Prevalence and Distribution of Genotypes of Cryptosporidium Parvum in Feedlots in the Western United StatesEPA Grant Number: R828038
Title: Prevalence and Distribution of Genotypes of Cryptosporidium Parvum in Feedlots in the Western United States
Investigators: Atwill, Edward R. , Danaye-Elmi, Cyrus , Epperson, William B. , Grotelueschen, D. M. , Hoar, Bruce , McCluskey, B. J. , Sischo, William M.
Current Investigators: Atwill, Edward R. , Brewster, D. , Carpenter, L. V. , Danaye-Elmi, Cyrus , Epperson, William B. , Grotelueschen, D. M. , Hoar, Bruce , Smith, B.
Institution: University of California - Davis , South Dakota State University , University of Nebraska at Lincoln
EPA Project Officer: Nolt-Helms, Cynthia
Project Period: April 1, 2000 through March 31, 2002 (Extended to February 28, 2002)
Project Amount: $248,461
RFA: Drinking Water (1999) RFA Text | Recipients Lists
Research Category: Drinking Water , Water
Description:The overall goal of the proposed research is to determine the prevalence of fecal shedding, distribution of genotypes, and associated risk factors for Cryptosporidium parvum (C. parvum) infection in populations of feedlot cattle in the United States. Infection with C. parvum in calves raised on commercial dairy farms is quite common. Cumulative incidence of infection often exceeds 90% within the first 30 days of life and as many as 107 oocysts/g may be shed in the feces of infected calves. In contrast, relatively little is known regarding the prevalence and intensity of fecal shedding of C. parvum in feedlot cattle. Although the older age of feedlot cattle suggests that C. parvum shedding will be of low intensity, these confined animal feeding operations (CAFO's) are comprised of cattle from a wide variety of geographical locations, animals which may be under varying levels of physiological stress and which are fed variable levels of grain which may collectively enhance the shedding of this zoonotic parasite. Recent evidence indicates that there are distinct genotypes of C. parvum which may differ in infectivity and virulence for humans and other mammalian hosts. Potential strain or genotype differences of C. parvum within populations of feedlot cattle may exist. To address these animal and human health issues and to develop strategies for minimizing environmental contamination of C. parvum from feedlot cattle, our project has the following objectives:
- Determine the prevalence and concentration of C. parvum oocysts in fecal samples from feedlot cattle in the United States. This will allow us to determine the significance of feedlot cattle as an environmental source of oocysts and to begin to calculate valid loading equations for the rate at which feedlot operations produce C. parvum oocysts.
- Determine the distribution of genotypes of C. parvum actively shed by feedlot cattle. This objective is designed to determine which genotypes of C. parvum are present in United States feedlot cattle. We will determine how genotypes are spatially distributed and whether geographic origin is predictive of genotype.
- Determine animal and pen-level management factors associated with a fecal sample testing positive for specific genotypes of C. parvum. This objective is designed to identify feedlot management practices which will minimize water quality and public health impacts from CAFO's and provide critical input for Comprehensive Nutrient Management Plans targeted for this segment of the cattle industry.
Approach:We will conduct a cross-sectional survey of feedlot cattle from at least 5 states, including but not limited to California, Colorado, Nebraska, South Dakota, and Washington. Within each state, 3 to 6 feedlots will be identified by cooperating researchers for voluntary inclusion in the study. For each feedlot, 4 pens will be selected for the study, with 65 fecal samples randomly collected from each pen, or 260 samples per feedlot. A standardized questionnaire will be administered for each pen. This sampling design will provide us with a diverse sample of management styles and animal types to examine potential risk factors associated with a fecal sample testing positive for C. parvum. Given that cattle arrive at feedlots from sources throughout North America, our sampling strategy is likely to collect samples from cattle from the majority of states within the continental U.S., as well as Canada and Mexico.
Fecal samples will be tested for presence of oocysts using a direct immunofluorescent assay. Mixed-effects logistic regression will be used to determine the significance and strength of association between potential risk factors and the probability of testing positive for C. parvum. We will evaluate four probability distributions (binomial, poisson, negative binomial, betabinomial) for modeling the sensitivity of our diagnostic assay. Based on the most appropriate model for assay sensitivity and the prevalence estimates from our multi-state cross-sectional survey, we will generate a set of equations which predict the loading rate of C. parvum oocysts per Kg of fecal material as a function of feedlot management practices. We will target two unlinked polymorphic loci for PCR-RFLP genotyping, Cryptosporidium oocyst wall protein and the SSU rRNA gene, with confirmatory DNA sequencing of the amplicons on a subset of isolates.