Circovirus is sometimes the problem - but not always.
Production systems with 10-35% death loss in grow-finish, 10-15% mortality in nurseries, and small family farms with continuous-flow facilities and subtle but nagging mortality throughout have all benefitted from the amazing response to commercial circovirus vaccines.
Get a proper diagnosis before assuming circovirus is the problem, because sometimes circovirus isn't the culprit after all.
Case Study No. 1
A 4,000-head contract finisher called to report his weekly death loss was rising due to circovirus. Working with the producer's fieldman, I necropsied several emaciated pigs with lesions, including adhesions around the heart and lungs, consistent with strep.
Other pigs had swollen spleens and livers, indicative of salmonella, while some pigs had very few gross lesions except for swollen lymph nodes and moderate levels of lung consolidation or pneumonia. None were typical of normal circovirus lesions.
I treated the pigs for salmonella, since diarrhea was one of the main clinical signs associated with fall-out pigs, and sent in tissues for diagnostic evaluation. I assured the producer and his fieldman that circovirus was not the issue, and reminded them that the pigs in question were vaccinated with a one-dose commercial circovirus vaccine.
To my surprise, the diagnostic results yielded high levels of circovirus in lung and lymph tissues. Several other organisms were found, including salmonella and strep. Pigs were negative for porcine reproductive and respiratory syndrome (PRRS) and swine influenza virus.
I shrugged off the circovirus results as pigs seemed to improve with the oral water medications for salmonella.
Unfortunately, death loss continued to rise after treatment, and I returned to the site two weeks later. Sure enough, there were wasting and fall-behind pigs. Extensive necropsies had lesions similar to the first set and again, did not look like circovirus lesions. Death loss and culls were approaching 10% seen earlier with circovirus. I resubmitted tissue samples with the same results — high levels of circovirus.
We initiated basic circovirus treatment — sorting and selling the fall-out pigs as quickly as possible.
I visited the nursery and noticed staff reloading vaccine belts with circovirus vaccine just prior to shipping pigs. That's when I found out pigs were being vaccinated for circovirus, but at 8-9 weeks of age instead of 3 weeks of age!
We quickly corrected the vaccination timing to 3 weeks of age. I believe the confusing necropsy signs were due to “partial but incomplete” vaccination protection. The remaining 85% of pigs in the producer's barns are performing superiorly.
Case Study No. 2
A producer called to report his circovirus vaccine was not working. He said pigs were melting into nothing, suffering from diarrhea and dying left and right on the finishing floor.
Over the phone, I reviewed the proper vaccine mixing and timing recommendations with the producer. Everything sounded in order.
A farm visit was scheduled and I shuddered to think this was a case of “vaccine failure.” Clinical signs on the finisher floor were just as the producer described: diarrhea with gaunt, emaciated pigs. Necropsies were consistent with signs of porcine proliferative enteritis or ileitis.
No tissues were submitted for diagnostic workup. Treatment through feed and water were implemented for ileitis, with good results, and vaccination for future placements was put in place. The producer and I were relieved circovirus wasn't the culprit.
Case Study No. 3
A new producer client, who called to say he'd read about circovirus in a magazine, had high death loss within the first two weeks postweaning and some sow breeding problems. He wanted to purchase circovirus vaccine at a time when the commercial vaccine was in very limited supply.
I learned from questioning him that no diagnostics had been performed. I explained it was unlikely circovirus was killing pigs so quickly in the nursery, and that I hadn't documented circovirus problems in any reproductive cases.
The producer agreed to bring some pigs in for necropsy. Post-mortem lesions with followup cultures were positive for Hemolytic E.coli. Water acidification and antibiotics successfully reduced the producer's postweaning death loss, and no vaccine was “wasted” on pigs that didn't need it.
Circovirus continues to “steal the show” from PRRS, but like its pesky counterpart, it is now getting blamed for “crimes” it didn't commit. We all know circovirus is a tremendously devastating disease. But before assuming it is always the issue, perform thorough diagnostics. If circovirus is implicated, work with your veterinarian for effective control strategies.