Flood victims in East Africa hit by Rift Valley fever epidemic


The people and livestock of Northeastern Province of Kenya and neighbouring Somalia have been severely hit by a complex epidemic of disease which broke out in December 1997. Medical and veterinary workers have struggled against continuing heavy rains to determine the extent of the epidemic and to collect samples to confirm the nature of the disease. Such rainfall over such a long period has not been experienced in Kenya this century.

Approximately 300 human deaths have been reported to the Kenyan authorities in Nairobi and incomplete reports from Somalia indicate less than 100 human deaths. Other sources put the death toll much higher. Livestock losses on both sides of the border number in the thousands. Reporting and investigation are severely hampered by the conditions and it will be some time before the toll can be estimated reliably.

Early reports of the outbreak had fuelled fears of an Ebola virus epidemic but this has been ruled out. The Kenya Medical and Veterinary Services, assisted by the World Health Organization (WHO) and its Collaborating Centre at the National Institute of Virology in South Africa, have identified Rift Valley fever (RVF) virus as the cause in many human cases and in some animals in the Garissa and Wajir districts of Kenya, as well as in towns on the Shebelle River in Somalia.

While there is no doubt that RVF is responsible for animal disease in the most affected area and in other sites in Kenya, some of the signs observed are not consistent with RVF in livestock and wild animals. Anthrax was thought to be involved but has not been confirmed. The conditions could favour many diseases including those transmitted by the broad range of biting insects that breed in the humid conditions. One such disease, bluetongue, is suspected in improved sheep outside the epidemic area. Contagious caprine pleuropneumonia, a killer disease of goats, has been confirmed near Garissa.

 

Normalized Difference Vegetation Images show good mosquito-breeding grounds in December 1997

FAO warns of high risk that disease will spread

FAO considers the epidemic an international emergency and warns that it could spread. An early warning message from FAO's EMPRES (Emergency Prevention System) and RADISCON (Regional Animal Disease Surveillance and Control Network) has been issued stressing that "the risk exists that the RVF epidemic could expand considerably from its present relatively restricted focus in Kenya and Somalia". The southern and southeastern areas of Ethiopia are at very serious and immediate risk of spread of the disease.

The warning continues, "It is also conceivable that the disease might even cross the Red Sea and affect livestock and people in the Arabian Peninsula, for the first time on record, if conditions exist there for mosquito reproduction".

FAO Animal Health Officer, Peter Roeder, travelled to Kenya on 16 January to work with the Kenya Veterinary Services and WHO experts in putting together a clearer overall picture of the situation. He will also visit Ethiopia to put authorities on the alert.

Prediction of RVF epidemics is the best form of prevention

Effective containment of the current epidemic, given the limitations of available vaccines and the conditions in the country - where heavy rains have started again after a lull in December and many areas are simply unreachable - is almost impossible. Experts consider that vaccination in the face of established RVF epidemics has usually been applied too late to avert them or prevent considerable losses from occurring. Prophylactic immunization remains the only effective means of protecting livestock. However, the long intervals between epidemics - five to ten years in some areas, and more in others - makes it difficult to convince farmers and authorities of the need for continued preventive vaccination, even if it could be justified financially.

FAO is advocating prediction of the emergence of RVF epidemics as the best form of prevention. Monitoring of meteorological and remote sensing data (Cold Cloud Duration and Normalized Difference Vegetation Images) within a geographic information system can identify the unusual conditions that favour massive mosquito multiplication. Monitoring of livestock can indicate periods of increased viral activity. Preventive immunization of livestock could then be carried out in time to avert the most serious consequences.

22 January 1998

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