All tests for the disease as required by the International Organisation for Animal Health had been negative and there had been no indication of active viral replication, said Karan Beef veterinarian Dr Dirk Verwoerd on Wednesday.
"Everything supports our earlier conclusion that we were dealing with the remnants of an exposure that happened a long time ago in northern KZN."
A team of four vets from the Gauteng State Veterinary Office and Dr Verwoerd completed a range of investigatory procedures, including clinical evaluations and sampling at the Karan Beef's Heidelberg feedlot and Balfour abattoir on more than 2 000 animals as well as blood tests done at the Onderstepoort Veterinary Institute.
Karan Beef, which owns and operates the largest feedlot operation on the continent and processes cattle through its own abattoir, slaughtered 1 668 cattle the day after a few cattle with antibodies against foot-and-mouth disease (indicating exposure or vaccination) were found.
That precipitated the quarantine measures.
The testing followed the localised outbreak of the disease in the remote Ingwavuma area in northern Kwazulu-Natal in February. Among the animals slaughtered were 93 that came from the Blood River-Vryheid area, some 150km from the control zone.
This was the closest to the controlled area that Karan Beef had purchased cattle during the past several weeks.