Opportunistic pathogens prey on newly weaned pigs infected with a primary virus

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Around 50% of pigs weaned today likely are infected with a primary viral pathogen, like porcine reproductive and respiratory syndrome (PRRS) or swine influenza, reported Cameron Schmitt, DVM, Pipestone Veterinary Services, Pipestone, Minnesota.

A primary infection “leaves the door wide open for a host of pathogens” like Haemophilus parasuis, Pasteurella, Streptococcus suis and Mycoplasma hyopneumoniae, he told Pig Health Today.

Enteric pathogens like porcine epidemic diarrhea, rotovirus and Escherichia coli also easily infect weaned pigs undergoing stress.

“A host of pathogens are literally waiting at the point of weaning,” Schmitt said. “The pigs are weaned and go into a new barn with 2,400 other pigs. They go into a spiral because they aren’t eating and taking in calories to fight an infection by themselves.”

Schmidt recommends the use of gruel or creep feeding in the farrowing crate prior to weaning to help pigs start eating. By taking in some calories, the pigs start to develop good gut health that helps them handle weaning stress.

Preventing secondary pathogens

The way to ward off opportunistic pathogens is to prevent, minimize or eradicate PRRS. “If you don’t get rid of the primary insult, unfortunately, you will end up in the antibiotic camp,” Schmitt stated.

“I’d love to go antibiotic free. But today, we aren’t there as an industry,” he continued. “We are getting better, though, and starting to regulate our feed-grade antibiotics.”

The veterinary feed directive (VFD) rule now includes several enteric and respiratory medications requiring veterinarian supervision. “The industry has utilized antibiotics for growth promotion. The VFDs will force some swine systems to make improvements that they chose not to make because they had this crutch (antibiotics),” Schmitt added.

“I don’t see a reemergence of diseases like dysentery or atrophic rhinitis though. We’ve moved beyond this with normal sanitation and eradication techniques. The VFDs are going to force us to be better,” he concluded.

In the future, new technologies will help the industry better handle weaning. Enteric biome sequencing is underway to examine a pig’s intestinal biome.

“We are just scratching the surface today,” Schmitt said. “In the next 5 to10 years, we will have a better knowledge of what’s going on with good and bad flora that trigger an event.”