Prevalence of Giardia sp. Cryptosporidium parvum and Cryptosporidium andersoni (syn. C. muris) [correction of Cryptosporidium parvum and Cryptosporidium muris (C. andersoni)] in 109 dairy herds in five counties of southeastern New York.

A cross-sectional study was undertaken to determine the prevalence of Giardia sp. (G. duodenalis group), Cryptosporidium parvum and Cryptosporidium andersoni (C. muris) [corrected] in dairy cattle in three different age groups, and to evaluate the association of age and season with prevalence. One hundred and nine dairy farms, from a total of 212 farms, in five counties of southeastern New York volunteered to participate. On these farms, 2943 fecal samples were collected from three defined age groups. The farms were randomly assigned for sampling within the four seasons of the year. Each farm was visited once during the study period from March 1993 to June 1994 to collect fecal samples. Demographic data on the study population was collected at the time of sampling by interviewing the farm owner or manager. At collection, fecal samples were scored as diarrheic or non-diarrheic, and each condition was later related to positive or negative infection with these parasites. Fecal samples were processed using a quantitative centrifugation concentration flotation technique and enumerated using bright field and phase contrast microscopy. In this study, the overall population prevalence for Giardia sp. was 8.9%; C. parvum, 0.9%; and C. muris, 1.1%. When considering animals most at the risk of infection (those younger than 6 months of age) Giardia sp. and C. parvum was found in 20.1 and 2.4% of the animals, respectively. Giardia sp. and C. muris were found in all age groups. There was no significant seasonal pattern of infection for any of these parasites.