Chapter 5 - Sampling and Testing
5.5 Parasites

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5.5.1 Cysticercosis

5.5.1.1 Introduction

Cysticercosis is the presence in tissues of the immature form of various species of tapeworm. Each is associated with particular host species, as follows:
Cyst form Adult form Intermediate host
Cysticercus bovis Taenia saginata Cattle
Cysticercus cellulosae Taenia solium Swine

C. cellulosae is of particular public health significance, because humans can act as both a definitive and an intermediate host, and therefore develop cysts in tissues and organs.

5.5.1.2 Sample selection

Lesions appear as clear or white spheres, 6 to 10 mm in diameter, with a hollow center containing clear fluid. Old lesions may be calcified. Predilection sites are the masseter, tongue, heart, and diaphragm. When a lesion is found, a thorough search of these sites should be conducted for additional lesions.

See Chapter 17, Section 17.9.5.2, and Chapter 9, Section 9.5.5 of the MOP for further guidance.

5.5.1.3 Testing

Lesions of suspected cysticercosis should be submitted to the Centre for Food-Borne and Animal Parasitology (See Annex G) for laboratory confirmation. All lesions should be submitted fresh, with ice packs. Do not freeze.

If a definitive diagnosis cannot be made on fresh specimens, the Centre for Food-Borne and Animal Parasitology will fix the tissues in formalin and forward them to the St. Hyacinthe laboratory for histopathology. Do not submit samples directly to St. Hyacinthe.

5.5.1.4 Follow-up

Cysticercosis is a reportable disease under the Health of Animals Regulations. Suspected cases should be reported to the appropriate Area program specialist. Determine the origin of the animals to the best of your ability, as a traceback will be conducted by Animal Health inspectors to determine the source of the infection.

5.5.2 Trichinella

5.5.2.1 Description

The parasitic nematode Trichinella spiralis is still enzootic in several parts of the world. It is one of the smallest of all nematodes, measuring only 1.5 mm in length. Feeding of uncooked or inadequately heat-processed garbage to swine and poor sanitary conditions (e.g. rat infestation) in affected parts of the world are primarily responsible for the persistence of the parasite. This parasite also circulates in wild carnivores. Some of the subspecies which circulate in wildlife are more tolerant to freezing than that normally seen in swine.

5.5.2.2 Occurrence

Trichinosis is caused through the ingestion of raw and undercooked meat. At one time, pigs were the main species implicated, but with modern production methods of confinement raising and the control of garbage feeding, this has become quite rare. Cases in the arctic regions involve bear meat and walrus flesh. Horse meat has been implicated in some outbreaks in Europe.

5.5.2.3 Concern

Human infection with T. spiralis, or trichinosis, has a latency period of 4 to 28 days (average of 9 days). Symptoms include gastroenteritis, colic, nausea, fever, sweating, edema about eyes, muscular stiffness, swelling and pain, chills, insomnia, prostration and laboured breathing. As the ingested trichinae burrow through the intestinal wall, abdominal pain and mild diarrhea appear, followed by rheumatic muscular pains as the parasites migrate to and settle in the muscle, where they become encysted and remain stationary for the lifetime of the host. Trichinosis (heavy infestation) can be an extremely painful and long-enduring disease.

5.5.2.4 Program and sampling

The Canadian Food Inspection Agency's present policy to manage hazards related to the potential presence of Trichinella spiralis in pork is that of protecting the Canadian consumer through the use of appropriate processing techniques,i.e. cooking, freezing, or curing according to guidelines set out in Chapter 4, Annex B. While the results of routine monitoring of Canadian pork indicate that the risk of infection is virtually nonexistent, these precautions must remain in effect due to the presence of Trichinella spiralis in rats and other wildlife and the potential for this parasite to find its way into a domestic herd on a sporadic basis. Current advice to consumers in Canada regarding the need to ensure that pork is cooked at a minimum of 58°C is consistent with this precaution.

For the purposes of this section, pork is defined as the meat derived from all swine: market hogs, breeder hogs and wild boars raised in captivity.

The CFIA Trichinella control program includes the following elements:

  • listing of pig trichinellosis as a reportable disease under the Health of Animals Act;
  • conducting of regular serological surveys of the mature pig population in Canada (15,000 sows every 5 years);
  • testing of approximately 30,000 market hog carcasses at registered abattoirs each year using digestion test methods;
  • testing of approximately 3,000 breeder hog carcasses at registered abattoirs each year using digestion test methods;
  • testing of approximately 200 wild boar carcasses at registered abattoirs each year using digestion test methods;
  • promptly implementing eradication measures, which include herd quarantine and depopulation, when a positive case is found; and
  • controlling the feeding of food wastes or garbage under the provisions of the Health of Animals Regulations (sections 111-113). All pork producers who use food wastes (e.g. from grocery stores, bakeries, etc.) must be registered and be issued a permit. Meat and restaurant waste may not be fed to pigs, and premises are regularly inspected by CFIA officials.

This program, which is consistent with World Organization for Animal Health (OIE) guidelines, allows the CFIA to demonstrate that Canada's hog population is almost free of trichinae. Sporadic cases are promptly eradicated. To satisfy OIE/Animal Health surveillance needs and to maintain market access of Canadian pork products to other countries, it is necessary to test pigs at a monitoring level. It is sometimes also a requirement to test pigs or horses at a surveillance (screening) level to provide market access for Canadian pork products or horse meat to some countries or to identify potentially infected carcasses in quarantined or suspect herds.

Importing countries may have their own requirements regarding Trichinella testing. For more information on specific export requirement with regard to Trichinella controls, please consult the individual country requirements in Chapter 11, section 11.7.2, or the "Importing Country Requirements" module in the Meat Electronic Certification system, available to subscribers.

5.5.2.5 Control program - monitoring

5.5.2.5.1 Introduction

Monitoring is performed by CFIA staff to provide information on the prevalence of Trichinella infections in pork. There are three sampling plans in place: for market hogs; for sows and boars (breeder hogs); and for wild boars. Specimens are collected in abattoirs in adherence to centrally prepared sample submission schedules and are shipped to designated laboratories. Sample submission schedules are reviewed and modified as required on a yearly basis to reflect changes that have taken place during the previous year (e.g. variation in the number of slaughter establishments).

There is no hold and test requirement for monitoring programs. However, traceability (owner identification) must be maintained for follow-up actions in the case that specimens do react positive at the laboratory. Specimens should be individually wrapped and marked to ensure that trace-back to the infected farm of origin can be undertaken.

The cost for monitoring tests is borne by plant operators and is prorated according to slaughter volume. Costs for the testing are invoiced monthly by the Veterinarian in Charge for specimens collected during that period.

5.5.2.5.2 Market hogs

All market hogs slaughtered in abattoirs under federal inspection throughout a fiscal year are eligible for testing (a population of about 15,000,000 market hogs). The sampling size is about 30,000 carcasses, i.e. large enough to ensure that a prevalence in excess of 0.01% is detected with a confidence of 95%. For testing purposes, and to minimize shipping costs, the required 30,000 specimens are randomly divided into pools of 100 animals. Therefore, 300 sampling units are distributed among market hog establishments that slaughter more than 5,000 carcasses a year. The number of sampling units to collect is prorated according to slaughter volume. For establishments that slaughter less than 5,000 carcasses a year, specimens are collected in a random selection of establishments (100 specimens in each of four establishments per year).

As outlined, a sampling unit corresponds to a maximum of 100 specimens collected from 100 carcasses in one abattoir, during a randomly selected week. Specimens will be shipped to the Centre for Food-Borne and Animal Parasitology in Saskatoon early the following week. Every fiscal year, a detailed sample submission schedule is provided to all federally registered establishments slaughtering market hogs.

5.5.2.5.3 Breeder hogs

All sows and boars slaughtered in federal abattoirs throughout a fiscal year are eligible for testing. The sampling size is about 3,000 carcasses,i.e. large enough to ensure that a prevalence in excess of 0.1% is detected with a confidence of 95%. For testing purposes, and to minimize shipping costs, the required 3,000 specimens are randomly divided into pools of 100 animals. Therefore, 30 sampling units are distributed among breeder hogs abattoirs all across Canada. Because of the export of live animals to the U.S., the distribution of sampling units is not prorated according to slaughter volume. Instead, three sampling units per abattoir that slaughter sows and boars are required.

As mentioned, a sampling unit corresponds to a maximum of 100 specimens collected from 100 carcasses in one abattoir. Due to low slaughter volume in some cases, the Veterinarian in Charge may have to postpone the sampling from one week to meet the assigned quota. Specimens will be shipped to the Centre for Food-Borne and Animal Parasitology in Saskatoon early the following week after collection. It is expected that in some cases the 100 specimens quota will not be met. Each fiscal year, a detailed sample submission schedule is provided.

5.5.2.5.4 Wild boars

All wild boars slaughtered in federal abattoirs throughout a fiscal year are eligible for testing (a population of about 3,000 wild boars). The sampling size is about 200 carcasses, i.e. large enough to ensure that a prevalence in excess of 1.5% is detected with a confidence of 95%. For testing purposes, and to minimize shipping costs, the required 200 specimens are randomly divided into a pool of 10 animals. Therefore, 20 sampling units are distributed across wild boars abattoirs. The number of sampling units to collect is prorated according to slaughter volume. A sampling unit corresponds to a maximum of 10 specimens collected from 10 carcasses in one abattoir. Due to low slaughter volume, the Veterinarian in Charge has to purposely select different weeks spread over the year for the collection of the required number of specimens (refer to sample submission schedule for exact number). Specimens will be shipped to the Centre for Food-Borne and Animal Parasitology in Saskatoon early the following week after collection. It is expected that in some cases, the 10 specimen quota will not be met. Each fiscal year, a detailed sample submission schedule is provided to all federally registered establishment slaughtering wild boars.

5.5.2.5.5 Specimen collection for monitoring purposes

Consult the sample submission schedule to determine which week has been assigned to your establishment. For each week assigned, collect specimens from 100 market hogs, 100 sows or boars, or 10 wild boars at any time during the assigned sampling week. Collect 10 g of muscle from the pillars of the diaphragm from each animal selected. Animals from different herds should be selected as much as possible. Specimens should come from animals that the Veterinarian in Charge feels are at higher risk of being infected with T. spiralis. Animals from poorly managed herds (those with poor health status, poor feed conversion, etc.) or small operations (because of greater likelihood of contact with rats, illegal garbage feeding, outside grazing, etc.) can be considered at higher risk of being infected.

The sample plan number is the fiscal year and an underscore, followed by "M215", for example "2009_M215".

5.5.2.6 Surveillance (screening) programs

5.5.2.6.1 Surveillance for export purposes

Surveillance or screening of individual pork carcasses may be required for domestic or international trade reasons (e.g. export to Russia). Screening of horse carcasses is required for international trade only (export to the European Union or to Switzerland). Testing procedures to allow international trade are prescribed by importing countries. The testing of horse meat for export to the European Union is to be performed by the plant operator in an on-site laboratory that has successfully completed the process for CFIA accreditation described below. For export to the European Union, the testing method used must be one of the methods listed in Directive 77/96/EEC.

The Centre for Food-Borne and Animal Parasitology in Saskatoon is the designated authority to ensure that the methods used are adequate and that technicians conducting tests are competent. Plant operators wishing to become accredited to perform Trichinella testing must apply to the CFIA. Upon acceptance of the application, the following steps will have to be successfully completed:

  • establishment of a Quality System through creation of a Quality Manual (QM) and supporting quality documentation;
  • review and approval of the QM by the Centre for Food-Borne and Animal Parasitology;
  • training of technicians at the Centre for Food-Borne and Animal Parasitology in Saskatoon;
  • provision of an adequate laboratory facility and equipment at the designated test location;
  • on-site audits of the laboratory facility and Quality System;
  • on-site completion of proficiency samples; and
  • once accreditation is granted, certified technicians (trained by the Centre for Food-Borne and Animal Parasitology) will receive quarterly proficiency verifications and the laboratory will be subject to a site audit every two years.

In order to avoid freezing requirements imposed by some importing countries, hog plants may screen hog carcasses using a pooled digestion method. The plant operator is responsible for testing under a certified quality system (e.g. ISO 17025).

5.5.2.6.2 Surveillance of suspect pigs

Surveillance (screening) of pigs is also performed by the CFIA whenever animals from suspect herds are sent for slaughter at federally registered establishments. Porcine trichinellosis is a reportable disease under the Health of Animals Act and Regulations. When trichinellosis is reported by Public Health Authorities and suspected of originating from an animal slaughtered in an abattoir under federal inspection, or further to positive results from abattoir testing (monitoring or surveillance), follow-up screening of all animals from suspect herds must be initiated through regional and headquarters offices. All carcasses from suspect herds are identified and held from their arrival at the abattoir until final results are known. CFIA regional authorities shall be provided with the coordinates (producer ID, farm location, etc.) of the farm of origin of any pigs found positive. Herd mates of positive carcasses must be located and tested. As recommended by Health Canada, the testing of suspect carcasses should involve the examination of at least 5 g of tissue per animal in order to increase the sensitivity of the test. Carcasses found positive must be condemned.

5.5.2.7 Testing

5.5.2.7.1 Testing facilities

The following facilities should be available in establishments where trichina testing is performed in-plant:

  • A laboratory separate from other operations but attached to or within the associated establishment. Walls, ceiling and floor to be smooth and easily cleanable. For trichinoscopic examination, the inspection office is adequate for testing purposes, provided there is sufficient space to accommodate the additional equipment.
  • There should be adequate area to prepare and examine specimens, including area to clean and disinfect equipment after use.
  • There should be adequate ventilation, temperature, natural or artificial light that does not alter colour, and ability to darken the examination room.
  • There should be adequate facilities and disinfectants for staff to wash hands and to clean equipment and tools used after processing of samples.

5.5.2.7.2 Inspector's responsibilities in overseeing and controlling testing performed by plant operator

The Veterinarian in Charge should be familiar with the content of the quality manual produced by the operator as approved by the Centre for Food-Borne and Animal Parasitology in Saskatoon. CFIA inspectors should ensure:

  1. that a Quality System as described in the Quality Manual is in place;
  2. that each carcass under the current Quality System is properly tested;
  3. that internal audits of the Quality System are performed at least once a year, external audits at least once every other year, and audit results are readily available and are satisfactory;
  4. that check samples are run four times a year by personnel performing the testing and that corrective actions are taken whenever results are unsatisfactory;
  5. that each carcass is properly identified and segregated in a way that at any time until completion of testing a correlation can be established between carcasses being tested, specimens being analysed and the producer's identity;
  6. that technicians performing such testing are qualified by the Centre for Food-Borne and Animal Parasitology;
  7. that tested carcasses as well as boxes containing meat derived from carcasses tested and found negative are marked. The mark must be round with a diameter of 2.5 cm. In the center must be the capital letter T with arms 1 cm long and 0.2 cm wide. Under the letter T the initials CA must appear (0.4 cm high). The mark is a controlled item and must be handled in the same manner as meat inspection legend stamps. It is acceptable to use the carcass serial number applied at the time of slaughter in lieu of the mark just referred to provided that this method of identification is part of the Quality System of the establishment and can offer sufficient guarantee that the meat packaged and labelled with the mark T is derived from carcasses tested with negative results.
  8. in case of a presumptive positive, refer to section 5.5.2.6, Surveillance (screening) programs.

5.5.2.7.3 Testing methods recognized by the CFIA

Testing procedures for international trade are determined by trading partners and the CFIA. For specific requirements concerning acceptable testing methods for each country, please consult Chapter 11, section 11.7.2, or the "Importing Country Requirements" module in the Meat Electronic Certification system.

5.5.2.7.4 Trichinoscope

Notwithstanding the extensive use of the pooled digestion methods, and in agreement with requirements of the importing country, the trichinoscopic examination can be used occasionally as an acceptable alternative for certification (e.g. export of frozen pork to Russia). The following section describes operating instructions when using a trichinoscope.

Sample Collection:

  • Collect approximately 50 g of tissue from both pillars of the diaphragm into clean plastic bags, or onto a clean tray.
  • Record the tattoo or other markings of the carcass to maintain the identity of the sample.
  • If the plant has in-plant testing, monitored carcasses are to be held pending results. If the plant does not have testing facilities, and sampling units must be collected in order to obtain a representative sampling, carcasses should not be retained.

Equipment Required:

  • trichinoscope (overhead, Leitz or Zeiss) or Microscope, 30-100X magnification, preferably stereoscopic;
  • compressorium (heavy glass plates with screws and bolts);
  • curved scissors (8-10 cm in length; nail scissors);
  • forceps 8-12 cm; and
  • tray or plastic bags for samples.

Operating Procedures:

  • Use one compressorium for seven animals, identify sample and compressorium by number.
  • Cut slivers of muscle approximately 2 x 2 x 5 mm and place one sliver on each field of the bottom plate of the compressorium. The pieces should be cut parallel to the muscle fibers and close to the insertion of the muscle to the tendinous part. Slivers should be cut from various parts of both pillars. Four slivers are to be examined per animal, and seven animals per plate.
  • Press top plate on bottom plate by applying slight lateral movements, then tighten the screws. The tissue should form a thin, transparent layer through which print is legible.
  • Clean the lenses and light source of the trichinoscope and then examine each field systematically. The extruded tissue fluid, especially that in close vicinity to muscle, should also be closely examined. The samples should be scanned at low magnification (x30 or x40), using the higher magnification for more detailed examination.

5.5.2.7.5 Trichomatic-35

For domestic purposes, the Trichomatic-35 is no longer an acceptable testing alternative and its utilization should be discontinued.

5.5.2.7.6 Double separatory funnel

The Double Separatory Funnel Procedure for the Detection of Trichinella larvae in horse meat as well as in pork is an acceptable method to the CFIA. Details about this method can be obtained from the Centre for Food-Borne and Animal Parasitology in Saskatoon. This method is currently in the process of being accepted by the European Union and will be used as the method of choice to certify horse and pork meat for export to those countries. In the interim, the pooled digestion method as described in Directive 77/96/EEC should be used.

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