Bovine cryptosporidiosis in Denmark. 1. Prevalence, age distribution, and seasonal variation.

During the period 1.7. 1981-30.6. 1983 the prevalence of infection with cryptosporidia in Denmark was studied by examination of autopsy material from 3358 animals and feces samples from 911 animals. The material was submitted for routine diagnostic examination. Diagnosis of Cryptosporidium infection was based on the detection of oocysts in smears from the mucosa of the small intestine, from colon contents, or from feces samples. Smears were stained by a modified Ziehl-Neelsen technique. Infection with cryptosporidia was demonstrated in 471 specimens, representing 11% of the total of 4269 animals examined. Highest prevalence was found among calves of 4-30 days old, with a peak in the age group 8-14 days (24.8% positive). Low-grade excretion of oocysts was observed in 2-5% of animals older than 1-2 months. No distinct seasonal variation was observed, but there was a tendency for the frequency to be highest in the 2nd quarter of the year and lowest in the 4th quarter.