Farm Factors Associated with Reducing Cryptosporidium Loading in Storm Runof from Dairies
Journal of Environmental Quality , 37 , 2008

Miller, W.A., Lewis, D.J., Pereira, M.D.G., Lennox, M.S., Conrad, P.A., Tate, K. W., Atwill, E. R.

A systems approach was used to evaluate environmental loading of Cryptosporidium oocysts on fi ve coastal dairies in California. One aspect of the study was to determine Cryptosporidium oocyst concentrations and loads for 350 storm runoff samples from dairy high use areas collected over two storm seasons. Selected farm factors and benefi cial management practices (BMPs) associated with reducing the Cryptosporidium load in storm runoff were assessed. Using immunomagnetic separation (IMS) with direct fl uorescent antibody (DFA) analysis, Cryptosporidium oocysts were detected on four of the fi ve farms and in 21% of storm runoff samples overall. Oocysts were detected in 59% of runoff samples collected near cattle less than 2 mo old, while 10% of runoff samples collected near cattle over 6 mo old were positive. Factors associated with environmental loading of Cryptosporidium oocysts included cattle age class, 24 h precipitation, and cumulative seasonal precipitation, but not percent slope, lot acreage, cattle stocking number, or cattle density. Vegetated buff er strips and straw mulch application signifi cantly reduced the protozoal concentrations and loads in storm runoff , while cattle exclusion and removal of manure did not. h e study fi ndings suggest that BMPs such as vegetated buff er strips and straw mulch application, especially when placed near calf areas, will reduce environmental loading of fecal protozoa and improve stormwater quality. h ese fi ndings are assisting working dairies in their eff orts to improve farm and ecosystem health along the California coast