A meeting of the Global Rinderpest Eradication Programme (GREP) was held in Rome from 30 September to 2 October 2002.
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The GREP Secretary reported to the meeting that in the two years since the last meeting rinderpest had been confirmed and reported to OIE only in two farms near Karachi in Sindh Province of Pakistan (the most recent in October 2000) and in African buffaloes in Meru National Park in central Kenya in early-to-mid 2001. There was also evidence from participatory epidemiological studies that rinderpest could have been affecting cattle herds belonging to the Murle and Jie pastoralists east of the Nile in southern Sudan in late 2000 to mid-2001, although this was not confirmed. These reports all relate to the three known persisting reservoirs of infection previously identified and there has been no reason to suspect that rinderpest has occurred outside these reservoirs. Indeed, accruing surveillance data increasingly support its absence elsewhere. The absence of rinderpest from recent emergencies and disasters is quite remarkable and very different from the situation that existed less than a decade ago. It is clear that significant progress has been made over the past two years.
The absence of rinderpest from recent emergencies and disasters is quite remarkable and very different from the situation that existed less than a decade ago |
Passive surveillance with investigation of suspicious disease outbreaks combined with active disease searches in Punjab and Sindh and serosurveillance studies suggest that the rinderpest virus is no longer present in Pakistan. Afghanistan remains free - massive movements of buffaloes and some cattle from Pakistan to Afghanistan, with onward trade to the Islamic Republic of Iran, have not been accompanied by rinderpest, even though most of the animals originate from from Punjab and Sindh. Herd immunity levels must now be extremely low as there has been no rinderpest vaccination in Afghanistan for more than five years and in Pakistan for more than two years; even prior to that coverage was extremely low.
Asia is now free from rinderpest for the first time in millennia |
Participatory disease search and serosurveillance studies in Yemen suggest that the virus died out in the country about five years ago. Very little vaccination has been practised there for some years now. Thus, it is conceivable that Asia is now free from rinderpest for the first time in millennia. Surveillance data continue to accrue in support of that premise.
It was decided by all stakeholders working in the Sudan (the Government of the Sudan and a non-governmental organization [NGO] network coordinated by FAO Operation Lifeline Sudan), together with colleagues from the Pan African Programme for the Control of Epizootics (PACE), that the suspected outbreak of rinderpest in cattle belonging to the Murle people in early 2001 should be addressed by mass immunization in an attempt to “immunosterilize” the Murle and Jie livestock in particular. This was carried out during the latter half of 2001 and early 2002. Investigation of suspicious occurrences of “stomatitis-enteritis” by all parties since mid-2001 has not revealed any cases of rinderpest. Participatory disease searches by PACE staff has similarly failed to detect any clinical disease. Thus, it would appear that the Sudan no longer harbours rinderpest. From 2001, vaccination was limited to east of the Nile, and since June 2002 it has no longer been allowed anywhere in the country. Nor is vaccination practised in neighbouring countries, except for the anachronous maintenance of part of the “cordon sanitaire” in Central Africa.
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However, despite the growing confidence that the Asian lineage 3 and African lineage 1 viruses might now be extinct, it will be some time in the future before disease and serological surveillance can be expected to provide unequivocal evidence that the rinderpest virus has been eliminated. Strengthening surveillance in key high-risk areas is now a priority to provide the necessary information.
Serosurveillance studies backed up by clinical disease surveillance, conducted by Terra Nuova for the PACE-Somalia National Project, have made a significant contribution to understanding the extent of the endemic focus and the periodicity of the epidemic cycle. A clear understanding of both these issues is important before attempting to define interventions. Serological data have been fed into the stochastic state transition rinderpest disease model being developed by Dr Jeffrey Mariner for PACE's Community-based Animal Health and Participatory Epidemiology (CAPE) Unit and GREP, which represents a further advance in epidemiological understanding.
In brief, the current working hypothesis is that the epicentre of the endemic zone lies within the area covering the southern half of Transjuband extending southwest from Afmadu into North Lamu in Kenya. Epidemic extensions occurring at intervals of approximately four-to-five years, and strongly influenced by drought, extend the area as far as Beletweyne, the Shebelle River and the coastal plain of southern Somalia to the north and east, Mandera and Gedo to the north, Meru National Park to the west and Tsavo National Park to the south. Occasional, more widespread, epidemics carry the virus into Masailand, even as far as Loliondo and the Serengeti National Park in the United Republic of Tanzania to the west and Mkomazi Game Reserve to the east. Work is continuing, through PACE, to clarify the situation and will probably lead to a refined understanding of the critical area for rinderpest maintenance in the near future.
In June 2002, the Interafrican Bureau for Animal Resources (IBAR) and PACE convened a meeting in Nairobi to consider how to approach the issue of rinderpest persistence in the Somali pastoral ecosystem. This meeting was both valuable and successful: in essence, the outcome was an endorsement of the need to initiate action for timely eradication. It was considered, although not unanimously, that participatory disease search techniques should be able to detect areas of active infection, even with the mild strain, if teams could be trained and deployed in the field. Even if this approach was not totally effective, at least a sufficient proportion of incidents could be detected for interventions (focal vaccination) to reduce the reproductive rate to below one, leading subsequently to extinction.
The United Republic of Tanzania is receiving support from FAO as an emergency measure to strengthen surveillance for rinderpest in the north of the country because of concerns that an incursion of rinderpest might not be detected. Investigation of epidemiologically significant events in cattle and buffaloes has not detected rinderpest to date.
It was concluded that, throughout most of the world, the emphasis is shifting from control through emergency or routine vaccination to disease surveillance and reporting. Indeed, the stage has been reached where there no longer appears to be any justification for routine mass vaccination programmes. There are only two justifications for vaccination at present:
The major challenge currently facing GREP is that of ensuring the timely elimination of the Somali pastoral ecosystem reservoir before the virus reinvades the countries adjacent to the reservoir and those linked to it, even intermittently, by trade in cattle. Should progress falter, the world will be very vulnerable to a devastating resurgence of rinderpest. This vulnerability is highlighted by disturbing rumours of trade being established between southern Somalia and countries in Southeast Asia. Should rinderpest accompany this movement of livestock, it could prove disastrous for the trading prospects of African countries.
Verification of freedom from rinderpest through the OIE pathway continues |
Verification of freedom from rinderpest through the OIE pathway continues; significant progress has been marked by Nepal becoming the first country to be recognized as being free from infection after having progressed through the entire pathway, with Myanmar and Thailand also being recognized as free from the disease.
The priority issues of strengthening the GREP/OIE mechanism for verification of freedom from rinderpest, regionalization to promote ownership and commitment, and establishment of certification committees are second in importance only to the timely elimination of the last focus of rinderpest persistence.
If current confidence in the success of eradication efforts in many countries proves to be well-founded, the goal of internationally verified freedom from rinderpest by the year 2010 will still be just about achievable. However, the next year is critical and will require intensive action to be focused on the eastern African rinderpest reservoir and sustained until eradication is achieved before the end of 2003. This result would represent a slippage of one year in terms of what was planned in 2000 because of lack of progress with respect to the lineage 2 focus. If either action and achievement are delayed for any reason, or if free areas are reinvaded through expansion of the virus outside the reservoir, the whole timetable will need to be rethought.
The meeting addressed the issue of how to eradicate rinderpest from the Somali pastoral ecosystem rather than advising on the systems for global verification of freedom, as had originally been intended. It was clearly agreed that responsibility for eradicating rinderpest from Africa lies with IBAR. The Bureau's responsibilities include the following:
THE OIE-GREP PATHWAY TO GLOBAL RINDERPEST FREEDOM
Other meeting recommendations
The meeting endorsed the recommendations of the June meeting held in Nairobi by the African Union (AU)-IBAR/PACE and the Kenyan Veterinary Department to address the situation of mild rinderpest in eastern Africa as the basis for PACE action. It was recognized that to do so would require IBAR to address certain issues including, inter alia:
AU-IBAR is requested to expedite, by means of action plans, the registration, production and storage of quality-assured, safe, pure, efficacious and potent vaccines that facilitate differentiation between vaccinated animals and those that have been infected with wild virus. Specifically, these vaccines are to include the vaccinia recombinant vaccine developed by the International Laboratory of Molecular Biology (ILMB), the chimaeric vaccine developed by the Institute for Animal Health (IAH) Pirbright Laboratory and the proposed marker protein additive vaccine.
The meeting reiterated and endorsed the recommendations made at the Organization of African Unity (OAU)-IBAR/International Atomic Energy Agency (IAEA) Technical Cooperation Project RAF/5/053 meeting on serosurveillance held in Nairobi in April 2002. Relevant abstracts of the text are included in the box.
DIAGNOSIS AND SURVEILLANCE OF RINDERPEST For the diagnosis and surveillance of rinderpest, the objective is to develop rapid, inexpensive and simple diagnostic tests for rinderpest and peste des petits ruminants (PPR). The following recommendations have been made to improve further upon the recommendations on the combinations of tests that were adopted during the regional workshop, “Update on technologies for surveillance of rinderpest freedom”, held in Dakar, Senegal, 19-30 November 2001.
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Kenya: investigation of rinderpest suspicion in Laikipia
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In late October 2002, the Director of Veterinary Services of Kenya notified OIE of clinical and pathological findings in cattle on a ranch in Laikipia near Rumuriti in Rift Valley Province of central Kenya that raised suspicions of rinderpest. Coming a year after the confirmation of rinderpest in African buffaloes of nearby Meru National Park in 2001, this was a cause for serious concern. The ranch is situated on both sides of the main stock route from Maralal to Rumuruti. The ranch also adjoins ranches grazed by pastoralists' livestock. Thirty-five yearling cattle out of 457 cattle of all ages were reported to have died. Investigations were launched rapidly and samples for rinderpest diagnosis were submitted to the National Veterinary Research Centre Muguga Laboratory, KARI. Subsequently, a team of veterinarians from the Kenyan Veterinary Services and OAU-IBAR/PACE visited the area in early November to carry out field investigations. Clinical and post-mortem examination of cattle on the ranch did not reveal any signs of rinderpest, nor did investigations at ranches in the surrounding area. The results of laboratory diagnostic investigations by RT-PCR (reverse transcription-polymerase chain reaction) on eye swabs, tissues and buffy coats; AGIDT (agar-gel immunodiffusion test), serum antibody assay by ELISA and virus neutralization test (VNT) were all reported to be negative. Investigations focusing on both cattle and wildlife continue with teams working in the surrounding farms and ranches. It is hoped that these will support the conclusion that rinderpest can be ruled out as the cause of the initial suspicions.
Source: Kenya Veterinary Services.
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United Republic of Tanzania:investigation of suspected rinderpest in buffalo in Maswa Game Reserve, Shinyanga Region
On 15 September 2002, the Director of Veterinary Services in the United Republic of Tanzania received a report of abnormal mortality among buffalo in Maswa game reserve (MGR). A field investigation team consisting of staff from both the wildlife and veterinary services was dispatched within two days. The mission observed various species of wildlife, including 900 buffaloes in MGR and 500 buffaloes in Serengeti National Park, as well as giraffe, greater kudu and eland. Except for a lion-kill buffalo, neither carcasses nor skeletons were found. The animals appeared to be in good body condition and did not show any indication of diarrhoea, lachrymation or nasal discharge. Necropsies conducted on the lion kill and a second buffalo that was euthanized in the southern Serengeti (pneumonic lesions in the right lobe of the lung) did not show lesions indicative of rinderpest. The first had multiple abscesses in both lungs, which were found to result from tuberculosis (culture and isolation in the Central Veterinary Laboratory [CVL], Temeke). The samples collected from the second animal were found to be negative for rinderpest in immunocapture ELISA, and sera were negative for rinderpest antibodies.
PACE Tanzania commissioned the Tanzania Wildlife Research Institute (TAWIRI) to collect buffalo sera from wildlife in, among other sites, the MGR, jointly funded by an FAO Technical Cooperation Programme project and the national PACE project. The sample collection costs are approximately US$ 100 per sample. Serum samples submitted to CVL-Temeke were all negative for rinderpest antibodies by H-competitive ELISA. Consequently, rinderpest was ruled out as the cause of mortality reported among buffalo in MGR. This was the first real test of the newly defined Tanzanian national contingency plan against rinderpest. The Tanzanian Veterinary Services remain on high alert for such suspicious events.
Source: Tanzania Veterinary Services.
Yemen: investigation of suspected rinderpest in a calf in Sana'a
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A seven-week-old calf in the old city of Sana'a was the cause of a rinderpest alarm in September. This was one of three similar calves originating from a Friesian dairy farm. They had been sold through a market before being sold on to a butcher, who kept them for a few days. Diarrhoea was noticed, together with a lesion on the gum reminiscent of rinderpest. When investigated by staff of the Department of Animal Resource's Strategy Unit, one week after the appearance of the mild clinical signs, the calf was afebrile and its two companions were apparently normal. Eye and mouth swabs were tested by the rinderpest penside test with apparently positive results, raising an alarm. However, the test had been performed with test units that were several years beyond their expiry date and with an incorrect suspension buffer; this invalidated the results. [Moral of the story: never use expired diagnostic reagents and always follow the manufacturer's instructions.] Subsequent tests with new penside units, by the AGIDT and by immunocapture ELISA at the Central Laboratory in Sana'a were all negative. One of the calves was seropositive. Further investigations involved trace-back to the farm of origin, where no indications of rinderpest were seen; numerous penside tests were performed on eye swabs, with negative results. Sera from non-vaccinated cattle were also negative by competitive ELISA. The last rinderpest vaccination had taken place in March 2000. The dam of the affected calf had not been vaccinated whereas the dam (over seven years old) of the seropositive calf had been. The calf was necropsied 11 days after onset of clinical signs without finding any lesions suggestive of rinderpest, except possibly for some slight haemorrhages suggestive of “zebra striping” in the large intestine.
Source: Yemen Department of Animal Resources.
Comments
It is gratifying to note the rapid response of the national veterinary services in all these cases and Kenya's fulfilment of OIE reporting obligations. The recognition of these events and the rapid response to them inspire confidence in the ability of national veterinary services to detect rinderpest should it occur and indicate that rinderpest surveillance systems are functional. The time to be concerned would be when we no longer hear of such events occurring, for that would indicate that surveillance systems for rinderpest have ceased to work. Experience from other countries suggests that, ideally, one should detect and investigate in the order of one suspicious stomatitis-enteritis event per year per 100 000 head of cattle in a rinderpest-free at-risk country (see Performance indicators for rinderpest surveillance, IAEA Tecdoc 1261). The investigations described here are not the only ones being carried out. Future Bulletins will carry reports on other examples of functioning rinderpest disease surveillance systems, including the extremely active disease investigation system being operated in the Sudan in collaboration between the Government of the Sudan, the national PACE project and the FAO Operation Lifeline of Sudan working with NGOs.
