Incursions of foot-and-mouth disease virus into Europe between 1985 and 2006.

Foot-and-mouth disease (FMD) is one of the biggest threats to animal health in European countries. In the last 22 years (1985-2006), FMD has occurred 37 times in 14 European countries. Serotype O was most frequently involved in these outbreaks followed by A, C and Asia 1. Sometimes, epidemics were very limited and at other times, they were the cause of devastating economic losses. In most cases (22/37), the origin of the outbreaks could not be determined. For some of these outbreaks, however, routes of introduction and spread were identified through epidemiological inquiries. Moreover, in some cases, the origin of the virus was also traced by phylogenetic analysis of the partial or complete sequences of VP1 genes. Lessons learned from the outbreaks are still useful as most of the same risk factors persist. However, efforts made by FMD-free countries to help those where the disease is endemic are a valuable strategy for the reduction of the global risk. The present and the future potential sources of FMD infection need to be identified to best focus European efforts.

Mass vaccination and herd immunity: cattle and buffalo.

The design of effective programmes for emergency response to incursion of epizootic diseases of cattle, for exclusion of such diseases and for implementation of progressive control in enzootic situations leading to eventual virus elimination, is currently largely empirical. This needs to be remedied to provide more cost-effective use of vaccines and more effective control. At population level, protective effects of immunisation can extend well beyond the individual, influencing the dynamics of viral propagation within the whole population, non-vaccinated as well as vaccinated. This concept of herd immunity and application of the resulting epidemiological principles, combined with experience gained from disease control programmes such as the Global Rinderpest Eradication Programme has much to offer in designing effective science-based control programmes. This paper explores practical exploitation of the herd immunity principle by considering some of the factors which militate against mass vaccination achieving effective levels of herd immunity and, with these in mind, suggesting ways to optimise the efficiency of mass vaccination programmes.

Participatory epidemiology in disease surveillance and research.

Participatory epidemiology is the application of participatory methods to epidemiological research and disease surveillance. It is a proven technique which overcomes many of the limitations of conventional epidemiological methods, and has been used to solve a number of animal health surveillance and research problems. The approach was developed in small-scale, community animal health programmes, and then applied to major international disease control efforts. The Global Rinderpest Eradication Program adopted participatory epidemiology as a surveillance tool for controlling rinderpest. This approach was subsequently used in both rural and urban settings in Africa and Asia, for foot and mouth disease, peste des petits ruminants and highly pathogenic avian influenza. Participatory disease surveillance has made an important contribution towards controlling both rare and common diseases. This paper reviews the principal applications of participatory epidemiology and highlights the lessons learned from field applications. In addition, the authors examine future challenges and consider new areas for research.

A heterogeneous population model for contagious bovine pleuropneumonia transmission and control in pastoral communities of East Africa.

Pastoral cattle live in highly structured communities characterized by complex contact patterns. The present paper describes a spatially heterogeneous model for the transmission of contagious bovine pleuropneumonia (CBPP) developed specifically for pastoral communities of East Africa. The model is validated against serological data on the prevalence of CBPP infection in several communities of southern Sudan and against livestock owner information on community structure, livestock contact and cattle exchange. The model is used to assess the impact of alternative control strategies including mass and elective vaccination programmes, potential treatment regimes and the combination of vaccination and treatment in a single unified strategy. The results indicate that the eradication of CBPP using mass vaccination with currently available vaccines is unlikely to succeed. On the other hand, elective control programmes based on herd level vaccination, treatment of clinical cases or a combination of both vaccination and treatment enabled individual livestock owners to capture a large benefit in terms of reduced animal-level prevalence and mortality experience. The most promising intervention scenario was a programme which combined the vaccination of healthy animals with treatment of clinical cases.

Experience with eradicating rinderpest by vaccination.

Rinderpest was such a devastating disease throughout Africa, Asia and Europe, capable of shaping the destinies of governments as well as the livelihoods of producers and consumers alike, that all sectors of society demanded that scientists should strive to develop a means of protecting cattle against the constant risk. The history of vaccination as a tool for the control of rinderpest is a long one but finally spawned a vaccine which certainly ranks highly among the safest and most efficacious of vaccines. Having this Tissue Culture Rinderpest Vaccine (TCRV) available generated aspirations of global rinderpest control and even eradication, which could now be considered feasible.

Use of participatory epidemiology in studies of the persistence of lineage 2 rinderpest virus in East Africa.

In 1994, rinderpest virus of African lineage 2 was detected in East Africa after an apparent absence of more than 30 years. In 1996, a disease search, based on participatory epidemiological techniques supplemented by serological and virological analyses, was undertaken in southern Somalia and north-eastern Kenya to collate past and current epidemiological information about rinderpest-compatible disease events, and to test the hypothesis that African lineage 2 rinderpest virus persists in populations of transhumant cattle in the Somali ethnic areas. The findings in Afmadu in Lower Juba led the search for rinderpest to the communities in the Bardera area and then on to the Kenya/Somalia border areas between Mandera and El Wak. The herders had a specific knowledge of the clinical signs of rinderpest and provided detailed and accurate descriptions of cases. They differentiated between classical acute rinderpest and a milder syndrome characterised by an ocular discharge and diarrhoea, few oral lesions, corneal opacity and occasional mortality. The studies provided evidence for the endemic occurrence of rinderpest back to at least 1981, with a periodicity of five years in the incidence of the disease. After a period of high mortality in 1992 to 1993, around Afmadu, herders reported a mild disease, with occasional increases in mortality, from other areas of Lower Juba and the Gedo Region. Reports by herders of a rinderpest-compatible disease in the El Wak area were pursued until active cases were located and rinderpest was confirmed.

Rinderpest surveillance performance monitoring using quantifiable indicators.

This paper describes an objective system of monitoring the performance of disease surveillance. The system was developed through dialogue with a number of countries in Africa and adopted as part of the Global Rinderpest Eradication Programme of the Food and Agriculture Organization of the United Nations. The performance monitoring system uses a clinical stomatitis-enteritis case definition, an outbreak investigation classification scheme, and a series of eight performance indicators to measure the sensitivity, specificity and timeliness of the surveillance system. Field-testing indicates that the approach is successful when good record-keeping is practiced and highlights the importance of dialogue in helping to ensure that the system is simple and acceptable. The system provides a quantitative measure of the efficacy of national disease surveillance programmes and of the quality of data derived from such programmes for use in international disease control, animal health information exchange and trade risk analysis.

The control of rinderpest in Tanzania between 1997 and 1998.

In January 1997, Tanzania requested international assistance against rinderpest on the grounds that the virus had probably entered the country from southern Kenya. Over the next few months, a variety of attempts were made to determine the extent of the incursion by searching for serological and clinical evidence of the whereabouts of the virus. At the clinical level, these attempts were hampered by the low virulence of the strain, and at the serological level by the lack of a baseline against which contemporary interpretations could be made. Once it became apparent that neither surveillance tool was likely to produce a rapid result, an infected area was declared on common-sense grounds and emergency vaccination was initiated. The vaccination programme had two objectives, firstly to prevent any further entry across the international border, and secondly to contain and if possible eliminate rinderpest from those districts into which it had already entered. On the few occasions that clinical rinderpest was subsequently found, it was always within this provisional infected area. Emergency vaccination campaigns within the infected area ran from January to the end of March 1997 but were halted by the onset of the long rains. At this time, seromonitoring in two districts showed that viral persistence was still theoretically possible and therefore a second round of emergency vaccination was immediately organized. Further seromonitoring then indicated a large number of villages with population antibody prevalences of over 85%. These populations were considered to have been 'immunosterilized'. Although no clinical disease had been observed in them, it was decided to undertake additional vaccination in a group of districts to the south of the infected area. Serosurveillance indicated that rinderpest could have been present in a number of these districts prior to vaccination. Serosurveillance in 1998 suggested that numerous vaccinated animals had probably moved into districts outside the infected and additional vaccination areas, but did not rule out the continued presence of field infection.

Dealing with animal disease emergencies in Africa: prevention and preparedness.

Emergency preparedness planning for animal diseases is a relatively new concept that is only now being applied in Africa. Information can be drawn from numerous recent disease epidemics involving rinderpest, contagious bovine pleuropneumonia (CBPP) and Rift Valley fever. These examples clearly demonstrate the shortcomings and value of effective early warning with ensured early reaction in the control of transboundary animal disease events. In concert, the Food and Agriculture Organization (FAO), through the Emergency Prevention-System for Transboundary Animal and Plant Pests and Diseases (EMPRES), and Organisation of African Unity/Inter-African Bureau for Animal Resources (OAU/IBAR), through the European Commission-funded Pan-African Rinderpest Campaign (PARC), have been actively promoting the concepts and application of emergency preparedness planning and should continue to do so under the proposed successor of PARC, namely: the Pan-African Programme for the Control of Epizootics (PACE). The potential partnership between the normative function of the FAO in developing and promoting emergency preparedness and the implementation of improved national and regional disease surveillance by PACE and other partners could witness the commencement of more progressive control of epidemic diseases in Africa and greater self-reliance by African countries in coping with transboundary animal disease emergencies.

Disease prevention and preparedness: the Food and Agriculture Organization Emergency Prevention System.

In 1994, the Food and Agriculture Organization undertook to revitalise its activities in the control of transboundary animal disease by establishing a new special programme known as the Emergency Prevention System (EMPRES) against transboundary animal and plant pests and diseases. The emphasis of the EMPRES livestock component is placed on pre-empting outbreaks and losses experienced by agriculture through the enhancement of local capacity to detect and react rapidly to plague events. EMPRES concentrates on the co-ordination of the Global Rinderpest Eradication Programme--a time-bound eradication programme--whilst addressing the progressive control of the most serious epidemic diseases within a broad framework of emergency preparedness. Programme activities are discussed in relation to early warning, early reaction, facilitating research and co-ordination. In addition to rinderpest, particular attention has been paid to contagious bovine pleuropneumonia, a re-emerging disease in Africa targeted for strategic attention, and foot and mouth disease, for which co-ordinated regional control in Latin America and South-East Asia has been initiated. Tactical responses to other disease emergencies such as African swine fever, classical swine fever (hog cholera), Rift Valley fever, peste des petits ruminants and lumpy skin disease are described.

Rinderpest: a case study of animal health emergency management.

The history of rinderpest and control of the disease in Africa and Asia is reviewed briefly. The present distribution of rinderpest virus in relation to its phylogenetic lineages is presented. Rinderpest-free countries bordering rinderpest-infected countries are considered to be under permanent threat of a transboundary rinderpest incursion and therefore face continuous and serious emergency situations. The nature of these emergencies in relation to the remaining foci of the three lineages is described. It is argued that the Global Rinderpest Eradication Programme (GREP) eradication strategies now need to focus on the use of epidemiological studies to define foci of infection and guide targeted, pulsed vaccination campaigns rather than broad, routine vaccination. The emergency posed by the re-emergence of African lineage 2 virus in East Africa and the challenge of mild rinderpest is explored in some detail as a phenomenon which may be more widespread than has been assumed. Points at which the future of GREP is threatened are illustrated and means of removing some of the dangers are suggested. The lessons which need to be learnt from the experience of the Indian National Project on Rinderpest Eradication and the Pan-African Rinderpest Campaign are discussed, including the value of strengthening surveillance systems in accordance with the Office International des Epizooties Pathway and how to cope with the problem associated with cryptic foci of rinderpest persistence--perhaps the greatest challenge facing GREP. The value of vaccine buffer zones is considered in detail and the authors conclude that unless those zones are of considerable depth and are well maintained, they are unlikely to prevent dissemination of the virus. The role of emergency preparedness planning in preventing the spread of rinderpest is discussed, with the understanding that effective surveillance, as a component of emergency preparedness planning, is safer than vaccination as a means of ensuring that the disease does not re-enter or penetrate a population. The swift initiation of a programme for the eradication of rinderpest from Pakistan is seen as the key issue in dealing with the Asian lineage rinderpest emergency. Development and implementation of strategies with the benefit of experience gained in Africa and India could provide a rapid resolution of the emergency.

Nasal obstruction caused by nutritional osteodystrophia fibrosa in a group of Ethiopian horses.

A severe, advanced case of nutritional osteodystrophia fibrosa is described in a 10-year-old gelding with primary upper respiratory obstruction and chronic weight loss, which was one of a group of similarly affected horses in Ethiopia. The diagnosis was based on the clinical signs, gross lesions, histopathology and management history. The affected bones had suffered severe mineral depletion.

Foot-and-mouth disease in Ethiopia from 1988 to 1991.

During the period 1988 to 1991 samples from 16 foot-and-mouth disease outbreaks in Ethiopia were examined at the National Veterinary Institute, Ethiopia, and at the FAO World Reference Laboratory for Foot-and-Mouth Disease, UK. Typing of the virus responsible was possible in 13 of these outbreaks representing 10 separate disease events; 8 of these were caused by serotype O and 2 by serotype SAT2. This is the first record of the presence of serotype SAT2 foot-and-mouth disease virus in Ethiopia. In contrast to earlier studies serotypes A and C were not detected.

Peste des petits ruminants in Ethiopian goats.

An outbreak of disease characterised by fever, ocular and nasal discharge, coughing and sneezing, oral necrosis, diarrhoea, enteritis and pneumonia in goats was shown by the use of specific cDNA probes to have been peste des petits ruminants, confirmed for the first time in Ethiopia. Both morbidity and mortality rates were high in goats but sheep were not affected.

Agents associated with neonatal diarrhoea in Ethiopian dairy calves.

Faeces samples collected from diarrhoeic dairy calves in the first 8 weeks of life were examined for the presence of 5 enteropathogens. The majority of the 108 diarrhoea cases occurred in the first 5 weeks of life and a commercial ELISA kit detected bovine enteric coronavirus (BEC) in 38.9%, serogroup A rotavirus (RV) in 16.7% and K99 (F5) fimbrial adhesin-positive Escherichia coli (K99 ETEC) in 11.1 per cent. Concurrent infections of these enteropathogens were detected in 14.8% of samples (30.8% of samples positive for these agents). No evidence of cryptosporidial infection was found using a differential staining method on faecal smears nor was salmonella excretion detected. On 2 of the 8 farms only BEC was present; the other 6 farms were positive for all 3 agents. It is concluded that BEC is the major infectious cause of neonatal calf diarrhoea in the Ethiopian dairy herds studied with RV and K99 ETEC also contributing to morbidity, either alone or as mixed infections.

Development of monoclonal antibody ELISA for simultaneous detection of bovine coronavirus, rotavirus serogroup A, and Escherichia coli K99 antigen in feces of calves.

A rapid ELISA was developed for simultaneous detection of bovine coronavirus (BCV), rotavirus (RV) serogroup A, and Escherichia coli K99 antigen in feces of calves. A mixture of 3 monoclonal antibodies specific for BCV, RV, or K99 was used successfully to capture the antigens; the same antibodies labeled with peroxidase were used to detect BCV, RV, or K99. The triple ELISA was compared with standard reference diagnostic methods by examining feces from experimentally and naturally infected and healthy calves. All the components of the test were highly specific (greater than 90%) and sensitive (BCV, 77%; K99, 93%; RV, 100%) when used in a format requiring short incubation steps at 20 C and visual recording of results.

Failure to establish congenital bluetongue virus infection by infecting cows in early pregnancy.

Two groups of 10 pregnant cows were inoculated with bluetongue virus type 11 at either 40 or 60 days of gestation. All the cows became infected as judged by the detection of viraemia and seroconversion but they showed no clinical signs. Seventeen of the cows produced live calves none of which showed any evidence of prenatal infection. After challenge with the same virus all the calves became viraemic and seroconverted. The response to challenge of the two groups did not differ from that of a control group challenged at the same time. It was concluded that the infection of pregnant cows in early gestation with this virus did not result in the transplacental infection of the fetuses and did not produce immunotolerant, latently infected calves.

DNA probes for the detection of toxin genes in Escherichia coli isolated from diarrhoeal disease in cattle and pigs.

DNA gene probes specific for genes coding for heat labile toxin (LT), heat stable toxins (STpa, STpb) and Vero-cell toxins (VT1, VT2) were used to examine 1031 diarrhoeal disease isolates of E. coli (345 from cattle and 686 from pigs). Of the bovine strains, 60 hybridized with the STpa probe and most possessed the K99 (F5) or F41 adhesin. Five bovine strains possessed STpb genes and five either VT1 or VT2 genes. Of the porcine strains, 245 hybridized with one or more gene probes. Of 160 K88 (F4) positive strains, 133 possessed both LT and STpb genes, whilst 17 possessed LT or STpb or STpa alone or in combination. Ten K88 strains did not possess toxin genes. Isolates bearing the K99 (F5) adhesion possessed either STpa, STpb and VT2 genes alone or in combination; in one isolate only the LT gene was detected. Isolates belonging to serogroup 0138:K81 were more heterogeneous as to their toxin genes; of the 60 strains, fourteen carried only VT2 genes, thirty-two carried VT2, STpa and STpb genes, one carried LT, VT2, STpa and STpb genes, two carried STpb gene, four carried STpa and STpb genes, one carried LT and VT2 genes, two carried LT and STpa genes, whilst four carried none. Twenty-four percent of all toxigenic strains apparently did not possess adhesins.