Lack of Transmission of Chronic Wasting Disease to Cynomolgus Macaques.

Chronic wasting disease (CWD) is a fatal prion disease that can infect deer, elk and moose. CWD was first recognized in captive deer kept in wildlife facilities in Colorado from 1967-1979. CWD has now been detected in 25 states of the USA, 2 Canadian provinces, South Korea, Norway and Finland. It is currently unknown if humans are susceptible to CWD infection. Understanding the health risk from consuming meat and/or products from CWD-infected cervids is a critical human health concern. Prior research using transgenic mouse models and in vitro conversion assays suggest that a significant species barrier exists between CWD and humans. To date, published epidemiologic studies of humans consuming cervids in CWD endemic areas have found no evidence to confirm CWD transmission to humans. Previously, we reported data from ongoing cross-species CWD transmission studies using two species of non-human primates as models. Squirrel monkeys (SM) and Cynomolgus macaques (CM) were inoculated by either intracerebral or oral routes with brain homogenates from CWD-infected deer and elk containing high levels of infectivity. SM were highly susceptible to CWD infection while CM were not. In the current study, we present new data for seven CWD-inoculated CM euthanized from 11-13 years post CWD-inoculation and eight additional uninoculated control CM. New and archival CM tissues were screened for prion infection using the ultrasensitive RT-QuIC assay, immunohistochemistry and immunoblot. In this study, there was no clinical, pathological or biochemical evidence suggesting that CWD was transmitted from cervids to CM. IMPORTANCE Chronic wasting disease (CWD) is a fatal prion disease found in deer, elk and moose. Since first discovered in the late 1960's, CWD has now spread to at least 25 states of the USA, 2 Canadian provinces, South Korea, Norway and Finland. Eradication of CWD from endemic areas is very unlikely and additional spread will occur. As the range and prevalence of CWD increases, so will the potential for human exposure to CWD prions. It is currently unknown if CWD poses a risk to human health. However, determining this risk is critical to prevent a similar scenario as what occurred when mad cow disease was found to be transmissible to humans. In the current study, we used cynomolgus macaque monkeys as a surrogate model for CWD transmission to humans. After 13 years, no evidence for CWD transmission to macaques was detected clinically or using highly sensitive prion disease screening assays.