Note from Bovine Veterinarian Editor Geni Wren: Even though this article written by my colleague, Pork Editor JoAnn Alumbaugh, live from the American Association of Swine Veterinarians’ conference, is about disease transmission in swine, the basic tenets of what these experts are saying hold true for beef and dairy cattle as well. Protection is not just about vaccination, it’s about humans, handling, biosecurity and good management. And that crosses over all livestock in our care.
Boehringer Ingelheim (BIVI) hosted its Swine Health Seminar as a kick-off to the 44th annual American Association of Swine Veterinarians meeting being held in San Diego this week. Dr. Edgar Diaz discussed the “infection chain,” and the need to include vertical transmission in discussions related to disease. Vertical transmission refers to generational transfer of disease (from sows to pigs through the sow’s milk, placenta, etc.), while horizontal transmission is from one individual to another through contact.
“It’s not as simple as just vaccinating the pigs,” says Diaz. “We put a lot of effort into vaccinating at pre-weaning or in the nursery, when we need to be looking at interventions before and after that time.”
Dr. Dale Polson followed up with a presentation on vertical transmission of Porcine Reproductive and Respiratory Syndrome (PRRS), which continues to cost the pork industry millions of dollars every year.
“We’re still dealing with PRRS virus, but we’re older and wiser, and we’re less likely to overlook the vertical transmission of PRRS,” says Polson. “PRRS control efforts will not – and cannot – work in a sustained and effective manner without considering vertical transmission. Further, without exception, management of vertical transmission is a non-negotiable for effective PRRS control.”
Some of the tools used by veterinarians to control vertical transmission are vaccines, bio-management and bio-containment, explains Polson, but one of the biggest factors is people. “Good people can make a big difference in how PRRS is managed,” he stresses. “People, collectively, need to collaborate to effectively manage PRRS’ vertical transmission.”
Dr. Darin Madson has done extensive research on porcine circovirus 2 (PCV2) and vertical transmission at Iowa State University. He reports that most herds and swine production sites in the United States are positive and/or infected with PCV2. Infection is often protracted and transmission, in general, is nasal-oral or fecal-oral, however it can be secreted or excreted.
“Dam infection can occur at any time,” he says. “The virus is robust, hardy and difficult to kill. It lasts a long time and is very different from the PRRS virus. It will be there a long time no matter how hard you try to get rid of it.
“With dam infection, you get fetal infection,” he continues. “PCV2 can cross the placenta and infect fetuses. It can be shed for a least 27 days post-partum, and it is infectious, but the significance of this route in unknown.”
Dr. Jim Lowe rounded out the program with a general discussion of the industry and how it deals with animal-health issues. He believes veterinarians and producers need a better understanding of the role vaccine plays: It can improve clinical signs but it doesn’t stop transmission.
“It’s a high-cost business today,” he says. “With high costs you have high risks, and we have to make sure we’re making decisions that generate the right kind of profit for our producers.
We need to provide science-based solutions that are repeatable over time.”