世界牛疫撲滅に疫学の果たした役割

Abstract

Smallpox and rinderpest are two extinct viral diseases in recent years. The last case of Smallpox was eradicated in Somalia in 1977 by WHO and rinderpest in Kenya in 2001 by FAO/OIE. There were many features in common between the two diseases, for instance, both viruses have single serotpype; post vaccination immunity is almost life-long etc. The eradication of rinderpest was a major triumph of the veterinary profession.When JP-15 campaign (1962-1976) was terminated after all clinical rinderpest cases were eliminated. However, toward the end of 1970s rinderpest surfaced again in both West and East Africa and moved toward the central Africa. The OAU/IBAR called for another African campaign (PARC) which started in 1986 with support of FAO and EEC. FAO Expert Consultation held in 1987 approved to expand the campaign in two other regions, namely West Asia (WAREC) and South Asia (SAREC). These two campaigns started in 1989 covering all infected countries in the world. PARC terminated its activities in 1998, and WAREC ended in 1994. However, SAREC was divided into two parts, India and Pakistan. The campaign in India called Rinderpest Operation Zero (1989-1996) was implemented in close collaboration with Bhutan, Nepal and Sri Lanka. The campaign in Pakistan was implemented between 1999 and 2002.In 1989, OIE Expert Consultation was held in Paris, and the plans for strengthening surveillance programs of these campaigns were discussed. The outcome of this consultation included the time-bound plans for surveillance for clinically visible rinderpest cases and for sero-positive subclinical cases. This surveillance program, now known as “OIE Pathway”, became mandatory obligation to all the member countries involved in these campaigns. Later, OIE Pathway was also applied to the Global Rinderpest Eradication Program (GREP) of FAO under its new program called EMPRESS, which started in 1994.Extensive studies on rinderpest in wildlife during PARC (1986-1998) in Tanzania and Kenya supported the hypothesis that wildlife were not acting as a long term reservoir of rinderpest virus and that new wildlife epidemics require incursion of virus from another source presumably from cattle. This indicated that mass vaccination of cattle is effective to terminate rinderpest in wildlife. However, wildlife surveillance continued in East Africa under the follow up program called PACE (2000-2006) with improved methodologies. Particular attention was paid to the triangle area in Kenya, Ethiopia and Somalia known as Somali Ecosystem. The last confirmed case occurred in 2001 in buffalo in Meru National Park in Kenya.Some examples of the benefits brought by the world-wide eradication of rinderpest are listed.