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

Figures & data

Figure 1. Soil orders map of Western Canada (Alberta, Saskatchewan and Manitoba) with range of caribou (Rangifer tarandus spp.) and CWD-endemic region. (Map source: Agriculture and Agri-Food Canada, 2010, v.3.1).

Table 1. Characteristics of soils in prairie provinces

Regions of prairie provinces	Great Groups	pH	SOM content in surface horizon	Texture	Diagnostic Horizon	Comments
Southern Alberta, Saskatchewan and Manitoba	Black Chernozems	6.5–7.5	5–9.5%	Sandy loam to clay loam	Ah, Ap, Ahe	A grassland soil whose diagnostic horizon is formed by high levels of organic matter additions from the roots of grasses.
	Brown Chernozems	6.5–7.5	2.5–3.4%	Loam, clay loam
	Vertisolic soils	7.2–8.5	1–6%	Clay loam, clay	Bss	Associated with high clay glacio-lacustrine landscapes; characterized by shrinking and swelling of clays.
	Solonetzic soils	8–9	1–2%	Clay	Bn or Bnt	A grassland soil with high sodium levels in the B horizon; usually associated with a clay-rich B horizon and high Na content.
Western and Northern Alberta and Manitoba	Regosolic soils	4–8	< 1%	Sandy, loamy sand	No B hor.	Weakly developed soils found throughout prairie provinces wherever pedogenic conditions prevent the formation of B horizons.
Central and Northern Alberta	Gray Luvisols	4.5–5.5	1–2% in mineral horizon	Sandy loam, loam	Bt	A forest soils where dominant process is eluviation of clay (and sometimes organic substances) from the Ae horizon and its deposition in the Bt horizon. Above-ground SOM input: LFH horizon.
Western Alberta, Northern Saskatchewan and Manitoba	Brunisols	5–6.5	~2%	Sandy loam, loam	Bm	A forest soil whose properties are not strongly enough developed to meet the criteria for the Luvisolic or Podzolic Orders.
Northern-east Manitoba	Cryosols	4–7	< 1% in min. hor. or 10–30% in org. hor.	Mostly fine-textured from sandy to silt loam	Bcr	Common in the subarctic forest area in Cryosolic soils are formed in either mineral or organic materials that have permafrost.
Central Manitoba	Gleysols	< 5	< 1% in min. hor. or 10–30% in org. hor.	Sandy-loam	G	Diagnostic bluish-gray color reflects the occurrence of a reducing (anoxic) environment
Northern Alberta and Central Saskatchewan and Manitoba	Organic soils	4.5–6.5	> 30%	NA	O	Soils of the Organic order are composed largely of organic materials. They include most of the soils commonly known as peat, muck, or bog and fen.

Figure 2. Hamster scrapie prions (PrP^HY) bind to mineral fractions of soils S1 and S2. Identical amounts of 10% brain homogenate (BH^HY) were incubated with soils overnight at room temperature. Samples were fractionated through a sucrose cushion to separate bound PrP^HY from unbound; both pellet (bound PrP^HY) and supernatant (unbound PrP^HY) were analyzed for presence of PK-resistant PrP^HY by western blot with 3F4 antibody. Soil S1 with clay texture and montmorillonite-kaolinite mineralogical composition binds more PrP^HY compared with soil S2 with sandy-loam texture and Illite-kaolinite composition.

Figure 3. Distribution of some soil characteristics in the soil surface horizons across western Canada: (A) clay content in the surface soil horizons, % of texture; (B) mineralogical composition of surface soil horizons: Mte, montmorillonite; Kte, kaolinite; Qtz, quartz; Ch, chlorite; ORG, organic horizon without mineral fraction. First is dominant mineral followed by remaining occurred minerals; (C) soil organic matter content in the surface soil horizons, %; (D) humus content in the surface soil horizons, %; (E) soil pH.

Figure 4. Influence of HA on PrP^Sc: (A) interactions between HA and PrP^CWD affect PrP^CWD recovery and molecular weight. Identical amounts of 10% brain homogenate (BH^CWD) were incubated with water (control) and HA (1g/L, 2.5 g/L and 25 g/L) overnight at room temperature. Samples were analyzed for presence of PK-resistant PrP^CWD by western blot with Bar224 antibody. (B) HA affect hamster scrapie prion (PrP^HY) binding to Mte. 10% brain homogenate (BH^HY) was incubated with Mte ± HA (1 g/L and 25 g/L) overnight at room temperature. Samples were fractionated through a sucrose cushion to separate bound PrP^HY from unbound; residual (r; adsorbed on the Eppendorf tube PrP^HY), pellet (p; bound PrP^HY) and supernatant (s; unbound PrP^HY) were analyzed for presence of PK-resistant PrP^HY by western blot with 3F4 antibody.