Factors associated with the likelihood of Giardia spp. and Cryptosporidium spp. in soil from dairy farms
2003
Barwick, R.S. | Mohammed, H.O. | White, M.E. | Bryant, R.B.
A study was conducted to identify factors associated with the likelihood ofdetecting Giardia spp. and Cryptosporidium spp. in the soil of dairy farms in a watershed area. Atotal of 37 farms were visited, and 782 soil samples were collected from targeted areas on thesefarms. The samples were analyzed for the presence of Cryptosporidium spp. oocysts, Giardia spp.cysts, percent moisture content, and pH. Logistic regression analysis was used to identify riskfactors associated with the likelihood of the presence of these organisms. The use of the land atthe sampling site was associated with the likelihood of environmental contamination withCryptosporidium spp. Barn cleaner equipment area and agricultural fields were associated withincreased likelihood of environmental contamination with Cryptosporidium spp. The risk ofenvironmental contamination decreased with the pH of the soil and with the score of the potentiallikelihood of Cryptosporidium spp. The size of the sampling site, as determined by the samplingdesign, in square feet, was associated nonlinearly with the risk of detecting Cryptosporidium spp.The likelihood of the Giardia cyst in the soil increased with the prevalence of Giardia spp. inanimals (i.e., 18 to 39%). As the size of the farm increased, there was decreased risk of Giardiaspp. in the soil, and sampling sites which were covered with brush or bare soil showed a decreasein likelihood of detecting Giardia spp. when compared to land which had managed grass. Thenumber of cattle on the farm less than 6 mo of age was negatively associated with the risk ofdetecting Giardia spp. in the soil, and the percent moisture content was positively associated withthe risk of detecting Giardia spp. Our study showed that these two protozoan exist in dairy farmsoil at different rates, and this risk could be modified by manipulating the pH of the soil.
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