Since the Manual on the diagnosis of rinderpest was first published in 1986 the geographical distribution of the disease has shrunk dramatically. The first edition was commissioned by the Food and Agriculture Organization of the United Nations (FAO) to support international and national rinderpest eradication campaigns that were about to be launched in Africa, India, West Asia and South Asia in response to the widespread recrudescence of the disease in the early 1980s. The Pan-African Rinderpest Campaign (PARC), the Indian Rinderpest Operation Zero and the Western Asia Rinderpest Eradication Campaign (WAREC) achieved spectacular success completing their strategic phases of mass vaccination; clinical rinderpest has been largely eradicated from East and West Africa, leaving only one persistent focus in an area north of Lake Turkana and a second in the Awash Rift Valley of Ethiopia; northern India, likewise, is essentially free of the disease and Operation Rinderpest Zero is currently concentrating its efforts in southern India; and, similarly, within four years of launching the campaign, the WAREC coordinators announced in 1993 that all 11 participating countries in the Near East were free of overt rinderpest. These successes have stimulated FAO, in collaboration with the International Office of Epizootics (OIE), to establish a Global Rinderpest Eradication Programme (GREP); given peace on earth this is likely to be achieved. Mass vaccination has stopped in the operational areas and the eradication campaigns have now entered the technically more difficult and demanding phase of "active disease surveillance". The keystone for success in disease surveillance is rapid, accurate diagnosis. In the eight years that have elapsed since the first edition of the manual was distributed, a veritable flood of new diagnostic procedures have been developed, resulting from the exponential advances in molecular biology and immunology. Although it is too early for many of the new techniques to have become routine, several are now available, for example monoclonal antibodies that identify specific rinderpest antigens and differentiate between closely related morbilliviruses. Specialist laboratories now have techniques to amplify virus genome from field samples by polymerase chain reaction (PCR) and obtain the nucleotide sequence from the PCR product, enabling rapid identification of the geographic origin of the isolate. A seminal development has been the promotion and international standardization of enzyme-linked immunosorbent assays (ELISA) for rinderpest antibodies by the Joint FAO/IAEA Division of the International Atomic Energy Agency, Vienna, Austria, in collaboration with the Institute for Animal Health, Pirbright Laboratory, United Kingdom. All the countries where rinderpest is enzootic have the resources and expertise to run the ELISA which, together with the availability of specific monoclonal antibodies, allows differentiation between antibodies to the viruses of rinderpest and peste des petits ruminants.
Containment is part and parcel of the active disease surveillance phase. The objective is to prevent spread of rinderpest virus from a newly detected focus, the main methods being an enforced total ban on animal movement within the vicinity of the focus and ring vaccination around the focus. Currently used vaccines based on Plowright's attenuated cell culture-adapted RBOK strain or cell-culture derivatives of Nakamura's attenuated lapinized strain are excellent and safe immunogens, but they are labile at ambient temperatures. This weakness has been overcome with the development of Mariner's ultra-dry Vero-cell derivative of Plowright's strain (Thermovax); vials of Mariner's vaccine are still potent after exposure to 30°C for 30 days. Meanwhile, the new breed of molecular engineers have exploited the known high immunogenicity of rinderpest virus to hone their skills in fashioning recombinant virus vaccines. Three groups - one in the United States, a second in Japan and the third in the United Kingdom - have succeeded, and it is likely that one or more of these recombinant rinderpest vaccines will fill the need for a safe non-infectious rinderpest vaccine for use in immune-barrier zones and in ring vaccination.
This edition of the manual has the same organization as the first edition - three parts and appendixes. Part I deals with the presumptive field diagnosis, Part II contains guidelines for the collection and submission of specimens for diagnosis and Part III, the longest section, describes proven confirmatory diagnostic methods .The appendixes outline the preparation of hyperimmune anti-rinderpest serum, cite recipes of stock solutions and demonstrate the calculation of 50 percent end-point dilutions.
Rapid, accurate diagnosis is an essential precursor for the global eradication of rinderpest virus. It is hoped that this second edition of the Manual on the diagnosis of rinderpest will enable personnel of the active disease surveillance teams and district and central laboratories to refresh their diagnostic skills and help rid the world of rinderpest. A rinderpest-free world would be of immense economic benefit to developing countries currently threatened by the disease.
