Longitudinal study of frequency of diarrhea and rotavirus species A in suckling calves from a small-scale family dairy farm in Brazil.

Neonatal diarrhea is a recurring health issue impacting the economy and productivity of dairy cattle herds worldwide. Bovine rotavirus A (BoRVA) is a major viral agent in the etiology of neonatal calf diarrhea. This prospective longitudinal study determined the frequency of diarrhea and BoRVA detection in suckling calves from a small-scale family-farming dairy cattle herd in southern Brazil. A total of 169 fecal samples were collected from 60 suckling calves at 7 (n = 60), 14 (n = 56), and 21 (n = 53) days after birth. The fecal samples were classified, based on fecal consistency, as diarrheic (n = 60), pasty (n = 83), or normal (n = 26). The detection of BoRVA RNA was performed using silver-stained polyacrylamide gel electrophoresis. The G and P genotypes of BoRVA circulating in the herd were determined by RT-PCR, followed by Sanger sequencing. BoRVA was detected in 46.7% (28/60) of the calves. Calves with diarrhea (26.7%, 16/60) had a higher detection rate of BoRVA compared to those with pasty (12%, 10/83) and normal (7.7%, 2/26) fecal samples. Regarding age, most of the BoRVA-positive calves were 7 days old (67.9%, 19/28), followed by 14 days old (25%, 7/28), and 21 days old (7.1%, 2/28). Two distinct BoRVA genotype combinations, G6P[5] and G10P[11], were identified in the herd. This study provides insights into the prevalence and circulating genotypes of BoRVA in a small-scale family-based dairy cattle herd in southern Brazil.