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NEWS from FAO : New animal disease threats |
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Source: http://www.fao.org/english/newsroom/news/2003/13841-en.html |
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A global early warning system would help control the current upsurge in epizootic emergencies... It seems as though nothing could stop the foot-and-mouth disease epidemic
that devastated UK livestock early in 2001. Just days after veterinarians had diagnosed 27 infected pigs at a rural abattoir, the government imposed a
national ban on all movement of animals. But it was too late - sheep infected by the pigs were already being transported to markets across the
country and abroad. By 13 March, the FMD virus was confirmed in continental Europe, and Britain had launched a massive campaign of "stamping out" that cost the lives of 3.75 million farm animals, the livelihoods of thousands of farmers, and massive damage to the rural economy and the tourist industry. But was the scale of death and disruption inevitable? A recent analysis by FAO's Emergency Prevention System (EMPRES) for transboundary animal diseases suggests that delays in both detecting the outbreak and imposing a ban on animal movements may have favoured the disease's rapid and wide spread. Furthermore, livestock disease experts in Europe had warned months earlier of a dramatic deterioration in the FMD situation worldwide and called for a reappraisal of European countries' control strategies. For EMPRES, the UK's FMD outbreak illustrates an alarming trend: after a steady decline over the past century in the incidence and extent of epidemic livestock diseases in Europe, long-established responses to epizootic threats are no longer adequate.
"Weakest link". Upsurges in animal disease emergencies worldwide are linked to the increased mobility of people, goods and livestock, changes in farming systems and climate, and the weakening of many livestock health services. For this reason, FAO, in partnership with the International Office of Epizootics and the World Health Organisation, is now developing proposals for a Global Early Warning System on Transboundary Animal Diseases (TADs) that would combine the OIE's official disease-reporting system with "innovative methods of disease intelligence". The system would be tightly focussed on major epizootics - such as FMD, rinderpest, Rift Valley fever, African swine fever and avian influenza - and would build on existing national and international disease reporting structures. It would also use a mix of formal and informal techniques, including comprehensive sero-monitoring, abattoir monitoring and incentive-aided disease searching." EMPRES's eight years experience in fighting transboundary animal diseases - from small FMD outbreaks to full-blown rinderpest epidemics - has pinpointed key weaknesses in veterinary epidemiology's traditional approach to disease introduction and geographical distribution. For example, the 1997 FMD outbreak in Taiwan, province of China, spread across the whole island in less than two months, striking 6,000 farms and forcing the slaughter of 3.8 million pigs. But the infection is believed to have gone undetected for as much as six weeks beforehand, apparently because the first cases of FMD - a disease unknown on Taiwan since 1929 - were mistakenly diagnosed as Swine Vesicular Disease. Attempts to stem the spread of the virus also failed because it struck during the Chinese New Year, when market movements of animals increase. This association of risk factors fostered the introduction and spread of the disease, and shows the importance of differential diagnostics in disease emergency preparedness. Transboundary diseases may also arrive from new, unexpected sources. An FMD outbreak in Algeria in 1999 was traced to livestock brought from West Africa across the Sahara which, until then, had been regarded as a natural protective barrier. As in the UK, EMPRES says, the Maghreb outbreak showed that the disease is finding new routes of introduction. Known traditional patterns may need to be re-assessed frequently as changes occur throughout the world. In many developing countries, disease-monitoring systems are based primarily on passive reporting of outbreaks, rather than active disease surveillance, and there is poor coordination of field and laboratory veterinary services. An outbreak of African Swine Fever (ASF) in 2000 among pigs shipped to Dar-es-Salaam, Tanzania, probably originated in known endemic foci in neighbouring countries, and was facilitated by delays in reporting and investigation. High mortality rates among pigs outside the capital, suggestive of acute ASF, were simply not communicated to the country's central epidemiology unit. Better early warning might also have helped block recent outbreaks of Rift Valley fever (RVF), a mosquito-borne viral zoonotic disease that also affects humans. An RVF outbreak in East Africa in 1997-8 not only caused heavy livestock losses and human deaths, but also seriously disrupted the subregion's valuable livestock export trade to the Middle East. In September 2000, the disease was reported for the first time outside the African continent, in Saudi Arabia and Yemen, again causing human deaths and major livestock losses in the livestock population. In all cases, RVF was detected first in humans, i.e. long after the disease had established itself in the livestock population, without being reported. Earlier detection of viral circulation in domestic animals would have avoided the spread of the disease into the human population. Disease intelligence. EMPRES says preventing similar disasters in the
future requires action focused on improving farmer and veterinary awareness,
identifying possible new routes of disease introduction and trends in animal
movements, and improving communication among laboratories and between human
health institutions and veterinary services. Disease intelligence is a prerequisite to effective early warning. In-country surveillance usually
makes use of the formal data-gathering mechanisms. Disease intelligence goes
further and makes use of additional information sources, many of them informal and often outside the standard national surveillance system.
Disease intelligence helps boost awareness of disease threats and developments that may otherwise remain undetected. |
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