Serological and epidemiological analysis of an outbreak of gastroenteritis among military recruits in Germany caused by Cryptosporidium parvum.

Background: Cryptosporidium spp. cause enteritic disease worldwide. Besides those patients with an impaired immune system, the general population is also at risk. Patients and Methods: Stool samples from participants of a military field exercise were tested for enteritic pathogens and sera were analyzed for Cryptosporidium-antibodies. All participants received a questionnaire for assessing possible risk factors. Results: After a 5-day field training, 201 of a total of 450 soldiers (45%) developed acute gastroenteritis. Immediate microbiological analysis ruled out enteropathogenic bacteria and viruses as the cause of the disease. Only after hospitalization of one of the patients diagnostic procedures were expanded to the identification of parasites and Cryptosporidium parvum was identified. In addition, 14 fecal samples of 217 specimens were subsequently identified in a Cryptosporidium antigen ELISA. A serological analysis of 214 sera revealed 72% positive for specific IgG antibodies compared with 17% of a control group of soldiers who had not participated in the field training (relative risk 3.38; 95% CI 2.39-4.77; p < 0.001). Analysis of specific IgM levels was less conclusive. Epidemiological analysis of questionnaires correlated drinking of tap water, or consumption of various meals with gastroenteritis. However, the source of contamination could not be identified. Conclusion: Cryptosporidium spp. can cause acute enteritis even in healthy, young adults as demonstrated by this outbreak. Using serological methods, the extent of the outbreak could be estimated in a retrospective analysis.