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

Author: Kopecky KE.

Summary: A study was undertaken to determine the relationship between concentration of paratuberculosis-infected herds and soil types in Wisconsin. Locations of farms on which paratuberculosis had occurred between 1971 and 1975 were obtained from the Wisconsin Department of Agriculture.

The disease occurred mainly in the rolling and undulating areas. Fifty percent of the infection herds were in the southwestern "driftless area" and the southeast uplands; 43% occurred in the western part of the northern silty and loamy uplands; the other 7% were scattered in the east and east-central part of the state. The disease did not necessarily occur in the areas of high cattle concentration.

It was concluded that the disease persisted in regions with acid soils but not in regions with alkaline, calcereous soils.

Study link: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=833032&query_hl=38

Authors: Michel AL, Bastianello SS.

Institution: Tuberculosis Laboratory, Onderstepoort Veterinary Institute, Private Bag X5, Old Soutpansroad, 0110, Onderstepoort, South Africa. anita@moon.ovi.ac.za

Summary: During a serological survey for ovine paratuberculosis a total of 145934 ovine serum samples from 2019 farms throughout South Africa were tested by means of the AGID assay.

Fifty-two infected farms were identified in the Western Cape and Eastern Cape provinces. Links between infected farms in the two provinces were established. Examination of the distribution of infected farms in the Western Cape indicated a positive correlation between acid soils and occurrence of infection.

In an attempt to increase the sensitivity and facilitate screening of large numbers of sera two commercial ELISA systems were evaluated for their potential use in a future monitoring program. Sera from histologically positive sheep and known negative sheep flocks were used. The highest sensitivity (50. 9%) was found if both ELISA systems were run concurrently and the results of both systems combined.

Study link: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=11118715&query_hl=21

Authors: Reviriego FJ, Moreno MA, Dominguez L.

Institution: Seccion de Sanidad v Produccion Animal, Junta de Castilla y Leon, Avila, Spain.

Summary: Relationships between soil type and ovine and caprine paratuberculosis in the Avila region (central Spain) were evaluated using data from a cross-sectional study of the most-important diseases of small ruminants in this Spanish region between 1996 and 1997. Questionnaire data from 61 herds (38 ovine and 23 caprine) and 1451 serum samples (1041 ovine and 410 caprine) were used. Herd paratuberculosis (herds were scored as positive to paratuberculosis if any of the serum samples was positive in an agar-gel immunodifussion) was the outcome of interest, whereas soil type in the municipality where farms were located was the predictor variable.

Other variables related to soil and soil usage, and herd size, replacement, main food production and animal species were also introduced into the multivariable logistic regression.

The final model contained only two independent variables: the predictor variable soil type (coded as two dummy variables ST-1 and ST-2) and herd size (dichotomized at the highest quartile). The estimated Odds Ratios were 25.9 (95% CI: 1.6, 411) for ST-1 (entisols as soil type) and 3.5 (95% CI: 0.3, 45) for ST-2 (inceptisols as soil type).

Study link: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=10665950&query_hl=15

Authors: Johnson-Ifearulundu YJ, Kaneene JB.

Institution: Population Medicine Center, College of Veterinary Medicine, Michigan State University, East Lansing 48824-1316, USA.

Summary:A cross-sectional study was conducted from June through December 1996 to identify management-related risk factors for herd-level M. paratuberculosis infection. Data were collected from 121 participating herds. A two-part questionnaire was administered to gather data on current and previous management practices and herd productivity…

There were 80 herds with one or more positive animals and 41 herds with no positive animals in the sample (66% herd-level prevalence). Twenty-six herds (21%) were dropped from further analyses because they had only one positive cow. Twelve herds (10%) were dropped from analysis because of missing data. The resulting sample used for statistical modeling included 46 positive herds and 37 negative herds (55% herd-level prevalence). A multi-variable logistic-regression model was used to evaluate the results.

The variable 'use of an exercise lot for lactating cows' was associated with a three-fold increase in odds of a herd being positive for M. paratuberculosis infection (O.R. = 3.01, C.I. = 1.03-8.80); 'cleaning of maternity pens after each use' was associated with a three-fold reduction in odds of a herd being positive for M. paratuberculosis infection (O.R. = 0.28, C.I. = 0.08-0.89); 'application of lime to pasture areas in 1993' resulted in a ten-fold decrease in odds of a herd being positive for M. paratuberculosis infection (O.R. = 0.10, C.I. = 0.02-0.56).

Study link: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=9879579&query_hl=14

Authors: Johnson-Ifearulundu Y, Kaneene JB.

Institution: Population Medicine Center, College of Veterinary Medicine, Michigan State University, East Lansing 48824, USA.

Objective: To determine prevalence of paratuberculosis among dairy cattle herds and to identify associated soil-related risk factors.

Sample Population: Serum and soil samples for 121 Michigan dairy herds.

Procedure: Blood samples were collected from cows at each farm and tested for Mycobacterium paratuberculosis, using an antibody ELISA. Soil samples were collected from pastures and exercise lots; pH and available iron content were determined. A questionnaire was administered to collect data regarding farm management practices and productivity.

Conclusions: Prevalence of paratuberculosis-positive dairy herds in Michigan (54%) was greater than expected, but prevalence of paratuberculosis-positive cattle (6.9%) was within anticipated values. These prevalences were associated positively with acidic soil and increased soil iron content. Application of lime to pasture areas was associated with reduced risk of paratuberculosis.

Study link: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=10328429&query_hl=4