Cryptosporidium em bezerros destinados à exploração leiteira no Estado do Rio de Janeiro: padronização de técnicas moleculares, caracterização genotípica e influência do manejo na infecção

Abstract

Bovine cryptosporidiosis is of great relevance for Brazilian livestock, especially in young animals. Calves infected by Cryptosporidium may present low productivity, eliminating a great amount of infectious forms in the environment, especially those with clinical diarrhea. The aims of this study were: compare two DNA extraction techniques using a commercial kit and a researchers adapted protocol; analyze several annealing temperatures used in the PCRNested reactions for the gene target 18S and GP60, in addition to two types of DNA fragments staining in agarose gel (ethidium bromide and gelred); determine the occurrence of Cryptosporidium species and subtypes in calves up to one year of age, throughout PCR technique for the gene targets 18S and GP60 and analyze the influence of management modifications in the percentage of infection in calves. The standardization results demonstrate a higher sensitivity of the commercial kit and gelred, with the establishment of new temperatures for a better performance of the applied techniques. After sequencing, three species of Cryptosporidium were observed infecting calves at different ages. At pre-weaning fase (< 2 months) 10% of animals were infected by C. parvum, while 15% and 2% of animals in post-weaning fase (≥ 2 months) were infected by C. andersoni and C. ryanae respectively. Moreover, it was also possible to notice in this study that the implementation of some changes at the farm management could be of great help for reducing the dissemination of the disease between the animals and the environmental contamination.