to estimate number of animal mortality and
morbidity, (iv) animal-human RVF epidemiological modelling to generate human morbidity
and mortality that would arise from the animal cases. Human case data was used to estimate
disability adjusted life years (DALYs). Quantitative livestock and economic CBA in Excel
combined animal simulation outputs, production indices and product prices to estimate value
of livestock sector losses under each control strategy. Benefits of alternative strategies
represented saved losses, compared to the baseline strategy. The evaluation criteria for the
alternate control strategies were net present value of incremental benefits over costs. Social
network analysis showed that, at national level, stakeholders had mobilised for and
institutionalized OH through formal structures. The reverse was true at sub-national level.
Alternate strategies that assumed improved vaccination coverage (3-5 fold) implemented 2-3
years before the hypothetical epidemic, showed the highest benefits ~livestock sector benefit
cost ratio of 1.1 to 5.0 and public health sector cost effectiveness of KES 2,847 to KES
3,485 per DALY averted. Considering that RVF outbreaks occur at sub-national level, where
both OH has not been institutionalized and the baseline vaccination strategy continues to be
adopted, in case of an incursion, the next epidemic would have a similar magnitude as the
2006/2007.
