Foot and Mouth Disease (FMD) - Risk posed by the importation of meat (beef)

"What is the risk of importing Food & Mouth Disease in imported beef?"
Foot and Mouth Disease (FMD) - Risk posed by the importation of meat (beef) - Articles
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Foot and Mouth Disease (FMD) is a highly contagious, highly infectious viral disease that affects (primarily) cloven-hooved species. The risk of importing meat contaminated by the Foot and Mouth Disease Virus (FMDV) can be evaluated and reduced by implementing effective, scientifically-sound safeguards.

The World Organization for Animal Health (OIE), the intergovernmental organization responsible for improving animal health worldwide, is responsible for designating the FMD status for participating countries.

Recommendations for the importation of live animals, fresh meat, meat products, embryos (etc.) into FMD-free countries are made by The Terrestrial Animal Health Code (TAHC). These recommendations are based on the current understanding of the FMDV, as well as the pathogenesis and epidemiology of FMD. They are designed to reduce the risk of importing this virus as much as reasonably practicable.

The information provided here will assist in properly evaluating the probability of introducing the Foot and Mouth Disease Virus (FMDV) into a country through the importation of beef from a country that has not been designated as "FMD-free" by the OIE.

A very brief overview of FMD

FMD is a highly contagious, highly infectious viral disease that affects (primarily) cloven-hooved species.

Animals that are exposed to the FMDV and become infected, typically develop clinical disease quite soon (~2-14 days) after initial infection. It is rare for domesticated animals to not show at least some clinical signs - signs which should readily alert owners and/or caretakers that the animals are diseased. Most of the time, especially in cattle, these signs are very overt and dramatic, such that diseased animals are not easily overlooked.

In the acute phase of FMDV infection, the virus usually spreads quite widely throughout the body, and can be isolated from blood, milk, oral secretions, nasal secretions, etc. This suggests that virus could be present in the muscle tissue of animals at the time of slaughter, especially if the animals are clinically affected/sick.

Carrier animals, that is animals that have recovered from the disease but continue to harbor and shed the organism for a limited period of time, are quite rare, but may occur. The infection usually seems to persist in the nasal passages and pharynx in carrier animals.

Some species, notably swine, are known as 'virus factories" since they frequently excrete huge amounts of infectious FMDV particles. Infected cattle on the other hand, while they do shed FMDV organisms, do not do so to nearly the same extent.

FMDV is quite sensitive to the pH in it's micro-environment, and evidence suggests it is deactivated below a pH of ~6.0 and above ~9.5. The virus survives fairly well in cold environments (39F), and for very long periods of time below freezing. FMDV has shown decreased survival at temperatures of ~65F and above, with very rapid degradation occurring at 122F and greater. It is also quite susceptible to a number of commonly available disinfectants (eg. Virkon-S®, sodium hydroxide, citric acid), although it does show some greater resistance to others (eg. phenols, iodophores, hypochlorite), especially when there is simultaneously organic matter present.

After an animal is slaughtered, lactic acid accumulates in the muscle tissues as glycogen is depleted, which results in a lowering of the pH from ~7.0 to ~5.5. The length of time required for this pH decline varies due to a number of conditions (eg. rapid chilling results in slower pH decline) but is essentially always complete by ~24 hours post-slaughter. This process of post-mortem 'acidification' is unique to muscle tissue, and as such does not occur within the bones, glandular tissue, such as the lymph nodes, and viscera.

Foot and Mouth Disease Factors to be considered

To evaluate the probability of introducing Foot and Mouth Disease (FMD) into a country through the importation of beef from a country not designated as “FMD-free” by the World Organization for Animal Health (OIE), a number of factors must be considered.

  • The source of the animals from within the country that is exporting the beef.
  • The probability that animals infected with the FMDV would be slaughtered.
  • The probability that meat from infected and viremic animals would be harvested for export, and/or that virus-contaminated product would come into contact with meat to be exported.
  • The likelihood that the meat would contain infectious virus particles upon arrival in the importing country.
  • The probability that susceptible animals in the importing country would be exposed to meat containing infectious FMVDV.
  • The likelihood that the animals exposed to the raw meat receive an infectious dose of FMDV, develop disease, and cause additional infections to occur.

FMD status of countries

Countries that are not "FMD-free" but have an official FMD control program in place will often have zones that are declared by the OIE to be "FMD-free." FMDV vaccination may, or may not, be practiced in these zones.

Very specific criteria in the Terrestrial Animal Health Code (TAHC; Chapter 8.8, "Infection with foot and mouth disease virus.") must be met by countries applying to have areas/regions within their borders officially recognized as FMD-free zones, either with vaccination (Article 8.8.2.) or without vaccination (Article 8.8.3.).

Figure 1. FMD‐free zones in Brazil shows how the different states in Brazil are categorized by the OIE with respect to FMD as of May 2015, and it is apparent that much of the country falls within an FMD-free zone where vaccination against FMDV is practiced.

According to the recent Annual Livestock Report by the Brazilian Beef Exporters Association, the majority of the cattle production in Brazil seems to be in the central region of the country within FMD-free zones (Figure 2) and (Figure 3) although some cattle are also apparently raised in the western states, which do not have a recognized FMD status (Figure 1).

According to the Annual Livestock Report, and the Association's website "only a strip of land in the north of Brazil is not [FMD] free yet" and "190 million heads [sic]" out of the "estimated 209.13 million heads [sic]" are located inside FMD-free zones.

The TAHC (Chapter 8.8) has specific recommendations for the importation of live animals, fresh meat, meat products, embryos (etc.) into FMD-free countries. These recommendations are based on the current understanding of the FMDV, as well as the pathogenesis and epidemiology of FMD. They are designed to reduce the risk of importing this virus as much as reasonably practicable. That is, they appear to err on the side of caution as much as possible.

Export of Beef

The Terrestrial Animal Health Code (TAHC) outines criteria for exporting beef from FMD-free and FMD-infected zones.

Export of beef from FMD-free zones to FMD-free countries

The TAHC outines criteria for FMD-free countries which are importing meat or meat products from FMD-free zones within infected countries (Articles 8.8.20 and 8.8.21). These specify "residency requirements" in the FMD-free zone of the animals being slaughtered, as well as requiring pre- and post-mortem inspection at an approved slaughter plant. If vaccination is being practiced in the FMD-free zone, the guidelines also require exclusion of the "head, including the pharynx, tongue, and associated lymph nodes..." (8.8.21.3) from the consignment of meat.

Although animals that originate outside of an FMD-free zone may, under strict housing, biosecurity, health, and transportation guidelines (Article 8.8.8), be slaughtered in an FMD-free zone, the meat from these animals may not be sold for export to FMD-free countries. In fact, no meat destined for export (even from FMD-free-zone animals) may be harvested/produced at the same time that FMD-infected-zone animals are being harvested in an FMD-free zone facility. The TAHC also specifies that "thorough cleaning and disinfection" of the slaughter plant must occur before animals whose meat is intended for export can be slaughtered (8.8.8.6).

Export of beef from FMD-infected zones to FMD-free countries

If a country is willing to import meat from a slaughter facility which is in an FMD-infected zone in a country that has an official FMD-control program in place, there are even more stringent guidelines outlined in the TAHC (8.8.22) These guidelines have very explicit requirements regarding the vaccination, health, biosecurity, transportation and slaughter of animals whose meat is destined for export designed to minimize the likelihood of animals being slaughter that are infected with FMDV.

In addition, the entire consignment of meat for export from an FMD-infected zone facility is to: 1) "come from deboned carcasses...[with] the major lymph nodes removed," (8.8.22.2a), 2) be held for at least 24 hrs post-slaughter (8.8.22.2b), and 3) have a pH of "less than 6.0...in the middle of both the longissimus dorsi muscle" (8.8.22.2b).

Risks associated with meat contamination

Risk of exported meat being contaminated with FMDV

If the practices outlined in the "Export of beef" section are followed as outlined, it seems very, very unlikely that beef produced in FMD-infected countries is likely to contain any viable FMDV at the time of export according to the following factors:

  1. The source of the animals from within the country that is exporting the beef.
  2. The probability that animals infected with the FMDV would be slaughtered.
  3. The probability that meat from infected and viremic animals would be harvested for export, and/or that virus-contaminated product would come into contact with meat to be exported.

The USDA:FSIS recently (11/9/15 - 11/20/15) conducted an audit in Brazil ("Evaluating the Food Safety System Governing the Production of Meat Products Intended for Export to the United States of America") which addressed numerous areas of concern (eg. chemical residues, STEC, etc.) as well as FMD. The audit report notes:

"While on-site, the FSIS auditors were able to confirm that the appropriate APHIS requirements for the control of foot-and-mouth (FMD) disease were being met at all five establishments intending to export raw beef to the United States. Official government inspectors examined the coronary bands (hooves), lips, and snout of each individual animal slaughtered. The FSIS auditors also noted that establishment employees routinely measured the pH of each half-carcass after passing the maturation chamber. Verification of this activity was conducted by off-line government inspectors throughout the production day, and the inspectors made appropriate records of their inspections."

Risk of meat being contaminated upon arrival in importing country

Factor 4 to be considered in assessing the risk of importing FMDV is "the likelihood that the meat would contain infectious virus particles upon arrival in the importing country." If the beef is not further processed before being exported from the FMD-infected country (that is, it is transported immediately in a chilled or frozen state to the importing country) there would seem to be little effect on the likelihood of infectious FMDV particles being present, since under these storage/transportation conditions any virus present would be fairly likely to persist. Cross-contamination of product with FMDV in transit seems very unlikely to occur.

Risk of potentially contaminated meat causing FMD in importing country

The final two factors outlined (5 & 6) concern the remote, but theoretical, probability that meat containing infectious FMDV particles is able to infect animals in the importing country, and cause a (propagating) infection.

The most conceivable route by which a susceptible animal (ruminant or swine) could become infected by theoretically-contaminated meat in the US would for it to consume meat which contains an infectious dose of viable FMDV. This means that the meat would have had a relatively high dose of infectious particles remaining on/in it upon arrival in the country, and that the virus survived any handling and heating of the meat before being consumed.

According to the "Swine Health Protection Act" it is permissible to feed swine "garbage" which includes "[a]ll waste material derived in whole or in part from the meat of any animal" (9 CFR 166.1). However these regulations also clearly stipulate that all feed waste must be heated to a minimum of 212F for at least 30 minutes prior to feeding (9 CFR 166.7). Any FMDV in the 'garbage' should easily and completely be inactivated under these conditions.

Animal proteins derived from mammalian tissues are prohibited from feed for ruminants (21 CFR 589), with some exceptions. "Meat products" are permitted, but only if they have been "inspected" and "have been cooked and offered for human food, and further heat processed for feed" (21 CFR 589.2000.a). Therefore, although these regulations are primarily intended to minimize the risk of transmission of Bovine Spongiform Encephalopathy (BSE), they also substantially reduce, if not eliminate, the risk of establishing an FMDV infection in ruminants from meat possibly contaminated with the FMDV.

The opportunity for an FMD outbreak to propagate (factor 6) in a population of susceptible animals is dependent on numerous factors, such as the species that first becomes infected, the proximity to, or opportunity for direct contact with other susceptible animals and farms, and the rapidity with which the FMD is diagnosed. In most scenarios, once a case of FMD occurs in an FMD-free country which does not vaccinate against FMDV infection, the infection spreads very rapidly, not only within the herd, but also locally, regionally and even nationally.

Safeguards against FMD

A multiplicity of effective, scientifically-sound safeguards is recommended to reduce the risk of importing FMDV into an FMD-free country through the import of meat.

These safeguards are best prioritized as follows:

  1. reducing the likelihood that FMDV exposed or infected animals are slaughtered for export purposes,
  2. ensuring that the carcass/meat is properly handled and checked to make sure that post-mortem conditions are optimal for FMDV inactivation and that cross-contamination does not occur,
  3. removing high-risk tissues prior to export,
  4. ensuring that any susceptible animals in the importing country cannot be exposed to imported meat which has not been heat-treated, and
  5. diagnosing any FMDV infections within the FMD-free country as soon as possible.

FMD Transmission by Meat - Questions and Answers

Question 1. Can FMDV be transmitted by meat, and if so, for how long after the animal has been slaughtered?

Answer 1. Yes, there is at least theoretically a possibility that transmission of FMDV could occur by way of meat, since the virus can be found in the blood and tissues of infected animals. However, countries such as Brazil have established "FMD-free zones" within their borders which meet very specific OIE criteria for animal movement, disease surveillance, and biosecurity. In addition, diseased animals are not permitted to be slaughtered (in either FMD-free zones or FMD-infected zones), and safeguards are in place to significantly reduce any chance that even recently-infected (pre-clinical) animals or carrier animals would ever be slaughtered. In addition, if the muscles in the carcass undergo the normal, expected post-mortem changes, any FMDV that may be present there should be inactivated within ~24 hours. If, somehow, the meat of an infected animal was slaughter for export, and if, somehow, the virus survived the normal post-mortem pH changes (as checked in the longissimus dorsi muscles), it would still have to survive additional safeguards in the US in order to be able to infect a susceptible animal!

Question 2. The producers heard that foot and mouth could be transmitted by meat, but only if the bone is in the cut of meat. If it is boneless, is there then no transmission risk?

Answer 2. There is, biologically-speaking, almost never a situation in which there is truly "no" or "zero" risk. However, if a carcass has:

  1. come from an uninfected animal,
  2. been harvested in a plant that has followed proper cleaning and disinfection protocols,
  3. been deboned,
  4. had the head and associated tissues (tongue, pharnyx, etc.) removed,
  5. had the major glandular tissues (lymph nodes) removed,
  6. had the viscera removed, and
  7. undergone the normal post-mortem changes (see above) then there is essentially an "almost-zero" risk posed by the importation of meat.

Sources Referenced

Brazil Beef Exporters Association. "Brazilian Livestock Profile. Annual Report 2016."

Canadian Food Inspection Agency. "Food and Mouth Disease Hazard Specific Plan."

Center for Food Security and Public Health, Iowa State University. "Foot and Mouth Disease."

Savell, Jeffrey W., Texas A&M University. "White Paper: Beef Carcass Chilling: Current Understanding, Future Challenges."

U.S. National Archives and Records Administration. "Code of Federal Regulations"

USDA:APHIS: Brazil 2015 Final Audit Report

World Organization for Animal Health (OIE): "Terrestrial Animal Health Code"

Authors

Mastitis and Milk Quality Milking Equipment Performance Bovine Hoof Health On-farm Food Safety Epidemiology Dairy

More by Ernest Hovingh, DVM, PhD