Novel approaches to rotavirus

July 10, 2015

4 Min Read
Novel approaches to rotavirus

Piglet diarrhea can take on many forms. We commonly see viral, bacterial and protozoal causes. Although a few causes of diarrhea can affect all ages of swine, most infectious agents only cause symptoms in young swine. The coronavirus infections such as porcine epidemic diarrhea virus have received the bulk of the newsworthy articles in the last year. We appear to be having an increase in cases due to rotavirus. Though not as severe as PEDV, these tend to mixed infections that many times contain three types of rotavirus with or without E. coli, PEDV and coccidiosis.

Rotavirus is a viral infection of swine affecting primarily suckling pigs and pigs soon after weaning. The villi in the intestine are tiny, fingerlike projections where the bulk of the absorption of nutrients and liquids occur. Without this absorptive area, the nutrients and liquids pass through the piglet.

Unlike the coronavirus infection that completely mows off these villi, the rotavirus infection functionally snips off the tips of the intestinal villi. In both infections, the pigs are able to regain absorbing nutrients and liquids once the villi grow back. The rotavirus-affected piglet mortality is much less because the affected villi grow back much quicker due to the partial snipping.

As with many infectious causes in all species, life used to be simpler. Rotavirus was once just rotavirus. Now we have rotavirus with subgroups A, B, C and E that infect piglets. We commonly see Types A, B and C in commercial swine. Since this diarrhea has a viral cause, antibiotic treatments are of no use. Immunizations of the sows and feedback have been common approaches to pass on immunity to the piglets for controlling the disease. Although this has worked well with rotavirus A and B, it has been less likely to help with rotavirus C and post-weaned pigs that are beyond the time period that the dam’s colostrum can prevent disease. Some of the rotavirus types are difficult to grow, so the traditional use of autogenous vaccines without typical antigen growth has been difficult. In these areas, we search for novel ways to limit the effect of the virus while helping the pigs through the course of the disease.

Case 1

We were called to a 400-sow farrow-to-finish farm with a history of diarrhea in suckling pigs. Diarrhea would begin three to five days after birth. About 25% of the litters would be affected, and nearly 100% of the piglets in an affected litter would show signs of disease. Mortality in affected litters was 20%, which was 10% higher than unaffected litters. Laboratory analysis of submitted tissues showed rotavirus type A. Since these pigs were quite young when showing signs and there were vaccines available, we chose to use a commercial vaccine. We also reviewed all feedback protocols on the farm.

Subsequent groups of sows were vaccinated with a modified-live, commercial rotavirus vaccine at five and two weeks prefarrowing. Sow groups that were vaccinated twice had litters with fewer than 5% incidence of clinical signs, and mortality dropped back to 10%.

Case 2

We work with a 2,500-sow farm that places pigs weekly into wean-to-finish facilities. The weaned pigs showed diarrhea in the weekly deliveries to varying degrees. We went back to the sow unit to determine the root cause. The sow unit reported very little concern with diarrhea in farrowing at that time. Laboratory work was done on a number of occasions with E. coli and rotavirus types A, B and C being diagnosed. In this round of deliveries, E. coli treatments with antibiotics against laboratory-confirmed antibiotic sensitivities were unrewarding.

Since we appeared to be dealing with a primarily viral case, we needed to look for some other approaches to control. In this case, we used a polyphenol called Grazix Porcine-W to treat pigs. Grazix W was used in the drinking water for three days in a row when pigs were placed. These polyphenols have been designed to reduce gut inflammation and minimize gut damage in times of insult. The clinical diarrhea did not stop completely in these weaning pigs. Mortality did go down in these groups. The other note made by growers was that pigs appeared to continue to eat through diarrhea concern, with a lower number of fallouts in the group.

Many forms of diarrhea occur in young pigs. Since diarrhea in many cases just looks like diarrhea, it is necessary to work with your veterinarian to get the proper diagnosis. Once you have an accurate diagnosis, a proper prevention or treatment plan can be established with measurements put in place to evaluate success. Antibiotics do not work on viral or protozoal causes, so immunization, antiviral/antiprotozoal, enhancing and supportive therapies are forms of control and treatment. Technology will continue to bring new ideas to immunization and treatment of viral concerns in the future.  

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