Indirect effects of soil and water on animal health

Association of pneumonia in foals caused by Rhodococcus equi with farm soil geochemistry

OBJECTIVE

To quantify and compare geochemical factors in surface soils from horse-breeding farms with horses with pneumonia caused by Rhodococcus equi (affected farms) and horse-breeding farms with no history of pneumonia caused by R equi (unaffected farms).

SAMPLE POPULATION

Soil from 24 R equi-affected farms and 21 unaffected farms.

PROCEDURE

Equine veterinary practitioners throughout Texas submitted surface soil samples from areas most frequented by foals, on R equi-affected and unaffected horse-breeding farms in their practice. Soil samples were assayed for the following factors: pH, salinity, nitrate, phosphorus, potassium, calcium, magnesium, sodium, sulfur, zinc, iron, manganese, and copper. Median values for all factors were recorded, and differences between affected and unaffected farms were compared.

RESULTS

Significant differences in soil factors were not detected between affected and unaffected farms; hence, there was no association between those factors and R equi disease status of the farms.

CONCLUSIONS AND CLINICAL RELEVANCE

The surface soil factors monitored in this study were not significant risk factors for pneumonia caused by R equi. As such, it is not possible to determine whether foals on a given farm are at increased risk of developing disease caused by R equi on the basis of these factors. Data do not support altering surface soil for factors examined, such as alkalinization by applying lime, as viable control strategies for R equi.