Rotavirus is a disease agent that all pigs are repeatedly exposed to early in life. The virus can cause gastroenteritis in pigs that ranges in severity from severe to subclinical.
There are many different strains of the virus. Pigs can be infected and potentially be made ill from rotavirus multiple times because there is poor cross-protection among different strains of the virus. Therefore, immunity against one strain doesn’t necessarily protect against another.
A group of researchers at the University of Minnesota Veterinary Diagnostic Laboratory, led by Dr. Kurt Rossow and Doug Marthaler, developed polymerase chain reaction (PCR) tests to detect the three most common rotavirus groups circulating in pigs. Designated Group A, B or C, these tests have been used for testing diagnostic cases over the past 15 months. Figure 1 summarizes the distribution of the viruses from these cases.
These data are not necessarily representative of the prevalence of these viruses in pigs, generally. However, the graphs illustrate a trend in prevalence by rotavirus group among the various age groups of pigs submitted to our laboratory as enteric disease cases.
It’s worth noting that Group C rotavirus is the dominant type detected in pigs less than 1 week of age. There is a pronounced shift toward a higher prevalence of Group A rotavirus, postweaning, with rotavirus detected in over 80% of the samples tested.
It is also worth noting that mixed infections are highly prevalent at all age groups, increasing with age. Currently, only a Group A vaccine is commercially available because the other rotaviruses are very difficult to grow outside of the pig.
Maximize Protection, Minimize Exposure
Controlling the severity of disease associated with rotavirus is a function of maximizing immune protection and minimizing exposure. Lactogenic immunity from the continuous nursing of sows with prior exposure to rotavirus provides effective protection against the disease in young pigs. Any disruption in nursing can interrupt this protection and leave the pig susceptible to disease.
The virus is quite hardy in the environment, but strict sanitation measures reduce the concentration of the virus and subsequent exposure for pigs. This is important for weaned pigs since the lactogenic protection is no longer available, and adequate active immunity may not have been developed in young pigs.
Click to view graphs.
Kurt Rossow, DVM;
Albert Rovira, DVM;
Jeremy Schefers, DVM;
Jerry Torrison, DVM
University of Minnesota Veterinary Diagnostic Laboratory