Monitoring of chronic wasting disease (CWD) (IV)

Abstract

The European Commission requested an analysis of the Chronic Wasting Disease (CWD) monitoring programme in Norway, Sweden, Finland, Iceland, Estonia, Latvia, Lithuania and Poland (9 January 2017–28 February 2022). Thirteen cases were detected in reindeer, 15 in moose and 3 in red deer. They showed two phenotypes, distinguished by the presence or absence of detectable disease‐associated normal cellular prion protein (PrP) in lymphoreticular tissues. CWD was detected for the first time in Finland, Sweden and in other areas of Norway. In countries where the disease was not detected, the evidence was insufficient to rule out its presence altogether. Where cases were detected, the prevalence was below 1%. The data also suggest that the high‐risk target groups for surveillance should be revised, and ‘road kill’ removed. Data show that, in addition to differences in age and sex, there are differences in the prion protein gene (PRNP) genotypes between positive and negative wild reindeer. A stepwise framework has been proposed with expanded minimum background surveillance to be implemented in European countries with relevant cervid species. Additional surveillance may include ad hoc surveys for four different objectives, specific to countries with/without cases, focusing on parallel testing of obex and lymph nodes from adult cervids in high‐risk target groups, sustained over time, using sampling units and a data‐driven design prevalence. Criteria for assessing the probability of CWD presence have been outlined, based on the definition of the geographical area, an annual assessment of risk of introduction, sustained minimum background surveillance, training and engagement of stakeholders and a surveillance programme based on data‐driven parameters. All positive cases should be genotyped. Sample sizes for negative samples have been proposed to detect and estimate the frequency of PRNP polymorphisms. Double‐strand sequencing of the entire PRNP open reading frame should be undertaken for all selected samples, with data collated in a centralised collection system at EU level.

Sporadic cases of chronic wasting disease in old moose – an epidemiological study

“…We have shown that these cases also have an epidemiological pattern that differs from CWD as observed in North America and Norwegian reindeer. The terms ‘Nor-16CWD’, ‘atypical CWD’, ‘sporadic CWD’ and ‘Ly-’ have been used for the CWD cases as observed in Nordic moose [18, 28, 47]. We support the use of the term ‘sporadic chronic wasting disease’ (with acronym sCWD) for these cases.…”

“…In scientific communication, as well as in communication related to management and control and standards for trade with animals and animal products, there is a need for a terminology which differentiate diseases with different characteristics, this includes CWD. In the scientific literature, CWD in Nordic moose has been considered one entity based on prion properties of which the two main important common features are (1) a truncated c-terminal of the prion [18] and (2) no detection of prions in lymphoid tissue with traditional diagnostic methods () [28]. We have shown that these cases also have an epidemiological pattern that differs from CWD as observed in North America and Norwegian reindeer.…”

“…After the detection of a CWD case, intensified surveillance was implemented in the area. This included education and facilitating sampling, which has been shown to enhance reporting and sampling from both hunted and risk animals [28]. There was also an increased testing of hunted animals.…”

“…Analysis of these can contribute to the understanding of the underlying epidemiology of these cases in moose. Whereas a first joint analysis was recently published [28], this study contribute to further analyses, including Monte Carlo simulation of the probability of detection of cases and analysis of age data of surveyed moose.…”

The European Union summary report on surveillance for the presence of transmissible spongiform encephalopathies (TSE) in 2022

“…In 2022, there was a substantial reduction of testing in both EU MS and Norway. The monitoring was mainly carried out on the category ‘hunted/killed animals fit for human consumption’ (78.9%), a target group with lower probability of disease, compared to the risk groups (FC, HSNHC, SUS) (EFSA BIOHAZ Panel et al, 2023 ). Ten MS tested 3202 cervids, compared to 5854 tested by eight MS in 2021 (−45.3%).…”