Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 5, 2005
Publication Date: October 1, 2005
Citation: Kuczynska, E., Shelton, D.R., Pachepsky, Y.A. 2005. Effect of bovine manure on cryptosporidium parvum oocyst attachment to soil. Applied and Environmental Microbiology. 71(10):6394-6397.
Interpretive Summary: There is concern regarding the contamination of surface and grounds waters with Cryptosporidium parvum. Several water-borne outbreaks of cryptosporidiosis have occurred in the past decade, the most severe in Milwaukee, WI where over 400,000 people were infected. Watershed monitoring studies indicate that contamination can occur via surface transport of oocysts to surface waters, or vertical transport to groundwater, from land-applied manures or fecal excretion. Previous laboratory studies have demonstrated that oocysts can become attached to or trapped in soil, thereby mitigating the impact on surface or ground water. However, the majority of studies have been conducted with purified oocystys. In nature, oocysts are released from manure as manure dissolves during rainfall. Bovine manure is a complex matrix consisting of microbial biomass, dietary fiber, bedding materials, urine, and fecal mucus. Consequently, it is important to understand how manure effects oocyst interactions with soils. This study was conducted to assess the effect of different manure dilutions vs. no manure on oocyst attachment to soil particles. The presence of manure enhanced the attachment of oocysts to soil particles; maximum attachment was observed with 0.1% manure as opposed to 1.0% manure. Oocysts readily detached from soil particles; the greatest percent detachment occurred with 1.0% manure. These results indicate that manures significantly effect oocyst attachment to soils in a complex manner.
Soils play an important role in minimizing Cryptosporidium parvum contamination of surface and ground water via oocyst entrapment and/or attachment. During manure dissolution, oocysts are released into the environment along with manure particulates that can potentially affect oocyst attachment to soils in a variety of ways. The objective of this work was to assess the effect of the bovine manure in initial attachment and subsequent detachment of oocysts to soils. One percent and ten percent manure suspensions were inoculated with purified Cryptosporidium parvum oocysts suspended in distilled water to give a concentration of ca. 105 oocysts /mL manure suspension. Manure-oocyst suspensions were added to 9 mL of a 1% suspensions (w/v) of sandy loam and clay loam soils giving final manure concentrations of 0.1 and 1%. Percent oocyst attachment was greater for clay loam than sandy loam soil. Manure enhanced attachment of oocysts to soil particles as compared with oocysts in soil suspension without manure, with the exception of the 1.0% manure-clay loam suspension. Soil-manure pellets were resuspended in fresh water and incubated a second time to assess the tendency for oocyst detachment. With one exception of the sandy loam-no manure suspension, the percentage or ratio of oocysts attached to soil vs. in water decreased indicating that oocyst attachment was readily reversible. The magnitude of detachment was consistently greater with manure than without, and in general greatest for the 1.0% manure suspension. Consequently, a higher percentage of oocysts attached to soil particles, and remained attached after resuspension, in the presence of 0.1% as opposed to 1.0% manure. These results indicate that oocyst attachment to soil is substantially affected by bovine manure in a complex manner and should have implications for how oocysts may be transported through or over soils.