Prevalence of cryptosporidiosis and other enteric pathogens in calves in France: effects of rotavirus, coronavirus and E. coli vaccination and transmission routes.

Newborn calf diarrhea is one of the most important diseases in bovine rearing, with various infectious origins. The aim of the study was to evaluate distribution of enteropathogens in calves, effect of vaccination and document transmission routes of cryptosporidiosis. In this study, 1159 stool samples were collected from calves and dams in France in: i) an experimental unit benefiting from high hygienic conditions and ii) farms selected on historical context of recurrent neonatal calf diarrhea. Stool samples were screened for enteric pathogens using the Speed-V-Diar-5© antigen test (Virbac Diagnostics) and Cryptosporidium spp. were additionally identified by PCR, genotyped and subjected to multilocus variant analysis (MLVA). The effect of prepartum vaccination against bovine coronavirus, rotavirus and E. coli was evaluated. Results showed that Cryptosporidium was the most frequent enteropathogen, followed by bovine rotavirus. Only 16% of calves were symptomatic when systematic vaccination of dams was performed. The Speed-V-Diar-5© antigen test (Virbac Diagnostics) achieved sensitivities for Cryptosporidium detection ranging from 67 to 70% in symptomatic calves depending of sites. For the first time, C. mortiferum and C. meleagridis were reported in symptomatic calves. A large diversity of C. parvum genotypes was identified in calves, only from the zoonotic families IIa and IId. The IIaA15G2R1 genotype represented the large majority of identified genotypes. The comparison of genotypes between calves and dams suggest that vertical transmission was not the primary route of transmission. Calf-to-calf transmission and environmental contamination probably play important roles in the spread of Cryptosporidium among calves.