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Title: Inactivation kinetics of Cryptosporidium parvum oocysts in swine waste lagoon and spray field

Author
item Jenkins, Michael
item Liotta, Janice - Cornell University - New York
item Bowman, Dwight - Cornell University - New York

Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/27/2012
Publication Date: 4/1/2013
Citation: Jenkins, M., Liotta, J., Bowman, D. 2013. Inactivation kinetics of Cryptosporidium parvum oocysts in swine waste lagoon and spray field. Journal of Parasitology. 99(2):337-342.

Interpretive Summary: Since the parasite Cryptosporidium (crypto for short) was the cause of several large-scale outbreaks of diarrhea and in some cases death in humans, it has become a public health concern. Other than sewage treatment facilities, and wildlife, the source of this parasite in the environment is animal agriculture. Researchers have shown, for example, that waste lagoons of large-scale swine operations can be a source of crypto. They have also shown that a small percent of the total amount of crypto observed in a lagoon may be infectious. This surviving fraction of crypto is an indication that crypto die-off occurs in waste lagoons. Waste from the lagoon is periodically applied to spray fields as irrigation water and plant nutrients. The waste from a lagoon can also contaminate surface waters with crypto during rain storms. To better understand how long crypto associated with swine operations can survive in a lagoon and spray field, USDA-ARS scientists at J. Phil Campbell, Sr., Natural Resource Conservation Center in Watkinsville, GA, and scientists at Cornell University in Ithaca, NY, performed experiments to determine the time it takes for 99 percent of live crypto to die-off in a swine lagoon and spray field of a large-scale swine operation in Georgia. Results of their study indicated that the time it takes to kill 99 percent of crypto in the lagoon was 13 weeks in the summer and 20 weeks in fall and winter. Crypto die-off in the spray field appeared to be in three phases: 1) a rapid initial die-off in the first day crypto is applied to spray field surface soil; 2) for the remaining surviving crypto they calculated that it could take as long as a year for 99 percent of the crypto to die-off; and 3) but after ten weeks in the spray field surface soil these surviving crypto disappeared and became undetectable. This study demonstrated that the waste lagoon/spray field system of swine waste management was effective at reducing the numbers of this infectious pathogen and the likelihood of their contaminating surface waters and threatening public health. This study will be of interest to state and federal environmental protection agencies.

Technical Abstract: Because of outbreaks of cryptosporidiosis in humans, Cryptosporidium has become a public health concern. Commercial swine operations can be a source of this protozoan parasite. Although the species distribution of Cryptosporidium is likely dominated by C. suis, a fraction may be comprised of the zoonotic C. parvum. To better understand the survival dynamics of Cryptosporidium oocysts associated with swine operations, two experiments each were performed to determine die-off rates of C. parvum oocysts in a swine waste lagoon (2009 and 2010) and its spray field (2010 and 2011). Sentinel chambers containing a lagoon effluent suspension of C. parvum oocysts (2(10)7 chamber-1) were submerged in the lagoon, and triplicate chambers were removed over time, the oocysts extracted, and assayed for viability. For the spray field experiment air-dried and sieved surface soil from the spray field was placed in sentinel chambers, hydrated to field capacity, and inoculated with lagoon effluent suspension of C. parvum oocysts (2(10)7 chamber-1). Chambers were buried 1.5 cm below the soil surface in three blocks. Triplicate chambers (one per block) and controls were removed over time, the oocysts extracted, and assayed for viability. Based on first order decay equation, die-off and days to reach 99% die-off (T99) were determined. Inactivation rate constants and T99-values determined for the two lagoon experiments were 0.3504 week-1 and 13.1 weeks, and 0.2292 week-1, and 20.1 weeks, respectively. Cryptosporidium parvum die-off in the spray field appeared to be in three stages: 1) rapid die-off at time-zero; 2) slow die-off of remaining oocysts; and 3) undetectable oocysts after ten weeks. The waste lagoon and spray field system of manure management at this large scale farrowing operation reduced the load of infective Cryptosporidium oocysts entering the environment, and the likelihood of contaminating surface waters and threatening public health.