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Understanding the Infection Chain Helps Reduce PRDC’s Impact

Veterinarians with Boehringer Ingelheim Vetmedica, Inc. (BIVI) introduced a new concept of disease control at the recent World Pork Expo.

Dubbed the Infection Chain, the concept is designed to minimize the impact of porcine respiratory disease complex (PRDC) in pigs and throughout the production system.

Brian Payne, DVM, swine technical manager for BIVI, explained how the production chain is very similar to the infection chain. “Often, the infection chain of swine pathogens are linked together.” He says it takes a systems approach to get to the root of the disease problem.

Eduardo Fano, DVM, swine technical manager at BIVI, focused on how the Infection Chain/Prevention Chain can prevent Mycoplasma pneumonia. There are three levels of production risks: level 1, replacement animals; level 2, sow herd; and level 3, wean-to-finish pigs.

The key factor is understanding the persistence of infection/shedding with mycoplasma. When there is sow herd instability, it can cause the production of more susceptible pigs, increasing the prevalence of the disease at weaning, he says.

“More sow-to-piglet disease transmission results in variability (in health status) between groups,” Fano says.

There is a connection between wean-to-finish prevalence and vertical transmission. “The higher the prevalence at weaning, the higher the clinical impact of Mycoplasma pneumonia is in finishing pigs,” Fano says.

In wean-to-finish pigs, prevalence at weaning translates into horizontal transmission downstream. “The industry has over-focused attention on the piglet vs the whole herd picture in understanding the prevalence picture for mycoplasma,” Fano says.

David Baumert, DVM, staff veterinarian at Cargill Pork, LLC, reviewed a case study of the PRDC Infection Chain in a production system. The study involved older herds that were mycoplasma positive but were very stable production flows.

Replacement gilts that had been moved into commercial sow herds turned up positive for mycoplasma, resulting in sow herd infection and respiratory disease instability, Baumert says.

Clinical disease occurred in the nursery, followed by significant economic losses in finishing that flowed through from the sow herd, he says. Multi-agent Infection Chain PRDC can result in an economic loss of $14-17/head.

It’s important to understand the pattern of circulation to understand the Infection Chain to target your intervention strategy, advises Reid Philips, DVM, PRRS technical manager at BIVI.

Baumert suggests introducing gilts early, 3-6 weeks of age, to avoid problems with mycoplasma and to deal with the issue of persistent infection in a herd.

“Pigs must be given a chance to develop immunity in order to give vaccine a chance to work,” he stresses.





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