Abstract:
A value chain approach was employed as the basis for sanitary management of both food safety
and animal disease risks. This was achieved through the integration of hazard analysis critical
control point (HACCP) and commodity-based trade (CBT) methodologies. That approach enabled
identification of and management of critical control points (CCPs) to enable an ‘appropriate level
of protection (ALOP)’ to be achieved, i.e. attainment of negligible risk. This work was done as
part of a project led by the Meat Board of Namibia and largely funded by the Millennium
Challenge Account – Namibia, aimed at improving market access for beef producers the Zambezi
Region (ZR) of Namibia, a foot and mouth disease (FMD)-infected zone.
In order to validate the technical basis for the approach, it was necessary to confirm that matured
(pH < 6.0), deboned beef from which the lymph nodes and fat had been removed, did not contain
detectable quantities of southern African Territories (SAT) serotype FMD viruses even when
derived from cattle in the acute stage of infection. This was done by experimental infection of
cattle in a bio-secure facility and testing of tissues derived from those cattle immediately after
slaughter and exsanguination. Tissues derived from healthy cattle after slaughter at the official
abattoir in the ZR were also subsequently tested for viral content. No evidence of infection was
found in those animals. Experimental infection involved intradermolingual inoculation of six cattle with three different
FMD SAT virus isolates obtained from outbreaks in cattle in the ZR. Forty-eight hours after
infection the animals were euthanized and exsanguinated (i.e. acute phase of infection) and
selected tissues collected and processed to determine viral genomic content. For the abattoir
survey, 148 cattle were sampled for identification SAT serotype viruses in specific lymph nodes
of carcasses derived from cattle slaughtered at the abattoir in the ZR. Sub-mandibular, pre-scapular
and popliteal lymph nodes from these cattle were examined based on the results of the prior
experimental infection study that showed those lymph nodes to consistently contain detectable
viral RNA levels. Conventional and real time PCR techniques were used for detection of FMD
virus RNA.
It was shown that immediately after slaughter and exsanguination, but before maturation, SAT
serotype virus RNA was undetectable in striated muscle or fat of acutely infected cattle using the
methods employed in this study. A weakness of the method employed in this study was the use of
a non-optimized protocol for isolating total RNA from fat tissue. However, high levels of virus
RNA were present in some lymph nodes; consistently in the three that were sampled routinely at
the abattoir in the ZR. Sampling of the 148 cattle derived mainly from high risk areas and
slaughtered at the abattoir failed to reveal presence of FMD virus RNA in any animal. The sample
size was however too small to attain statistical significance due to cessation of sampling caused
by a FMD outbreak in cattle in the ZR. These results confirm and extend previously published
findings on the safety of matured beef from which the bones and lymph nodes have been removed
even if such beef is derived from locations that are not recognised as free from FMD.
