Isolation and typing of Rotaviruses caused Calf Viral Diarrhea disease in cow farms of Tehran province

Rotavirus group A is the major cause of diarrhea in many animal species. Mortality of calves under one month due to rota viral diarrhea is prevalent in the country and brings enormous economic losses each year. Calves viral diarrhea is common in many regions of the country and a significant percentage of diarrheic calves infected with rotavirus. For rapid diagnosis of disease , the serology and molecular techniques can be used but for isolation and identification the causative virus due to specific structural and biological properties of the virus, the specific method in cell culture and cell lines, is required. Since no causative virus isolated and there is not accurate information on dominant serotype or serotypes in the country, due to the importance of this disease in health and livestock economics, tring in various aspects such as epidemiological studies, methods of detection, isolation and identification of genotype and efforts in preparation of vaccine by use virus strains isolated, it is very important and help to control, survellance and probably eradication the disease and the economic losses caused by this disease will largely prevented. Due to availability of vaccine production technology to become widespread of prevention and internal production of vaccine, needed to isolation and typing of circulating rotavirus strains. In this study, 41 diarrhetic feces samples was prepared from calves up to the age of one month from the industrial and semi-industrial farms in Tehran and Alborz province (townships of Shahriar, Eslam Shahr, Robat Karim, Savojbolagh, Varamin,Rey, Pakdasht and Damavabd) that were positive in the diagnosis of rotavirus infection by RT-PCR with primers VP6 gene. After preparation they are inoculated on MA104 cell culture, that best introduced by OIE , for isolation of rota virus. The tube cell cultures and constant flasks cell culture were used. After one early passage and four blind passages, in 13 samples (Shahriar, 5 Robat Karim, 3 Eslam Shahr, 1 Pakdasht) the cell damages (CPE) was observed. Eligible cultured cell with CPE to confirm the diagnosis were examined by RT-PCR. At first the two-step RT-PCR using primers VP6 gene of group A rotavirus were used. All of the samples were positive. For genotyping G, Semi nested PCR was performed using primers VP7 gene. In this study, 11 samples in genotyping, were G6, and two samples were G10. So in production of suitable vaccine for prevention of rotavirus diarrhea in these areas must be used these two type as predominant rotavirus strains.