Observations regarding the associations among soil pH, calcium or iron content and the incidence of paratuberculosis have a long history. The 1956 review article on Johne's disease by Doyle covers most of the early observations on association of soil type and paratuberculosis incidence and the 1997 review by Johnson-Ifearulundu complements it by covering more recent literature. The fact that this observed association (i.e. not a proven causal link), in particular concerning soil pH, has been made in England, France, The Netherlands, and the U.S. adds credibility to the idea that somehow soil composition and paratuberculosis are connected.

In addition, Johnson-Ilfearulundu and Kaneene recently showed by careful epidemiologic analysis that in the state of Michigan in the U.S. the practice of application of lime to pastures (a practice that should increase soil pH) in 1993 was associated with ten-fold lower odds of a dairy herd being serologically test-positive for M. paratuberculosis infection in 1996.

Source: http://www.johnes.org/biology/survival.html#16

• Distribution of Paratuberculosis in Wisconsin, By Soil Regions
• Paratuberculosis in Sheep: an Emerging Disease in South Africa
• Soil Type as a Putative Risk Factor of Ovine and Caprine Paratuberculosis Seropositivity in Spain
• Management-Related Risk Factors for M. Paratuberculosis Infection in Michigan, USA, Dairy Herds