Terrestrial Animal Health Code

Contents | Index Chapter 11.3. SECTION 11. Chapter 11.5.

Chapter 11.4.


Bovine spongiform encephalopathy


Article 11.4.1.


General provisions and safe commodities

The recommendations in this chapter are intended to manage the human and animal health risks associated with the presence of the bovine spongiform encephalopathy (BSE) agent in cattle (Bos taurus and B. indicus) only. For the purposes of official BSE risk status recognition, BSE excludes 'atypical BSE' as a condition believed to occur spontaneously in all cattle populations at a very low rate.

  1. When authorising import or transit of the following commodities and any products made from these commodities and containing no other tissues from cattle, Veterinary Authorities should not require any BSE-related conditions, regardless of the BSE risk status of the cattle population of the exporting country, zone or compartment:

    1. milk and milk products;

    2. semen and in vivo derived cattle embryos collected and handled in accordance with the recommendations of the International Embryo Transfer Society;

    3. hides and skins;

    4. gelatine and collagen prepared exclusively from hides and skins;

    5. tallow with maximum level of insoluble impurities of 0.15% in weight and derivatives made from this tallow;

    6. dicalcium phosphate (with no trace of protein or fat);

    7. deboned skeletal muscle meat (excluding mechanically separated meat) from cattle which were not subjected to a stunning process prior to slaughter, with a device injecting compressed air or gas into the cranial cavity or to a pithing process, and which passed ante- and post-mortem inspections and which has been prepared in a manner to avoid contamination with tissues listed in Article 11.4.14.;

    8. blood and blood by-products, from cattle which were not subjected to a stunning process, prior to slaughter, with a device injecting compressed air or gas into the cranial cavity, or to a pithing process.

  2. When authorising import or transit of other commodities listed in this chapter, Veterinary Authorities should require the conditions prescribed in this chapter relevant to the BSE risk status of the cattle population of the exporting country, zone or compartment.

  3. When authorising import of commodities according to the conditions prescribed in this chapter, the risk status of an importing country is not affected by the BSE risk status of the exporting country, zone or compartment.

Standards for diagnostic tests are described in the Terrestrial Manual.


Article 11.4.2.


The BSE risk status of the cattle population of a country, zone or compartment

The BSE risk status of the cattle population of a country, zone or compartment should be determined on the basis of the following criteria:

  1. the outcome of a risk assessment, based on the provisions of the Terrestrial Code, identifying all potential factors for BSE occurrence and their historic perspective. Member Countries should review the risk assessment annually to determine whether the situation has changed.

    1. Entry assessment

      Entry assessment consists of assessing, through consideration of the following, the likelihood that the BSE agent has either been introduced into the country, zone or compartment via commodities potentially contaminated with it, or is already present in the country, zone or compartment:

      1. the presence or absence of the BSE agent in the indigenous ruminant population of the country, zone or compartment and, if present, evidence regarding its prevalence;

      2. production of meat-and-bone meal or greaves from the indigenous ruminant population;

      3. imported meat-and-bone meal or greaves;

      4. imported cattle, sheep and goats;

      5. imported animal feed and feed ingredients;

      6. imported products of ruminant origin for human consumption, which may have contained tissues listed in Article 11.4.14. and may have been fed to cattle;

      7. imported products of ruminant origin intended for in vivo use in cattle.

      The results of surveillance and other epidemiological investigations into the disposition of the commodities identified above should be taken into account in carrying out the assessment.

    2. Exposure assessment

      If the entry assessment identifies a risk factor, an exposure assessment should be conducted, consisting of assessing the likelihood of cattle being exposed to the BSE agent, through a consideration of the following:

      1. recycling and amplification of the BSE agent through consumption by cattle of meat-and-bone meal or greaves of ruminant origin, or other feed or feed ingredients contaminated with these;

      2. the use of ruminant carcasses (including from fallen stock), by-products and slaughterhouse/abattoir waste, the parameters of the rendering processes and the methods of animal feed manufacture;

      3. the feeding or not of ruminants with meat-and-bone meal and greaves derived from ruminants, including measures to prevent cross-contamination of animal feed;

      4. the level of surveillance for BSE conducted on the cattle population up to that time and the results of that surveillance;

  2. ongoing awareness programme for veterinarians, farmers, and workers involved in transportation, marketing and slaughter of cattle to encourage reporting of all cases showing clinical signs consistent with BSE in target sub-populations as defined in Articles 11.4.20. to 11.4.22.;

  3. the compulsory notification and investigation of all cattle showing clinical signs consistent with BSE;

  4. the examination carried out in accordance with the Terrestrial Manual in a laboratory of brain or other tissues collected within the framework of the aforementioned surveillance and monitoring system.

When the risk assessment demonstrates negligible risk, the Member Country should conduct Type B surveillance in accordance with Articles 11.4.20. to 11.4.22.

When the risk assessment fails to demonstrate negligible risk, the Member Country should conduct Type A surveillance in accordance with Articles 11.4.20. to 11.4.22.


Article 11.4.3.


Negligible BSE risk

Commodities from the cattle population of a country, zone or compartment pose a negligible risk of transmitting the BSE agent if the following conditions are met:

  1. a risk assessment, as described in point 1) of Article 11.4.2., has been conducted in order to identify the historical and existing risk factors, and the Member Country has demonstrated that appropriate specific measures have been taken for the relevant period of time defined below to manage each identified risk;

  2. the Member Country has demonstrated that Type B surveillance in accordance with Articles 11.4.20. to 11.4.22. is in place and the relevant points target, in accordance with Table 1, has been met;

  3. EITHER:

    1. there has been no case of BSE or, if there has been a case, every case of BSE has been demonstrated to have been imported and has been completely destroyed, and

      1. the criteria in points 2) to 4) of Article 11.4.2. have been complied with for at least seven years; and

      2. it has been demonstrated through an appropriate level of control and audit, including that of cross contamination, that for at least eight years neither meat-and-bone meal nor greaves derived from ruminants has been fed to ruminants;

    OR

    1. if there has been an indigenous case, every indigenous case was born more than 11 years ago; and

      1. the criteria in points 2) to 4) of Article 11.4.2. have been complied with for at least seven years; and

      2. it has been demonstrated through an appropriate level of control and audit, including that of cross contamination, that for at least eight years neither meat-and-bone meal nor greaves derived from ruminants has been fed to ruminants;

      3. all BSE cases, as well as:

        • all cattle which, during their first year of life, were reared with the BSE cases during their first year of life, and which investigation showed consumed the same potentially contaminated feed during that period, or

        • if the results of the investigation are inconclusive, all cattle born in the same herd as, and within 12 months of the birth of, the BSE cases,

        if alive in the country, zone or compartment, are permanently identified, and their movements controlled, and, when slaughtered or at death, are completely destroyed.

The Member Country or zone will be included in the list of negligible risk only after the submitted evidence has been accepted by the OIE. Retention on the list requires that the information for the previous 12 months on surveillance results and feed controls be re-submitted annually and changes in the epidemiological situation or other significant events should be reported to the OIE according to the requirements in Chapter 1.1.


Article 11.4.4.


Controlled BSE risk

Commodities from the cattle population of a country, zone or compartment pose a controlled risk of transmitting the BSE agent if the following conditions are met:

  1. a risk assessment, as described in point 1) of Article 11.4.2., has been conducted in order to identify the historical and existing risk factors, and the Member Country has demonstrated that appropriate measures are being taken to manage all identified risks, but these measures have not been taken for the relevant period of time;

  2. the Member Country has demonstrated that Type A surveillance in accordance with Articles 11.4.20. to 11.4.22. has been carried out and the relevant points target, in accordance with Table 1, has been met; Type B surveillance may replace Type A surveillance once the relevant points target is met;

  3. EITHER:

    1. there has been no case of BSE or, if there has been a case, every case of BSE has been demonstrated to have been imported and has been completely destroyed, the criteria in points 2) to 4) of Article 11.4.2. are complied with, and it can be demonstrated through an appropriate level of control and audit, including that of cross contamination, that neither meat-and-bone meal nor greaves derived from ruminants has been fed to ruminants, but at least one of the following two conditions applies:

      1. the criteria in points 2) to 4) of Article 11.4.2. have not been complied with for seven years;

      2. it cannot be demonstrated that controls over the feeding of meat-and-bone meal or greaves derived from ruminants to ruminants have been in place for eight years;

    OR

    1. there has been an indigenous case of BSE, the criteria in points 2) to 4) of Article 11.4.2. are complied with, and it can be demonstrated through an appropriate level of control and audit, including that of cross contamination, that neither meat-and-bone meal nor greaves derived from ruminants has been fed to ruminants;

      and all BSE cases, as well as:

      • all cattle which, during their first year of life, were reared with the BSE cases during their first year of life, and which investigation showed consumed the same potentially contaminated feed during that period, or

      • if the results of the investigation are inconclusive, all cattle born in the same herd as, and within 12 months of the birth of, the BSE cases,

      if alive in the country, zone or compartment, are permanently identified, and their movements controlled, and, when slaughtered or at death, are completely destroyed.

The Member Country or zone will be included in the list of controlled risk only after the submitted evidence has been accepted by the OIE. Retention on the list requires that the information for the previous 12 months on surveillance results and feed controls be re-submitted annually and changes in the epidemiological situation or other significant events should be reported to the OIE according to the requirements in Chapter 1.1.


Article 11.4.5.


Undetermined BSE risk

The cattle population of a country, zone or compartment poses an undetermined BSE risk if it cannot be demonstrated that it meets the requirements of another category.


Article 11.4.6.


Recommendations for the importation of bovine commodities from a country, zone or compartment posing a negligible BSE risk

For all commodities from cattle not listed in point 1) of Article 11.4.1.

Veterinary Authorities should require the presentation of an international veterinary certificate attesting that the country, zone or compartment complies with the conditions in Article 11.4.3.


Article 11.4.7.


Recommendations for the importation of cattle from a country, zone or compartment posing a negligible BSE risk but where there has been an indigenous case

For cattle selected for export

Veterinary Authorities should require the presentation of an international veterinary certificate attesting that the animals:

  1. are identified by a permanent identification system in such a way as to demonstrate that they are not exposed cattle as described in point 3 b) iii) of Article 11.4.3.;

  2. were born after the date from which the ban on the feeding of ruminants with meat-and-bone meal and greaves derived from ruminants had been effectively enforced.


Article 11.4.8.


Recommendations for the importation of cattle from a country, zone or compartment posing a controlled BSE risk

For cattle

Veterinary Authorities should require the presentation of an international veterinary certificate attesting that:

  1. the country, zone or compartment complies with the conditions referred to in Article 11.4.4.;

  2. cattle selected for export are identified by a permanent identification system in such a way as to demonstrate that they are not exposed cattle as described in point 3 b) of Article 11.4.4.;

  3. cattle selected for export were born after the date from which the ban on the feeding of ruminants with meat-and-bone meal and greaves derived from ruminants was effectively enforced.


Article 11.4.9.


Recommendations for the importation of cattle from a country, zone or compartment posing an undetermined BSE risk

For cattle

Veterinary Authorities should require the presentation of an international veterinary certificate attesting that:

  1. the feeding of ruminants with meat-and-bone meal and greaves derived from ruminants has been banned and the ban has been effectively enforced;

  2. all BSE cases, as well as:

    1. all cattle which, during their first year of life, were reared with the BSE cases during their first year of life, and, which investigation showed consumed the same potentially contaminated feed during that period, or

    2. if the results of the investigation are inconclusive, all cattle born in the same herd as, and within 12 months of the birth of, the BSE cases,

    if alive in the country, zone or compartment, are permanently identified, and their movements controlled, and, when slaughtered or at death, are completely destroyed;

  3. cattle selected for export:

    1. are identified by a permanent identification system in such a way as to demonstrate that they are not exposed cattle as demonstrated in point 2) above;

    2. were born at least two  years after the date from which the ban on the feeding of ruminants with meat-and-bone meal and greaves derived from ruminants was effectively enforced.


Article 11.4.10.


Recommendations for the importation of meat and meat products from a country, zone or compartment posing a negligible BSE risk

For fresh meat and meat products from cattle (other than those listed in point 1) of Article 11.4.1.)

Veterinary Authorities should require the presentation of an international veterinary certificate attesting that:

  1. the country, zone or compartment complies with the conditions in Article 11.4.3.;

  2. the cattle from which the fresh meat and meat products were derived passed ante- and post-mortem inspections;

  3. in countries with negligible BSE risk where there have been indigenous cases, the cattle from which the fresh meat and meat products were derived were born after the date from which the ban on the feeding of ruminants with meat-and-bone meal and greaves derived from ruminants had been effectively enforced.


Article 11.4.11.


Recommendations for the importation of meat and meat products from a country, zone or compartment posing a controlled BSE risk

For fresh meat and meat products from cattle (other than those listed in point 1) of Article 11.4.1.)

Veterinary Authorities should require the presentation of an international veterinary certificate attesting that:

  1. the country, zone or compartment complies with the conditions referred to in Article 11.4.4.;

  2. the cattle from which the fresh meat and meat products were derived passed ante- and post-mortem inspections;

  3. cattle from which the fresh meat and meat products destined for export were derived were not subjected to a stunning process, prior to slaughter, with a device injecting compressed air or gas into the cranial cavity, or to a pithing process;

  4. the fresh meat and meat products were produced and handled in a manner which ensures that such products do not contain and are not contaminated with:

    1. the tissues listed in points 1) and  2) of Article 11.4.14.,

    2. mechanically separated meat from the skull and vertebral column from cattle over 30 months of age.


Article 11.4.12.


Recommendations for the importation of meat and meat products from a country, zone or compartment posing an undetermined BSE risk

For fresh meat and meat products from cattle (other than those listed in point 1) of Article 11.4.1.)

Veterinary Authorities should require the presentation of an international veterinary certificate attesting that:

  1. the cattle from which the fresh meat and meat products originate:

    1. have not been fed meat-and-bone meal or greaves derived from ruminants;

    2. passed ante- and post-mortem inspections;

    3. were not subjected to a stunning process, prior to slaughter, with a device injecting compressed air or gas into the cranial cavity, or to a pithing process;

  2. the fresh meat and meat products were produced and handled in a manner which ensures that such products do not contain and are not contaminated with:

    1. the tissues listed in points 1) and 3) of Article 11.4.14.,

    2. nervous and lymphatic tissues exposed during the deboning process,

    3. mechanically separated meat from the skull and vertebral column from cattle over 12 months of age.


Article 11.4.13.


Recommendations on ruminant-derived meat-and-bone meal or greaves

  1. Ruminant-derived meat-and-bone meal or greaves, or any commodities containing such products, which originate from a country, zone or compartment defined in Article 11.4.3., but where there has been an indigenous case of BSE, should not be traded if such products were derived from cattle born before the date from which the ban on the feeding of ruminants with meat-and-bone meal and greaves derived from ruminants had been effectively enforced.

  2. Ruminant-derived meat-and-bone meal or greaves, or any commodities containing such products, which originate from a country, zone or compartment defined in Articles 11.4.4. and 11.4.5. should not be traded between countries.


Article 11.4.14.


Recommendations on commodities that should not be traded

  1. From cattle of any age originating from a country, zone or compartment defined in Articles 11.4.4. and 11.4.5., the following commodities, and any commodity contaminated by them, should not be traded for the preparation of food, feed, fertilisers, cosmetics, pharmaceuticals including biologicals, or medical devices: tonsils and distal ileum. Protein products, food, feed, fertilisers, cosmetics, pharmaceuticals or medical devices prepared using these commodities (unless covered by other Articles in this chapter) should also not be traded.

  2. From cattle that were at the time of slaughter over 30 months of age originating from a country, zone or compartment defined in Article 11.4.4., the following commodities, and any commodity contaminated by them, should not be traded for the preparation of food, feed, fertilisers, cosmetics, pharmaceuticals including biologicals, or medical devices: brains, eyes, spinal cord, skull and vertebral column. Protein products, food, feed, fertilisers, cosmetics, pharmaceuticals or medical devices prepared using these commodities (unless covered by other Articles in this chapter) should also not be traded.

  3. From cattle that were at the time of slaughter over 12 months of age originating from a country, zone or compartment defined in Article 11.4.5., the following commodities, and any commodity contaminated by them, should not be traded for the preparation of food, feed, fertilisers, cosmetics, pharmaceuticals including biologicals, or medical devices: brains, eyes, spinal cord, skull and vertebral column. Protein products, food, feed, fertilisers, cosmetics, pharmaceuticals or medical devices prepared using these commodities (unless covered by other Articles in this chapter) should also not be traded.


Article 11.4.15.


Recommendations for the importation of gelatine and collagen prepared from bones and intended for food or feed, cosmetics, pharmaceuticals including biologicals, or medical devices

Veterinary Authorities of importing countries should require the presentation of an international veterinary certificate attesting that:

  1. the commodities came from a country, zone or compartment posing a negligible BSE risk;

OR

  1. they originate from a country, zone or compartment posing a controlled or undetermined BSE risk and are derived from cattle which have passed ante- and post-mortem inspections; and that

    1. vertebral columns from cattle over 30 months of age at the time of slaughter and skulls have been excluded;

    2. the bones have been subjected to a process which includes all of the following steps:

      1. degreasing,

      2. acid demineralisation,

      3. acid or alkaline treatment,

      4. filtration,

      5. sterilisation at >138°C for a minimum of 4 seconds,

      or to an equivalent or better process in terms of infectivity reduction (such as high pressure heating).


Article 11.4.16.


Recommendations for the importation of tallow (other than as defined in Article 11.4.1.) intended for food, feed, fertilisers, cosmetics, pharmaceuticals including biologicals, or medical devices

Veterinary Authorities of importing countries should require the presentation of an international veterinary certificate attesting that:

  1. the tallow came from a country, zone or compartment posing a negligible BSE risk; or

  2. it originates from a country, zone or compartment posing a controlled BSE risk, is derived from cattle which have passed ante- and post-mortem inspections, and has not been prepared using the tissues listed in points 1) and 2) of Article 11.4.14.


Article 11.4.17.


Recommendations for the importation of dicalcium phosphate (other than as defined in Article 11.4.1.) intended for food, feed, fertilisers, cosmetics, pharmaceuticals including biologicals, or medical devices

Veterinary Authorities of importing countries should require the presentation of an international veterinary certificate attesting that:

  1. the dicalcium phosphate came from a country, zone or compartment posing a negligible BSE risk; or

  2. it originates from a country, zone or compartment posing a controlled or undetermined BSE risk and is a by-product of bone gelatine produced according to Article 11.4.15.


Article 11.4.18.


Recommendations for the importation of tallow derivatives (other than those made from tallow as defined in Article 11.4.1.) intended for food, feed, fertilisers, cosmetics, pharmaceuticals including biologicals, or medical devices

Veterinary Authorities of importing countries should require the presentation of an international veterinary certificate attesting that:

  1. the tallow derivatives originate from a country, zone or compartment posing a negligible BSE risk; or

  2. they are derived from tallow meeting the conditions referred to in Article 11.4.16.; or

  3. they have been produced by hydrolysis, saponification or transesterification using high temperature and pressure.


Article 11.4.19.


Procedures for the reduction of BSE infectivity in meat-and-bone meal

The following procedure should be used to reduce the infectivity of any transmissible spongiform encephalopathy agents which may be present during the production of meat-and-bone meal containing ruminant proteins.

  1. The raw material should be reduced to a maximum particle size of 50 mm before heating.

  2. The raw material should be heated under saturated steam conditions to a temperature of not less than 133°C for a minimum of 20 minutes at an absolute pressure of 3 bar.


Article 11.4.20.


Surveillance: introduction

  1. Depending on the risk category of a country, zone or compartment with regard to bovine spongiform encephalopathy (BSE), surveillance for BSE may have one or more goals:

    1. detecting BSE, to a pre-determined design prevalence, in a country, zone or compartment;

    2. monitoring the evolution of BSE in a country, zone or compartment;

    3. monitoring the effectiveness of a feed ban and/or other risk mitigation measures, in conjunction with auditing;

    4. supporting a claimed BSE status;

    5. gaining or regaining a higher BSE status.

  2. When the BSE agent is present in a country or zone, the cattle population will comprise the following sectors, in order of decreasing size:

    1. cattle not exposed to the infective agent;

    2. cattle exposed but not infected;

    3. infected cattle, which may lie within one of three stages in the progress of BSE:

      1. the majority will die or be killed before reaching a stage at which BSE is detectable by current methods;

      2. some will progress to a stage at which BSE is detectable by testing before clinical signs appear;

      3. the smallest number will show clinical signs.

  3. The BSE status of a country, zone or compartment cannot be determined only on the basis of a surveillance programme but should be determined in accordance with all the factors listed in Article 11.4.2. The surveillance programme should take into account the diagnostic limitations associated with the above sectors and the relative distributions of infected cattle among them.

  4. With respect to the distribution and expression of the BSE agent within the sectors described above, the following four subpopulations of cattle have been identified for surveillance purposes:

    1. cattle over 30 months of age displaying behavioural or clinical signs consistent with BSE (clinical suspects);

    2. cattle over 30 months of age that are non-ambulatory, recumbent, unable to rise or to walk without assistance; cattle over 30 months of age sent for emergency slaughter or condemned at ante-mortem inspection (casualty or emergency slaughter or downer cattle);

    3. cattle over 30 months of age which are found dead or killed on farm, during transport or at an slaughterhouse/abattoir (fallen stock);

    4. cattle over 36 months of age at routine slaughter.

  5. A gradient is used to describe the relative value of surveillance applied to each subpopulation. Surveillance should focus on the first subpopulation, but investigation of other subpopulations will help to provide an accurate assessment of the BSE situation in the country, zone or compartment. This approach is consistent with Articles 11.4.20. to 11.4.22.

  6. When establishing a surveillance strategy, authorities need to take into account the inherent difficulties of obtaining samples on farm, and overcome them. These difficulties include higher cost, the necessity to educate and motivate owners, and counteracting potentially negative socio-economic implications.


Article 11.4.21.


Surveillance: description of cattle subpopulations

  1. Cattle over 30 months of age displaying behavioural or clinical signs consistent with BSE (clinical suspects)

    Cattle affected by illnesses that are refractory to treatment, and displaying progressive behavioural changes such as excitability, persistent kicking when milked, changes in herd hierarchical status, hesitation at doors, gates and barriers, as well as those displaying progressive neurological signs without signs of infectious illness are candidates for examination. These behavioural changes, being very subtle, are best identified by those who handle animals on a daily basis. Since BSE causes no pathognomonic clinical signs, all Member Countries with cattle populations will observe individual animals displaying clinical signs consistent with BSE. It should be recognised that cases may display only some of these signs, which may also vary in severity, and such animals should still be investigated as potential BSE affected animals. The rate at which such suspicious cases are likely to occur will differ among epidemiological situations and cannot therefore be predicted reliably.

    This subpopulation is the one exhibiting the highest prevalence. The accurate recognition, reporting and classification of such animals will depend on the ongoing owner/veterinarian awareness programme. This and the quality of the investigation and laboratory examination systems (Article 11.4.2.), implemented by the Veterinary Services, are essential for the credibility of the surveillance system.

  2. Cattle over 30 months of age that are non-ambulatory, recumbent, unable to rise or to walk without assistance; cattle over 30 months of age sent for emergency slaughter or condemned at ante-mortem inspection (casualty or emergency slaughter, or downer cattle)

    These cattle may have exhibited some of the clinical signs listed above which were not recognised as being consistent with BSE. Experience in Member Countries where BSE has been identified indicates that this subpopulation is the one demonstrating the second highest prevalence. For that reason, it is the second most appropriate population to target in order to detect BSE.

  3. Cattle over 30 months of age which are found dead or killed on farm, during transport or at a slaughterhouse/abattoir (fallen stock)

    These cattle may have exhibited some of the clinical signs listed above prior to death, but were not recognised as being consistent with BSE. Experience in Member Countries where BSE has been identified indicates that this subpopulation is the one demonstrating the third highest prevalence.

  4. Cattle over 36 months of age at routine slaughter

    Experience in Member Countries where BSE has been identified indicates that this subpopulation is the one demonstrating the lowest prevalence. For that reason, it is the least appropriate population to target in order to detect BSE. However, sampling in this subpopulation may be an aide in monitoring the progress of the epizootic and the efficacy of control measures applied, because it offers continuous access to a cattle population of known class, age structure and geographical origin. Testing of routine slaughter cattle 36 months of age or less is of relatively very little value (Table 2).


Article 11.4.22.


Surveillance activities

In order to implement efficiently a surveillance strategy for BSE, a Member Country should use documented records or reliable estimates of the age distribution of the adult cattle population and the number of cattle tested for BSE stratified by age and by subpopulation within the country, zone or compartment.

The approach assigns ‘point values’ to each sample, based on the subpopulation from which it was collected and the likelihood of detecting infected cattle in that subpopulation. The number of points a sample is assigned is determined by the subpopulation from which the sample is collected and the age of the animal sampled. The total points accumulation is then periodically compared to the target number of points for a country, zone or compartment.

A surveillance strategy should be designed to ensure that samples are representative of the herd of the country, zone or compartment, and include consideration of demographic factors such as production type and geographic location, and the potential influence of culturally unique husbandry practices. The approach used and the assumptions made should be fully documented, and the documentation retained for seven years.

The points targets and surveillance point values in this chapter were obtained by applying the following factors to a statistical model:

  1. the design prevalence for Type A or Type B surveillance;

  2. a confidence level of 95%;

  3. the pathogenesis, and pathological and clinical expression of BSE:

    1. sensitivity of diagnostic methods used;

    2. relative frequency of expression by age;

    3. relative frequency of expression within each subpopulation;

    4. interval between pathological change and clinical expression;

  4. demographics of the cattle population, including age distribution and population size;

  5. influence of BSE on culling or attrition of animals from the cattle population via the four subpopulations;

  6. percentage of infected animals in the cattle population which are not detected.

Although the procedure accepts very basic information about a cattle population, and can be used with estimates and less precise data, careful collection and documentation of the data significantly enhance their value. Since samples from clinical suspect animals provide many times more information than samples from healthy or dead-of-unknown-cause animals, careful attention to the input data can substantially decrease the procedure’s cost and the number of samples needed. The essential input data are:

  1. cattle population numbers stratified by age;

  2. the number of cattle tested for BSE stratified by age and by subpopulation.

This chapter utilises Tables 1 and 2 to determine a desired surveillance points target and the point values of surveillance samples collected.

Within each of the subpopulations above in a country, zone or compartment, a Member Country may wish to target cattle identifiable as imported from countries or zones not free from BSE and cattle which have consumed potentially contaminated feedstuffs from countries or zones not free from BSE.

All clinical suspects should be investigated, regardless of the number of points accumulated. In addition, animals from the other subpopulations should be tested.

  1. Type A surveillance

    The application of Type A surveillance will allow the detection of BSE around a design prevalence of at least one case per 100,000 in the adult cattle population in the country, zone or compartment of concern, at a confidence level of 95%.

  2. Type B surveillance

    The application of Type B surveillance will allow the detection of BSE around a design prevalence of at least one case per 50,000 in the adult cattle population in the country, zone or compartment of concern, at a confidence level of 95%.

    Type B surveillance may be carried out by countries, zones or compartments of negligible BSE risk status (Article 11.4.3.) to confirm the conclusions of the risk assessment, for example by demonstrating the effectiveness of the measures mitigating any risk factors identified, through surveillance targeted to maximise the likelihood of identifying failures of such measures.

    Type B surveillance may also be carried out by countries, zones or compartments of controlled BSE risk status (Article 11.4.4.), following the achievement of the relevant points target using Type A surveillance, to maintain confidence in the knowledge gained through Type A surveillance.

  3. Selecting the points target

    The surveillance points target should be selected from Table 1, which shows target points for adult cattle populations of different sizes. The size of the adult cattle population of a country, zone or compartment may be estimated or may be set at one million because, for statistical reasons, one million is the point beyond which sample size does not further increase with population size.

    Table 1.Points targets for different adult cattle population sizes in a country, zone or compartment.

    Points targets for country, zone or compartment
    Adult cattle population size
    (24 months and older)    		Type A
     surveillance    		Type B
     surveillance
    >1,000,000300,000150,000
    1,000,000238,400119,200
    900,001-1,000,000214,600107,300
    800,001-900,000190,70095,350
    700,001-800,000166,90083,450
    600,001-700,000143,00071,500
    500,001-600,000119,20059,600
    400,001-500,00095,40047,700
    300,001-400,00071,50035,750
    200,001-300,00047,70023,850
    100,001-200,00022,10011,500
    90,001-100,00019,9009,950
    80,001-90,00017,7008,850
    70,001-80,00015,5007,750
    60,001-70,00013,3006,650
    50,001-60,00011,0005,500
    40,001-50,0008,8004,400
    30,001-40,0006,6003,300
    20,001-30,0004,4002,200
    10,001-20,0002,1001,050
    9,001-10,0001,900950
    8,001-9,0001,600800
    7,001-8,0001,400700
    6,001-7,0001,200600
    5,001-6,0001,000500
    4,001-5,000800400
    3,001-4,000600300
    2,001-3,000400200
    1,001-2,000200100

     

  4. Determining the point  values of samples collected

    Table 2 can be used to determine the point values of the surveillance samples collected. The approach assigns point values to each sample according to the likelihood of detecting infection based on the subpopulation from which the sample was collected and the age of the animal sampled. This approach takes into account the general principles of surveillance described in Chapter 1.4. and the epidemiology of BSE.

    Because precise aging of the animals that are sampled may not be possible, Table 2 combines point values into five age categories. The point estimates for each category were determined as an average for the age range comprising the group. The age groups were selected on their relative likelihoods of expressing BSE according to scientific knowledge of the incubation of the disease and the world BSE experience. Samples may be collected from any combination of subpopulations and ages but should reflect the demographics of the cattle herd of the country, zone or compartment. In addition, Member Countries should sample at least three of the four subpopulations.

     

    Table 2.Surveillance point values for samples collected from animals in the given subpopulation and age category.

    Surveillance subpopulation
    Routine
    slaughter1.    		Fallen
    stock2.    		Casualty
    slaughter3.    		Clinical
    suspect4.
    Age>1 year and <2 years
    0.010.20.4N/A
    Age>2 years and <4 years (young adult)
    0.10.20.4260
    Age>4 years and <7 years (middle adult)
    0.20.91.6750
    Age>7 years and <9 years (older adult)
    0.10.40.7220
    Age>9 years
    0.00.10.245

     

    If a country, zone or compartment determines, based on the demographics and epidemiological characteristics of its cattle population, that precise classification of the subpopulations ‘casualty or emergency slaughter, or downer cattle’ and ‘fallen stock’ is not possible, these subpopulations may be combined. In such a case, the surveillance point values accorded to the combined subpopulation would be that of ‘fallen stock’.

    The total points for samples collected may be accumulated over a period of a maximum of seven consecutive years to achieve the target number of points determined in Table 1.

    Surveillance points remain valid for seven years (the 95th percentile of the incubation period).


Article 11.4.23.


BSE risk assessment: introduction

The first step in determining the BSE risk status of the cattle population of a country or zone is to conduct a risk assessment (reviewed annually), based on Section 2. of this Terrestrial Code, identifying all potential factors for BSE occurrence and their historic perspective.

  1. Entry assessment

    Entry assessment consists of assessing the likelihood that a BSE agent has been introduced via the importation of the following commodities potentially contaminated with a BSE agent:

    1. meat-and-bone meal or greaves;

    2. live animals;

    3. animal feed and feed ingredients;

    4. products of animal origin for human consumption.

  2. Exposure assessment

    Exposure assessment consists of assessing the likelihood of exposure of the BSE agent to cattle, through a consideration of the following:

    1. epidemiological situation concerning BSE agents in the country or zone;

    2. recycling and amplification of the BSE agent through consumption by cattle of meat-and-bone meal or greaves of ruminant origin, or other feed or feed ingredients contaminated with these;

    3. the origin and use of ruminant carcasses (including fallen stock), by-products and slaughterhouse/abattoir waste, the parameters of the rendering processes and the methods of animal feed manufacture;

    4. implementation and enforcement of feed bans, including measures to prevent cross-contamination of animal feed; thorough epidemiological investigations of any indigenous case born after the date of the implementation of feed bans should be conducted.

The following recommendations are intended to assist Veterinary Services in conducting such a risk assessment. They provide guidance on the issues that need to be addressed when conducting a country-based assessment of BSE risk. They apply equally to self-assessment in preparation of dossiers for categorisation of countries. The recommendations are supported by greater detail in the questionnaire used for the submission of data for country assessment.


Article 11.4.24.


The potential for the entry of the BSE agent through the importation of meat-and-bone meal or greaves

This point is irrelevant if the exposure assessment outlined below in Article 11.4.27. indicates that meat-and-bone meal or greaves has not been fed, either deliberately or accidentally, in the past eight years. Nevertheless, documentation should be provided on the control systems (including relevant legislation) in place to ensure that meat-and-bone meal or greaves has not been fed to ruminants.

Assumption: That meat-and-bone meal or greaves of ruminant origin plays the only significant role in BSE transmission.

Question to be answered: Has meat-and-bone meal, greaves, or feedstuffs containing either been imported within the past eight years? If so, where from and in what quantities?

Rationale: Knowledge of the origin of meat-and-bone meal, greaves or feedstuffs containing either meat-and-bone meal or greaves, is necessary to assess the likelihood of entry of BSE agent. Meat-and-bone meal and greaves originating in countries of high BSE risk pose a higher likelihood of entry than that from low risk countries. Meat-and-bone meal and greaves originating in countries of unknown BSE risk pose an unknown likelihood of entry.

Evidence required:


Article 11.4.25.


The potential for the entry of the BSE agent through the importation of live animals potentially infected with BSE

Assumptions:

Question to be answered: Have live animals been imported within the past seven years?

Rationale: The likelihood of entry is dependent on:

Evidence required:


Article 11.4.26.


The potential for the entry of the BSE agent through the importation of products of animal origin potentially infected with BSE

Assumptions:

Question to be answered:What products of animal origin have been imported within the past seven years?

Rationale:The likelihood of entry is dependent on:

Evidence required:


Article 11.4.27.


The potential for the exposure of cattle to the BSE agent through consumption of meat-and-bone meal or greaves of ruminant origin

Assumptions:

Question to be answered: Has meat-and-bone meal or greaves of ruminant origin been fed to cattle within the past eight years (see Articles 11.4.3. and 11.4.4.)?

Rationale:  If cattle have not been fed products of animal origin (other than milk or blood) potentially containing meat-and-bone meal or greaves of ruminant origin within the past eight years, meat-and-bone meal and greaves can be dismissed as a risk.


Article 11.4.28.


The origin of animal waste, the parameters of the rendering processes and the methods of animal feed production

Assumptions:

Question to be answered: How has animal waste been processed over the past eight years?

Rationale: If potentially infected animals or contaminated materials are rendered, there is a risk that the resulting meat-and-bone meal could retain BSE infectivity.

Where meat-and-bone meal is utilised in the production of any animal feed, the risk of cross-contamination exists.

Evidence required:


Article 11.4.29.


Conclusions of the risk assessment

The overall risk of BSE in the cattle population of a country or zone is proportional to the level of known or potential exposure to BSE infectivity and the potential for recycling and amplification of the infectivity through livestock feeding practices. For the risk assessment to conclude that the cattle population of a country or zone is free from BSE risk, it should have demonstrated that appropriate measures have been taken to manage any risks identified.

nb: first adopted in 1992; most recent update adopted in 2015.

  1. See point 4) of Article 11.4.21.

  2. See point 3) of Article 11.4.21.

  3. See point 2) of Article 11.4.21.

  4. See point 1) of Article 11.4.21.

2018 ©OIE - Terrestrial Animal Health Code

Contents | Index Chapter 11.3. Chapter 11.5.