Science flashes warning signs on USDA Brazil proposal
— Part II: Details of OIE report on Foot-and-Mouth Disease
Key facts about the Footand-Mouth Disease virus (FMDV) shape recommendations from the World Organization for Animal Health (OIE) report.* The incubation period between infection and the onset of clinical signs ranges from 2-14 days, depending on dose, but most commonly is 3-5 days. The virus may be present in a variety of tissues and bodily fluids and excretions prior to the onset of clinical signs. Cattle and pigs usually exhibit obvious clinical signs but is often less easily recognized in small ruminants.
The virus persists longer at the site of lesions and in a high proportion of cattle, low levels of the virus can be detected in the oropharynx [orally] beyond 28 days after infection. In some, it can be detected up to 3.5 years post infection, meaning they are FMDV carriers. It has not been determined how much risk of infecting other cattle these carriers pose.
This incubation period is why OIE recommends a three-week quarantine period for animals intended for slaughter and export. The USDA Proposed Rule makes no such requirement for any quarantine.
In countries not FMDfree, OIE recommends complete segregation of animals eligible for export from animals in adjacent infected zones. The question is, how do you do that with a disease than can travel 30-70 miles in the air?
The OIE study examining the risk of spreading FMD through meat trading makes two sets of recommendations—for animals prior to slaughter and at slaughter—both of which are considered necessary to reduce the risk to negligible.
recommendations to greatly reduce the risk that an FMD-infected animal is presented for slaughter, include, but are not limited to, these recommendations:
• The animal has been vaccinated at least twice, with the last one not more than 12 months nor less than one month prior to slaughter;
• The animal was kept for the last 30 days in an establishment where FMD has not occurred within 6.2 miles during that time; and
• The animal is transported in a disinfected vehicle, directly from the quarantine establishment to slaughter, with no contact with other non-export animals.
Slaughter recommendations include:
• A slaughter facility officially designated for export;
• Assurance that no FMD was detected in the facility between the last disinfection before slaughter and the shipment of the meat;
• Pre-slaughter and postmortem inspection, within 24 hours before and after slaughter; and
The meat must come from deboned carcasses from which major lymphatic nodes have been removed. Prior to deboning, the carcasses must be held (maturated) above 2 degrees C (35.6 degrees F) for a 24-hour minimum following slaughter and the pH in the center of the Longissimis dorsi was below 6.0.
FMDV Survival in fresh meat
The OIE report notes that “the number of publications that provide actual data on virus survival in cattle carcasses, collected and stored so as to mimic beef slaughterhouse process is relatively few...” In addition, “Most of these studies involved cattle that had not been vaccinated against FMD,” as opposed to Brazilian cattle, which are supposed to be vaccinated.
The report also provided evidence that slaughterhouse procedures are critical, as FMDV can survive on a meat cloth at 4 degrees C (39.2 degrees F) for six weeks and on meat packaging materials for 33-398 days at same temperature and 85 percent humidity. The success of decontamination depends on the hygiene procedures of the facility and the virus concentrations on any contaminated materials.
The report also contained some telling risk qualification statements, in regards to presenting uninfected cattle for slaughter and to keeping the virus out of slaughter facilities.
“Cattle showing [obvious and specific] clinical signs have a high probability of being detected during antimortem or post-mortem inspection and constitute a low risk. However, infected cattle that do not show overt clinical signs associated with FMD, e.g., partially immune cattle, cattle infected with a mild strain of the virus, breeds of cattle that do not show obvious clinical signs or animals early in the incubation period, introduce additional risk to the process.
Preclinical infection represents the highest risk.
“The removal of potentially infected tissues and organs, for example, the head, feet, pharynx, etc., followed by maturation of the carcass according to the standards in the Code, will mitigate the risk, although not entirely [emphasis theirs]. It was shown that the FMDV can survive maturation in the lymph nodes and bone marrow and that these tissues might not be completely removed during the mitigation processes. Therefore, until more evidence on the amount of residual lymph node and bone tissue become available, the risk associated with deboned beef cannot be ascribed a negligible rating.
“Overall, the risk associated with deboned beef, when only considering OIE recommended risk mitigations applicable to the slaughtering process, although low, cannot be completely ignored based on current knowledge (2009).”
“Effective vaccination requires the vaccine strain to be antigenically matched (i.e., correct serotype and strain) to the challenge strain...This requires knowledge of the circulating field viruses...”
How effective is vaccination?
“High yielding dairy cows in the Middle East are not always protected from high level challenge with FMDV despite vaccination every ten weeks...” read the report.
“The protective effect of vaccination with an efficient vaccine, applied according to acceptable international standards, will very significantly reduce the probability of animals becoming infected and thereby reduce the risk of infective animals being presented for slaughter. However, if infection of vaccinated animals occurs, virus replication can take place, albeit often at reduced levels compared to unvaccinated animals, with or without the appearance of obvious clinical signs.” Vaccinated and infected animals can become carriers.
Further, at least two studies provided further caution.
One reviewed previous risk assessment and concluded that the risk mitigation methods discussed will effectively eliminate FMDV from beef, but in infected cattle, this elimination may not be complete and virus in organs from these animals will not be affected by maturation and deboning. Another classified the risk associated with viral survival after treatment of carcasses according to OIE recommendations as moderate for animals in the incubation period.
The OIE report includes a significant “Discussion” regarding FMDV in beef, which includes:
An old (1948) study claiming FMDV did not survive rigor mortis and carcass maturation; More recent (2002) studies that not all carcasses reached the required level of acidification but without data connected to FMDV survival; Bleeding carcasses and removal of bones and major lymphatic glands reduces the risk of residual FMDV survival in boneless beef, but would not be expected to eliminate these tissues entirely, leaving a residual but unquantified risk of FMDV survival; and There have not been many studies assessing susceptibility of species to infection by plausible routes. Therefore, without information on the amount of non-muscle tissue present in deboned meat and the ability of low level contamination to cause infection, it can be concluded the risk is very low but cannot be considered negligible.
“Alternative evidence” is the way the report refers to the fact that large quantities of deboned beef from FMD countries have been shipped to Europe from South America without causing FMD outbreaks.
“However, this does not provide categorical evidence for the absolute safety of the commodity, since other risk mitigation measures such as quarantine, surveillance and vaccination were also in operation that ensured a very low level of virus circulation in the livestock sector servicing the export industry. The question, therefore, remains as to what extent virus circulation needs to be understood and controlled before deboned beef becomes an acceptable risk.”
A key recommendation from the OIE study involves quarantine, but if some animals do not show symptoms, how can even a three-week quarantine be totally effective. How expensive would it be to blood test each animal? One study suggested vaccinating animals upon quarantine entry but that would be precluded by an OIE recommendation that vaccinations be prior to one month before slaughter, unless the quarantine period is lengthened to 30 days.
* “Qualitative Assessment of the Commodity Risk Factor for Spread of Foot-andmouth Disease Associated with International Trade in Deboned Beef, “ OIE ad hoc Group on Trade in Animal Products, 10/2009; D. J. Paton, UK; M Sinclair, South Africa; R Rodriguez, Argentina. — Steve Dittmer, Agribusiness Freedom Foundation
[This is Part II of a fourpart series originally published in the AFF Sentinel, an e-newsletter published by Agribusiness Freedom Foundation. Reprinted here with permission. Part III will appear next week. Contact the author at email@example.com, see current issues on Facebook, or view archived columns on agri businessfreedom.org.]