Manual on the preparation of rinderpest contingency plans
FAO, Rome 1999
download pdf version Contents | Introduction | Chapter 2 | Chapter 3 | Chapter 4 | Chapter 5 | Chapter 6
Visiting Scientist, EMPRES/Infectious Diseases Group, Animal
Health Service,FAO, Rome.
Professor of Veterinary Medicine, University of Ibadan, Ibadan, Nigeria.
Peter L. Roeder
Animal Health officer, EMPRES/Infectious Diseases Group, Animal Health Service, FAO, Rome.
William A. Geering
Consultant, EMPRES/Infectious Diseases Group, Animal Health Service, FAO, Rome.
Former Director, Animal and Plant Health, Bureau of Resource Sciences and Deputy Chief Veterinary Officer, Commonwealth of Australia
Rinderpest is a classic example of a transboundary animal disease (TAD). TADs are defined for FAO's Emergency Prevention System for Transboundary Animal and Plant Pests and Diseases EMPRES as diseases that are significant in terms of economics, trade and/or food security for several countries, that can easily spread to other countries and reach epidemic proportions and that require Cupertino between countries for control and management, including exclusion.
The OIE International animal health code includes rinderpest in List A diseases, which are defined as "communicable diseases which have the potential for serious and rapid spread, irrespective of national borders, which are of serious socio-economic or public health importance and which are of major importance in the international trade of animals and animal products". Various regional control and eradication campaigns have resulted in rinderpest being restricted to a few fairly well defined locations.
A "world without rinderpest" is envisaged by the year 2010.
This manual provides information on the nature of rinderpest and on the principles and strategic options relating to control and elimination of rinderpest in the event of its being reintroduced into a country that is free of disease and infection. It provides guidelines for individual countries to formulate their national policy on rinderpest control and eradication. The manual identifies the personnel, equipment and facilities needed in a national rinderpest contingency plan. A suggested outline of the format and contents of a national rinderpest contingency plan is also provided as a guide; this should be modified to suit the needs and circumstances of individual countries. Consideration has been given to the provisions in the OIE International animal health code in the preparation of the manual. It is suggested that this manual, which is based on the format of the Australian veterinary emergency plan (AUSVETPLAN) with some modifications, should be used together with the Manual on the preparation of national animal disease emergency preparedness plans, FAO, Rome, 1999.
Other sources of information on rinderpest which are recommended for use with this manual include:
This manual will be reviewed regularly and revised in the light of experience. Suggestions and recommendations for amendments should be forwarded to:
FAO Animal Health Service
Animal Production and Health Division
Viale delle Terme di Caracalla
00100 Rome, Italy.
Tel.: +39 06 5705 4798/6772
Fax: +39 06 5705 3023
Nature of the disease
Rinderpest, or cattle plague, is an acute, highly contagious viral disease of wild and domesticated ruminants and pigs. It is characterised by sudden onset of fever, oculonasal discharges, necrotic stomatitis, gastroenteritis and death.
In a fully susceptible population, as is the case in non-endemic areas, morbidity and mortality can approach 100 percent. With some strains of the virus, however, the disease may be mild with low mortality from infection.
Formerly widespread throughout Europe, Asia and Africa, rinderpest has now been limited to fairly well defined locations in South Asia, the Near East and eastern Africa. This has been achieved through various national and regional rinderpest eradication programmes. Global rinderpest eradication, which is being targeted for 2010, is being co-ordinated by FAO.
Rinderpest virus belongs to the morbillivirus genus of the paramyxovirus family. Other members of the genus include the measles virus of humans, the peste des petits ruminants virus of domesticated and some small wild ruminants, the canine distemper virus of dogs and wild carnivores and the morbilliviruses of aquatic mammals.
There is only one serotype of rinderpest virus, but the different strains vary in their pathogenicity.
Large domestic ruminants
Although all cloven-hoofed animals are probably susceptible to infection, severe disease occurs most commonly in cattle, domesticated water buffaloes and yaks. Breeds of cattle differ in their clinical response to rinderpest virus. Some breeds have developed a high innate resistance through selection by long association with the disease.
Sheep and goats are generally less susceptible but may develop clinical disease.
Asiatic pigs are susceptible and may suffer clinical disease. European breeds are less susceptible. The latter tend to undergo subclinical infection and play little or no part in the maintenance of the disease.
Camels are apparently not infected and appear to have no role in rinderpest transmission and maintenance.
Some species, such as African buffalo, eland, giraffe, lesser kudu and warthog and Asian antelopes, bovids and swine, are highly susceptible. Others, such as antelopes, hippopotamus and Indian blackbuck are less susceptible. There is no evidence to suggest that wildlife populations can maintain the disease indefinitely without concurrent disease in cattle.
Rinderpest does not infect humans.
Almost invariably, rinderpest spreads between herds and to new areas by the movement of infected animals. Infected cattle start shedding virus one or two days before the appearance of clinical signs. They continue to shed virus for about nine to ten days after the onset of fever, and generally harbour the virus for no more than three weeks. Infected cattle may spread virus through markets and transport it long distances before clinical evidence of the disease is observed.
Rinderpest virus is found in expired air, nasal and ocular discharges, saliva, faeces, milk, semen, vaginal discharge and urine. Infection is transmitted primarily by inhalation of expired air contaminated by infected drop-lets or by contact with secretions and excretions from infected animals. Transmission occurs mainly over short distances, but occasion-ally may occur over distances of up to 100 m or more at night, when the effects of high temperature and sunlight are minimal, especially in conditions of very high humidity.
Transmission through the oral route by ingestion of contaminated feed and water is possible. Infected meat stored at 4°C can remain infective for at least seven days. Feeding of infected meat and feed contaminated with infective secretions and excretions may serve as a source of infection for pigs, which may then transmit the disease to cattle.
Rinderpest is not transmitted by insect vectors.
At 4°C, rinderpest virus is most stable at pH values of 7.2 to 7.9 and is rapidly inactivated at pH less than 5.6 or greater than 9.6. The virus is inactivated rapidly at environmental temperatures by solar radiation and desiccation. Pasture is infective for six hours if unshaded or 18 to 48 hours if shaded. Contaminated bare enclosures are infective to cattle for no more than 48 hours and contaminated buildings for a maximum of 96 hours.
The virus is highly susceptible to many lipid-solvent disinfectants because it is enveloped. It is also susceptible to both acid and alkaline conditions. It is inactivated rapidly by autolysis and putrefaction and hence does not survive for more than 24 hours in the carcass of an animal that has died from the disease.
The virus is present in milk one or two days before appearance of clinical signs. Heat treatment or pasteurisation of milk is sufficient to inactivate the virus.
Rinderpest is capable, in certain situations, of causing devastating losses in cattle herds, but tends to have less impact in endemic areas and on partially immune populations. The disease may be peracute, acute or mild, depending on a number of factors inherent in the virus strain, the host and the system of management of the animals.
In peracute rinderpest, there is a sudden onset of fever, inappetence, depression, congestion of the visible mucous membranes and death within two to three days, before oral erosions develop.
The OIE International animal health code puts the incubation period of rinderpest as 21 days for purposes of zoosanitary measures. The route of infection, the dose and the virulence of the strain of virus may modify the incubation period. In general, the period between the first index case and the appearance of secondary cases is about two weeks. Typically, the disease is heralded by a sudden onset of pyrexia, which may last anything from between three and five days to two weeks, before returning to normal. This is accompanied by restlessness, depression, inappetence and a significant fall in milk yield. Respirations are shallow and rapid. One or two days later, serous oculonasal discharges and severe congestion of the mucous membranes of the eyes and nose are typically seen. Two to five days after the onset of fever, tiny, pinpoint greyish areas of necrosis appear on the gum and lips. The lesions increase in number, enlarge and coalesce to form a thick, yellow pseudo-membrane covering the oral mucosa including the lateral and ventral aspects of the tongue. The necrotic debris easily desquamates, leaving shallow erosions with red layers of basal cells. Similar erosions can also be seen on the mucous membranes of the nose, the vulva and the vagina. Salivation is stimulated, the saliva being initially mucoid and then mucopurulent. A distinctive foul odour exudes from the mouth. Diarrhoea starts one to three days after the appearance of oral lesions. The faeces are initially thin and dark in colour, and may later become watery and contain mucus, shreds of epithelium and specks of clotted blood. Occasionally the liquid faeces may be red in colour.
Affected animals arch their backs and strain; sometimes exposing congested and eroded rectal mucosae.
Respirations are laboured and painful and there may be an audible grunt on expiration. In fatal cases the diarrhoea continues to worsen, causing rapid dehydration and visible wasting. Sternal recumbency follows and death supervenes 6 to 12 days after the onset of fever. If animals survive, the erosions heal, diarrhoea stops and a prolonged convalescence follows, with recovery to full health taking many weeks. Pregnant cows commonly abort in the convalescent period.
Skin lesions, which appear as a maculo-papular rash on the less hairy parts of the body such as the groin and axillae, have been described.
The evolution and clinical signs of mild rinderpest are similar to those of the classic syndrome but are less marked. One or more of the cardinal features may be absent or only present transiently, particularly oral erosions, which may be meagre. Most affected cattle recover, and convalescence is short. A frequent sequel of mild infections is activation of latent pathogens, notably protozoa, occurring four to six days after the start of the prodromal fever. The signs of the activated infection may predominate and mask the appearance of clinical signs of rinderpest.
Sheep and goats
Small ruminants more commonly suffer the subacute form of the disease, characterised by transient fever without remarkable systemic disturbances. In areas where peste des petits ruminants (PPR) is endemic, most rinderpest-like syndromes are more likely to be PPR. However, acute rinderpest can occasionally be seen in small ruminants. Clinical manifestations are similar to those seen in cattle, and consist of fever (rectal temperatures of 41 to 42°C), focal to coalescent necrotic stomatitis, oculonasal discharges, conjunctivitis, pneumonia and diarrhoea.
Asiatic breeds of pigs may suffer peracute or acute rinderpest. Peracute disease is characterised by sudden onset of fever and death without further premonitory signs. Acute disease in these breeds of pigs is manifested by sudden onset of fever, inappetence, depression, shivering, vomiting and epistaxis. Shallow erosions, diarrhoea, progressive but rapid dehydration and emaciation precede death.
Wild ungulates differ markedly in their manifestation of rinderpest infection. Buffaloes react with a clinical syndrome essentially the same as that in cattle, whereas lesser kudus exhibit profuse discharge of tears and corneal opacity progressing to death from dehydration and starvation. Any unexplained incidence of morbidity and mortality in wild ungulates in areas where there is a risk of rinderpest should be viewed with suspicion and investigated thoroughly. Generally, strains of rinderpest virus that produce mild disease in cattle may cause severe disease in susceptible wildlife species.
The carcass is dehydrated, sometimes emaciated and soiled with loose faeces. The eyeballs are sunken and encrusted with mucopurulent discharges. The muzzle and external nares may be encrusted with similar exudates. The oral cavity usually contains necrotic material and areas of erosion from desquamated epithelium, primarily on the gums, buccal papillae, lateral and ventral aspects of the tongue and the soft palate. In severe cases, these erosions extend to the pharynx, the oesophagus and the forestomach. Lesions consisting of congestion, oedema, haemorrhages and erosions may also be seen in the abomasum and the small intestines. The large intestines, from the caecum to the rectum, may show varying degrees of congestion, erosions and linear haemorrhages (usually described as zebra striping), especially around the ileo-caecal valve and the caecal tonsils. These haemorrhages are bright red in fresh carcasses or greenish-black in stale or decomposing ones. The mucosa of the upper respiratory tract may be congested and show haemorrhages. The lungs may be normal in animals that died in the early stages of the disease or show congestion and interlobular and alveolar emphysema in older cases. The lymph nodes in early deaths may be swollen and oedematous but in late deaths may be shrunken and grey, with radial streaks in the cortex. The spleen is usually normal but occasionally may have subserosal haemorrhages along its margins.
Microscopic findings consist essentially of extensive lymphocytolysis with depletion of the lymphocytes in the germinal centres of lymph nodes and the spleen. The epithelial cells of the alimentary tract reveal areas of necrosis and ulceration with formation of multinucleated giant cells as well as intranuclear and intracytoplasmic inclusion bodies in lymphatic cells and alimentary tract epithelial cells.
There is only one immunogenic type of rinderpest virus and immunity to one strain will protect against all other known strains. One vaccine will thus protect against all field strains. Serum antibodies are first detectable within one week of infection with classical rinderpest strains. However, animals infected with mild strains may take ten days or longer to develop neutralising antibodies, as do animals vaccinated with tissue-culture rinderpest vaccine (TCRV). For all practical purposes, animals are immune one week after vaccination, although serum antibody titres do not peak for about three weeks. Serum neutralising antibodies are a major component of active immunity against infection and have an important role in recovery.
In endemic areas and those where vaccination is routinely carried out, calves acquire passive immunity with the intake of colostrum from their immune dams and the antibody can persist for up to 11 months, preventing vaccine virus from generating an immune response.
Rinderpest should be suspected when there is any unusual occurrence of morbidity associated with a stomatitis-enteritis syndrome characterised by nasal and ocular discharge with any two of the following signs: fever, oral erosions or lesions, excessive salivation, diarrhoea and death. The mild form of rinderpest causes the most difficulty, as one or more of the characteristic features may be missing from the syndrome observed. Lesions may be limited to ocular discharge with only a fleeting appearance of limited oral lesions in a small proportion of affected calves. Only the younger age groups may be affected, the morbidity rate may be low even in them and the mortality rate may be so low as to be indistinguishable from expected mortality in these age groups.
Epidemiological features, as well as clinical and pathological signs, are highly suggestive of rinderpest. However, clinical signs of rinderpest may be similar to those seen in other diseases in which fever, oculonasal discharges, stomatitis and/ or diarrhoea may be prominent features. These include fatal mucosal disease (MD) syndrome of the bovine virus diarrhoea disease (BVD) complex, some forms of malignant catarrhal fever (MCF), foot-and-mouth disease (FMD), peste des petits ruminants (PPR), infectious bovine rhinotracheitis (IBR) and bovine papular stomatitis (BPS). Other diseases that need to be considered in the differential diagnosis of rinderpest are contagious bovine pleuropneumonia (CBPP) and East Coast fever (ECF). Epidemiological features and laboratory diagnostic tests are important in distinguishing between these diseases.
Bovine malignant catarrhal fever.
Although rinderpest and BMCF resemble each other in their clinical and pathological features, morbidity rates are generally lower in BMCF. Bilateral, centripetal corneal opacity, accompanied by blepharospasm, photophobia and hypopyon, is a feature only of BMCF. However, corneal opacity is also commonly associated with rinderpest in some wildlife species, especially lesser kudu. Diagnosis is confirmed by polymerase chain reaction (PCR) or histopathology.
FMD can be distinguished from rinderpest by the presence of lameness and by the low mortality and vesicular stomatitis in FMD as opposed to the necrotic stomatitis seen in rinderpest. Diarrhoea, which is commonly a prominent sign of rinderpest, is not a feature of FMD. Diagnosis is confirmed by virus isolation and/or antigen detection.
Mucosal disease/bovine virus diarrhoea.
BVD, usually an inapparent to relatively mild disease syndrome lasting a few days, may be seen in cattle at any age, but particularly in calves. Morbidity is usually high but mortality is generally low. MD, on the other hand, is a severe disease of young, growing cattle in which few animals may be affected but, invariably, fatally. Differentiation of MD from rinderpest is achieved by laboratory tests, including virus isolation, immunofluorescence staining, PCR, antigen detection or detection of rising antibody titres.
Infectious bovine rhinotracheitis.
This disease may be confused with rinderpest when diarrhoea is not a prominent feature of the latter. Otherwise, the disease caused by the IBR virus is characterised essentially by upper respiratory symptoms. Mortality rates are lower than in rinderpest. It is confirmed by virus isolation and/or antigen detection.
Contagious bovine pleuropneumonia.
Diarrhoea, oral necrosis and erosions are not seen in CBPP. The evolution of clinical disease is more protracted in CBPP because of the longer incubation period.
Severe emaciation, exercise intolerance and moist, suppressed coughs are features of CBPP. Lung lesions are characteristic.
East Coast fever.
The presence of the tick vector and absence of effective tick control, when considered together with other clinical signs and the results of microscopic examination of blood and lymphoid tissues, are useful in the differentiation of ECF from rinderpest.
Diagnostic procedures for rinderpest and detailed instructions on collection, preservation and dispatch of samples are contained in the FAO Manual on collection and submission of diagnostic specimens to the World Reference Laboratory for Rinderpest, the FAO Manual on the diagnosis of rinderpest and the OIE Manual of standards for diagnostic tests and vaccines. Laboratory confirmation of a presumptive diagnosis of rinderpest may be achieved by tests designed to detect live virus, virus antigen, virus genetic materials or antibodies against the virus (in unvaccinated animals).
Collection and transport of diagnostic specimens.
Preferred samples for virus isolation are:
For the detection of virus antigen, ocular secretions, necrotic gum debris and samples of the spleen, lymph nodes and tonsils should be collected. Virus shedding in secretions and excretions starts towards the end of the incubation period before the appearance of clinical signs. It peaks during the febrile/mucosal erosion phase and then declines and stops early in the convalescent period.
Samples are best collected from animals that are febrile and have mucosal erosions and clear lacrymal secretions. It is generally better to collect samples from as many animals as possible to maximise the chances of positive results.
Two sets of tissue samples should be collected, one chilled and the other fixed in formolsaline. Those for virus isolation should be preserved in transport medium (phosphate buffered saline, pH 7.6) with antibiotics and antifungals but without glycerol, which kills the virus. Samples for virus isolation should be transported to the laboratory as quickly as possible, chilled but not frozen. If storage is imperative for a period of time, samples should be kept at -70°C (not -20°C).
Whole blood (without anticoagulants) should be collected and centrifuged after clotting to obtain the serum needed for virus antibody detection. Serum should be stored at 4°C for short-term or -20°C for longer-term storage.
Each sample should be put in a strong water-tight primary container which is then wrapped in absorbent material, placed in a strong leak-proof secondary container and then into a solid outer covering. This should be labelled with waterproof ink for dispatch to the national diagnostic, regional and/or world reference laboratories. Information about the carrier, airway bill number and flight time should be sent to the laboratory ahead of dispatch.
Isolation of virus from lymphoid tissues or blood leucocytes is done in cell cultures and is essential for subsequent virus characterisation and molecular epidemiological studies.
However, the technique requires trained expertise and aseptic tissue culture facilities, and therefore can only be carried out in well-equipped national and specialised regional and world reference laboratories.
Three techniques widely used for rinderpest antigen detection and prescribed by the OIE Manual of standards for diagnostic tests and vaccines are the agar-gel immunodiffusion test (AGID), the counterimmunoelectrophoresis (CIE) and the immunocapture enzyme-linked immunosorbent assay (ICE).
AGID and CIE detect precipitating antigens in excretions, secretions and tissue samples. ICE may be used for definitive diagnosis and the differentiation of rinderpest from PPR.
Other techniques that may be used for antigen detection include immunohistochemical staining, immunofluorescence, electron microscopy and a penside, monoclonal antibody-based, latex particle agglutination test which is still under evaluation for field use.
Detection of virus genetic material.
Rinderpest virus genetic material can be detected by reverse transcription polymerase chain reaction (RT-PCR), which is a very specific and sensitive technique that requires specialist expertise and equipment. This technique is carried out in the collaborating centres and world reference laboratories and in national laboratories that have the required expertise and facilities. Nucleotide sequencing provides phylogenetic information of epidemiological significance.
A monoclonal antibody-based and specific competitive enzyme-linked immunosorbent assay (ELISA) is widely used and has largely replaced the virus neutralisation test for rinderpest antibody detection. This is a robust test but it cannot differentiate antibodies caused by vaccination from those caused by field virus.
RISK ASSESSMENT OF RINDERPEST INVASION
A risk assessment of possible introduction of rinderpest into the country is essential for formulating a national policy for rinderpest control and elimination. The main risk factors to be considered include:
the likelihood that hidden foci of rinderpest infection still remain in the country in domestic livestock or wild animals; the location and proximity of the nearest known endemic foci; likely future livestock movement patterns into the country, through trading, smuggling, transhumance, nomadism or civil disturbances, particularly from rinderpest danger zones; the status of neighbouring countries, based not only on their rinderpest occurrences and present disease status, but also on the quality of their veterinary services and likely ability to detect and control any rinderpest introduction; possible socio-economic consequences of any rinderpest introduction; the difficulty of eradication if there is a breakdown. A statement about the risk profile should be made expressing the probability as extreme, high, medium or low, based on the perceived socio-economic consequences of rinderpest incursion into the country such as: production losses; effect on food security and poverty alleviation; restriction of livestock trade; environmental effects, such as decimation of wildlife. It is necessary to identify measures that would be needed to reduce these risks, such as a ban on importation of live susceptible animals from high-risk areas, and border quarantine and control.
Strategies for rinderpest control and eradication.
This manual addresses a situation where rinderpest invades a country, or a zone within a country, which was formerly considered free from rinderpest. Should such an emergency occur, all initiatives should be directed at rapid containment of the disease in the primary focus or zone and eradication within the shortest possible time to avoid spread and possible progression to endemic status. There are a number of epidemiological and other factors that are favourable to eradication of rinderpest:
The virus is fragile and susceptible to environmental factors and disinfectants/ chemicals.
The short incubation period, ease of spread and high mortality in fully susceptible animals should enable early recognition of acute cases.
Animals that have recovered from the disease do not become virus carriers and have lifelong immunity; there is only one serotype.
Transmission is almost always by direct contact between infected and susceptible animals. Indirect transmission by fomites, contaminated animal products or insects is relatively unimportant.
However, rinderpest eradication can sometimes be complicated by: the existence of mild disease; difficulty in detecting the disease in some wildlife species; disease occurring in areas that are relatively inaccessible because of natural barriers (topographical features) or situations of human origin (social unrest, civil wars, etc.) the smallest size that is consistent with effective disease containment and OIE guidelines. In deciding its shape and size, consideration should be given to topographical features, physical barriers, administrative borders and the resources available for enforcement and surveillance.
This is the area surrounding the infected zone. Its size will depend on realistic assessment of the resources available for surveillance.
DISEASE CONTROL OPTIONS
Three options for dealing with a rinderpest disease emergency should be considered:
Stamping out by slaughter is the preferred option in:
Modified stamping out with ring vaccination may be preferred for:
Quarantine and ring vaccination without slaughter may, on the other hand, be the preferred option in countries where:
OPTION ONE: STAMPING OUT
This option is designed to contain an incursion of rinderpest so as to eliminate it in the shortest possible time. It requires intensive surveillance, immediate quarantining of infected herds, imposition of strict movement controls and slaughter of all susceptible species of animals in infected premises, with immediate payment of
fair compensation for slaughtered animals. This is certainly the most desirable strategy for rapid elimination of introduced rinderpest and is the most cost-effective option.
The advantage of complete herd slaughter is that it eliminates very rapidly the source of
infection for other animals. Indirect transmission is unlikely as long as carcasses are disposed of safely. After slaughter, meat and meat products rapidly become insignificant as regards disease transmission. Disease tracing and enhanced surveillance will be required to determine the origin and extent of infection, so that adequate zones can be declared for rinderpest control purposes and, subsequently, to assist in proving regained freedom from the disease and infection.
The essential elements of stamping out include:
Actions to be taken in the infected zone
Movement of susceptible livestock species out of the infected zone should be prohibited. One exception could be the movement of apparently healthy animals from non-affected premises direct to an abattoir for slaughter. This must be done under strict zoosanitary control. It may also be necessary to transport animals to a site of destruction and disposal within the infected zone. Movement of susceptible animals into the zone is prohibited or subject to special permit. Restrictions should be placed on human and vehicular traffic in and out of the zone, and any movements should be subject to proper cleaning and decontamination on exit.
Slaughter and disposal.
All susceptible livestock species in the infected premises should be slaughtered, whether clinically ill or not. The carcasses should be disposed of by burying or burning. Fair compensation should be paid as soon as possible, preferably at the time of slaughter.
Depopulated premises, equipment, clothing and other protective outfits in dairy animal housing and feedlots should be cleaned with detergents/soaps and then decontaminated with oxidising agents such as sodium or calcium hypochlorite and alkalis such as sodium hydroxide or sodium carbonate. Faeces and effluents should be treated with sodium carbonate, which is effective even in the presence of organic matter, before burial or burning.
Dangerous contact premises.
These are premises in the area immediately surrounding the infected premises/herds/villages in which epidemiological investigations show high likelihood that rinderpest infection may have been introduced, although no overt disease has yet been seen. They include premises elsewhere into which cattle or other susceptible animals have been introduced from infected herds during the critical period.
Such premises should be placed under strict quarantine and subjected to intense active surveillance.
If any infected animal is detected, the area is automatically considered to be infected premises. All such holdings, premises, villages or settlements with susceptible species of livestock should be visited daily to examine the animals for clinical disease. This must continue for at least 21 days after the last clinical case has been slaughtered in the infected premises.
A thorough epidemiological investigation should be carried out in the infected zone to define the source of infection and to detect other possible primary introductions and onward spread. Tracing forwards and backwards is essential to determine where the virus came from and to discover any secondary outbreaks which might have resulted from movement of animals from infected premises.
Where a significant wildlife population exists and there is a risk of rinderpest introduction, active disease surveillance and serosurveillance should include wildlife. This will involve serological surveys and close monitoring of morbidity and mortality in susceptible wildlife, requiring close collaboration with the wildlife authorities.
A standstill order should be imposed and enforced in the infected zone, if necessary with active support from military and police authorities. It must apply to all susceptible livestock species for a minimum of 21 days after slaughter of the last clinical case, assuming disease surveillance is effective. It should include closure of livestock markets and cancellation of all livestock events during the period. Ideally, abattoirs and slaughterhouses/slabs should be prohibited from slaughtering susceptible livestock species in the area. It may be necessary to provide an alternative supply of meat.
Abattoirs can safely recommence operations not less than 21 days after the last affected animal has been slaughtered, assuming that disease surveillance is effective. Prolonged prohibition carries the risk that the community will develop alternative means of slaughter, which may render planned control efforts ineffective. Milk should be heat-treated to destroy any virus.
Actions to be taken in the surveillance zone
Within the surveillance zone, all holdings (premises, villages or settlements) with susceptible livestock species should be visited weekly to examine the animals for clinical disease. This must continue for at least 21 days after the last clinical case in the infected zone has been slaughtered.
Movement out of the zone must be by special permit after clinical examination of all animals in the herd/premises, but movement of susceptible livestock species into the zone is allowed. Risk enterprises such as dairy and meat processing plants are allowed to operate, subject to a high level of hygienic practice in all stages of their operations. Additional information on these aspects may be found in the enterprise manuals of the AUSVETPLAN on:
Proof and verification of rinderpest elimination
Elimination of rinderpest will be verified when active rinderpest surveillance shows that there are: no new cases of clinical disease occurring; no seroconversion in cattle or other susceptible species in the infected and surveillance zones; and evidence of effective veterinary infrastructure.
For disease investigation and surveillance, it will be necessary to:
Additional details of procedures for disease and serological surveillance can be found in the Recommended procedures for disease and serological surveillance as part of the global rinderpest eradication programme (GREP), FAO/IAEA TECDOC, Vienna, 1994.
According to the OIE International animal health code (1999), for rinderpest: " should there be a localised rinderpest outbreak in an infection-free country, the waiting period before infection-free status can be regained shall be as follows: six months after the last case, where stamping out without vaccination and serological surveillance is applied."
Acceptance of renewed freedom will require intensive active disease surveillance in the infected and surveillance zones using repeated disease search and other epidemiological survey techniques. Case finding should include the use of carefully designed questionnaire surveys with ensured community participation.
Evidence will be required that the following investigations and activities were carried out:
Where wildlife species are relatively numerous and have been implicated in previous rinderpest incidents, active disease surveillance must include efforts to investigate thoroughly any possible morbidity and mortality in these species.
OPTION TWO: MODIFIED STAMPING OUT WITH RING VACCINATION
If total eradication is not a feasible option, modified stamping out can provide rapid control of an outbreak. This consists of the immediate imposition of strict movement controls, slaughter of clinically affected animals in the infected herd(s), premises, villages or settlements, combined with ring vaccination of in-contact as well as other susceptible livestock in the infected zone. The term "modified stamping out", according to the International animal health code, is used whenever stamping out measures are not implemented in full. Details of modifications should be given. This option is designed to reduce the number of infected animals shedding virus and the number of susceptible animals. It creates, in the area surrounding the infected herds, a ring of immune animals protected from the risk of developing rinderpest after exposure from the known infected herds or from an undetected source.
These aims can be achieved relatively quickly. Within one week from vaccination, animals respond with a serviceable degree of immunity. Animals incubating rinderpest at the time of vaccination must be expected to develop clinical disease, so fresh clinical cases are to be expected for up to 21 days after vaccination has been completed, even if vaccination has been 100 percent effective. Virus shedding from these animals ceases within another 14 days, making a total of 35 days.
The essential elements of this strategy include:
Countries that do not export livestock and livestock products may wish to note that vaccinated animals are solidly immune and do not become inapparent carriers. They could be retained without risk of compromising eradication and serosurveillance, as long as they are permanently identifiable.
Actions to be taken in the infected zone
Strict movement controls should be imposed on all susceptible livestock species in the infected zone. Susceptible animals In this zone should be vaccinated.
Slaughter and disposal.
Clinically sick animals should be slaughtered to reduce virus shedding, thus minimising the risk of transmission within and from the herd. Carcasses of dead and slaughtered animals should be buried or burnt on the premises or at a nearby site accessible to the infected premises/area.
All in-contact animals in the affected herds and other herds in the infected zone should be vaccinated. Although a number of countries produce their own vaccines, it is important that a source of high-quality vaccines conforming to OIE standards is identified in advance. These vaccines may be conventional or thermostable versions of the tissue culture rinderpest vaccine.
In future, other novel types such as recombinant vaccines may become available for field use.
The vaccination programme must be structured. At least two independent vaccination teams are required to work in the infected zone. The first vaccinates the remaining members of the infected herd or herds, of which a proportion will be incubating the disease. The second undertakes vaccination of surrounding herds in a ring around the infected herd(s), premises or settlements in the infected zone, starting from the outside of the ring and working inwards. The size of the ring should be determined by the ability to complete vaccination within one week or less.
It is better to define several rings to be vaccinated successively, starting with the area at highest risk, than to have one ring which takes an excessively long time to complete.
Affected herds should never be assembled with neighbouring herds at communal crushes for vaccination, as this greatly increases the risk of transmitting infection, both within the infected zone and to herds in the surveillance zone often. It is expedient to consider an entire community, centred on a village and perhaps sharing a common watering-point, as an infected herd. Attaining a sufficiently high level of herd immunity might require a second round of vaccination within four to six weeks. Vaccination coverage needs to be monitored closely.
The target should be to raise the herd immunity levels to above 75 percent. It is necessary to identify the vaccinated animals permanently, for example by ear notching, so that their presence will not compromise later serosurveillance studies required for demonstrating freedom from infection. Such vaccinated animals need to be identified for slaughter at the stage of seeking OIE approval for return to rinderpest-free status for export trade purposes.
This should be imposed within the infected zone. For it to be effective, police or military enforcement may be necessary. Closure of livestock markets, abattoirs and slaughterhouses in the infected zone should remain in force for at least 56 days after vaccination has been completed.
It might be necessary to provide alternative sources of meat or to consider moving animals for slaughter under escort. Restocking with susceptible livestock should not be done until at least 56 days after the last clinical case has been slaughtered or vaccination has been completed, whichever is the later. Adequate public awareness campaigns should be carried out.
Within the zone, all premises, villages or settlements with susceptible livestock species should be visited daily to examine the animals for clinical disease. This must continue for at least 21 days after the last clinical case has been slaughtered or vaccination has been completed, whichever is the later.
Actions to be taken in the surveillance zone
This area surrounds the infected zone. Its size will depend on a realistic assessment of the resources available for enforcement and surveillance. Within the zone, all livestock holdings (premises, villages or settlements) with susceptible livestock
species should be visited weekly to examine animals for clinical disease. This must continue for at least 21 days after the last clinical case in the infected zone has died or has been slaughtered or until vaccination has been completed, whichever is the later.
In some circumstances, a sanitary cordon consisting of a buffer zone and a surveillance zone would be needed to separate a rinderpest-infected area from a rinderpest-free one.
Susceptible livestock species may move into the buffer zone but must remain for at least 21 days. To prevent secondary outbreaks of rinderpest, susceptible livestock species in this zone should be vaccinated if transiting animals develop the disease.
The surveillance zone of the sanitary cordon is subjected to a high level of disease surveillance but no rinderpest vaccination is carried out.
Slaughter of vaccinated animals
After the disease has been eliminated and repeated active disease search and serosurveillance confirm absence of rinderpest infection, the country may wish to seek OIE verification of freedom from infection in order to regain its former status as a rinderpest-free country. For countries that are involved in international trade in livestock and livestock products, which may require rinderpest antibody-free status, it will be necessary to slaughter vaccinated animals when the disease has been eliminated and active and serological surveillance confirm freedom from infection.
Proof and verification of rinderpest elimination
The International animal health code (1999) states: "Should a localised rinderpest outbreak occur in an
infection-free country, the waiting period before infection-free status can be regained shall be as follows: six months after the slaughter of the last vaccinated animal where stamping out complemented by emergency vaccination (vaccinated animals should be clearly identified with a permanent mark) and serological surveillance are applied."
Acceptance of renewed freedom will require active disease surveillance and other epidemiological survey techniques as described under option one.
OPTION THREE: QUARANTINE AND RING VACCINATION
Should a localised outbreak of rinderpest occur in a zone within a rinderpest-free country and stamping out by slaughter is not possible, the country may wish to carry out limited emergency vaccination of susceptible domestic livestock in the zone.
Two rounds of vaccination within six months (immunosterilization) should be carried out.
The essential elements of this option include:
SPECIAL NEEDS FOR NOMADISM, TRANSHUMANCE AND RELATIVELY INACCESSIBLE AREAS
Special provisions will be made for rinderpest control and elimination in relatively inaccessible areas and under a transhumant or nomadic system of husbandry. Special strategies have to be designed to overcome the major constraints and to ensure farmers’ confidence in planned control measures. Some of the methods that have yielded positive results include:
Proof and verification of rinderpest elimination
It will be necessary to carry out seromonitoring of the vaccinated animals to confirm herd immunity levels. Repeated active disease search and serosurveillance in all susceptible livestock and wildlife species should be carried out in the infected and surveillance zones. The OIE International animal health code (1999) provides that the waiting period before infection-free status can be regained shall be 12 months after the last case or last vaccination (whichever occurs later) where emergency vaccination with-out slaughter (vaccinated animals should be clearly identified with a permanent mark) and serological surveillance are applied.
SELECTED STRATEGY IF RINDERPEST BECOMES ESTABLISHED
It is unlikely that an outbreak of rinderpest would not be eliminated if it were detected and responded to in time. However, if the size of an outbreak outstrips the resources available for control and ring vaccination is unable to arrest the spread, the affected country would have to revert to a policy of mass immunisation. This would be targeted at known and suspected infected areas together with areas considered to be at high risk for spread of the disease, such as livestock movement routes. The aim should be to carry out several rounds of vaccination over one or two years and then to discontinue vaccination once the disease had been eliminated. Blanket vaccination of the entire susceptible population will be carried out and the effectiveness of vaccination monitored serologically. If there are significantly large areas of the country that can still be regarded as uninfected, the country may establish a sanitary cordon to separate the infected from the free areas. This is a belt of two zones, a buffer zone and a surveillance zone, separating a rinderpest-infected area from a rinderpest-free area.
Susceptible livestock species may move into the first belt of the buffer zone under veterinary supervision. All susceptible livestock in this zone will be vaccinated to prevent occurrence of any secondary outbreaks. The second belt of the sanitary cordon, the surveillance zone, is subjected to a high level of disease surveillance without vaccination of resident susceptible livestock.
Organisational arrangements during a rinderpest emergency campaign
In the even of an animal disease emergency, each country will be expected to have established the following organisational structures which will be needed during a rinderpest emergency campaign.
NATIONAL ANIMAL DISEASE EMERGENCY PLANNING COMMITTEE
This is a statutory committee whose composition and functions in relation to dealing with animal disease emergencies, including rinderpest emergencies, are stated in Chapter 1 of the Manual on the preparation of national animal disease emergency preparedness plans, FAO, Rome, 1999.
CONSULTATIVE COMMITTEE ON EMERGENCY ANIMAL DISEASES (CCEAD)
This technical committee should have the responsibility, among other things, of recommending activation of the rinderpest emergency plans. Its composition and functions are stated in Chapter 2 of the Manual on the preparation of national animal disease emergency preparedness plans.
RINDERPEST EXPERT TEAM
This frontline team is an example of the specialist diagnostic teams provided for in Chapter 4 of the Manual on the preparation of national animal disease emergency preparedness plans. The team will undertake field investigation, assess the evidence for a rinderpest emergency and advise the Chief Veterinary Officer (CVO) or an equivalent officer, such as the Director of Veterinary Services (DVS).
It should comprise at least:
The team should be maintained in permanent readiness, with ensured mobility and essential equipment and with alternatives identified in case of non-availability. The equipment includes pre-prepared sampling kits, mobile accommodation, communication equipment, protective clothing and disinfectants.
The rinderpest expert team would be expected to:
NATIONAL ANIMAL DISEASE CONTROL CENTRE
Provision should be made in the national animal disease emergency preparedness plan to establish a permanent national animal disease control centre with the functions described in Chapter 2 of the Manual on the preparation of national animal disease emergency preparedness plans.
LOCAL ANIMAL DISEASE CONTROL CENTRES
For implementation of the rinderpest emergency plan, it will be necessary to establish one or more temporary local animal disease control centres situated close to the outbreak site(s). The functions of the centre(s) are as described in Chapter 2 of the Manual on the preparation of national animal disease emergency preparedness plans.
For dealing with a rinderpest emergency, each local animal disease control centre should be equipped with:
The local animal disease emergency control centre should be organised into the following team:
Infected premises team.
Under the supervision of an experienced field veterinary officer, staff would be involved in slaughter, disposal, decontamination, quarantine, movement restriction and active disease search in the infected premises of the infected zone.
Disease surveillance team.
This team, under the supervision of a veterinary epidemiologist, would be involved in enforcement of movement restrictions and active disease and serological surveillance in the surveillance zone.
Where the national policy on rinderpest control involves vaccination, a group should be charged with vaccination of the relevant herds in the infected zone and in the buffer zone as necessary.
Stores and administration.
For ease of operations and promptness in response, a stores and administration unit should be established at the local animal disease control centre. It should be responsible for the supply of all equipment and chemicals needed for slaughter, disposal and decontamination during a rinderpest emergency. This unit would also co-ordinate:
Public relations team.
It will be essential to have in place a public relations unit for public awareness and information on the presence of rinderpest, the rationale for the national control policy and the necessity for enforcement of movement restrictions and quarantine.
Each country should ensure that staff are regularly trained in procedures for diagnosing and dealing with rinderpest. National authorities should arrange for the regular training of all veterinary and support staff who may be engaged in dealing with rinderpest outbreaks. The training programme should include:
Key members of the veterinary services should have the opportunity of seeing clinical cases of rinderpest as part of their training. The competence of staff in this area should be maintained by regular training exercises at the national and local levels. These should include simulated disease control operations.
Public veterinary services rely on stockowners or private veterinarians attending farm animals to report the possibility of rinderpest. Reporting must be prompt and accurate, so that all outbreaks are identified as soon as possible without raising false alarms.
Prompt and accurate reporting can only be achieved if the veterinary professionals, auxiliary staff and stockowners are aware of the danger of rinderpest and are familiar with the signs of the disease. To this end, countries should maintain awareness of the disease in both the veterinary profession and the agricultural community.
Material should be aimed at veterinary students and at practising veterinarians. Veterinary schools should be provided with simple, professionally sound explanatory material that outlines in an intelligible manner:
The veterinary profession at large should be regularly provided with information on current notification and control procedures and on the epidemiological situation in the country and elsewhere.
For the agricultural community, disease awareness campaigns should be targeted primarily at stockowners and non-professional personnel who regularly visit herds or flocks, such as extension staff, artificial insemination personnel and livestock hauliers.
The campaigns should emphasise:
The following support plans will be needed to provide the backing for implementation of the rinderpest contingency plan.
Each country should have legal provisions to ensure that a campaign against rinderpest is rapidly and successfully concluded. Such legislation should be clearly understood by all involved with disease control and should encompass:
Each country should ensure that it has provision for access to emergency funds, budgetary powers and financial resources to cover the cost of dealing with all aspects of a rinderpest emergency. The main areas of expenditure are :
The farming community can be expected to co-operate only if valuation is fair and compensation for slaughtered stock is paid promptly. National authorities should endeavour to ensure that payments are made at the time of slaughter or soon after.
EARLY WARNING CAPABILITIES
Each country will be expected to have developed efficient and effective early warning capabilities in the areas of :
All resources required should be documented in detail and arrangements made to ensure their availability.
The officer responsible for maintenance and issue of the materials should be readily available at the local animal disease control centre. This officer’s contact address, e-mail address and telephone and fax numbers during and outside office working hours must also be readily available.
Each country should have readily available at the local animal disease control centre or at some other convenient place the following minimum equipment for dealing with rinderpest emergency:
Each national veterinary authority should ensure that it has available at all times the services of a rinderpest diagnostic laboratory either in its own country or elsewhere, such as a regional and/or world reference laboratory for rinderpest. National rinderpest laboratories should be equipped and skilled to provide a rapid laboratory diagnosis, especially in initial cases of rinderpest.
The minimum requirement is to be able to carry out a test for rinderpest by an antigen detection method of high specificity, such as the agar-gel immunodiffusion (AGID) test and the immunocapture enzyme-linked immunosorbent assay (ICE). In addition, the national laboratory should be equipped to carry out competitive ELISA for antibody detection, which is useful for serosurveillance as well as seromonitoring. The laboratory should keep in stock all reagents necessary for rapid initial diagnosis.
In all suspected primary outbreaks, suitable specimens must be collected and packed according to a set procedure. The samples should be quickly transported to the national laboratory. Definite arrangements should be made for dispatch of specimens from the national laboratories to regional and world reference laboratories for rinderpest. All laboratories handling material likely to contain rinderpest virus should operate under internationally acceptable security conditions.
CONTINGENCY PLANS FOR VACCINES AND VACCINATION
Depending on the strategy selected by the country, the control of a rinderpest outbreak by emergency vaccination may be a primary requirement or may be instituted when the outbreak threatens to become extensive. As part of their contingency plans, countries should establish or have access to facilities for prompt supply of vaccine. Countries may consider maintaining some limited strategic vaccine reserves at the national level sufficient for the initial first round of vaccination. Alternatively, arrangements can be made with neighbouring countries for vaccine banks to be maintained at the regional level, with agreed and documented drawing rights. Contingency plans for the supply of additional quality-assured vaccines should also be made.
Cold chain facilities should be established for the distribution of vaccines so that they are kept cool, i.e. at 4°C or lower, at all times. The cold chain facilities should be available at the point where vaccine is delivered to a country for further distribution and at or near local disease control centres for distribution to the veterinarians and auxiliary staff who will administer the vaccine.
Refrigerated storage and transport facilities should be available for the distribution of the vaccine in conditions that maintain the viability of the vaccine virus. Vaccination equipment should be held at national/state centres or at some other convenient place. Sufficient vaccination needles should be stocked, so that each herd can be vaccinated with a fresh unused needle.
Each country should prepare a list of personnel who can be called upon to participate in an emergency vaccination programme.
The action plan is a set of instructions covering most aspects of the controls to be implemented during rinderpest emergency, from first suspicion of the disease to final eradication. In addition, countries should prepare detailed standard operating procedures which apply to rinderpest as well as other epidemic diseases. Enterprise
manuals containing zoosanitary codes of practice in high-risk enterprises such as meat and dairy processing plants should also be available.
Meanwhile, countries may wish to consult the
AUSVETPLAN manuals on:
The investigation phase is said to exist when a report with low probability of rinderpest is received by the veterinary services.
It should be a legal obligation of any citizen suspecting the presence of rinderpest to report that suspicion to a member of the veterinary or animal health services. In practice, a suspicious index case is most likely to be reported to the
Field Veterinary Officer (FVO).
On receipt of such information, the FVO should immediately carry out investigations and collect such neccessary information as the location of index case(s) and clinical and epidemiological features.
The FVO should also:
Provincial Veterinary Officer (PVO).
On receipt of information from the FVO, the PVO should:
Chief Veterinary Officer (CVO).
Based on the results of investigation, the CVO should instruct the PVO to declare either a false alarm and winding-down of operations or a progression to the alert phase.
If clinical and epidemiological results are highly indicative of rinderpest, officers should carry out the following duties.
Chief Veterinary Officer:
Provincial Veterinary Officer:
Field Veterinary Officer:
Rinderpest expert team (RET).
Following adequate briefing by the FVO, the RET should:
The epidemiological report from a primary outbreak by the RET should describe:
On the basis of these findings, the head of the team should advise the local or national disease control centre on:
The operational phase is initiated when rinderpest has been confirmed and the CVO declares, through the national animal disease control centre, that a rinderpest emergency exists in the country. This information should then be sent by the CVO to global authorities, such as OIE and FAO-EMPRES, and relevant regional rinderpest control organisations, such as OAU/IBAR. Various teams in the local animal disease control centre(s) would be expected to go into operation as listed below.
Option one: stamping out
Where the national policy on rinderpest control is stamping out by slaughter, the following activities would be carried out.
Infected premises team.
This team can be divided into subunits charged with various aspects of slaughter, disposal, decontamination, quarantine and movement restrictions. The team should:
Disease surveillance team.
This team should:
Stores and administration.
This unit will be responsible for:
Public relations office.
A public relations team will be expected to:
Option two: modified stamping out with ring vaccination
If the national policy on rinderpest control is modified stamping out and vaccination, the units should be deployed as follows
Infected premises team.
This team would be charged with slaughter of affected animals, disposal of carcasses, decontamination of affected premises, quarantine and movement restrictions in the infected zone, as detailed above under option one.
This team should:
Disease surveillance team.
This team will be expected to carry out active disease surveillance in the surveillance zone, involving weekly visits to examine animals in the zone for clinical disease and to collect samples for serosurveillance.
Stores and administration.
The activities to be carried out by this team are defined above in option one.
The functions to be carried out are as described above in option one.
Option three: quarantine and ring vaccination
Infected premises team.
This team will be expected to carry out proper disposal of carcasses of animals that have died of the disease, and decontamination in the infected zone.
This team will be expected to carry out immediate perifocal vaccination in the infected zone and mark vaccinated animals permanently.
Disease surveillance team.
This team will be expected to carry out repeated active disease search and serosurveillance in both the infected zone and the surveillance zone.
This phase may exist when rinderpest is not confirmed as well as when the disease is confirmed. When investigations carried out during the alert phase fail to confirm the disease, the CVO will instruct the PVO and FVO to notify all organisations and persons previously informed of suspected rinderpest occurrence and possible emergency that the situation has ceased to exist.
If rinderpest is confirmed, the stand-down phase begins as soon as all necessary operations for containment, control and elimination are completed to the satisfaction of the CVO, as head of the national animal disease control centre. Winding-down operations should not be delayed and must be systematic, gradual and supervised by the head of the local animal disease control centre.