It’s back: Clinical outbreak of PCV2 in genetic herds reported
A clinical outbreak of porcine circovirus type 2 (PCV2) occurred this past winter in otherwise healthy, well-vaccinated herds, Clayton Johnson, DVM, of Carthage Veterinary Service, told Pig Health Today.
“These were very healthy herds…that destabilized for PCV2,” Johnson said. They’re genetic herds, at the top of the health pyramid, and are negative for pathogens such as porcine reproductive and respiratory syndrome virus and Mycoplasma hyopneumoniae.
The signs of PCV2 showed up primarily in young post-weaning pigs. They had classic porcine circovirus-associated disease. It was a primary challenge, not disease secondary to another infection. The farms were all stocked from different sources. Management at the farms was similar, but none of them shared staff and none used the same feed mill. The only commonality among the herds was their status as genetic herds, he said.
Flashback to 2006
“It felt in many ways like it was in 2006, 2007 again, except these were extremely well-vaccinated populations,” Johnson said, who added that commercial vaccines were used and the vaccination protocol was robust, including a full regimen for gilts and pigs.
“We weren’t doing any mass vaccinations with the sow farms…but that is something that we’ve been rethinking since theses outbreaks,” he continued.
The PCV2 vaccines have been “amazing” and have been used for years with tremendous success, Johnson said, but indicated that since the virus is evolving, vaccines that worked before may not be effective today on all farms.
A search for the cause of the outbreak has led to extensive research. Help is being provided by Kansas State University, which is performing next-generation sequencing. The predominant type of PCV2 circulating in US herds — PCV2d — has been found, but so far, sequences haven’t all been the same. PCV2a and PCVb are also circulating in US swine herds.
It’s too early to tell if other pathogens triggered the PCV2d outbreak, but testing has turned up one agent that will be investigated further. Johnson later explained that the agent found is parvovirus 7, but much isn’t known yet about this pathogen in swine or whether it has anything to do with the PCV2d outbreak.
“Number one, the pigs never lie. The pigs are telling us there’s a problem, so it’s going to force us to do some trial and error….We need to run pigs throughout challenge programs” with PCV2 and the parvovirus found as well as any other cofactors found, he said.
Antibody levels will need to be measured and maternal antibody interference considered, which is something that hasn’t been a concern before with PCV2 vaccines. But again, “the pigs are telling us something’s different [and] we can’t put our heads in the sand…” nor assume research conducted years ago is still relevant, Johnson said.
Posted on September 16, 2019