G and P genotypes of group A rotavirus from diarrhoeic calves born to cows vaccinated against the NCDV (P[1],G6) rotavirus strain.

A total of 71 group A rotavirus field strains, detected by polyacrylamide gel electrophoresis and enzyme immune assay, were submitted to genotyping by a multiplex nested-reverse transcription-polymerase chain reaction (RT-PCR). Faecal samples were obtained from calves with diarrhoea, between January 2000 and December 2001, from 14 dairy and beef cattle herds located in Mato Grosso do Sul, Sao Paulo and Parana States, Brazil. Thirty-five rotavirus field strains were detected in faeces from calves born to vaccinated dams with inactivated commercial vaccine containing the rotavirus Strain P[1],G6 from seven herds while 36 rotavirus field strains were obtained from diarrhoeic calves from other seven herds without rotavirus vaccination. Identification of P and G rotavirus genotypes was possible in 94.3% (67/71) of the strains. However, G genotype could not be identified in two strains, P genotype in another strain and both genotypes were not detected in a third strain. P and G rotavirus genotype associations were identified in rotavirus field strains from non-vaccinated and vaccinated herds at similar rates of 94.4% (34/36) and 94.3% (33/35), respectively. In non-vaccinated herds binary combinations were P[l],G6 (three herds, 12 strains), P[1],G8 (three herds; six strains), P[5],G6 (two herds; 10 strains) and P[l],G8 (one herd; four strains). The genotype P[l 1],G6 was the most frequent (three herds; 12 strains) in vaccinated herds, followed by P[5],G6 (two herds; three strains), and P[11],GS (two herds; eight strains). Mixed infections were observed in one non-vaccinated herd (two strains) and in four vaccinated herds (10 strains). Identification of binary combinations was not possible in one strain from non-vaccinated herds and two strains from vaccinated herds. Unusual genotypes were more frequent (91.4%) in non-vaccinated herds than those from prototypes of bovine rotavirus strains. Nebraska calf diarrhoea virus (NCDV)-like genotype was found in none of the rotavirus field strains detected in diarrhoeic calves born of vaccinated dams.