Molecular characterization of bovine rotavirus strains circulating in northern Italy, 2003-2005

A total of 232 stools collected from calves with rotavirus infection in herds located in northern Italy from 2003 to 2005 was investigated. Determination of the rotavirus G and P types was carried out using nested RT-PCR. G6 was the most prevalent genotype, accounting for 78.5% of samples, G10 accounted for 9.9% of samples and viruses of G8 type were found in 4.7% of samples. In 3% of samples, viruses were not classified due to concomitant infection with more G type strains, whereas viruses in 3.9% of samples could not be characterized with any of the G-specific primers used in this study. Most common P types were P[11] and P[5], accounting for 65.1% and 25%, respectively. In 2.6% of cases, samples reacted with multiple P-specific primers; no P[1] serotype was identified. The G6P[11] combination was predominant throughout the study period, i.e. 52.5% in 2003, 50% in 2004 and 40% in 2005. The incidence of G6P[5] increased from 13.1% in 2003 to 27% in 2004 and 25.5% in 2005. The G10P[11] combination decreased markedly from 18% in 2003 to 2.6% in 2004, rising again to 7.3% in 2005. G8P[11] viruses were similarly present in 2003 (5%) and 2004 (4.3%), declining slightly in 2005 (1.8%).