Many may remember the mad cow disease epidemic in the United Kingdom during the mid-nineties. But what is mad cow disease and where did it come from? Bovine spongiform encephalopathy (BSE) or commonly referred to as mad cow disease is a fatal neurodegenerative disease primarily found in cattle. BSE is not well understood, but the normal prion proteins alter into pathogenic (harmful) form that causes damage to the central nervous system. BSE is primarily acquired from cattle eating other parts of meat-and-bone from other ruminants that may have already been infected with the disease.
BSE is divided into two types, classical and atypical. Classical BSE originated in the United Kingdom in the late 1980’s and there is strong epidemiologic and laboratory evidence that exists for a causal association between a new human prion disease called Creutzfeldt-Jakob disease (vCJD) in people. This disease has an unusually long incubation period measured in years and is an unconventional transmissible agent that causes fatal brain diseases. The second type, atypical BSE is considered rare and because it spontaneously arises in older animals. Majority of the time in animals eight years or older, but on August 28, 2018, a 6-year-old mixed breed cow was discovered to have a case of atypical BSE after an on-farm collection in Florida. It is believed that both types are not transmitted between cattle or humans.
There are various signs when a cow has classical or atypical BSE. The incubation period for classical BSE is estimated to be 2 to 8 years. The clinical signs may include gait abnormalities, low carriage of the head, hyper-responsiveness to stimuli, tremors and behavioral changes such as aggression, nervousness or apprehension and changes in temperament. The nonspecific signs include loss of condition, weight loss, teeth grinding and decreased milk production. Many of these signs will worsen gradually over a few weeks to several months, but rare cases can move more rapidly. Once clinical signs appear, BSE is always progressive and fatal. The final stages are characterized by recumbency, coma and death.
Since atypical BSE arises spontaneously, it is still incompletely understood. Research experiments have reported varying clinical signs, with some researchers concluding that atypical can be distinguished clinically from classical BSE, and other reporting that the spectrum of clinical signs overlap. Some studies report hyperresponsiveness to tactile facial stimuli, but not to light or sound. Behavioral, sensory and motor signs were all seen. Another study reported Holstein cattle had decreased activity, hyperresponsiveness to stimuli, ataxia mainly of the hindlegs, difficulty rising and little aggression.
Please reach out to the University of Florida Extension office in your county for more information, we will keep you up to date on this topic as it progresses and more information is made available.
For more information on the Florida case, go to the USDA website.