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