Rift Valley Fever (RVF) Preventive measures for Middle Eastern countries Updated November 2007

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1 Regional Representation For the Middle East 1. RVF in brief 1 Rift Valley Fever (RVF) Preventive measures for Middle Eastern countries Updated November 2007 Rift Valley fever (RVF) is a peracute or acute, febrile, mosquito-borne, zoonotic disease caused by a virus of the family Bunyaviridae, genus Phlebovirus. It usually presents in epizootic form over large areas of a country following heavy rains and flooding, and is characterised by high rates of abortion and neonatal mortality, primarily in sheep, goats and cattle. The susceptibility of different breeds to RVF varies considerably. Some indigenous African animals may have only inapparent infections, while exotic or other breeds suffer severe clinical disease with mortality and abortion. Susceptible, older nonpregnant animals and some other species usually do not show signs of disease. Camels have been regularly involved in the RVF epidemics in East Africa and Egypt. Clinical disease is not seen in adult camels, but abortion occurs and some early post-natal deaths have been observed. Signs of the disease tend to be nonspecific, rendering it difficult to recognise individual cases. During epidemics, however, the occurrence of numerous abortions and mortalities among young animals, together with disease in humans, is characteristic. RVF has a short incubation period: hours in lambs. A biphasic fever of up to 41 C may develop, and the fever remains high until shortly before death. Affected animals are listless, disinclined to move or feed, and may show enlarged superficial lymph nodes and abdominal pain. Lambs rarely survive longer than 36 hours after the onset of signs of illness. Animals older than 2 weeks may die peracutely, acutely or may develop an inapparent infection. Some animals may regurgitate ingesta and may show melaena or bloody, foul-smelling diarrhoea and bloodstained mucopurulent nasal discharge. Icterus may sometimes be observed, particularly in cattle. In addition to these signs, adult cattle may show lachrymation, salivation and dysgalactia. In pregnant sheep, the mortality and abortion rates vary from 5% to almost 100% in different outbreaks and between different flocks. The death rate in cattle is usually less than 10%. The hepatic lesions of RVF are very similar in all species, varying mainly with the age of the infected individual. The most severe lesion occurring in aborted fetuses and newborn lambs is a moderately to greatly enlarged, soft, friable liver with a yellowish-brown to dark reddishbrown colour with irregular congested patches. Numerous greyish-white necrotic foci are 1 OIE, Manual of diagnostic tests and vaccines for Terrestrial Animals, chap

2 invariably present in the parenchyma, but may not be clearly discernible. In adult sheep, the lesions are less severe and pinpoint reddish to greyish-white necrotic foci are distributed throughout the parenchyma. Haemorrhage and oedema of the wall of the gallbladder are common. Hepatic lesions in lambs are almost invariably accompanied by numerous small haemorrhages in the mucosa of the abomasum. The contents of the small intestine and abomasum are dark chocolate-brown as a result of the presence of partially digested blood. In all animals, the spleen and peripheral lymph nodes are enlarged, oedematous and may have petechiae. Microscopically, hepatic necrosis is the most obvious lesion of RVF in both animals and humans. In fetuses and neonates of cattle and sheep, foci of necrosis consist of dense aggregates of cellular and nuclear debris, some fibrin and a few inflammatory cells. There is a severe lytic necrosis of most hepatocytes and the normal architecture of the liver is lost. In about 50 % of affected livers, intranuclear inclusion bodies that are eosinophilic and oval or rod-shaped are found. Mineralisation of necrotic hepatocytes is also seen. In adult animals, hepatic necrosis is less diffuse and in sheep, icterus is more common than in lambs. In humans, RVF infections are usually inapparent or associated with a moderate to severe, nonfatal, influenza-like illness. A minority of patients may develop ocular lesions, encephalitis, or severe hepatic disease with haemorrhagic manifestations, which is generally fatal. RVF virus has caused serious human infection in laboratory workers. Staff should either be vaccinated and work under containment level 3, work under containment level 4 conditions, or wear respiratory protection. Particular care needs to be exercised when working with infected animals or when performing post-mortem examinations. No significant antigenic differences have been demonstrated between RVF isolates and laboratory-passaged strains from many countries, but differences in pathogenicity have been shown. Infection of humans by mosquito vectors is a striking feature in countries, such as Egypt, with a relatively small population of animal hosts and a large population of mosquitoes. RVF usually occurs in epizootics in Africa, which may involve several countries in a region at one and the same time. These follow the periodic cycles of exceptionally heavy rain, which may occur very rarely in semi-arid zones (25-35-year cycles), or more frequently (5-15-year cycles) in higher rainfall savannah grasslands. Low level undetectable RVF activity may take place in inter-epizootic periods. RVF should be suspected when unusually heavy rains are followed by the occurrence of abortions together with fatal disease marked by necrosis and haemorrhages in the liver that particularly affect newborn lambs, kids and calves, concurrent with the occurrence of an influenza-like illness in farm workers and people handling raw meat. Preventative measures to protect workers from infection should be employed when there are suspicions that RVF-virus-infected meat and tissue samples are to be handled.

3 2. Commonly asked questions on RVF During the consultative meeting held in Rome in , a questionnaire was circulated to the expert seeking answers to pertinent questions that are frequently asked by veterinarians and public health officials. The consensus answers are summarized below: Recovered and immune animals are safe to trade and eat; Immune animals can never be viraemic and are safer than susceptible animals; If animals are IgG antibody positive and IgM antibody negative they pose no risk to humans or livestock; If they are IgM antibody positive then there is a possibility that RVF virus has recently been active; The Smithburn strain of modified live virus vaccine is very useful, (apart from its well known abortigenic properties); There is a need for a human vaccine; Chilled meat presents little or no danger for export; A ban on livestock trade in pre-epizootic or epizootic conditions is fully justified; A ban can be safely lifted three to six months after the last evidence for RVF virus activity; Infected areas remain infected if vectors are present; There is a risk that RVF may extend its range by movement of infected vectors to receptive areas in the Middle East and Asia. 3. Monitoring the RVF by modeling the vector activity AO in action 6 The ecology of RVF has been intensively explored in East Africa. Historical information has shown that pronounced periods of RVF virus activity in Africa have occurred during periods of heavy, widespread and persistent rainfall now associated with El Niño events. As an example, the outbreak of December 1997 in Kenya followed times above average rainfall. The outbreak then rapidly spread to Somalia and Tanzania, with human cases estimated at Incriminated vectors were floodwater Aedes species whose breeding habitats are known as dambos in Kenya, which are temporary ground pools in the fringe of main rivers. Periods of persistent rainfall raise the ground water table to a level where the breeding sites of Aedes become flooded and the eggs regain their moisture. Eggs harbouring the RVF virus will hatch in great number and finally female adults can transmit the virus to susceptible hosts during blood meals. Widespread rainfall in the region is caused by the changing characteristic of the Intertropical Convergence Zone, the zone of confluence of air currents from north and south in the African continent, as a consequence of El Niño events triggered by large scale changes in sea surface temperature in the Pacific and Indian Oceans. Vegetation responds to increased rainfall and variation can be easily measured by satellite. In East Africa, vegetation index maps have been used together with ground data in monitoring vector populations and RVF viral activity, which established a correlation between these two 2 FAO, UNDP, OU/IBAR, November 2001, Reducing the risk of Rift Valley Fever, The Combined Report of the Consultative Meeting of Experts Reducing the Risk of Rift Valley Fever Transmission, held at FAO, Rome on 15 th 16 th May 2001, and the Technical Meeting Reducing the Risk of Rift Valley Fever Virus Transmission in the Horn of Africa held in the Silver Springs Hotel, Nairobi on 21 st -22 nd June 2001.

4 parameters. In a more prospective way, vegetation measurements can be used to forecast RVF before it reaches epidemic proportions. Data sets used in these predictions include satellite outputs, which are used to generate various indices including vegetation index (NDVI) or Cold Cloud Duration (CCD) which are correlated with rainfall. Predictive models have been greatly improved by the addition of Pacific and Indian Ocean Sea Surface Temperature anomaly measurements, together with the rainfall and NDVI data. Risk maps are then produced by calculating vegetation index and rainfall anomalies comparing current conditions to long-term mean conditions. Resulting maps show areas experiencing above normal rainfall. Increased potential for RVF epizootic virus activity is forecast by such model and then warning message could be made Recommendation for Middle Eastern countries RVF has the potential to quickly spread to the Horn of Africa (Somalia, Djibouti, Ethiopia). As a large traditional livestock trade exists between countries in the Horn of Africa and countries in the Middle East, a major challenge is to manage the risk of spreading RVF with such livestock shipments. Importing countries must be given adequate safety assurances with respect to RVF, while the livestock trade, which is vital for the livelihoods of agropastoralists in both regions, is maintained as far as possible. From 1999 to 2001, the disease spread from the Horn of Africa to Yemen and Saudi Arabia, causing human suffering and mortalities, severe losses in young animals and disruption in the regional trade of live animals.sporadic cases have continued to appear in Saudi Arabia in subsequent years, where stringent measures are implemented to control the outbreaks (restriction of animal movements, systematic control of mosquitoes, vaccination with a live, attenuated vaccine and surveillance). Direct and indirect economic losses have been estimated to exceed 75 million US$ per year 4. Joint planning and the implementation of programmes, based on OIE recommendations 5 by animal health authorities in both exporting and importing countries could achieve this. This was the main recommendation made by experts on this issue, during notably: the regional meeting on the epidemiology of Rift Valley Fever in the Arabian Peninsula and its applications for animal and human health and livestock trade was organized, in Sharja (UAE) in November 2004, jointly by the OIE Commission for the Middle East Regional Emergency Veterinary Committee (REVC) and the Red Sea Livestock Trade Commission (LTC), an autonomous body under the African Union s Interafrican Bureau for Animal Resources (see appendix 1). 3 FAO, EMPRES WATCH, November 2006, Possible RVF activity in the Horn of Africa 4 Shimshony A., Economides P., 2006, Disease prevention and prparedness for animal health emergencies in the Middle East, Rev. sci. tech. Off. Int. Epiz., 25 (1), OIE, Animal Terrestrial Health Code, 2006, Chapter ,

5 the FAO/UNDP Expert Consultation on Risk Assessment and Risk Reduction of RVF Transmission in Trade Exchanges between the Horn of Africa and the Arabian Peninsula was held in May The meeting proposed a framework of action, which includes activities to be carried out by both exporting and importing countries during periods of epizootic RVF, pre-epizootic RVF conditions and between epizootics. The proposals are summarized in the table n 1. Level of RVF risk Activity in exporting country Activity in importing country HIGH Define extent of infection Cease all imports of livestock from affected regions Epizootic RVF Longitudinal monitoring of infection in livestock populations (i.e. clinical surveillance, virus isolation/ IgM antibodies) Determine the point at which virus activity has returned to preepizootic levels Resume trade 3-6 months after the last evidence of infection OR when the country considers the high risk has disappeared Increase vigilance at ports of entry POTENTIALLY HIGH Pre-epizootic conditions identified Increase the level of monitoring in known RVF epizootic areas, such as floodplains, by clinical surveillance for abortion in livestock, disease in humans and serology in livestock Consider vaccination of trade stock at least one month before movement Increase random sampling at ports for evidence of recent infection (IgM antibody in the absence of a history of vaccination) If vaccinated animals are to be accepted they should be randomly sampled at ports for IgG antibodies LOW Interepizootic period Monitor sentinel herds in highrisk areas (floodplains, etc.) Consider vaccination of all trade animals at 9-12 months of age Regular random sampling of trade animals for IgM antibodies Table n 1: Framework proposed by An FAO/UNDP Expert Consultation on Risk Assessment and Risk Reduction of RVF Transmission in Trade Exchanges between the Horn of Africa and the Arabian Peninsula the interregional workshop on RVF control and preventive strategies organised by the OIE Regional Representations for Africa and Middle East in collaboration with FAO and AU/IBAR and held in Cairo June (see appendix 2). 6 FAO Animal Health Manuals - 15 Preparation of Rift Valley fever contingency plans (2003) (ftp://ftp.fao.org/docrep/fao/005/y4140e/y4140e00.pdf') 7 OIEME, Report of the OIE/FAO/AU-IBAR conference on RVF Control and Preventive Strategies, Cairo, June 2007

6 Appendix 1: Recommendation of the conference of the epidemiology of Rift Valley Fever in the Arabian Peninsula and its applications for animal and human health and livestock trade was organized, in Sharja (UAE) in November 2004 Appendix 2: Recommendations of the OIE workshop on Rift Valley fever control and prevention strategies, Organised in collaboration with FAO and AU-IBAR, Cairo, Egypt, June 2007 Appendix 3: documents of interest

Appendix 1: OIE ME Commission REVC AU-IBAR Red Sea LTC EPIDEMIOLOGY OF RIFT VALLEY FEVER IN THE ARABIAN PENINSULA AND ITS IMPLICATIONS FOR ANIMAL AND HUMAN HEALTH AND LIVESTOCK TRADE SHARJA (UAE),

RVF may have a wider distribution in the region, than is currently believed.

RVF epizootic periods are extremely rare in the region and are correlated with periods of a high El Nino activity.

implemented in RVF pre-epizootic, epizootic and inter-epizootic periods in the region.

Within each country, high risk areas should be defined, based upon the highest levels of sero-positivity in animals and the ecology of the area.

7 Appendix 1: OIE ME Commission REVC AU-IBAR Red Sea LTC EPIDEMIOLOGY OF RIFT VALLEY FEVER IN THE ARABIAN PENINSULA AND ITS IMPLICATIONS FOR ANIMAL AND HUMAN HEALTH AND LIVESTOCK TRADE SHARJA (UAE), November 2004 Considering that: RECOMMENDATIONS RVF is a Regional Problem, which has a considerable impact upon animal and public health and upon livestock trade in the region. RVF may have a wider distribution in the region, than is currently believed. There is a general lack of baseline temporal and spatial information on RVF virus activity throughout the Region, efforts should be made to undertake studies to remedy the situation. RVF epizootic periods are extremely rare in the region and are correlated with periods of a high El Nino activity. Participants recommended that: OIE member countries in the Middle East and Greater Horn of Africa should discuss trading issues related to RVF in order to reach a consensus on the strategies to be implemented in RVF pre-epizootic, epizootic and inter-epizootic periods in the region. Each country should determine the distribution of RVF virus following an epizootic period, by a post-epizootic serological survey. Within each country, high risk areas should be defined, based upon the highest levels of sero-positivity in animals and the ecology of the area. Countries should establish some competence in the identification of RVF vector species, their population dynamics and feeding biology. Countries in the region are urged to establish emergency preparedness and contingency plans for a RVF epizootic, to promote a regional network and to discuss their capacities and strategies in order to react to RVF epizootic model predictions. Member countries should address issues related to trading activities. These should consider the long inter-epizootic periods, when very little or no virus activity is taking place and the pre & epizootic periods, as identified by a predictive model. They should especially address the time of onset and removal of any trade restrictions taken in the relevant situations. It is suggested that a period of three to six months after the last recorded evidence for any virus activity, should be taken as a guideline. Participants expressed their wishes to improve the exchange of information on RVF in the region and urged member countries to establish their trade regulations following the OIE standards.

8 Appendix 2: OIE workshop on Rift Valley fever control and prevention strategies CONSIDERING THAT Organised in collaboration with FAO and AU-IBAR Cairo, Egypt, June 2007 Original: English Recommendation 1. Numerous outbreaks of Rift Valley fever (RVF) have occurred in Eastern Africa causing heavy casualties in cattle, sheep, goats and camels as well as in humans; 2. RVF occurs historically in the sub-saharan African continent, Madagascar and the Arabian Peninsula, but a change in risk factors could favour outbreaks of the disease in previously uninfected countries posing a threat to human and animal health; 3. There is a need for countries adjacent to known infected countries to develop and implement appropriate surveillance and early warning programmes; 4. The disease is endemic in many countries and epidemics tend to occur at irregular spatial and temporal intervals depending on climatic and environmental conditions that favours the breeding of the insect vector and it is therefore important for countries to be equipped with appropriate technologies to be able to establish contingency plans to predict and prepare for future occurrences; 5. The disease can best be controlled by animal vaccination and vector control that need to be maintained and applied well in advance of expected risk periods for occurrence of the disease; 6. Outbreaks of RVF has a significant impact on the trade of ruminants especially from the Horn of Africa to the Middle East with a consequent significant loss of income for livestock owners in the affected areas; 7. The negative impact of RVF on regional trade can be significantly alleviated if countries are capacitated through good veterinary governance to develop and apply sanitary measures for disease control and prevention to satisfy the appropriate level of sanitary protection required by importing countries; 8. The control of the disease will require a common effort from national; regional and international organisations such as OIE, FAO, WHO, UNICEF and AU- IBAR.

9 THE WORKSHOP ON RIFT VALLEY FEVER CONTROL AND PREVENTION STRATEGIES RECOMMENDS THAT: 1. The OIE continue to develop surveillance guidelines for vector-borne diseases taking into consideration the effect of climatic changes on the global spread of these diseases. 2. Training and technical assistance be provided to countries by international organisations and donors to equip countries within the risk areas of Africa and the Middle East to rapidly diagnose the disease and to undertake predictive epidemiological studies for contingency planning. 3. The OIE continues its efforts within African and Middle East countries to promote and develop good veterinary governance to enable countries to effectively prevent and control the disease at the animal source. 4. The OIE and FAO continue to support the accelerated development and registration of diagnostic tests and vaccines for RVF. 5. Countries in the Region with the support of OIE, FAO and AU-IBAR the OIE Regional Representations in Africa and in the Middle East and their related Regional Animal Health Centres develop a regional strategy for the prevention and control of RVF in support of the GF-TAD s program. 6. OIE and FAO supports countries of the two regions in developing a model based on risk parameters, including agro-climatic, to forecast potential RVFV activities particularly within the framework of the related Regional Animal Health Centre. 7. Close collaboration and communication between OIE, FAO and WHO and national veterinary and public health authorities should be improved and maintained in the surveillance and control of RVF and rapid actions following the detection of disease in either humans or animals. 8. Countries should ensure compliance with their obligations on animal disease reporting by promptly reporting all outbreaks of RVF to the OIE for incorporation into the OIE World Animal Health Information System (WAHIS). 9. Exporting and importing countries follow the standards, guidelines and recommendations of the OIE regarding international trade of ruminants and products with respect to RVF with particular attention to the application of diagnostic tests, quarantine and the application of vaccines. 10. Countries in the Middle East and Africa continue to support Recommendation No. 3 adopted during the seminar in Cairo from 11 to 13 October 2004 by putting into effect the health certificates for intra-regional trade in animals and animal products between the two regions. Countries of the region agree on a regional certification with respect to exports of ruminants and ruminant products only to the extent necessary to protect human and animal health without unnecessarily restricting trade.

10 Appendix 3 : Documents of interest Disease cards: OIE: FAO: Recognizing rift valley fever - FAO Animal Health Manuals 17 ftp://ftp.fao.org/docrep/fao/006/y4611e/y4611e00.pdf WHO OIE Recommendations: Terrestrial Code Manual diagnostic and vaccines Contingency plans Preparation of Rift Valley fever (RVF) contingency plans (2003) FAO Animal Health Manuals 15 ftp://ftp.fao.org/docrep/fao/005/y4140e/y4140e00.pdf Netherlands National Disease Contingency Plans: Australia National Disease Contingency Plans: uid=2b29abf1-cbe5-d8f1-c8c5-f5ca4780dbd8&sitename=aahc

Rift Valley Fever. What is Rift Valley Fever?

Rift Valley Fever. What is Rift Valley Fever? Rift Valley Fever What is Rift Valley Fever? Rift Valley fever (RVF) is a peracute or acute insect-borne disease of man and animals, historically restricted to Africa. An outbreak of RVF in animals frequently