Enhancing prevention and control of Rift Valley fever in East Africa by intersectoral assessment of control options

Permanent URI for this collectionhttps://hdl.handle.net/10568/32817

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Public health benefits from livestock Rift Valley fever control: A simulation of two epidemics in Kenya
(Journal Article, 2016-12) Kimani, T.; Schelling, E.; Bett, Bernard K.; Ngigi, M.; Randolph, Thomas F.; Fuhrimann, S.
In controlling Rift Valley fever, public health sector optimises health benefits by considering cost-effective control options. We modelled cost-effectiveness of livestock RVF control from a public health perspective in Kenya. Analysis was limited to pastoral and agro-pastoral system high-risk areas, for a 10-year period incorporating two epidemics: 2006/2007 and a hypothetical one in 2014/2015. Four integrated strategies (baseline and alternatives), combined from three vaccination and two surveillance options, were compared. Baseline strategy included annual vaccination of 1.2–11% animals plus passive surveillance and monitoring of nine sentinel herds. Compared to the baseline, two alternatives assumed improved vaccination coverage. A herd dynamic RVF animal simulation model produced number of animals infected under each strategy. A second mathematical model implemented in R estimated number people who would be infected by the infected animals. The 2006/2007 RVF epidemic resulted in 3974 undiscounted, unweighted disability adjusted life years (DALYs). Improving vaccination coverage to 41–51% (2012) and 27–33% (2014) 3 years before the hypothetical 2014/2015 outbreak can avert close to 1200 DALYs. Improved vaccinations showed cost-effectiveness (CE) values of US$ 43–53 per DALY averted. The baseline practice is not cost-effective to the public health sector.
Quantifying the burden of Rift Valley fever in humans using disability adjusted life years, Kenya
(Thesis, 2013) Orinde, A.B.
Rift Valley Fever (RVF) virus causes severe epidemics in livestock and humans resulting in considerable economic losses from disruption of livestock production, market chain and morbidity and mortality in humans. Public and private sector costs were incurred through service delivery for prevention and control. At the public health sector, RVF epidemic resulted in severe public health consequences of high morbidity and mortality (a total of 684 human cases with 155 deaths in Kenya). The losses are primarily incurred by households in terms of lost income due to illness, loss of human life and household’s expenditures in caring for the patients. This study estimated the burden of disease due to RVF in humans using Disability adjusted life years (DALYs), assessed human health RVF epidemiological parameters and private and public health costs during the last RVF epidemic in the 2006/2007 in Kenya. Family members who cared for an infected person in an eligible household and key informant in the public health sector in Garissa, Baringo and Kilifi districts and public health leaders at the national level were interviewed to aid in estimation of the private and public health costs. An eligible household was a household that had an RVF cases during the 2006/2007 outbreak as identified from the line list. Secondary data from the Ministry of Health and published literature were reviewed for epidemiological parameters including age and sex categorized incidences and mortality rates in order to compute DALYs using methods developed by the World Health Organization and World Bank. A total of 127 eligible households were enrolled into the study and one member interviewed in each household. Those interviewed in these households included 54% males and their xvii ages ranged from 19 to 81 years old with 40 and 45 years as mode and median age, respectively. The RVF virus predominantly infected males during the outbreak with a crude incidence of 0.7 per 1,000 population compared to females at 0.5 per 1,000 population. Total DALYs lost during the 2006/2007 outbreak was 4,035 (3.4 DALYs per 1000 population) for the reported cases of human RVF, representing 0.7% of the total DALYs for Kenya and estimated household costs of USD 120 for every human case reported. In comparison, HIV/AIDS and malaria are the leading causes of DALYs in Kenya at 24.2% and 7.2% of the total DALYs respectively. Rift Valley Fever is a zoonotic disease and it causes a considerable number of person DALYs yet it has not been considered prioritized by the policy makers’ in terms of resource allocation for prevention and control. Results from this study provide vital data on burden of RVF for use by the Government and other institutions to guide in health policy making and resource allocations for prevention and control of RVF to prevent future outbreak in Eastern Africa region.
Rift Valley fever in Kenyan pastoral livestock: Individual-based demographic model to analyse the impact of Rift Valley fever
(Presentation, 2015-03-09) Fuhrimann, S.; Kimani, T.; Hansen, F.; Bett, Bernard K.; Zinsstag, Jakob; Schelling, E.
Background Rift Valley Fever (RVF) is a viral zoonosis and a mosquito-borne disease caused by a phlebovirus in the family Bunyaviridae. It affects livestock, humans and wildlife. Epidemic outbreaks of RVF in East Africa, which occur after heavy rainfalls in cycles of 5-15 years, have caused next to human morbidity and mortality considerable economic losses throughout the livestock production and market chain. Objective Establishment a pastoral livestock demographic model to simulate 10 year alternating normal and drought periods and RVF epidemics. Methods We developed an individual-based C++ language with Borland C++ builder 6 model, to simulate livestock dynamics in North Eastern-Province during normal and drought periods, tracked over days and years. During RVF epidemics and with different control measures, animals were stratified into susceptible, exposed, infectious and recovered. The following scenarios were modeled (i) the demographic dynamics of cattle, camels, sheep and goats; (ii) an RVF outbreak in livestock and (iii) impacts of control measures (combinations of vaccination, sanitary measures, surveillance and vector control). Results/Conclusions Sheep and goat populations increase fastest (9-23%) annually during normal years while cattle and sheep populations show fastest decline during drought. In infected areas, mainly sheep (59%) are infected followed by goats (44%), cattle (31%), and camels (5%). Sheep and goats are most likely to spread the RVF through livestock trade. Slaughtered infected sheep are an important risk factor to human RVF infection. After the 2006/2007 outbreak, 2%, 40%, 30% and less than 1% of cattle, sheep, goats and camels acquired immunity. After seven years, only 4%, of sheep and goats remain immune. Our results will assist in the assessment of cost-benefit and cost-effectiveness of interventions which should improve future intersectoral livestock – public health contingency planning.
Economic analysis of alternate Rift Valley fever control options from a multisectoral perspective
(Conference Paper, 2012-11-11) Kimani, T.M.; Schelling, E.; Ngigi, M.; Randolph, Thomas F.
Rift Valley fever is a viral zoonosis that primarily affects people, cattle, sheep, goats, camels, buffalos, dromedaries, antelopes and wildebeest. The two most recent RVF epidemics in Kenya occurred in 1997/1998 and in 2006/2007 with severe socio-economic consequences in multiple sectors of the national economy. This study was undertaken to provide policy evidence on cost-effectiveness and benefits associated with alternate control options as well as the one health institutional arrangements for its improved prevention and control from both a public health and livestock perspectives. The approach employed multistage process that involved; mapping of one health stakeholders; an institutional analysis; simulation of different options (combinations of vaccination, sanitary measures, surveillance, vector control and awareness campaigns) using an individual-based epidemiological model and economic modeling to estimate costs of control per disability adjusted live year averted and benefits to the livestock sector and national economy. Up to 28 different agencies are relevant and need to be considered in one health collaborations to RVF prevention and control. The stakeholders go beyond the line animal and public health sectors. Socio network analysis reveals denser networks and stronger relational linkages between the public health stakeholders while the reverse is true for animal health stakeholders. Centrality statistics measures of Degree, Betweeness and Closeness identified the two health sectors, and the community as being the actors who linked clusters within the network. A non health ministry emerged as the actor demonstrating the highest closeness. The study concludes that a narrow scope of one health approach through collaboration of animal and human health agencies leaving out other non health actors and the livestock keepers could weaken control of zoonoses. Preliminary cost-benefit analysis of animal vaccination demonstrates good returns to investment (cost benefit ratio of greater than 1).
Cost effectiveness analysis of participatory disease surveillance in Kenya
(Poster, 2012-08-20) Hannah, H.; Kimani, T.; Grace, Delia; Randolph, Thomas F.
Effective surveillance for infectious diseases is an essential and resource-consuming activity for mitigating unwanted consequences for animal and public health. Allocation of scarce resources for surveillance must be considered against alternative prevention and control measures and regularly reviewed. Few studies estimate cost-effectiveness and benefits of different animal disease surveillance approaches and systems. In this study, we considered the benefits and resource costs of participatory epidemiology (PE) surveys and participatory disease surveillance (PDS) compared with routine passive surveillance. Focusing on a 6-month interval in a primarily pastoralist district in Kenya, basic performance indicators for surveillance measured were (1) number of outbreaks; (2) number of samples generated from suspected outbreaks; (3) number of positive laboratory confirmations. Costs of passive surveillance and interventions mounted were determined for the 6-month interval. In the same district, PE surveys were conducted in randomly selected communities to determine the number of outbreaks of notifiable cattle diseases in the same 6-month interval. Additional information was collected on the scale of morbidity and mortality for historical outbreaks (numbers and duration), the value of individual animals and the number of active outbreaks. Costs associated with mounting PE visits were ascertained and extrapolated to district level. One month after completion of PE visits, district level stakeholders were interviewed to determine the response, if any, to outbreaks detected during the visits. The study provides cost effectiveness estimates at a district level for the 6-month interval, including losses which occurred from outbreaks missed by passive surveillance and costs if PE were applied at regular intervals. In addition, the findings consider available prevention and control responses and provide decision-makers with evidence to inform future application of participatory approaches in animal disease surveillance.
Rift Valley fever in Kenyan pastoral livestock: Simulation with an individual-based demographic model
(Poster, 2012-08-20) Fuhrimann, S.; Kimani, T.; Hansen, F.; Bett, Bernard K.; Zinsstag, Jakob; Schelling, E.
Rift Valley Fever (RVF) is a viral zoonosis and a mosquito-borne disease caused by a phlebovirus in the family Bunyaviridae. It affects livestock, humans and wildlife. Epidemic outbreaks of RVF in East Africa, which occur after heavy rainfalls in cycles of 5-15 years, have caused next to human morbidity and mortality considerable economic losses throughout the livestock production and market chain. Establishment of a pastoral livestock demographic model simulating alternating normal and drought periods (appropriate for the Sahel) and RVF epidemics. We have developed an individual-based model to simulate the following scenarios (1) the demographic dynamics of cattle, camels, sheep and goats in North Eastern-Province; (2) an RVF outbreak in livestock and the RVF immunity status afterwards; and (3) impacts of control measures (combinations of vaccination, sanitary measures, surveillance, vector control and awareness campaigns). The baseline and RVF-attributable mortalities can be simulated and show the losses due to RVF. Further, we can retrieve proportions of affected animals, grouped in species, age classes and sex, as well as the number of infected slaughtered and sold animals. Sheep and goats are most likely to spread the disease through livestock trade. Slaughtered infected sheep are an important risk factor to human RVF infection. Our results assist in the assessment of cost-benefit and cost-effectiveness of interventions which should improve future intersectoral livestock – public health contingency planning. The ratio of susceptible/immune hosts can further support the prediction system by consideration of the immunity levels years after a previous outbreak.
Economic analysis of Rift Valley fever prevention and control options from a multi-sectoral perspective in Kenya
(Presentation, 2012-08-20) Kimani, T.; Schelling, E.; Ngigi, M.; Randolph, Thomas F.
Participatory disease surveillance: Cost effectiveness relative to passive surveillance in Kajiado County, Kenya
(Poster, 2012-08-20) Hannah, H.; Kimani, T.; Irungu, P.; Grace, Delia; Randolph, Thomas F.
Effective surveillance for infectious diseases is an essential and resource-consuming activity for mitigating unwanted consequences for animal and public health. Allocation of scarce resources for surveillance must be considered against alternative prevention and control measures and regularly reviewed. Few studies estimate cost-effectiveness and benefits of different animal disease surveillance approaches and systems. In this study, we considered the benefits and resource costs of participatory epidemiology (PE) surveys and participatory disease surveillance (PDS) compared with routine passive surveillance. Focusing on a 6-month interval in a primarily pastoralist district in Kenya, basic performance indicators for surveillance measured were (1) number of outbreaks; (2) number of samples generated from suspected outbreaks; (3) number of positive laboratory confirmations. Costs of passive surveillance and interventions mounted were determined for the 6-month interval. In the same district, PE surveys were conducted in randomly selected communities to determine the number of outbreaks of notifiable cattle diseases in the same 6-month interval. Additional information was collected on the scale of morbidity and mortality for historical outbreaks (numbers and duration), the value of individual animals and the number of active outbreaks. Costs associated with mounting PE visits were ascertained and extrapolated to district level. One month after completion of PE visits, district level stakeholders were interviewed to determine the response, if any, to outbreaks detected during the visits. The study provides cost effectiveness estimates at a district level for the 6-month interval, including losses which occurred from outbreaks missed by passive surveillance and costs if PE were applied at regular intervals. In addition, the findings consider available prevention and control responses and provide decision-makers with evidence to inform future application of participatory approaches in animal disease surveillance.

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