Spatial correlation between the prevalence of transmissible spongiform diseases and British soil geochemistry

Abstract

Transmissible spongiform encephalopathies (TSEs) are a group of fatal neurological conditions affecting a number of mammals, including sheep and goats (scrapie), cows (BSE), and humans (Creutzfeldt-Jakob disease). The diseases are widely believed to be caused by the misfolding of the normal prion protein to a pathological isoform, which is thought to act as an infectious agent. Outbreaks of the disease are commonly attributed to contaminated feed and genetic susceptibility. However, the implication of copper and manganese in the pathology of the disease, and its apparent geographical clustering, have prompted suggestions of a link with trace elements in the environment. Nevertheless, studies of soils at regional scales have failed to provide evidence of an environmental risk factor. This study uses geostatistical techniques to investigate the correlations between the distribution of TSE prevalence and soil geochemical variables across the UK according to different spatial scales. A similar spatial pattern in scrapie and BSE occurrence is identified, which may be linked with increasing pH and total organic carbon, and decreasing iodine concentration. However, the pattern also resembles that of the density of dairy farming. Nevertheless, despite the low spatial resolution of the TSE data available for this study, the fact that significant correlations are detected indicates there is a possibility of a link between soil geochemistry, scrapie, and BSE. It is suggested that further investigations of the prevalence of TSE and environmental exposure to trace metals should take into account the factors affecting their bioavailability.

Potential role of soil properties in the spread of CWD in western Canada

“…42 At the same time, total organic carbon in topsoils of the British Isles has been correlated with incidence rates of scrapie. 43 Our data also show a change in PrP CWD recovery and molecular weight during incubation with HA (Fig. 4A).…”

Influence of landscape factors and management decisions on spatial and temporal patterns of the transmission of chronic wasting disease in white-tailed deer

“…Recent research indicated CWD risk was associated with increased clay soils in Colorado (Walter et al, 2011), corresponding to laboratorybased studies where clay soils have higher PrP sorption capacity (Jonson et al, 2006). Field-based studies of scrapie in Great Britain have found inconclusive or the opposite effects with clay soils (Imrie et al, 2009;Saunders et al, 2012). We suggest that in this region, less clay in soils may be related to factors favouring increased deer density and the CWD focal areas may be in places where transmission is occurring mostly through contact with infectious animals and the density effect overwhelms the possible effect of prions persistence in soils.…”

“…In vitro and laboratory assays have indicated that prions bound to clays may have greater infectivity (Johnson et al, 2006) while field studies by Walter et al (2011) showed an association between CWD in mule deer and a higher percentage of clay soils within the deer's home range. A study of scrapie and BSE in Great Britain found a spatial correlation between these two diseases and increased pH and organic carbon in soils but nothing discernable related to clay particles (Imrie et al, 2009).…”

A Case–Control Study on the Origin of Atypical Scrapie in Sheep, France

“…of the few epidemiologic studies conducted on this topic (32)(33)(34)(35) were rarely conclusive but such associations are diffi cult to demonstrate with observational data. Among different mechanisms that should be explored to understand occurrence of atypical scrapie, we believe that toxic exposure should not be overlooked.…”