Prion Disease Clusters in West Michigan

The state of Michigan has a list of reportable diseases, including a range of infectious agents such as viruses, pathogenic bacteria, and parasites. This list includes a variety of infectious agents such as viruses, pathogenic bacteria, and parasites, as well as prion disease, which is unique in its mode of transmission. Prion diseases occur when a normal protein in the brain becomes misfolded, leading to the accumulation of plaques in the brain that give it a spongy appearance (CDC, 2021). These diseases affect all mammalian species, including humans, and the most common type is called Creutzfelt-Jakob Disease (CJD). CJD can occur spontaneously, due to a genetic defect, or through contact with contaminated meat or surgical instruments (Case Western Reserve University School of Medicine, 2023). It is always fatal and has no known cure (CDC, 2021).

CJD is rare, affecting about one to two people per million worldwide each year, with around 400-500 cases in the US annually (Case Western Reserve University School of Medicine, 2023). The disease has a long incubation period, sometimes taking up to 40-50 years to show symptoms. Once symptoms appear, however, the disease progresses rapidly, leading to death (CDC, 2021). Symptoms include dementia, unsteady gait, hallucinations, and myoclonus (Case Western Reserve University School of Medicine, 2023).

Clinicians in Michigan must report suspected and confirmed cases of CJD to public health officials. Additionally, active surveillance of Chronic Wasting Disease (CWD), a prion disease of the white-tailed deer, has been conducted since the first MI case in 2015 (Ott-Conn, Blanchong, & Larson, 2021). CDC states that there is insufficient evidence that CWD is transmissible to humans, but the WHO recommends keeping all potential sources of prion disease out of the human food chain (CDC, 2021).

CWD is becoming increasingly prevalence in Michigan deer populations, particularly in Kent County with the highest apparent incidence of the disease between 2015 and 2019 (Ott-Conn, Blanchong, & Larson, 2021). Additionally, CJD in humans spiked in the past 12 months, with five cases totaling two clusters of CJD cases reported in Grand Rapids hospitals (Rong et al., 2023). According to CDC (2021), there is no evidence yet to suggest a link between CWD and CJD, yet mounting evidence suggests that CWD may be transmissible to humans, as recent studies show CWD transmissibility to humanized mice. The afflicted humanized mice in Hannaoui et al. (2022) shed infectious prion particles in feces, indicating the possibility of fecal-oral CWD transmission in humans.

It is unclear whether the high CWD incidence in Kent County is related to the recent clusters of CJD in Grand Rapids. However, if CWD does make the jump to humans, the community will face significant risk. Prions remain infectious in the environment for years and are almost impossible to neutralize using standard sterilization techniques (Belay & Schonberger, 2005). Thus, regular monitoring of wastewater in high CWD/CJD counties for infectious prions associated with CWD and CJD is necessary to detect early exposure and prevent community harm. Although the cost of wastewater surveillance is high, the benefit of early detection and subsequent exposure mitigation may pay for itself in the event of CWD zoonotic transmission to humans. The MI COVID-19 wastewater surveillance network could be expanded to include monitoring levels of other infectious agents, including prions, and may benefit from any extra funding brought in by prion surveillance programs (State of Michigan, n.d.). The proactive step of wastewater surveillance expansion may provide a vital opportunity to mitigate the potential risk of a zoonotic jump of CWD to humans.