RVF


To the grazing field, Afar, Ethiopia

Cattle going to the grazing field in Afar region, Ethiopia (photo credit: ILRI/Apollo Habtamu).

Climate change influences the occurrence and transmission of a wide range of livestock diseases through multiple pathways. Diseases caused by pathogens that spent part of their life cycle outside the host (for instance, in vectors or the environment) are more sensitive in this regard, compared to those caused by obligate pathogens.

A newly published book, The Climate-Smart Agriculture Papers, brings together some of the latest research by agricultural scientists on climate-smart agriculture in eastern and southern Africa. The 25 chapters of the book highlight ongoing efforts to better characterize climate risks, develop and disseminate climate-smart varieties and farm management practices, and integrate these technologies into well-functioning value chains.

In a chapter on climate change and livestock diseases, scientists from the International Livestock Research Institute (ILRI) use two well-studied vector-borne diseases—Rift Valley fever and tick-borne diseases—as case studies to describe direct pathways through which climate change influences infectious disease-risk in East and southern Africa.

Access the chapter, Climate change and infectious livestock diseases: The case of Rift Valley fever and tick-borne diseases by Bernard Bett, Johanna Lindahl and Delia Grace.

The hidden dangers of irrigation in Kenya

By Imogen Mathers

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For farmers in Kenya, creative ways to irrigate crops can be the difference between a harvest failing or thriving. In this drought-prone country, access to reliable water sources is a daily challenge.

Few would argue with the need for better irrigation. Yet certain techniques introduced by the government to spur food production have dangerous side effects, warns Bernard Bett, a veterinary epidemiologist at the International Livestock Research Institute (ILRI) in Kenya.

The pools and canals that underpin flood irrigation create ideal conditions for mosquitoes to thrive, and are a draw for wildlife to gather and drink. This confluence of elements forms a perfect petri dish for zoonotic diseases such as malaria and dengue to circulate between wildlife, livestock, humans and insects.

Instead, Bett suggests exploring alternative techniques such as drip irrigation, a small change that can play a big part in keeping people safe from vector-borne diseases.

The interview was recorded on 18 March 2016 at One Health for the Real World, a symposium in the United Kingdom organised by the Dynamic Drivers of Disease in Africa consortium and the Zoological Society of London.

This article was originally published on SciDev.Net. Read the original article.

Cow in Kenya

Cow in Kenya. A new Rift Valley fever risk map for Kenya will help develop prevention and control measures to combat the disease in the country (photo credit: ILRI/Stevie Mann).

A new Rift Valley fever risk map for Kenya, based on data from a period spanning over 50 years, will be an important tool for use in developing measures to prevent and control the disease in the country.

Rift Valley fever is a viral disease that affects animals such as cattle, sheep, camels and goats. It is also a zoonotic disease, meaning it can be transmitted from animals to people.

Rift Valley fever epidemics occur every 3 to 10 years in specific regions of the Greater Horn of Africa, southern and western Africa and in the Arabian Peninsula, resulting in high rates of infection and death among people and livestock.

In Kenya, the most recent outbreaks of the disease occurred in 1997-98 and 2006-07. Experts agree that the severity of Rift Valley fever epidemics can be reduced through the use of effective early warning systems followed by rapid implementation of prevention and control measures.

In 2008, international experts and decision-makers from eastern Africa developed a risk-based decision support framework designed to guide responses during various stages of the Rift Valley fever disease cycle.

Now, a team of researchers from Kenya, the Netherlands and the United States of America has added to the arsenal of tools to prevent and control Rift Valley fever by using surveillance data from 1951 to 2007 to develop a Rift Valley fever risk map for Kenya.

The map shows the risk of an outbreak of the disease for each of the 391 administrative divisions in the country (based on the 1999 administrative map), classifying the divisions as high, medium or low risk.

The authors of the study say that the Rift Valley fever risk map will provide the Government of Kenya with an evidence-base from which it can respond to a Rift Valley fever epidemic warning as well as develop long-term prevention and control programs in high-risk areas.

The map is published in an article in the journal PLOS ONE (25 Jan 2016): Predictive factors and risk mapping for Rift Valley fever epidemics in Kenya

Citation
Munyua, P.M., Murithi, R.M., Ithondeka, P., Hightower, A., Thumbi, S.M., Anyangu, S.A., Kiplimo, J., Bett, B., Vrieling, A., Breiman, R.F. and Njenga, M.K. 2016. Predictive factors and risk mapping for Rift Valley fever epidemics in Kenya. PLOS ONE 11(1): e0144570.

Orma Boran cattle crossing a river in Kenya

Orma Boran cattle crossing a river in Kenya. Both cattle and people can be infected with Rift Valley fever (photo credit: ILRI /Rosemary Dolan).

Recent climate predictions suggest East Africa may be in line for an epidemic of Rift Valley fever – an infectious disease which can hit people, their livestock and livelihoods, and national economies hard.

Data from the Climate Prediction Center and International Research Institute for Climate and Society suggest there is a 99.9% chance there will be an El Niño occurrence this year, with a 90% chance it will last until March/April 2016.

At least two of the most recent Rift Valley fever epidemics in East Africa—those in 1997-98 and 2006-07—were associated with El Niño weather patterns, with Kenya suffering losses amounting to US$32 million.

Given the strong predictions of an El Niño occurrence, and the established association between El Niño and Rift Valley fever risk, countries in the Horn of Africa need to start preparing to manage the developing risk.

In particular, public education on the linkages between the expected weather patterns and disease risk is vital to minimize human exposure to the disease should an epidemic occur.

Read the full article by Bernard Bett, a veterinary epidemiologist at the International Livestock Research Institute (ILRI).

Orma Boran cattle crossing a river in Kenya

Orma Boran cattle crossing a river in Kenya (photo credit: ILRI/Rosemary Dolan).

The Dynamic Drivers of Disease in Africa Consortium is a research program that works to understand the relationships between ecosystems, zoonotic diseases, health and wellbeing in order to inform effective public health interventions.

Under this program, multidisciplinary country teams are studying four zoonotic diseases: henipavirus infection in Ghana, Lassa fever in Sierra Leone, Rift Valley fever in Kenya and trypanosomiasis in Zambia and Zimbabwe. The focus is on how changes in biodiversity, land use and climate affect disease transmission.

The development of irrigation schemes is thought to influence pathogen transmission in people and animals in several ways. For example, masses of stagnant water and high humidity support the development of disease vectors like mosquitoes. In addition, irrigated areas are likely to have a higher density of animal hosts like chicken and small ruminants.

In order to investigate the influence of irrigation and changes in biodiversity on the distribution of zoonoses, a cross-sectional study was carried out in Tana River County, Kenya, home to the Hola Irrigation Scheme. The zoonoses of interest were Rift Valley fever, Q fever, brucellosis, West Nile virus, dengue fever and leptospirosis.

Irrigation causes a decline in biodiversity as wildlife habitats are cleared to make way for crop agriculture. However, the linkages between biodiversity and disease risk remain unclear. It was also found that areas with a rich diversity of hosts have higher prevalence of multiple zoonotic pathogens as compared to areas with lower host diversity.

The study also found that while irrigated areas are infested with multiple species of mosquitoes (including primary vectors of Rift Valley fever), their high population densities alone are not enough to sustain the transmission of pathogens; reservoir hosts (for example, birds for West Nile virus) or other persistence mechanisms are required.

These and other findings from the study were presented at the 49th annual scientific conference of the Kenya Veterinary Association which was held in April 2015.

View the presentation, Land use, biodiversity changes and the risk of zoonotic diseases: Findings from a cross-sectional study in Tana River County, Kenya

Rift Valley fever, a viral disease that is endemic in sub-Saharan Africa, Saudi Arabia and Yemen, causes abortion and stillbirth in livestock and can cause serious conditions such as haemorrhagic fever and encephalitis in humans.

Download a brief that illustrates how scientists at the International Livestock Research Institute (ILRI) are working to identify key drivers for Rift Valley fever occurrence and transmission, and develop decision support tools to guide responses at various stages of the epidemic cycle of the disease.

Developed after the last devastating Rift Valley fever outbreak in Kenya in 2006-07, these research outputs are designed to enable decision-makers to take timely, evidence-based decisions to prevent and control future epidemics and reduce their impacts.

In particular, the Government of Kenya has incorporated the decision support tool in its Rift Valley fever contingency plan and local governments in the country regularly use outputs from ILRI’s work to assess their level of preparedness.

The Rift Valley fever virus is a mosquito-borne pathogen that causes explosive outbreaks of severe human and livestock disease in Africa and Arabian Peninsula. The rapid evolution of outbreaks of Rift Valley fever generates exceptional challenges in its mitigation and control.

A decision-support tool for prevention and control of Rift Valley fever in the Greater Horn of Africa identifies a series of events that indicates increasing risk of an outbreak and matches interventions to each event.

This poster, prepared for the Tropentag 2014 conference, presents information from a study that assessed the effectiveness of targeted vaccination in mitigating the impacts of outbreaks of Rift Valley fever.

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Mitigation of the impacts of Rift Valley fever through targeted vaccination strategies

This week, ILRI staff are participating in the Tropentag 2014 International Conference in Prague, Czech Republic (17-19 September 2014). There is also a dedicated ILRI@40 side event on livestock-based options for sustainable food and nutritional security and healthy lives.  See all the posters.

 

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