Cases illustrate this common virus was the sole infectious culprit.
Rotavirus is an enteric virus that is common in the swine population. The disease is very mild, except in very young pigs or in animals that are naïve. Exposure occurs via the oral route from fecal contamination of the environment.
In the newborn or very young pig, this exposure takes place from the pen or crate or from the surface of its mother's body. Clinical signs of the disease occur within hours after exposure, with watery diarrhea being the prominent sign. The virus attaches to the villi of the small intestine and causes damage, which allows fluid to escape the body into the lumen of the gut.
In the early stages of the disease, the pig will still nurse but is becoming dehydrated. Frequent diarrhea caused by fluid loss causes rapid dehydration and death.
Case Study No. 1
A 1,250-sow, farrow-to-wean farm was involved in a porcine reproductive and respiratory syndrome (PRRS) elimination program. No animals had been introduced into the herd for over four months and manure feedback was not being done. There were no prefarrow vaccinations being given. Weaned pigs were negative for PRRS by both polymerase chain reaction and enzyme-linked immunosorbent assay tests.
Over a period of 4-6 weeks, there was a gradual increase in clinical diarrhea in 2-5 day-old piglets. Gilt litters were first affected and then older sow litters were involved. Oral and injectable antibiotics given to affected pigs did not improve the clinical picture. Mortality was not significant, but pig quality declined in the affected litters.
The farm was farrowing large numbers of sows and power washing with cold water only. Ready-to-farrow sows were being loaded into wet crates. Fall weather and temperature variation also caused stress on newborn pigs.
Diagnostics were performed on newly affected pigs, and the only finding was rotavirus. The pigs were negative for PRRS, E. coli, salmonella, clostridium and coccidiosis.
After much discussion, it was decided to provide manure feedback from the farrowing area to the sows due to farrow. The power washer was repaired so hot water could be used for washing. After washing, farrowing rooms were disinfected and allowed to dry before placing new sows. Staff was reminded to scrape manure out of farrowing crates several times a day for sows not yet farrowed. Within three weeks, the diarrhea virtually disappeared.
Case Study No. 2
A 600-sow, farrow-to-wean batch farm produced about 96 litters every four weeks. The farm had internal multiplication with some replacement animals produced in each batch. Gestating sows were housed about half in pens and half in stalls. The farm used a commercial E. coli vaccine in sows prior to farrowing.
When the diarrhea in young pigs occurred, the owner tried both oral and injectable treatments, but had very poor response. There was low mortality, but weaning weights declined and overall pig quality was compromised.
When the third group in a row had litters that showed diarrhea, I was called in. Tissues from untreated pigs were collected and submitted for diagnostics. Porcine rotavirus was the only finding. Further investigation revealed that the litters being affected were from sows that gestated in stalls. It was suspected that sows or gilts that gestated in pens were able to cross expose/immunize each other from oral/fecal exposure, and their litters were unaffected.
The owner decided to give manure feedback from farrowing to sows prefarrow to accomplish exposure. The subsequent batch that farrowed had no litters with diarrhea. Farrowing crate scraping and collection of material continues to be done for each batch five days a week for 2-3 weeks. This feedback process has continued to provide excellent control of neonatal diarrhea caused by rotavirus.
There are some commercial vaccines available for control of rotavirus. With many herds trying to minimize effects of PRRS, feedback exposure methods have been curtailed. Thus, segments of many sow farms have females with minimal immunity to rotavirus.
Whenever there is any health challenge, it is very important to communicate with your veterinary advisor. A thorough investigation of all aspects of the farm should be done. As was shown in these two cases, each farm is unique, and clinical disease can occur even when procedures seem to be correct. Good records and clinical examination are vital to finding the causes of the problem. Accurate diagnostics and critical farm evaluation can determine the best course of action.