What is Rift Valley Fever?
Rift Valley Fever (RVF) is a virus transmitted by mosquitoes and blood feeding flies that usually affects animals but also affects humans. The virus was first identified in 1931 during an epidemic among sheep. Since then outbreaks have been reported in SSA, North Africa, and in 2000 Saudi Arabia and Yemen.
The occurrence of RVF is known to follow periods of widespread and heavy rainfall associated with the development of strong ITCZ. Heavy rainfall floods mosquito breeding habitats, known as "dambos" in East Africa, providing an ideal environment for naturally infected mosquito eggs to hatch (Figure 1)/
Figure 1: Rift Valley Fever Ecology
In 2006-2007, outbreaks in Kenya, Somalia, Tanzania, Sudan, and Madagascar caused > 200,000 human infections and led to roughly 500 deaths. In Kenya alone, the outbreak cost $32 million in livestock losses and international export bans. An outbreak in 1997 caused 170 haemorrhagic fever associated deaths and ~27,500 infections. The most serious outbreak on record occurred in Kenya 1950-51, and resulted in the death ~100,000 sheep (Greenhalgh, 2015).
Predicting outbreaks
Enso is recognised to be linked with outbreaks of RVF in East Africa. 2015 stood out to be one of the top three El Nino events since 1950, Sudan, Ethiopia, Somalia, Kenya and Tanzania were identified as areas at risk for RVF due to substantially elevated rainfall (figure 2)
Figure 2: 2015 projections of extreme rainfall and RVF outbreaks
Climate Change
More extreme rainfall events are projected in East Africa with warmer temperatures. These events will create the necessary conditions for more RVF outbreaks not only in East Africa, but also potential for it to expand its geographical range (Martin, 2008).
Future projections
A study 'Environmental Change and Rift Valley fever in eastern Africa: Projecting Beyond Healthy Futures', focussed on the Republics of Burundi, Kenya, Rwanda, Uganda and Tanzania. The two pathway scenarios RCP4.5 and RCP8.5, indicate increased temperatures, rainfall and variability. Results highlight high- risk of future RVF outbreaks, including parts of East Africa that are currently unaffected. The results also highlight the risk of spread from/ to the study area, and possibly further afield. The greatest projected changes in RVF outbreaks are in Kenya and Tanzania. Changes remain stable up to 2050, when compared with baseline results, even declining in central/ eastern Uganda (RCP4.5), before increasing by the end of the century. Positive changes are most evident to the West of Lake Victoria (Berundi, Rwanda and Western Uganda) and in Western Kenya, especially under RCP8.5 by the end of the century.
The study also combined results of a spatial assessment of social vulnerability to the disease in Eastern Africa. Predisposition to RVF is greatest where the boarder of North-eastern Uganda, North-western Kenya and South Sudan meet, because of the co-occurrence of highly seasonal rainfall, relatively high densities of livestock, high levels of poverty and poor infrastructure, including health services. Under RCP4.5 risk decreases in Southern and Central Uganda, however increases in Central Kenya. For RCP8.5 risk patterns are similar however, RVF has expanded again in central and Southern Uganda, and is greater in Western Kenya.
Results show that with increasing extreme precipitation events, there is a clear need to remain vigilant and to invest not only in early warning systems, but also in addressing the socio-economic factors that underpin social vulnerability in order to effectively mitigate future impacts (Taylor, 2016).
What is Rift Valley Fever?
Rift Valley Fever (RVF) is a virus transmitted by mosquitoes and blood feeding flies that usually affects animals but also affects humans. The virus was first identified in 1931 during an epidemic among sheep. Since then outbreaks have been reported in SSA, North Africa, and in 2000 Saudi Arabia and Yemen.
The occurrence of RVF is known to follow periods of widespread and heavy rainfall associated with the development of strong ITCZ. Heavy rainfall floods mosquito breeding habitats, known as "dambos" in East Africa, providing an ideal environment for naturally infected mosquito eggs to hatch (Figure 1)/
Figure 1: Rift Valley Fever Ecology
Predicting outbreaks
Enso is recognised to be linked with outbreaks of RVF in East Africa. 2015 stood out to be one of the top three El Nino events since 1950, Sudan, Ethiopia, Somalia, Kenya and Tanzania were identified as areas at risk for RVF due to substantially elevated rainfall (figure 2)
Figure 2: 2015 projections of extreme rainfall and RVF outbreaks
Climate Change
More extreme rainfall events are projected in East Africa with warmer temperatures. These events will create the necessary conditions for more RVF outbreaks not only in East Africa, but also potential for it to expand its geographical range (Martin, 2008).
Future projections
A study 'Environmental Change and Rift Valley fever in eastern Africa: Projecting Beyond Healthy Futures', focussed on the Republics of Burundi, Kenya, Rwanda, Uganda and Tanzania. The two pathway scenarios RCP4.5 and RCP8.5, indicate increased temperatures, rainfall and variability. Results highlight high- risk of future RVF outbreaks, including parts of East Africa that are currently unaffected. The results also highlight the risk of spread from/ to the study area, and possibly further afield. The greatest projected changes in RVF outbreaks are in Kenya and Tanzania. Changes remain stable up to 2050, when compared with baseline results, even declining in central/ eastern Uganda (RCP4.5), before increasing by the end of the century. Positive changes are most evident to the West of Lake Victoria (Berundi, Rwanda and Western Uganda) and in Western Kenya, especially under RCP8.5 by the end of the century.
The study also combined results of a spatial assessment of social vulnerability to the disease in Eastern Africa. Predisposition to RVF is greatest where the boarder of North-eastern Uganda, North-western Kenya and South Sudan meet, because of the co-occurrence of highly seasonal rainfall, relatively high densities of livestock, high levels of poverty and poor infrastructure, including health services. Under RCP4.5 risk decreases in Southern and Central Uganda, however increases in Central Kenya. For RCP8.5 risk patterns are similar however, RVF has expanded again in central and Southern Uganda, and is greater in Western Kenya.
Results show that with increasing extreme precipitation events, there is a clear need to remain vigilant and to invest not only in early warning systems, but also in addressing the socio-economic factors that underpin social vulnerability in order to effectively mitigate future impacts (Taylor, 2016).
Hi!
ReplyDeleteThere are many reasons why urban communities can be more vulnerable to RVF outbreaks, such as due to densely populated areas and poor water distribution systems ect. But are there any reasons as to why rural communities may be more vulnerable to RVF outbreaks than urban communities?
Rural areas are particularly vulnerable to RVF, as it largely affects livestock, such as sheep and cattle, which are more than often farmed in rural areas. In fact RVF occurs sporadically in rural areas and mainly affects pastoralists in these remote areas. This therefore meant that for many years it was not a priority for public health ministers and policy makers. It is only since, RVF is spreading further to areas where there is high economic impacts, has RVF risen in priorities for policy makes.
DeleteLastly in terms of increase variation in precipitation. Rural areas can be particularly at risk to flooding due to sea level rise