The infection was detected as part of a national surveillance effort, so never entered the food chain and poses no human health risk, state agriculture officials said Wednesday.
The 6-year-old mixed breed beef cow tested positive for atypical bovine spongiform encephalopathy. Unlike the classical form of the disease spread by contaminated feed made from infected animals, the atypical version appears spontaneously and rarely, officials said.
It’s not known what causes the atypical version, although it typically occurs in older cattle.
The cow was tested as part of the USDA’s surveillance system that inspects animals deemed unsuitable for slaughter, a press release said. State and federal agriculture officials are investigating.
It’s not known what risk the case poses to the state’s cattle industry. The Florida agency declined to make anyone available to answer questions and in a brief email said there’s no evidence atypical mad cow causes brain disease in humans.
However, Germany’s national health institute, where mad cow is more prevalent, said in a 2014 report that the atypical form of the disease can be transmitted to humans if undercooked diseased meat is eaten. The atypical version is also likely the cause of infected feed that spreads the classical form, the study said.
Mad cow has been linked to a form of Creutzfeldt-Jakob disease, a rare, degenerative, fatal brain disorder that usually appears in older people. After cows were infected in Europe, nearly 200 people came down with the disease. It’s believed the disease is carried in a prion, a protein smaller than a virus that can cause abnormalities in the brain in older cows, said ZooMiami veterinarian Frank Ridgley.
The disease was first diagnosed in the United Kingdom in 1986, where hundreds of thousands of cows were infected. It has since been detected in other countries. In the U.S., only five cases have been confirmed until now, in California, Alabama, Texas and Washington. The last U.S. case was in July 2017, when an 11-year-old cow showing signs of the disease tested positive.
Worldwide, about 90 cases of the spontaneous, atypical form had been documented by 2014, the German report said.
“We get briefly informed about it in vet school and if there’s any importation of animals, that’s always addressed and usually they have to be watched,” Ridgley said. “But U.S. vets and the ag department have not really been in the war zones like Europe. We’re always being vigilant, but we haven’t had the on-the-ground experience like in Europe.”
In the U.S. cattle are also often slaughtered before the age at which spontaneous mad cow is detected, he said.
After it was discovered in Europe, the U.S. banned feed in 1997 that uses cow parts and other animals that might carry the disease. The UK now excludes any animals older than 30 months from its food supplies.
Now that a case has been detected, it’s likely agriculture officials will conduct a lengthy review. In previous cases, they examined offspring and any cattle that might be connected to the infected animal, as well as records for the entire herd, and traced feed to look for possible sources.
“This detection shows just how well our surveillance system works,” Agriculture Commissioner Adam Putnam said in a statement.
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