Several reports have been sent to the United States Department of Agriculture’s Agricultural Research Service concerning the recent spread of an unknown epidemic on a farm in Montana. The report describes that cattle started exhibiting strange and abnormal behavior. Particularly, the cows started losing weight drastically and without any obvious reason, producing a reduced amount of milk and having problems with orientation (Broucek et al., 2017). The study of the relevant literature revealed that one of the potential causes of the disease might be bovine spongiform encephalopathy (BSE) or ‘mad cow disease’ due to prions (Houston and Andréoletti, 2019). The latter is named PrPSc and is considered to be a misfolded form of protein PrPC that can be replicated and transmitted among the same species and also to other species.
In this regard, it is fair to suspect that BSE could be transmitted to humans through the ingestion of diseased cattle meat. In humans, transmitted prions cause a disease that is called the new variant of Creutzfeldt–Jakob disease (vCJD) (Thomas, 2019). It is associated with developing neurological and psychological problems, mental deterioration, change in behavior, and reduced coordination. However, according to the European Centre for Disease Prevention and Control (2017), the average incubation period of this type of prion disease in humans is ten years, whereas, for cattle, it is two times less. Thus, there is a high risk that farmers already have vCJD but without any symptoms yet. For this reason, I was sent to the farm to collect the brain tissue sample of the recently dead animals, and some of the supposedly affected farmers were invited to the research center. That was done in order to confirm or reject the original hypothesis concerning BSE and vCJD.
Indeed, the laboratory results show that both the cattle and some farmers have isoforms of PrPC prion protein – PrPSc. As for the cattle, the brain tissue of the dead animals was collected as this method is the only one that can provide reliable results (U.S. Food & Drug Administration, 2020). On the other hand, Thomas (2019) maintains that in humans, the disease can be detected by the analysis of the lymphoid tissue. However, first, the patients were tested on electroencephalogram and MRI, and some small changes in their brains were detected. Therefore, the lymphoid tissue was analyzed to get more certain results. In the laboratory, the first step included the conventional histopathology analysis of the brain and lymphoid tissues. Next, an immunohistochemistry test was conducted to identify whether the sample tissues have PrPSc prion protein. As a result, the laboratory tests fully approved the initial hypothesis.
Both ‘mad cow disease’ and vCJD are relatively recently discovered diseases. The first case of BSE was registered in 1986 in the U.K., and the first case of vCJD was reported just several years later in the same country (Kim et al., 2016). The original cause of the BSE was found to be a meat-and-bone meal. For this reason, our investigation of the disease’s etymology started from the food that the cattle consume. The farm manager explained that they use several domestically produced supplements and two imported ones – from Brazil and the U.K. – to feed their cows. A further search for the cause of the epidemic revealed that just recently, there was also one case of BSE detected in Somerset, U.K. (McCarthy, 2021). Next, I talked with the farm manager in Somerset and found that they used to buy the supplements from the same company in the U.K. as our farmers in Montana. Therefore, the primary source of the BSE and vCJD epidemic was identified.
Unfortunately, there is no treatment developed to cure both BSE and vCJD. Usually, the sick animals die in a period of two weeks to several months. As for the affected farmers, they can live as long as 12 years after the first symptoms appear. In this regard, it is suggested that all the cattle on the farm be quarantined until all the animals and farmers are tested.