In cataloguing some of the experiences of early warning given below, several important points should be taken into consideration - the fruit of lessons learned or not learned over the years during TAD outbreaks and efforts for their control. The examples chosen cover a worldwide geographical area and range from smaller outbreaks of foot-and-mouth disease (FMD) to those that developed into epidemic proportions.
The Executive Committee of the European Commission for the Control of FMD clearly warned member countries about the dramatic deterioration of the FMD situation worldwide. One of the follow-up recommendations of its 65th session was to urge countries to reappraise their strategies and operations to account for these new realities
The most recent major FMD outbreak in the United Kingdom (UK) was recorded in 2001. Before the 1981 Isle of Wight (UK) occurrence, the last major epidemic in the UK was in 1967/68. Many articles and publications were generated on this episode, such as the Report of the Committee of Inquiry on FMD (called the Northumberland Report), which illustrated the importance of early detection of an epidemic. The studies, parameters and policy generated by the 1967/68 outbreak quickly developed into a model. However, with the recent UK 2001 epidemic, new data and parameters have been generated and will be used for further studies on the epidemiology of the disease and to develop new models.
A retrospective analysis of the UK epizootic shows that a delayed warning was responsible for the wide spread of the disease in the country. Indeed, the introduction of the FMD virus has been confirmed to have occurred early in February or late January, while clinical detection took place only on 20 February, about three weeks after initial introduction. It has also been advanced that an earlier introduction of a national ban on animal movements (introduced instead officially on 23 February 2001) would have greatly contained the spread of the FMD epidemic - by approximately 43 percent. Indeed, by the time the national ban on livestock movements was implemented, 74 cases were already incubating in other parts of the country.
If the early warning mechanism at national level showed some signs of weakness, it can also be questioned whether or not the introduction of FMD in Europe was somehow predictable, and if the international community could have been more active in alerting national authorities.
During its 65th session in November 2000, the Executive Committee of the European Commission for the Control of FMD (EUFMD) clearly warned member countries about the dramatic deterioration of the FMD situation worldwide. One of the follow-up recommendations of this meeting was to urge countries to reappraise their strategies and operations to account for these new realities. This declaration came as an echo of the recommendations of the meeting of the Research Group, held earlier in September 2000, and from the results of the expert elicitation workshop on the risk of introduction of FMD to Europe.
However, it must be highlighted that, at the time, there was a consensus of experts that the FMD threat to Europe would come mainly from its southeastern region, particularly from Turkey. The results of the above-mentioned workshop also indicated that the first point of introduction of FMD to Europe was more likely to be the Balkans, followed by eastern Europe, southern Europe and, to a lesser extent, western Europe and the "Islands" (UK).
Consequently, although the reintroduction of FMD to Europe was not a complete surprise in the current epidemiological situation worldwide, the pattern of introduction of the disease was fairly different from what had been imagined earlier.
Given the globalization of trade and the wide distribution of FMD in the world, it is likely that FMD-free countries will have to face other incursions of the disease in the future. It is therefore critical to develop emergency preparedness and contingency plans at national and regional levels to prevent the occurrence of other disasters.
In 1997, an epidemic of FMD broke out in Taiwan Province of China and spread throughout the island in less than two months.
An outbreak was first detected in Hsinchu province (western part of the main island) on 14 March 1997, and successive cases were reported in the same prefecture on 17 March. Following these outbreaks, emergency vaccination of pigs and susceptible zoo animals was carried out by the authorities, to control the spread of the disease and particularly to protect the eastern part of the main island.
Nevertheless, the entire island, measuring 380 by 140 km, was infected in approximately 50 days, from the first reported FMD case on 14 March until 3 May 1997. During that period, more than 6 000 farms were infected and 3.8 million pigs were slaughtered, while 13 million doses of vaccine were used during the vaccination exercise.
FMD spread in Taiwan Province of China
It is believed that the FMD infection could have been present on the Taiwanese mainland six weeks before the disease was first detected. How can such a delay in disease recognition be explained?
First, Taiwan Province of China had been free of FMD since 1929, which may explain a lack of awareness with regard to the disease. Furthermore, swine vesicular disease (SVD), which cannot clinically be distinguished from FMD, had been observed in 1997, suggesting that FMD could have been misdiagnosed as SVD. In addition, the disease appeared at the time of the Chinese New Year, a period traditionally known for an increase in animal movements. This association of risk factors certainly fostered the introduction and spread of the disease in the island, and shows the importance of differential diagnosis in disease emergency preparedness.
The FMD outbreak in the Maghreb is an excellent illustration of disease spread through new routes of introduction. Increase in trade exchanges, improvement of means of communication and transportation create opportunities for TADs to enter new populations and areas
FMD infection has been cyclic in the Maghreb region for several decades. The infection has been regularly introduced into the region from the east and west. Its main routes of introduction have been from Egypt and the Libyan Arab Jamahiriya in the east (the Tunisian FMD virus infections of 1969, 1975, 1979, 1982 and 1989) or from the west through either South America (1977) or Spain (1983). Throughout this period, the Sahara desert has played the role of a protective barrier, preventing disease infection and spread from the infected countries of West Africa.
Algeria. In 1999, FMD was detected in beef cattle near the capital city, Algiers. A limited spread eastward and westward to different localities was also reported (see map). In total, 165 farms and 139 communes were infected, while 1 605 animals were destroyed, 2 153 slaughtered and 1 270 685 vaccinated.
FMD spread in North Africa - 1999
Morocco and Tunisia. FMD occurrences were reported in Morocco on 25 February 1999, in the province of Oujda near the Algerian border. Only two outbreaks were reported in Tunisia: one on 2 March in Grombalia (Nabeul Governorate) and the other on 11 March in Jendouba, on the border with Algeria.
The 1999 FMD occurrence in Algeria registered a complete change in the epidemiological feature of FMD in the Maghreb region. The close relationship recognized between the Algerian FMD strain and strains found in West Africa showed the emergence of a new route of virus introduction into the Maghreb region, represented by the Sahara.
However, the disease spread in Algeria and neighbouring countries was limited for two main reasons:
As observed in the FMD epidemic in the United Kingdom, the FMD outbreak in the Maghreb is an excellent illustration of disease spread through new routes of introduction. Increase in trade exchanges, improvement of means of communication and transportation create opportunities for TADs to enter new populations and areas. Hence known traditional patterns may need to be reassessed frequently as changes occur throughout the world.
The absence of laboratory diagnostic capacity for ASF, the lack of disease awareness at national and regional levels, and the delay in disease reporting are the main shortcomings of the disease surveillance and early warning system with regard to the ASF epizootic in the United Republic of Tanzania
The presence of African swine fever (ASF) has previously been reported in the United Republic of Tanzania, with the most recent and serious outbreaks affecting the Mbeya and Kilimanjaro regions in the 1980s.
The 2001 ASF outbreak in the capital city, Dar-es-Salaam, was confirmed at Onderstepoort Veterinary Institute, South Africa, in May 2001, and occurred principally among pig units of pig meat traders receiving pigs from the northern regions of Mbeya, Morogoro, Dodoma, Tanga, Arusha and Kilimanjaro.
The virus was described to have no relation with the warthog related strains and closely resembled the Mozambique/Malawian strains, suggesting that the disease might have originated from these known endemic foci in the northern region of Malawi and eastern parts of Zambia, both of which border with Tanzania.
FAO assisted the Tanzanian Government in implementing an ASF emergency control programme, through the technical cooperation project "Emergency surveillance for rinderpest and other transboundary animal diseases" (TCP/URT/0067). Since a stamping-out policy was not adopted, alternative control measures were taken, such as the identification of affected pigs through epidemiological investigation, the implementation of quarantine measures and dissemination of information through the media on the main features of the disease to avoid further spreading.
On 20 February 2002, a workshop was held in Dar-es-Salaam, attended by Tanzania's senior animal health staff and a FAO consultant, to review the 2001 ASF outbreaks and the lessons learned. Delay in disease reporting and ineffective disease investigation seem to have been the main factors responsible for the spread of the disease
Although ASF was diagnosed in peri-urban areas of Dar-es-Salaam towards the end of May 2001, it is now known that there were high pig mortalities, suggestive of acute ASF, in the Mbeya area as early as February. These outbreaks were not properly investigated and the information was not communicated to the Central Epidemiology Unit of the Veterinary Services in the capital. There were further delays when the disease reached Dar-es-Salaam, as the first cases were seen and treated by a private veterinary practitioner and not reported to government veterinarians for at least two weeks. In addition, the laboratory diagnosis for ASF was not in place in Tanzania in 2001 and specimens had to be sent to Onderstepoort Veterinary Institute in South Africa for confirmation.
Furthermore, in late 2000, it was known that ASF was very active across the border in Malawi and this could have raised "alarm bells" since movement of pigs from this country into Tanzania is known to occur. Also, the local government authorities (LGAs) failed to strengthen the initial response actions of the municipal veterinary services with their own emergency response. The LGAs' negligence was attributed to lack of financial resources. Moreover, at the LGA level, no one was assigned to follow up and document all the outbreak cases until the Zoosanitary Unit intervened at the ministerial level. The emergency disease response mechanism was also not implemented at the national level, which could probably be attributed to the low disease priority status accorded earlier to ASF.
However, it is now realized that threats of ASF to Tanzania are increasing because of the recent upsurge of the disease in many parts of Africa, improved means of transport and expansion of the pig industry in the country.
In conclusion, the absence of laboratory diagnostic capacity for ASF, the lack of disease awareness at national and regional levels, and the delay in disease reporting are the main shortcomings of the disease surveillance and early warning system with regard to the ASF epizootic in Tanzania.
During the last six years, ASF has leapt to prominence in Africa as a re-emerging disease. In 1996, a devastating ASF epizootic occurred in Côte d'Ivoire, destroying a flourishing pig industry around Abidjan and also in the central and western parts of the country. The epidemic, which was introduced in April 1996 in Abidjan and rapidly spread in July to the central and western regions of the country, resulted in the loss of 80 percent of the commercial pig herd. The extension zones for ASF have followed illegal movements of pigs and pork products from the infected areas.
The disease was eradicated within a year, but at a very high cost, and the industry is only now showing signs of recovery.
The first case was recorded on 16 April 1996 among 43 pigs in a backyard piggery of Abidjan. At first, the farmer slaughtered some of the diseased pigs, but sold some others to farmers in Abidjan, fostering the spread of the disease. Two weeks later, on 1 May, one of the farmers whose pigs were affected by the disease decided to contact a veterinarian, who alerted the Direction of Veterinary Services and the Central Veterinary Laboratory. Lesions of acute ASF were apparent from clinical observations and the necropsy that was performed. The laboratory confirmation was carried out at the ASF reference laboratory in France on 21 May 1996. A preliminary epidemiological investigation revealed that the source of infection was likely to be product wastes that had been brought in from an ASF-infected country to feed the pigs.
In spite of early efforts to stamp out the epizootic, the disease spread to village pigs in various parts of the country, and can be related to:
Although ASF eradication in Côte d'Ivoire can be seen as a successful example of disease control as the disease was in fact eradicated, it should not be forgotten that this epidemic ruined all the efforts by the government and professionals for the development of the pig industry in the country. The economic loss was estimated at around 10 539 million CFA francs (US$14 000), and more than 25 percent of the national herd was lost.
The RVF regional initiative in West Africa shows that early detection of the disease could be a reality in the future if the system is actively instituted. However, interepizootic periods can be long and have a negative impact on disease awareness. The combination of the system with other disease surveillance initiatives could be a solution to keep stakeholders' interest and provide an important contribution to public health
Rift Valley fever (RVF) is a mosquito-borne viral zoonotic disease. The first recorded outbreak of RVF in Egypt in 1977 caused an estimated 200 000 human cases of the disease with some 600 deaths, as well as large numbers of deaths and abortions in sheep and cattle and other livestock species.
The disease occurrence in Mauritania in September 1998 also registered human deaths and huge livestock losses. An outbreak of the disease in East Africa in 1997-8 not only caused considerable livestock losses and human deaths, but also seriously disrupted the valuable East African livestock export trade to the Near East. This resulted in severe sociological problems, especially in Somalia, where ruminant trade is almost the only means of livelihood for many families and communities.
In September 2001, RVF was reported for the first time outside the African continent, in Saudi Arabia and Yemen, here also causing human deaths and major losses in the livestock population. It was considered the first documented RVF outbreak outside the African continent, although the virus could have been endemic in the wadi zones for some years in cryptic foci.
RVF sentinel herd monitoring in Mali
PHOTO COURTESY OF VINCENT MARTIN/EMPRES
On all these occasions, RVF fever was first detected in humans, while the disease was actually evolving in the livestock population without being reported. This observation has led to the conclusion that earlier detection of viral circulation in domestic animals would have been essential to avoid the spread of the disease to the human population.
In order to address this issue, FAO has been actively involved in strengthening early detection of the disease, particularly in West Africa where a regional RVF regional surveillance system was established in 2000. The project's activities have focused on developing early warning capacity at national and regional levels, combining classical disease surveillance techniques and the monitoring of climatic indicators stemming from satellite imagery.
Two years of regional surveillance in Mali, Mauritania and Senegal have shown the relevance of the system, which operates during the rainy season - considered as the high-risk period for the disease. After the 1998 epizootic, no viral circulation was observed in 2000 in Senegal and Mauritania, whereas some very low-level viral circulation was detected in Mali.
The absence of clinical signs of the disease was ascertained by field investigation missions in Mali. Follow-up field missions and serological surveys were carried out to ensure the disease would not develop into epizootic proportions. Population sensitization and education were also addressed to prevent human contamination whenever the disease occurs.
The RVF regional initiative in West Africa shows that early detection of the disease could be a reality in the future if the system is actively instituted. However, interepizootic periods can be long and have a negative impact on disease awareness. The combination of the system with other disease surveillance initiatives could be a solution to keep stakeholders' interest and provide an important contribution to public health.
The past decade has been rich in disease epizootics of different natures, often changing the traditional understanding of veterinary epidemiology concerning disease introduction and geographical distribution.
In the light of the most recent events, lessons should be learned to prevent the re-emergence of major disasters, focusing in particular on the following issues: