Epidemiological Assessment of the Rift Valley Fever Outbreak in Kenya and Tanzania in 2006 and 2007

Abstract

Abstract. To capture lessons from the 2007 Rift Valley fever (RVF) outbreak, epidemiological studies were carried out in Kenya and Tanzania. Somali pastoralists proved to be adept at recognizing symptoms of RVF and risk factors such as heavy rainfall and mosquito swarms. Sandik, which means "bloody nose," was used by Somalis to denote disease consistent with RVF. Somalis reported that sandik was previously seen in 1997/98, the period of the last RVF epidemic. Pastoralists communicated valuable epidemiological information for surveillance and early warning systems that was observed before international warnings. The results indicate that an all or none approach to decision making contributed to the delay in response. In the future, a phased approach balancing actions against increasing risk of an outbreak would be more effective. Given the time required to mobilize large vaccine stocks, emergency vaccination did not contribute to the mitigation of explosive outbreaks of RVF.* Address correspondence to Christine C. Jost, International Livestock Research Institute, P.O. Box 30709, Nairobi, 00100 Kenya. E-mail: c.jost@cgiar.org 66 JOST AND OTHERS approach, participants were asked to focus on the period when the RVF outbreak was observed and to divide the individual piles of counters previously used to rank the livestock species by numbers into two sub-groups: those that developed RVF and those that did not. For those that had RVF, the counters were further subdivided into the proportion that died and the proportion that recovered. This method provided an estimate of the incidence of RVF in each species during the outbreak, as well as the outbreak case fatality rates and the overall mortality rate during the outbreak.Abortions attributable to RVF. Using the results of the proportional piling exercise for the relative numbers of each livestock species as the starting point, participants were asked to allocate the counters into two groups in proportion to those livestock that were pregnant before the RVF outbreak and those that were not. For the pregnant group, participants next divided the counters in proportion to those animals that aborted because of RVF and those that carried their pregnancies to full term. The pregnant pile was then restored, and participants asked to divide the counters to represent the proportions that would have been expected to abort in a normal year (with no RVF outbreak) and those that would have carried to full term. Supplementary questioning probed the causes of abortion other than RVF.Disease impact matrix score. For each livestock species a matrix was constructed on the ground, with benefits derived from that species along the y axis and diseases on the x axis. Participants were given 100 counters and asked to allocate them among the livestock-associated benefits according to the relative importance of each benefit, with the most important benefit receiving the highest number of counters. The counters for each benefit were then sub-allocated to each disease to show the relative negative ...

Epidemic Situation of Rift Valley Fever in Egypt and Saudi Arabia

“…Up till now, the virus transmission from human to human not documented. A strategy called "One Health" was applied by cooperation between all collaborating authorities in Saudi Arabia on both animal and human hosts to prevent and control the disease [33,36]. During the outbreak, active surveillance surveys to detect the RVF cases among animals and humans to locate infected areas for animal vaccination [8,9,26].…”

Response to Rift Valley Fever in Tanzania: Challenges and Opportunities

“…Awareness about RVF signs and its clinical manifestations and knowledge on early warning is still low among lay community members particularly agro-pastoral communities (Jost et al, 2010). Studies have shown that the knowledge of pastoral communities on risk practices including eating raw meat, raw milk, touching and herding aborted animals and consuming products from such animals is still limited (Amwayi et al, 2010).…”

“…In a recent survey regarding awareness among agropastoral and pastoral communities in Serengeti ecosystem has shown that only 5.3% of the community members were aware of zoonotic risk of RVF (R. Fyumagwa unpubl.). In the 2007 RVF epidemic, the Maasai of northern Tanzania had low levels of traditional knowledge concerning livestock diseases (Jost et al, 2010). It is argued that the Maasai now have less ability to utilize indigenous knowledge on diseases due to dependence on ecotourism and crop cultivation for their livelihoods, and have greater access to veterinary services (Jost et al, 2010).…”

“…In the 2007 RVF epidemic, the Maasai of northern Tanzania had low levels of traditional knowledge concerning livestock diseases (Jost et al, 2010). It is argued that the Maasai now have less ability to utilize indigenous knowledge on diseases due to dependence on ecotourism and crop cultivation for their livelihoods, and have greater access to veterinary services (Jost et al, 2010). However, as RVF happens in cycles of 4 to 15 years it is difficult for them to recognize the start of an RVF outbreak.…”

“…Even in the recent outbreak of 2006/ 2007 the affected East African countries did not have contingency plans for response to RVF when FAO issued an alert on a possible outbreak. Due to delays in implementation on response activities, the efforts made in providing vaccination to livestock at risk did not contribute much in preventing the spread of the disease (Jost et al, 2010;Munyua et al, 2010). The preparation of NRVF-EPRP in Tanzania is the commitment to strengthen emergency preparedness and response against possible re-occurrence and spread of RVF.…”