Centre for Advanced Disease Research and Diagnosis (CADRAD), Indian Veterinary Research Institute, Izatnagar-243122, India.
Rotaviral diarrhoea is one of the most important diseases in world, a cause of death of millions of children in developing countries and causing great economic loss to livestock industry. Bovine rotavirus (BRV), is a segmented ds RNA virus of family Reoviridae and is leading cause of neonatal calf diarrhea. Rotavirus infection, a non-viremic disease, causes diarrhea in young calves. Infection mostly occurs through ingestion of faeces-contaminated material. Incubation period is very short. Affected animals show watery diarrhea, and fatal results are often observed due to severe dehydration. Pathological lesions reveal mucosal congestion and catarrhal exudate in lumen of small intestine. Concurrent infection with other pathogens can potentiate BRV disease severity. Diarrhoea occurs due to malabsorption due to destruction of enterocytes, activation of enteric nervous system and secretion of viral enterotoxin, NSP4. Point mutations and gene reassortment can also take place with BRV, as seen in avian influenza viruses, generating diversity of rotaviruses. BRV can be isolated in both primary cell cultures (calf kidney cells) and cell lines (MA 104, MDBK or PK-15). For viral diagnosis various tests are employed viz. electron microscopy, electro-pherotyping, antigen capture ELISA, dot-immunobinding, immuno-fluorescence, immunoperoxidase, passive HA and latex agglutination tests. Virus characterization and molecular typing is performed using RT-PCR, RFLP, nested RT-PCR, multiplex-RT-PCR and dot blot hybridization tests. Newer technologies include sequencing and oligonucleotide microarray hybridization, which are sensitive, specific and capable of vividly discriminating mixed rotavirus infections. For prevention and control of BRV in young calves, good management practices alongwith vaccinating dam with inactivated BRV vaccine a few weeks before parturition, is followed globally. Mucosal immunity is more important in providing resistance to infection, therefore, critically more important is the presence of antibody via colostrum in gut lumen of young calves. Now there is a trend for development of new generation efficacious vaccines like DNA vaccine using group specific VP6 protein; subunit vaccines employing BRV-VP4 protein; virus-like particles (VLPs), containing VP2, VP6 and VP7 proteins; and plant-based edible vaccine expressing immunogenic BRV-VP4 antigen inducing higher antibody titers in serum as well as colostrums.
