Submitted to: Applied and Environmental Microbiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/5/2010
Publication Date: 9/1/2010
Publication URL: http://aem.asm.org/cgi/content/full/76/17/5757?maxtoshow=&hits=10&RESULTFORMAT=&fulltext=jenkins&searchid=1&FIRSTINDEX=0&resourcetype=HWCIT
Citation: Jenkins, M., Liotta, J., Lucio-Forster, A., Bowman, D. 2010. Concentrations, viability, and distribution of Cryptosporidium genotypes in lagoons of swine facilities in Southern Piedmont and Coastal Plain watersheds of Georgia. Applied and Environmental Microbiology. 76(17):5757-5763. DOI: 10.1128/AEM.00434-10. Interpretive Summary: Waste lagoons of large-scale swine operations have been implicated as a potential source of Cryptosporidium, a protozoan parasite, as well as Cryptosporidium parvum the parasites that infects calves and is pathogenic to humans (causing diarrhea). Because effluent from swine waste lagoons is applied to cropped and hayed fields, the potential for surface water contamination and risk to public health exists. Little is known, however, about the distribution of Cryptosporidium species, their concentrations, and the extent to which they are alive and potentially infective in swine waste lagoons. Scientists at the USDA-ARS J. Phil Campbell, Sr., Natural Resource Conservation Center and Cornell University systematically sampled ten swine waste lagoons from ten different swine operating facilities (three farrowing, two nurseries, four finishing, and one gestation facility) once a month for one year. Parasite concentration, parasite viability/potential infectivity, and distribution of Cryptosporidium species and specific genetic types were determined. Results of sample analyses indicated that Cryptosporidium parasites were observed at each of the twelve sampling times at each waste lagoon. With the exception of a nursery facility (which was at 12%) the percent of Cryptosporidium parasites that were viable and potentially infective ranged between 2 and 4% of the total number of parasites counted in samples to determine their concentrations. The vast majority of the Cryptosporidium parasites in the waste lagoons were dead. The genetic analysis of the parasites extracted from the effluent samples were determined to be mainly (75%) Cryptosporidium parasites which are specifically adapted to pigs, and potentially pathogenic to humans with compromised immune systems, but not pathogenic to healthy humans. Other genetic types of Cryptosporidium were identified, but only five of the 407 samples analyzed were identified as the Cryptosporidium parvum calf type that is pathogenic to humans. Results of this research indicate that although swine waste lagoons are likely to be contaminated with Cryptosporidium parasites, the likelihood of the presence of the genetic type that is pathogenic to humans is very low, and, thus, the human health risk associated with swine waste lagoons is low. This information can be used by the pork industry, agricultural extension agencies, and environmental protection agencies to ensure safe application and management of swine waste effluent.
Technical Abstract: Waste lagoons of swine operations are a source of Cryptosporidium oocysts. Few studies, however, have reported on oocyst concentrations in swine waste lagoons; none have reported on oocyst viability status; nor has there been a systematic assessment of species/genotype distribution across different types of swine facilities. Ten swine waste lagoons associated with farrowing, nursery, finishing, and gestation operations were each sampled once a month for a year. Oocysts were extracted from triplicate 900 ml effluent samples, enumerated by microscopy, and assessed for viability by dye exclusion/vital stain assay. DNA was extracted from processed samples, and 18S rDNA genes amplified by PCR and sequenced for species and genotype identification. Oocysts were observed at each sampling time at each lagoon. Annual mean concentration of total oocysts and viable oocysts ranged between 24 and 51, and 0.6 and 12 oocysts ml-1 effluent, respectively. The distribution of species and genotypes was dominated (95 to 100%) by Cryptosporidium suis, and Cryptosporidium pig genotype II at eight of the lagoons. The lagoon at the gestation facility was dominated by C. muris (90%), and one farrowing facility showed a mix of pig genotypes, C. muris, and various genotypes of C. parvum. The zoonotic C. parvum bovine genotype was observed five-times out of 407 18S rDNA sequences analyzed. Our results indicate that pigs can have mixed Cryptosporidium infections, but infection with C. suis is likely to be dominant.