Chapter 9 – Canada Health Accredited Herd Enzootic Bovine Leukosis Program

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9.1 The Disease

Etiology

Bovine leukemia virus (BLV) is a retrovirus in the family Retroviridae and is the causative agent of enzootic bovine leukosis (EBL).

Susceptible species

Natural infection has been shown to occur in cattle (Bos Taurus and Bos Indicus), water buffaloes and capybaras. Experimental infection has been demonstrated in a number of other species, including sheep.

Distribution

Leukosis in cattle was originally described in Europe in the 19th century. BLV is now common in Canada, the United States and South America and also exists in other countries around the world. Although distributed worldwide, prevalence rates for BLV vary widely among countries and on production type. Dairy cattle generally have higher prevalence rates than beef cattle likely due to their close housing conditions and management practices. A number of countries are recognized as officially free from BLV infection. The European Union (EU) and their domestic legislation have an eradication policy for BLV and a number of countries and regions in the EU have achieved BLV-free status.

Transmission and epidemiology

Cattle are infected with BLV mainly through transfer of blood and blood products that contain infected lymphocytes. The major target cells of BLV are the B lymphocytes with the virus integrating randomly into the deoxyribonucleic acid (DNA) of the host cell in a provirus state, allowing viral persistence and sustained antibody response. Cow to cow or calf transmission can occur by the transfer of blood through routine husbandry practices such as tattooing, dehorning, rectal palpation and injections. Vertical transmission may occur transplacentally from an infected dam to her fetus, intrapartum by contact with infected blood or postpartum from the dam to the calf through ingestion of infected colostrum or milk. It is also believed that colostrum can have a protective effect when it contains large amounts of maternal BLV antibodies (whether a calf is infected by BLV or just has BLV maternal antibodies presents a diagnostic challenge in these young animals). Any material that is blood contaminated or lymphocyte rich has the potential to infect animals with BLV. As well, mechanical transmission may occur in areas with large numbers of biting flies such as tabanids. Many other bodily fluids such as urine, feces, saliva, respiratory secretions, semen, uterine fluids, and embryos, have been examined and have not been shown to transmit the virus or appear to represent a very low risk of virus transmission.

Pathogenesis and clinical signs

When exposed to BLV, not all cows become infected. Those that do become infected remain infected for the remainder of their life. Despite a strong humoral response against the virus, BLV evades the immune surveillance (hides within the lymphocytes) and persists for the life of the infected animal. Most infections are sub-clinical and inapparent, with 30 to 70% animals going on to develop persistent lymphocytosis (PL) in their blood, and less than 10% developing tumours or lymphosarcoma. Lymphosarcomas are seen typically in animals over 3 years of age with the most common in the 4 to 8 years age group. Signs will depend on the site of the tumour and could include signs related to the gastrointestinal tract, losing body condition and decreasing appetite, enlarged visceral and peripheral lymph nodes, drop in milk production and weakness. At necropsy, lymph nodes and a wide range of tissue are found to be infiltrated with neoplastic cells. The abomasum, right auricle of the heart, spleen, intestine, liver, kidney, omasum, lung and uterus are the organs most frequently involved. Whether or not an animal becomes infected or develops any of the other forms of the disease (PL, lymphosarcoma) appears to depend on such factors as the animal's immune status, the random integration of provirus in the host cell disrupting normal functions, and the amount of the viral dose.

Treatment or vaccine

No vaccine against BLV is commercially available. There is also no treatment for the disease.

Differential diagnosis

Diagnosis of BLV infection is made by serology, persistent lymphocytosis (PL) is identified by hematology, and lymphosarcoma is identified by histopathological examination of the tumour obtained by biopsy or necropsy. Because of the wide range of clinical findings, EBL can be included on the differential list for many diseases. Cases of sporadic lymphosarcoma (also called juvenile, thymic or and cutaneous forms) in animals which are BLV-negative may resemble lymphosarcoma resulting from BLV infection.

Laboratory diagnosis

Infection with the BLV is life long and gives rise to a persistent antibody response; therefore, serology is the most common and reliable way to diagnose infection with BLV. Both agar gel immunodiffusion (AGID) using serum and enzyme-linked immunosorbent assay (ELISA) using serum or milk are internationally recognized serological tests for BLV. The ELISA is used most commonly for routine diagnostic due to its high sensitivity and specificity along with its affordable cost, ease of use and availability. The AGID is unsuitable for milk samples because of lack of specificity and sensitivity. Polymerase chain reaction (PCR) can be used to identify the BLV agent in lymphocytes in body fluids or tissues such as tumours of infected animals.

The animals for which antibody detection is unreliable are either calves that still have maternal antibodies from a BLV positive cow or newly infected animals that have not yet seroconverted. Some rare animals are also undetected by serology due to proviral variants. Antibodies can first be detected 3 weeks up to 16 weeks after infection depending on the response of the animal and the test being used. Maternal antibodies have been shown to protect calves against infection and may take up to 6 or 7 months to disappear. There is no way of distinguishing passively transferred antibodies from those antibodies resulting from active infection. Therefore, serology is unreliable in diagnosing BLV during the early stages of infection or in calves < 6 months of age. However, the World Organisation for Animal Health (WOAH; founded as Office International des Épizooties (OIE)) states that PCR can be used as an adjunct to serology for confirmatory testing in young calves with colostral antibodies.

Public health

Research has been done to determine whether BLV causes disease in humans, specifically through the consumption of milk from infected cows. There is no conclusive evidence for the transmission from cattle to humans and therefore BLV is not considered at present a human health hazard. Further research is needed however to determine whether BLV may play a role in human disease.

9.2 Policy and principles of control

Policy statement

The Canada Health Accredited Herd Enzootic Bovine Leukosis (CHAH – EBL) program is offered to bovine producers by the Canadian Food Inspection Agency (CFIA) as a voluntary program. It is carried out in cooperation with producers, accredited veterinarians, approved laboratories, CFIA and national stakeholder organizations. The program is designed to give producers a means of detecting, controlling and eradicating the bovine leukemia virus within their herd. It is the bovine producer who makes the decision to enrol in the CHAH-EBL program on a voluntary basis. However, once the producer is participating in the CHAH-EBL program, their compliance with the program standards and rules is mandatory to maintain their accreditation.

The overall objective of the CHAH-EBL program is to provide owners with the opportunity to have their herds identified as negligible risk with respect to EBL, thereby improving the marketing competitiveness for livestock from CHAH-EBL herds. The CHAH-EBL program has been specifically designed to meet the bovine import requirements of the European Union (EU).

Authority

Enzootic bovine leukosis is an annually notifiable disease for which Canada must submit an annual report to the WOAH indicating their presence within Canada. The WOAH has guidelines in Chapter 11.6 of the Terrestrial Animal Health Code for a EBL free country, zone, compartment and herd, and recommendations for the importation of cattle for breeding or rearing. CFIA feels that a CHAH-EBL Group within a CFIA approved artificial insemination centre would be equivalent in protection to an EBL free herd or compartment.

Canada does not have any specific regulations or mandatory disease control policies with respect to EBL. The primary role of the CFIA in the CHAH-EBL herd status program is to establish the national standards and rules of the CHAH-EBL program, as well as being its administrator and status assessor. The CFIA is also responsible for CHAH-EBL program testing; this includes conducting all initial and confirmatory EBL testing. Accredited veterinarians deliver the CHAH-EBL program.

Import requirements of other countries for cattle may be based on enrollment and certification in the CHAH-EBL program.

Principles of control

The CHAH-EBL program is based on the following principles:

  • detecting and removing any infected animals
  • movement controls and testing on all incoming animals to prevent re-infections
  • monitoring the animals to ensure the status of the herd remains negligible risk

To achieve CHAH-EBL certification status, the enrolled herd must meet all of the program requirements. The core program has the following elements:

  • enrollment, inventory and qualification testing
  • annual inventory and testing
  • immaculate record keeping and inventory management
  • a herd closed to animals not on the CHAH-EBL program with additions added only according to prescribed testing procedures

Private licensed veterinarians are accredited by the CFIA to deliver the CHAH-EBL program. These accredited veterinarians deliver the program and ensure the necessary tests and requirements are completed and provide professional consultations to the livestock owner. Testing is done or supervised by the accredited veterinarian. The work that they do is paid for by the owner. CFIA staff then assesses the testing and annual report for a decision on certification.

In order for an owner to be successful in attaining his or her goal of CHAH-EBL accredited status, there must be good communication among all the parties involved. It is the joint responsibility of the owner, the accredited veterinarian and the CFIA district veterinarian to review and resolve situations as they arise.

Case definitions

Reactor

A bovine is classified as a reactor if 1 or more of the following are present:

  1. An atypical or presumptive positive result on an EBL screening test. These results are reported as inconclusive on the laboratory reports and subjected to confirmatory testing by the CFIA Saint-Hyacinthe Laboratory – Retrovirology Centre of Expertise.
  2. An inconclusive EBL test result reported by the CFIA Saint-Hyacinthe Laboratory – Retrovirology Centre of Expertise. Retesting, as directed by the CFIA Retrovirology Centre of Expertise is required.
  3. A positive EBL test result on confirmatory testing reported by the CFIA Saint-Hyacinthe Laboratory – Retrovirology Centre of Expertise, but for a calf less than 6 months of age. Retesting, as directed by CFIA Retrovirology Centre of Expertise, is required.
Confirmed positive case
An EBL-positive animal is any animal that has been confirmed positive for EBL by CFIA Saint-Hyacinthe Laboratory – Retrovirology Centre of Expertise. The official serological test used to confirm diagnosis is the ELISA. In some instances PCR could be used as an adjunct to serology for confirmatory testing such as calves less than 6 months with colostral antibodies.

9.3 Roles and responsibilities

9.3.1 Producer Responsibilities

  • complying with all the CHAH-EBL program procedures (standards) and adhering to the conditions as stipulated on form CFIA/ACIA 4285
  • obtaining the services of a veterinarian accredited to deliver the CHAH-EBL program
  • identifying animals in the herd with an approved tag
  • providing necessary facilities and assistance for inspection and handling of the animals
  • keeping relevant records of all bovines on the premises and moving onto or off of the premises
  • providing to the accredited veterinarian, and/ or the CFIA district veterinarian, upon request, any supporting documentation or missing information that is necessary to reconcile the inventory, herd testing or to complete the annual certification process
  • being aware of the epidemiology of EBL infection, and immediately reporting to the accredited veterinarian any signs of EBL in animals
  • following the current relevant biosecurity standard: the Biosecurity for Canadian Dairy Farms: National Standard or the Canadian Beef Cattle On-Farm Biosecurity Standard.

9.3.2 Accredited veterinarian responsibilities

Program delivery

In accordance with the national standards, program delivery is carried out by an accredited veterinarian. Sampling for EBL testing is done by accredited veterinarians. It is always the accredited veterinarian's responsibility to complete the annual inventory report, reconcile testing, and recommend the herd for certification to the CFIA district veterinarian.

Accredited veterinarians delivering this program are responsible for the following:

  • reviewing the requirements of the program and responding to questions of the owner applying for or enrolled in the program
  • teaching the owner to recognize the clinical signs of enzootic bovine leukosis, providing information on the epidemiology of the disease, biosecurity and herd management
  • assessing the facilities on the premises proposing to participate in the program
  • conducting a herd inventory
  • assessing the health of the herd to determine whether any bovine is demonstrating signs of enzootic bovine leukosis
  • reconciling records to ensure that the herd meets the program requirements
  • reporting any discrepancies in the procedures outlined in the CHAH–EBL program
  • signing reports, including the annual inventory report, and submitting them to the CFIA district office for review
  • collecting and submitting or oversight of samples to the CFIA Saint-Hyacinthe Laboratory – Retrovirology Centre of Expertise following CFIA's approved protocol
  • ensuring that all samples that submitted are identified as enrolled in the CHAH-EBL program and that they are submitted to CFIA Saint-Hyacinthe Laboratory – Retrovirology Centre of Expertise, using the CFIA/ACIA 3841 form
  • taking appropriate sanitary precautions and chain of custody measures when collecting and submitting samples
  • reviewing of all herd test results and reporting all reactors, anomalies or omissions to the district veterinarian
  • reconciling the identification, inventory and testing of the herd

9.3.3 CFIA responsibilities

Administrator, status assessor and program oversight

  • providing training and granting accreditation under a CFIA Accredited Veterinarian Agreement (CFIA 1625) to private veterinarians who are interested in delivering the CHAH-EBL program
  • providing required forms for CHAH-EBL program
  • receiving and reviewing completed applications for enrollment into the CHAH-EBL program
  • informing the herd's accredited veterinarian of any outstanding requirements that prevent enrollment of the herd
  • reviewing/auditing the annual herd inventory report and herd test results, and verifying that herd inventories, testing, and any additions have been completed according to program procedures
  • verifying, during the annual herd review, that the veterinarian delivering the program is a veterinarian accredited to deliver the CHAH-EBL program
  • if qualifying, recommending certification or renewal of certification for the CHAH–EBL herd
  • suspending or revoking CHAH-EBL certified status in the event of reported irregularities, failure to follow program procedures or a EBL-positive animal
  • performing any retesting as requested by the CFIA Saint-Hyacinthe Laboratory – Retrovirology Centre of Expertise related to a reactor animal or an inconclusive test result
  • investigating herds that are suspended, assessing and approving their corrective action plan
  • reinstating or revoking CHAH-EBL certified status based on fulfilment of their corrective action plan
  • informing the CFIA animal health specialist(s) responsible for the CHAH-EBL program of the status of all CHAH herds located in their district in a timely manner
  • developing, modifying and updating the program procedures (standards) and forms required for the programs
  • liaising with provincial and national stakeholders
  • providing policy clarification upon request
  • developing and maintaining an accessible up-to-date report of all CHAH-EBL certified herds
  • verifying to interested parties that a herd is a CHAH-EBL certified herd

CFIA Saint-Hyacinthe Laboratory – Retrovirology Centre of Expertise

  • determining approaches to collect and submit samples
  • performing and interpreting tests on serum or milk samples in accordance with the latest version of official protocol for the diagnosis of EBL
  • confirming presumptive positives or atypical EBL test results
  • requesting any retesting required of a EBL positive or reactor animal
  • notifying the appropriate district veterinarian and CHAH-EBL program specialists of confirmed positive EBL animals
  • contributing to policy and program design, and providing scientific supports to CFIA program specialist(s) and district veterinarians
  • responsible for development, modifications and updates to the official laboratory protocols, approaches and quality assurance program related to the CHAH-EBL program

9.4 Program standards

9.4.1 Preliminary activities for accredited veterinarians

1. Schedule a meeting with the local Canadian Food Inspection Agency (CFIA) district veterinarian to undergo the training necessary to obtain CFIA accreditation in the CHAH-EBL program. During this meeting, the CFIA district veterinarian will review the terms and conditions for herd certification, and discuss the duties and procedures that the accredited veterinarian must follow for the delivery of the CHAH-EBL Program.

2. Read and familiarize themselves with the CHAH-EBL module of the Accredited Veterinarian's Manual of procedures.

3. Once accredited for the CHAH-EBL function, the accredited veterinarian makes arrangements with the interested owner to assess the facilities, herd management, and record-keeping practices. These steps should be undertaken to gauge the degree to which the accredited veterinarian believes the producer can be successful, and to identify any necessary changes in record keeping or management that would facilitate meeting the CHAH EBL program requirements.

4. A major part of the success in eradicating EBL from a herd depends on the recommendations that the accredited veterinarian gives to the owner regarding the particular situation of its herd. The accredited veterinarian should be familiar with the clinical signs of EBL, the current features of diagnosis of this disease and the recommended management and biosecurity practices that an owner could follow to attain certification status for their herd. A general summary of biosecurity guidelines is available in appendix 3.

5. Individual, pooled or bulk milk testing is a cost-effective way for the owner to initially investigate if a herd is a good candidate for CHAH-EBL qualification and working towards establishing an EBL free herd before enrolling in the official program. This could be done before completing the official testing under the CHAH-EBL program.

6. Advise owners to contact the CFIA district office in their area to obtain an application form and to learn what is required to participate, attain and to maintain certification.

9.4.2 Application and criteria to apply

7. The herd owner is advised to obtain an application: Form CFIA/ACIA 4285 – Canada Health Accredited Herds Bovine Leukemia Virus (CHAH-EBL) – Conditions and Agreement from the local CFIA district veterinarian. The application/contract specifies the terms and conditions required to accredit and maintain a herd as CHAH-EBL. See also Appendix 1.

8. The herd owner is advised that the application must be completed and submitted to the local CFIA district veterinarian for approval and signature before the herd's accredited veterinarian commences any testing intended to qualify a herd as a CHAH-EBL herd.

9. The owner meets with the district veterinarian and accredited veterinarian to review the terms and conditions for herd certification and to discuss the duties and procedures that must be followed before commencing any testing. An outline of the testing requirements as well as the actions that must be followed should serologically positive animals be found is reviewed. The owner is given instructions regarding restrictions on purchasing of animals and embryos.

10. Only owners of a herd of cattle that has been established for 2 years may apply to participate.

11. Only herds where each animal is identified by an approved tag may participate in the CHAH-EBL program.

12. Upon application to become a CHAH-EBL herd, the owner shall maintain and make available to an inspector or accredited veterinarian all records including all animals purchased and removed from his herd.

9.4.3 Qualification

13. Initially a herd must have 2 negative herd tests, and an accompanying inventory report, to qualify as a CHAH-EBL herd. All animals must be included in each herd test and have reacted negatively. Testing intervals must be at least 4 months but no more than 12 months apart. This period of herd testing is called the qualification period.

14. The accredited veterinarian performs the sampling and submission of samples during the qualification period. Qualification samples are submitted to the CFIA Saint-Hyacinthe Laboratory – Retrovirology Centre of Expertise using Form CFIA/ACIA 3841. Refer to Appendix 1 for instructions on Form CFIA/ACIA 3841.

15. Any additions, other than natural increases, to the herd during the qualification period must be added according to procedures outlined in the acquisitions and movement section of this document.

16. Any bovine semen and embryos/ova introduced into the herd during the qualification period must be added according to procedures outlined in the acquisitions and movement section of this document.

17. Following the receipt of each qualifying herd test result and inventory report (refer to Appendix 1 for instructions on CFIA/ACIA Annual inventory report) from the accredited veterinarian, it is the CFIA district veterinarian that reviews the test results and report. After the review and any necessary follow up, the CFIA district veterinarian completes official recommendation for CHAH-EBL Program Certification Form.

18. Positive animals and the calves born to positive animals since the last herd test must be removed and the herd would start again with the first test for qualification no less than 4 months after the positive animals and their calves have been removed.

19. Following the receipt of second negative qualifying herd test and complete acceptable inventory report, the CFIA district veterinarian will recommend the herd for CHAH-EBL Program certification. When certification is recommended, the herd is included in the accessible database of CHAH-EBL certified herds.

20. The date of this first certification becomes the anniversary date for the CHAH-EBL herd.

9.4.4 Annual anniversary date and deadlines for maintenance of certification

21. The annual anniversary date is the date of certification and the anniversary date will not change.

22. Once a herd is certified CHAH-EBL, annual herd testing with negative results and an annual herd inventory and associated report must be completed within one month before or after the herd anniversary date in order to maintain certification.

23. The annual inventory and audit report must be completed and signed by the accredited veterinarian responsible for the herd and documents the fact that all of the ongoing requirements have been met and can be submitted for review and approval by the CFIA veterinarian.

24. The annual inventory and audit report, and the annual herd testing results, are the responsibility of the accredited veterinarian and is submitted to the CFIA district office by the accredited veterinarian. Following receipt of the annual herd testing and annual inventory and audit report, the CFIA district veterinarian conducts a review of the documents and herd and decides whether to recommend maintenance of CHAH-EBL certified status.

9.4.5 Maintenance of CHAH-EBL certification

Record keeping

25. A major key to success in certifying a herd as a CHAH-EBL herd is the ability of the accredited veterinarian to provide information on the cattle at time of the annual inventory report that allows for timely auditing of the CHAH-EBL herd. Incomplete test records or inventory records make it difficult or impossible to verify livestock movement and testing for a farm seeking to attain or maintain CHAH-EBL status, and may compromise herd certification.

Identification

26. All the animals must be identified by an approved tag and recorded on the annual inventory report and the test reports. All new tags applied should be cross-referenced against all other available identification for the animal, and a note should be made in the report recording the reason for a new ear tag.

Annual Inventory and Audit Report

27. The annual herd inventory and audit report is completed by the accredited veterinarian and lists the following:

  • identification of each bovine on the premises at the time of the inventory;
  • notation of the animals included in the annual herd test. These animals would also be documented on the CFIA/ACIA Form 3841 for sample submission and testing;
  • notation of any animals that were not tested on the previous herd tests. If the animals were born on the farm since the last herd test, then a natural increase notation beside the description of the animal should be made. If animals have been purchased or brought into the herd for any other reasons, the information and testing concerning the animal should be noted, and brought to the attention of the district veterinarian; and
  • all bovines that have entered, moved or left the premises since the last inventory:
    • All animals must be identified when a change in ownership occurs or when animals are moved from their usual location (for example, exhibition, insemination centre, sales barn or auction barn).
    • Owner records are required for every bovine that is born on, or enters the premises. Acquisitions of live bovines or embryos must include documentation that they were done in the prescribed manner as outlined in the acquisitions and movement section (9.4.6) of this document.
    • Owner records of every bovine that leaves the herd (for example, sales receipts, notation of deaths).

Clinical Suspect

28. Any animals with clinical signs of EBL must be reported to accredited veterinarian. The animal must undergo testing if EBL is suspected. Documentation of negative test results for the suspect case are included with the annual inventory and audit report. See 9.4.8 for procedures followed for an EBL positive result.

Annual Testing

29. Animals required to undergo annual testing in a CHAH-EBL herd include:

  • all animals over 24 months of age
  • embryo transfer animals, not included in a previous test, that were added to the herd without satisfactory evidence that the donor was from a CHAH-EBL herd and the source of the semen was either from a registered AI centre or on-farm collected semen from the CHAH-EBL herd
  • additions to the herd under 24 months that are not natural increases and were not included in a previous test
  • individual testing of the required animals must be completed within 1 month before or after the herd anniversary date
  • all samples are submitted to the CFIA Saint-Hyacinthe Laboratory – Retrovirology Centre of Expertise using Form CFIA/ACIA 3841 (Refer to Appendix 1)

9.4.6 Acquisitions and movement of live cattle and genetic material

Additions

30. Live animal additions from another CHAH-EBL herd may be admitted with no testing. Appropriate documentation including name and address along with documentation that the herd of origin is a certified CHAH-EBL herd is required.

31. Live animal additions from a non-CHAH-EBL herd may be admitted after the following procedures:

  • all testing is performed by the accredited veterinarian and submitted to the CFIA Saint-Hyacinthe Laboratory – Retrovirology Centre of Expertise
  • negative individual test result within 30 days preceding entry to isolation
  • isolation for 4 months
  • second individual negative test result after 4 months of isolation
  • entry into herd allowed after second negative test
  • only after being included in the next annual herd test, that occurs at least 4 months after the last individual EBL negative test in iv above, is the addition certified for sale with CHAH-EBL status
  • progeny born from additions are not eligible to be considered part of the CHAH-EBL herd until the uterine dam is eligible
  • the number of additions to a CHAH-EBL herd allowed in an upcoming year shall not exceed 25% of the total number of existing animals in the herd. Existing animals are defined as the number of animals in the herd listed on the last herd audit minus those animals that are sold from/leave the herd in the upcoming year

32. The accredited veterinarian must document animal additions to the herd in the annual inventory and audit report from the records that the owner shall provide. The onus is on the owner to ensure that additions to the herd are made in the prescribed manner, but it is the responsibility of the veterinarian to make due enquiry concerning any animals that have not appeared on previous herd tests or inventories, and to document their origin.

Exhibitions

33. Exhibition animals should not have contact with animals of lesser status that allows blood exchange, for example, through common equipment. Biosecurity measures must be in place to prevent contact. In such situation of casual contacts, animals must undergo individual testing 4 months after contact. Animals cannot be accorded CHAH-EBL status prior to this test. Isolation from the herd is recommended until the negative test result is received.

34. Exhibition animals that have had close, prolonged contact with animals of a lesser status for many days, or if blood was potentially exchanged, must undergo individual testing after a 4 months period of isolation from the herd.

Embryos and Semen

35. Embryos used in a CHAH-EBL herd must:

  • originate from a CHAH-EBL herd; or
  • embryos must be from donor animals free of clinical signs of EBL and properly handled between collection and transfer according to the IETS Manual by CETA certified practitioners. Embryo transfer calves from a non CHAH-EBL herd must undergo EBL testing in the CHAH-EBL herd (refer to Annual testing section).

36. Semen used in a CHAH-EBL herd must:

  • come from a donor bull resident in a CHAH-EBL herd at the time of semen collection; or
  • a donor bull that is part of the resident herd at a semen collection centre (Artificial Insemination (AI) Centre) approved under the Canadian Health of Animals Regulations to certify semen for export to EU; or
  • legally imported semen that has met Canadian import requirements and is equivalent to standards in section 35 above.

9.4.7 Sample submission and reporting of results

37. All testing is done by the CFIA Saint-Hyacinthe Laboratory – Retrovirology Centre of Expertise Results will be made available to the district veterinarian through the Laboratory Sample Tracking System (LSTS), who will subsequently provide the results to the accredited veterinarian. No copies of the results are sent to the owner of the animals as the point of contact is the accredited veterinarian. It is the accredited veterinarian's responsibility to inform the owner of their herd test results. A copy is provided by the laboratory to the owner only if a written request is received from the accredited veterinarian and the district veterinarian agrees.

9.4.8 Reactors and confirmed positive cases

Reactor

38. An atypical or presumptive positive on a EBL screening test (reactor animal) requires confirmation as a positive. The herd's certification status is amended based on the confirmatory testing result.

Confirmed Positive – Single Animal

39. The CHAH-EBL status of a herd is suspended when a single confirmed positive case is found on an annual test. Note the following:

  • the EBL-positive animal and any of its untested calves must be removed from the herd; an exception is possible when a calf is separated from the dam at time of calving
  • 4 months after removal of the EBL-positive animal and any untested calves, all cattle in the herd must be tested

  • following receipt of the negative herd test results, CHAH-EBL status of the herd is reinstated

    The aforementioned calf, separated from the dam at time of calving, may be considered part of the CHAH-EBL herd inventory after 24 months of age and after 2 negative tests at least 4 months, but no more than 12 months apart. Testing is to be done after the calf is at least 6 months of age.

Confirmed Positive – Multiple Animals

40. The CHAH-EBL status of a herd is suspended when multiple confirmed positive cases are found on an annual test. Note the following:

  • the EBL-positive animals and their untested calves must be removed from the herd; an exception is possible when a calf is separated from the dam at time of calving
  • the remaining cattle are subjected to testing as in section 9.4.3 Qualification

  • following receipt of the negative herd test results, CHAH-EBL status of the herd is reinstated

    The aforementioned calf, separated from the dam at time of calving, may be considered part of the CHAH herd inventory after 24 months of age and after 2 negative tests at least 4 months apart, but no more than 12 months. Testing is to be done after the calf is at least 6 months of age.

9.4.9 Suspension and cancellation

41. If the owner of the certified herd does not meet the ongoing requirements of the program, then the herd certification will be revoked.

If the owner of the certified herd contravenes the program rules, the CFIA will temporarily suspend the certification of the herd. After reviewing the situation, CFIA may reinstate certification, extend the suspension until a corrective action request is complied with, or revoke the certification of the herd. If the owner can not comply with the requirements of the program or does not want to keep the certification of its herd, then certification is revoked.

9.4.10 Information sharing

42. Information sharing requires all herd information including inventories, test results, documents related to purchases, sales of animals, embryos and deaths to be available to the owner, accredited veterinarian and CFIA.

43. CFIA will produce, distribute and/or publish a list of all certified CHAH-EBL herds to interested stakeholders.

9.5 Bovine semen production centres and the CHAH-EBL group

Note: Compliance with the CHAH EBL group of a CFIA approved AI centre does not remove any obligations under either the Artificial Insemination or Export Programs

The CHAH-EBL program is an on-farm program offered to livestock producers to control EBL in their cattle herds. The same principles of control for EBL may be applied to a group of animals in a CFIA approved bovine semen production centres with an opportunity to create a group of live animals that is negligible risk for EBL. As per the Artificial Insemination Program, only donor bulls and teaser males are permitted in bovine semen production centres.

This part of the CHAH-EBL program is designed to meet the live bovine import requirements of trading partners such as the European Union (EU). The centre would enroll in the CHAH-EBL group of CFIA approved AI Centre program on a voluntary basis. Once the centre is participating in the program, their compliance with the standards and rules of the CHAH-EBL group of CFIA approved AI Centre is mandatory to maintain their status.

CHAH-EBL group of a CFIA approved AI centre

The following standards and rules must be met by a bovine semen production centre to be approved as a group of live animals with negligible risk status for EBL.

1. The bovine semen production centre is approved by the CFIA to export bovine semen according to the standards of the Canadian Artificial Insemination Program (CAIP) under the authority of the Health of Animals Regulations. This includes the required AI centre minimum standards for sanitation, biosecurity, health and record keeping. Any other management system or facility would also need to meet or be equivalent to the relevant standards to be considered eligible to enrol in the CHAH-EBL Group of a CFIA approved AI Centre program.

2. The CHAH-EBL group of a CFIA approved AI centre has a preventive control plan (PCP) for EBL

The written biosecurity centre plans including a site plan, and management practices (for example, injections, blood collection and other biological samples, dehorning, ear-tagging and rectal palpation) that are suitable for the operation may only need to have minor additions to identify the CHAH-EBL specific issues for live animals. The EBL PCP is documented, implemented, and maintained as a condition for maintaining EBL negligible status

3. All cattle introduced into the bovine semen production centre CHAH EBL group of a CFIA approved AI centre come from:

  1. a CHAH-EBL herd

    or

  2. a non-CHAH-EBL herd and
    • if over 24 months of age have met all pre-entry and isolation requirements for a CFIA approved and export eligible bovine semen production centre. Pre-entry and isolation requirements are detailed in the Artificial Insemination Manual of Procedures.
    • if less than 24 months of age, have met all pre-entry and isolation requirements for a CFIA approved export eligible bovine semen production centre and the 'uterine' dam has been subjected to two diagnostic tests for EBL at an approved lab for EBL (refer to Accredited Veterinarians' Manual, Chapter 3.3 Laboratories) with negative results during the preceding 12 months at an interval of at least 4 months between tests. At least one of the uterine dam tests must have been carried out after weaning of the calf

    or

  3. a CFIA approved export eligible bovine semen production centre and either:

    • are over 24 months of age;

      or

    • if less than 24 months, the uterine dam has been tested as per b. second bullet above

      or

    • If less than 24 months of age, and the uterine dam was not tested as in b. second bullet above, the animals have been subjected to an additional diagnostic test for EBL while in the bovine semen production centre at an approved lab for EBL with negative results during the preceding 12 months with an interval of at least 4 months between the tests, one of which has been carried out while fully released into the bovine semen production centre.

4. All resident animals in the bovine semen production centre CHAH-EBL group are subjected to a diagnostic test for EBL at an approved lab for EBL at least annually.

5. No new animals have entered the CHAH- EBL group of CFIA approved AI Centre in the 4 months preceding an export shipment.

6. All animals from the CHAH-EBL Group of CFIA approved AI Centre that are part of an export shipment are tested for EBL within 30 days of export with negative results.

7. There has been no evidence of EBL either clinical or at post-mortem or a result of a diagnostic test in the four months preceding an export shipment from the compartment.

Note: All animals in a CHAH-EBL group must follow the applicable requirements of the CHAH-EBL program. This can be accomplished by the entire bovine semen production centre being enrolled in the program, or, a completely separate section within the centre where all animals within the separated area comply with the CHAH-EBL group requirements.

Suspension and re-approval

8. The CHAH-EBL group of a CFIA approved AI Centre's status is suspended when a confirmed EBL positive animal is found during any EBL testing of the group's animals. The following steps must be followed in such a case:

  1. All EBL positive animal(s), (and their calves if a non-bovine semen production centre) since the last negative test, must be removed from the CHAH-EBL Group of a CFIA approved AI Centre.
  2. If not already tested at the time of the positive test result, then all animals are subject to a diagnostic test for EBL at an approved lab for EBL, with negative results.
  3. 4 months after removal of the EBL positive animals, all the remaining cattle must be subjected to a diagnostic test for EBL at an approved lab for EBL.
  4. Following receipt of the negative test results for all remaining animals, the status of the CHAH-EBL Group of CFIA approved AI Centre is reinstated.

Roles and responsibilities

9. Bovine semen production centre operators are responsible for complying with all the applicable CHAH-EBL program standards and rules.

10. CFIA or accredited veterinarians are responsible for the required testing within the compartment and verifying all additions have met the applicable CHAH-EBL standards.

11. The CFIA is responsible for the CHAH-EBL program, oversight, approval and status assessment within of the CHAH-EBL Group of the CFIA approved AI centres.

12. A comprehensive list of the CFIA approved AI centres with approved CHAH-EBL Groups is maintained by the CFIA, at the national level.

Figure 1: Pathways to enter a CHAH-EBL group and export requirements. Description follows.
Figure 1: Pathways to enter a CHAH-EBL group and export requirements

There are three possible scenarios or pathways to enter into CHAH-EBL group within a bovine semen production centre:

The first scenario involves animals from a previously established CHAH-EBL herd or group being introduced into a CHAH-EBL group within a centre. This group must have been closed to new entrants for a minimum of 4 months, and these animals require no additional EBL testing to enter into the group.

The second scenario involves animals from a non-CHAH-EBL herd or group being introduced into a CHAH-EBL group within a centre. These animals would need to meet the EBL pre-entry and isolation requirements as per the Artificial Insemination Program Manual of one negative EBL test on farm, animal kept separate on farm for a maximum of 60 days before entry into the isolation facility. There must also be one negative EBL test after 21 days in AI entry isolation and before full release into the CHAH-EBL group. If animal is under 24 months, the uterine dam must have tested negative for EBL after weaning of the calf, and meet the testing specific testing requirements as outlined in Scenario 3 for the bull to be allowed to enter the CHAH-EBL Group.

The third scenario involves resident animals already in a Bovine Semen Production Centre (who have previously met the pre-entry and isolation requirements). There must be one negative EBL test while resident in the Centre, in the preceding 12 months. If less than 24 months, the uterine dam must have been either tested twice for EBL with an interval of greater than 4 months, or testes once and the calf tested using PCR once prior to entry into the CHAH-EBL Group isolation, or the animal had an additional EBL test with an interval of greater than 4 months for minimum of two EBL tests while resident in a centre.

The CHAH-EBL Group must follow the requirements outlined in section 9.5 of the CHAH-EBL program. This is accomplished by a CHAH-EBL area within the resident barn of centre or in separate building where all animals in this separated area are part of the CHAH-EBL Group and comply with the CHAH-EBL requirements. This separated area means the animals that are part of the CHAH-EBL Group are kept in an area that is laid out and managed in such a way that prevents any physical contact between the animals who are not officially part of the CHAH-EBL Group or with those of a lesser testing status. Alternatively, if all animals in the bovine semen production centre comply with the CHAH-EBL requirements, then the entire centre may be considered the CHAH-EBL Group.

For the CHAH-EBL group within the bovine semen production centre, the final export requirements are that no new animals be introduced into the CHAH-EBL group in the 4 months prior to the export of selected animals, and that all animals selected to be exported from the group are EBL test negative less than or equal to 30 days before departure. In addition to the final export requirements just listed, individual countries may have additional EBL requirements for export of live animals. Check valid export certificates for the specific details of each country's requirements.

Definitions

For the purpose of this Chapter

Accredited veterinarian
Means a veterinarian who is authorized under the Health of Animals Act to perform certain duties and functions in support of the Canada Health Accredited Herd – Enzootic Bovine Leukosis Program.
Approved tag
Means a tag, chip or other indicator approved by the Minister under subsection 173(1) and listed on the Agency's web site as an approved tag.
Certified herd
Means a herd confirmed as being a Canada Health Accredited Herd for the Enzootic Bovine Leukosis Program with respect to meeting the requirements listed in this Chapter.
Group
Means part of, or a complete establishment or multiple establishments under a common biosecurity management system containing an animal sub-population with a specific animal health status with respect to a specific disease for which the necessary surveillance, biosecurity and control measures have been applied. Establishment means the premises in which animals are kept.
Group with a negligible risk status for EBL
Means an establishment(s), in whole or partly (via separation) with a cohort of live animals confirmed as being at negligible risk under the Enzootic Bovine Leukosis Program as they meet the requirements listed in this Chapter.
Established herd
Means a group of cattle gathered and considered as a herd for at least 2 years and whose number of animal additions does not exceed 25% of the total number of individuals per year.
Isolation
Means that the animal shall be isolated in a building or pasture in which there is no contact with other cattle until having received a negative test result for Enzootic Bovine Leukemia Virus.
Preventive Control Plan:
A written document that demonstrates how hazards and risks to animal health are identified and controlled.
Positive bovine or animal
Refers to a confirmed positive case.
Separated area

Means the animals that are part of the CHAH-EBL Group are kept in an area that is laid out or managed in such a way that prevents any physical contact between the animals who are not officially part of the CHAH-EBL Group or with those of a lesser testing status.

The biosecurity plans of AI centre which enroll in the CHAH-EBL program must identify the CHAH-EBL Group specific criteria/sections. Adequate infrastructure and a biosecurity plans must be in place and maintained in order to prevent transmission of EBL (either by direct contact or fomites) to the satisfaction of the CFIA.

Appendices

Appendix 1: CHAH-EBL Forms and Distribution

Form CFIA/ACIA 4285 CHAH –EBL Conditions and Agreements Form

Purpose

This form is the contract that is signed by the owner to agree to enter their herd into the voluntary CHAH-EBL program and also abide by the general conditions specified.

Process

The herd owner is advised that the form must be completed and submitted to the local CFIA district veterinarian for approval and signature before the herd's accredited veterinarian commences any testing intended to qualify a herd as a CHAH-EBL certified herd. The CFIA district veterinarian retains the original and copies are distributed to the owner and the CFIA area and national CHAH-EBL program specialists.

Form CFIA/ACIA 3841 CHAH-EBL Test Report

Purpose

This form must be used for all EBL tests performed on herds enrolled in CHAH-EBL program. It records all animals tested including approved tag ID, age, sex, breed, any other identification, sample number/identification and test results. It provides a record of testing for the CHAH-EBL herd and for program monitoring, referencing, and auditing.

Process

The accredited veterinarian uses this form to submit the CHAH-EBL test samples to the CFIA Saint-Hyacinthe Laboratory – Retrovirology Centre of Expertise. Results are reported in the LSTS to the CFIA district veterinarian which are then sent to the accredited veterinarian.

Form CFIA/ACIA 4284 Canada Health Accredited Herd Certificate

Purpose

This is the certificate provided to the owner as proof as CHAH-EBL herd by CFIA.

Process

This form is signed by the CFIA CHAH-EBL area specialist and given to owner upon initially qualifying and is renew each year by endorsing the back of the certificate.

Appendix 2: Sampling and Submission Procedures

Sample Collection by the Accredited Veterinarian

  • For all samples use Form CFIA/ACIA 3841 CHAH-EBL Test Report.
  • All samples are submitted to the CFIA Saint-Hyacinthe Laboratory – Retrovirology Centre of Expertise. Milk testing by ELISA is also an WOAH and internationally recognised serological test for EBL.
  • Refer to Accredited Veterinarians Manual module 3.2 for general sampling and submission procedures.
    • In lieu of filling out the Animal Information Table of the Form 3841, accredited veterinarians must use the electronic submission template described in module 3.2 and follow the instructions as per the "Special procedure for submission to CFIA laboratories, applicable to samples from bovine tested in isolation (IAI notification), under the CHAH-EBL program and from sheep and goats, wild boar or cervids for export to Mexico" section of this module.
  • Collect samples of 5-10 mL of serum or whole blood without anticoagulant using a new disposable needle for each animal, according to the approved CFIA Saint-Hyacinthe Laboratory – Retrovirology Centre of Expertise laboratory's protocol.
  • Collect samples from each test-eligible animal within the herd. The definition of a test-eligible animal varies depending on the "stage" of testing of the herd. Check the herd's test history prior to arranging for the sampling to ensure that all animals are tested according to the program's protocol.

Samples are collected by the accredited veterinarian. A technician under the direct supervision of an accredited veterinarian may also be permitted to collect samples and undertake other specified tasks for the accredited veterinarian.

Sample Collection by the CFIA Veterinarian

  • Samples are collected by a CFIA veterinarian for any needed retesting of positive or atypical EBL test results or as requested by CFIA Saint-Hyacinthe Laboratory – Retrovirology Centre of Expertise
  • Use Form CFIA/ACIA 5439 – Animal Health (DC) Disease Control Specimen Submission. Include the reference number from the original testing submission.
  • All samples that are collected by a CFIA veterinarian for EBL testing must be sent to the CFIA Saint-Hyacinthe Laboratory – Retrovirology Centre of Expertise using the laboratory sample tracking system (LSTS).
  • A sample of 5-10 mL of serum or whole blood without anticoagulant should be collected using a new disposable needle for each animal.

Appendix 3: Biosecurity Measures to Maintain Your Herd Free of EBL

Prevent the introduction of infected cattle

Segregate and isolate newly introduced animals

Cattle additions should be isolated (no possible contact with your herd) for 4 months and following this period tested for EBL before introduction. Pay extra attention to the cleaning and disinfection of all material used for those animals to avoid transmission of potential infection to your herd. Consider that power washing of fluids contaminated with blood may aerosolize the virus and present a risk of transmission.

Segregate and isolate re-introduced animals

Avoid as much as possible contacts with animal of unknown or lesser EBL status (e.g. natural insemination, livestock shows, pasture adjacent to another herd, etc.). If not possible, segregate, isolate and test animals of your herd that had been subject to this kind of contact.

For embryo transfer, favor those coming from EBL-free dams and bulls.

Prevent the spread of EBL among your herd
Risk Factors Preventative Measures
Any material able to transmit blood or infected lymphocytes (a type of blood cells carrying EBL) between animals
  • Use individual, single-use needles and syringes during vaccination or therapeutic protocols
  • Use individual, single-use obstetrical sleeves
  • Use of disposable equipment (or at least cleaning, disinfection or sterilization of reusable materials and surgical instruments) in procedures such as dehorning, tattooing, implanting embryos, cauterizing, castration or ear-tagging
  • Use of electrical or gas burning devices rather than gouging equipment for dehorning
Colostrum and milk of an infected cow may carry EBL
  • Feed calves with colostrum or whole milk from confirmed non-infected dams or use pasteurized colostrum or milk replacer
  • Use and maintain the milking machines adequately and according to manufacturer standards
Biting insects may spread EBL by mechanically transferring infected cells
  • Eliminate or reduce insects, particularly in densely populated farm areas (e.g. milking areas, free-stalls, barns).
Plan, train and communicate

Producers and their employees, service providers, and visitors are aware of and follow the farm biosecurity measures listed above in order to prevent the introduction and spread of EBL.

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