Pathogenic bugs residing in the pig's gut don't get the attention they deserve. That is, they don't until the loose stools and tail-enders become noticeable and days to market become a sore point.
While many producers and their veterinarians have been concentrating on respiratory disease complexes, enteric diseases - some diagnosed only in the last five years - have been creeping into nurseries and grow-finish barns. Pigs don't often die, they just don't gain.
Dyersville, IA, producer Ralph Weber was fighting a nagging scours problem in his 60-lb. pigs. Poor-doers would waste away in the pen, stalling at 75 lb. Uneven penmates and puddly manure were the only clues to intestinal distress.
Weber and his veterinarian, Bryan Myers, with Tri-Vet Associates, Farley, IA, treated the pigs for ileitis after necropsied pigs showed lesions suggestive of ileitis. The drug therapy they chose helped at first, then its effectiveness diminished.
"We tried different antibiotics in the water and feed with little or no results. The pigs were strung out. Average days to market at 250 lb. for some pigs went to 240 days," recalls Weber. "Once a month, any pig that was getting bad, we'd pull out and sell as a cull."
A diagnostic workup revealed they'd been treating the wrong disease. Instead of ileitis, the pigs had Porcine Colonic Spirochetosis (PCS), caused by Serpulina pilosicoli.
"Clinically, PCS can look like ileitis," notes Myers. "But they are two different entities. In this case, pigs weren't responding to 100 grams of tylosin, so we dug deeper. We didn't get death loss but pigs would scour soon after moving into the finisher and not gain. At market, some were two to three weeks behind. We posted pigs and received a diagnosis through histopathology (a test that shows tissue changes that are characteristic of disease). Reports were positive for PCS."
PCS On Upswing "PCS and ileitis are by far the biggest enteric problems I see in grow-finish pigs," points out Myers. "And I see a lot of enteric disease."
Gerald Duhamel, DVM, a pathologist at the University of Nebraska, has probably done more work on PCS than anyone in this country. He says it is likely the bug has been here all along - the industry just wasn't paying attention. "PCS can be difficult to diagnose because many conditions look similar and it can be found with other infections."
Often misdiagnosed as mild swine dysentery, PCS is a close cousin of Serpulina hyodysenteriae, the pathogen that causes swine dysentery. In 1998 research, Duhamel found that control measures effective for swine dysentery, including sanitation, should be effective against PCS.
Duhamel calls PCS a production disease because it doesn't kill pigs; it just delays their growth. If combined with ileitis or salmonella, PCS will seem more severe, recovery takes longer and the response to treatment is variable. "And we see variation in severity of the disease based on diets and ingredients."
High-Health Risk Are high-health herds more susceptible? "We have seen S. hyodysenteriae isolates from high-health farms," continues Duhamel. "Pigs are under less crowded, stressful conditions, so diarrheal disease is more like S. pilosicoli. It becomes endemic."
Weber's 300-sow herd is considered high health. Four years ago, he depopulated and repopulated the herd. New animal introductions are kept to a minimum. Ninety-five percent of the herd is bred artificially and he raises most of his replacement gilts.
The three nursery buildings are separate from the farrowing and all production is all-in, all-out. At 60 lb., pigs move to two finisher buildings, divided rooms holding 200 or 300 head/room.
Although respiratory problems are nearly nonexistent in Weber's finisher, the herd did suffer a Porcine Reproductive and Respiratory Syndrome (PRRS) problem last winter. "We pulled Mecadox out of the nursery feed to treat the respiratory disease," says Myers. "That problem is now under control and the only thing we're fighting is enteric disease." Weber reinstated the use of 50 grams/ton of Mecadox to control enteric problems. Mecadox is approved for the control of two enteric diseases, swine dysentery and salmonellosis.
"It seems we work and work to figure which vaccine or medication to use to solve a problem," says Weber. "But by the time we figure it out, they seem to cure themselves. PCS didn't do that."
"High-health herds are getting weird bugs more frequently," says Kent Schwartz, a veterinary pathologist with Iowa State University's diagnostic laboratory.
"High-health herds have often successfully broken the cycle of true pathogens like Actinobacillus pleuropneumonia, swine dysentery and atrophic rhinitis, so we're left with bugs that are opportunistic and may express disease when in a high dose or in naive populations."
Ranking Enteric Diseases Opinions vary among pathologists as to significance of the different enteric diseases. University of Nebraska's Bruce Brodersen, DVM, puts ileitis high on the list with Salmonella cholerasuis second.
At the University of Minnesota, Jim Collins, DVM, director of the diagnostic lab, ranks salmonella, proliferative enteritis and "non-specific colitis" as the big three enteric diseases. He only sees occasional cases of PCS.
Another hindrance to diagnosis is that the polymerase chain reaction (PCR) test used to detect PCS is not widely available at diagnostic labs or used often enough to understand what's going on, points out Collins.
Schwartz says PCS exists but he's not sure it's always a primary disease. Instead, it shows up as a secondary pathogen and causes problems. He says PCS prevalence is on the rise in Iowa.
According to Schwartz, the organism causing ileitis, Lawsonia intracellularis, is highly prevalent. But disease due to the organism is far less common. "The bug isn't new," he says. "Management has allowed it to cause disease more often."
Another emerging problem, although Schwartz hesitates to call it an enteric disease, is Postweaning Multisystemic Wasting Syndrome (PMWS). "A viral infection, PMWS predisposes the pig to other diseases but is not the primary agent of diarrhea. Infected pigs are not able to mount an immune response.
"PMWS is on the increase," Schwartz adds. "In my opinion, the disease didn't exist five years ago in U.S. pigs. The virus is doing something different."
Clinical signs of PMWS appear at 6-8 weeks of age. Segregated early weaning helps reduce incidence and severity, while high-density, continuous-flow production triggers the syndrome. PMWS also has been reported in Canada and other parts of the U.S.
Also on the upswing, says Schwartz, is Salmonella typhimurium. "Ten years ago, S. choleraesuis was 95% of our isolates. Now it's barely 50%. The balance has shifted dramatically. Economically, it may not be a huge problem but with emphasis on food safety and salmonella reduction, it becomes a major issue."
Brad Gramm, senior technical services veterinarian with Pfizer Animal Health, points out that S. cholerasuis is more of a respiratory problem, while S. typhimurium is strictly enteric.
"Enteric organisms are making a comeback," maintains Gramm. "With the focus so much on respiratory control due to Porcine Respiratory Disease Complex, these organisms are being ignored. Producers who took enteric drugs out of their rations are finding recurrence of enteric diseases.
"I also wonder if we'll be seeing more enteric problems in weaned pigs put on concrete slats," says Gramm. "Twenty years ago, we got away from scours when we put pigs up on woven wire."
Enteritis Mystery And then there's the non-specific enteritis. A bout with scouring nursery pigs in a 550-sow operation had Don Bowden, DVM, stumped. He co-owns the unit near Winthrop, IA. The diagnostic lab couldn't find a pathogen.
"Pigs are active and they eat but they go through a two-week period where they don't gain and they're not efficient. They'll run a fever of 104 degrees F but they don't appear sick other than loose stools," he explains.
"We cultured non-hemolytic E. coli, but Kent Schwartz said we could culture that out of any pig, so that wasn't the problem. Veterinarians at the diagnostic lab have told me they're sick and tired of trying to diagnose non-specific enteritis in nursery pigs. It's very frustrating."
Bowden, whose son Jeremy manages the nursery and grow-finish phases, says they tried chlorinating the water with Clorox to bring down the pH, "but we didn't get the response we wanted." The Bowdens tried adding a commercial citric acid product to the water, zinc in the feed and, last fall, a chlortetracyline/tiamulin program. Nothing seemed to help.
"We switched back to 50 grams/ton of Mecadox all the way through the nursery and two to four weeks into the finisher and the enteritis problem disappeared," says the elder Bowden.
Don Bowden believes the enteritis is herd-specific. "Herds having this syndrome, and we could describe symptoms nursery to nursery, it doesn't matter what feeding program they're on, almost to a nursery when switched back to Mecadox, pigs improved," he says. As a control measure, he continues feeding pigs the 50 grams/ton rate to 100 lb. and steps down to 25 grams/ton to 150 lb.