Post-Weaning Scours in Pigs
Originally written by Spencer Wayne DVM; Peter Davies DVM, PhD; Jeff Bender DVM, MS. Special thanks to reviewers from the University of Minnesota, the National Pork Board, and the American Association of Swine Veterinarians.
This module provides a case study reviewing post-weaning scours and antibiotic use in swine. The module will present an outbreak scenario and highlight treatment measures for post-weaning scours as well as proper antimicrobial use and stewardship in veterinary medicine.
- Review different treatment options at the time of clinical diagnosis and after diagnostic confirmation.
- Identify the process for diagnosing post-weaning diarrheal and neurological diseases in pigs.
- Demonstrate understanding of how disease patterns and treatment success in swine production are affected by time and random variation.
- Review the concepts of the Veterinary Client Patient Relationship (VCPR) and the Animal Medicinal Drug Use Clarification Act (AMDUCA).
- Clinical Signs and Diagnosis
- Immediate Therapy Timplemented and Diagnostic Results
- Optional Reading
- Follow-Up and Prevention
- Going Forward
Clinical Signs and Diagnosis
One of your clients, Charlie McSqueel, calls you while you’re brewing your morning coffee. “Can you stop out at my east wean-to-finish barn today? I don’t know what’s wrong, but it’s got me really worried.”
You recall the place Charlie is describing. The wean-to-finish barn was built about four years ago. Charlie has a contract to buy 12-pound piglets (weaned pigs) from a large sow farm in the neighboring county. Every 25 weeks he receives a group of 2,000 pigs from this supplier. After about eight weeks, Charlie sells half of the pigs as 50-pound feeder pigs to another farmer. The rest of the pigs in this wean-to-finish barn are kept in the same building until they reach their final slaughter weight of 260 pounds, hence the name “wean-to-finish barn.” Charlie also has an identical barn just one mile to the west: soon after the east barn is filled, he fills the west barn with new pigs from the same source, so on average they are about two weeks younger.
“They’re dying!” he exclaims. “Two days ago it was five pigs, yesterday it was 12, and this morning I pulled out 24 dead pigs. I bet there’s another dozen that’ve died since I was in there! They’re all sucked up and skinny, and some of them look like they’ve got ‘streppy’ brain problems. The last group we had in this barn had a lot of problems too. We lost a lot of them, but I thought it was because of the PRRS (porcine reproductive and respiratory syndrome) outbreak that the sow farm was going through and assumed it was some kind of Strep suis. We’ve got to get a handle on this!” Sounds pretty dramatic. You tell Charlie that you’ll meet him at the barn at 2:00 that afternoon.
Clinical Signs—Post Mortem Exam Results
You see Charlie pacing by a pile of dead pigs as you pull up next to the barn. It looks like he’s added more than a few since you spoke with him. He greets you quickly. “No time for small talk, Doc. This is some serious stuff. I don’t know what to do.”
You walk over to the pile of dead pigs. “How many weeks have they been placed, Charlie?”
“Four weeks this Thursday.” The pigs were just like he described. You see that the pigs:
- have normal skeletal size and fairly normal fat and muscle condition.
- are very gaunt with their sides sucked in and are severely dehydrated.
- have eyes that are sunken well into the sockets.
- are slimy and wet.
You walk through the west wean-to-finish barn and everything seems to be great. Pigs are active, there is no evidence of diarrhea, you hear no coughing. No dead pigs. Whatever is affecting the pigs in the east barn does not seem to be here.
Back to the east barn. You open the door and hear nothing except the pit-fans whirring under the slatted floors. The pigs are not up and moving around like they were in the west barn. They’re not up investigating the new guest in their house. They’re not fighting over the feeder. They’re not woofing and barking at each other. They’re just laying there looking at you. You see several with wet hind legs and tails flicking over irritated, red anuses. Many pigs are gaunt and skinny. Some are stumbling and two are on their sides, paddling their legs, with neurological signs. You see small puddles of extremely watery diarrhea in each pen. You pick up one of the pigs and while you’re holding him, a stream of light-brown, watery diarrhea ejects from the pig.
You walk up to a pile of dead pigs in the alley and count around 20. All are gaunt and skinny, all have sunken eyes. You bring out your knife. Well into posting your fifth dead pig, you notice a common theme. The lungs look fine, with no obvious bacterial pneumonia. The pigs appear to have been eating well, and their stomachs have some feed in them. But…
The small intestines are a different story. The small intestine is completely filled with a thin fluid, and there is generalized edema throughout the mesentery. You cut into a few thin-walled loops of bowel, and milky fluid pours out. Good grief, you can see why the pigs looked dehydrated—so much fluid was inside the intestines!
Photo: The innards of a pig displayed during a post, holding up the small intestines for analysis. The small intestines are filled with fluid and there is generalized edema throughout the mesentery.
A farmer holding pig with irritated red anus.
A pig with its back facing the fence has light brown diarrhea. This is deduced from the wet, feces-covered back end, diarrhea on the gate directly behind the pig, and diarrhea on the ground directly behind the pig. This same pig is also hanging its head.
The alley with around 20 dead pigs that are gaunt and skinny with sunken eyes.
Immediate Therapy Timplemented and Diagnostic Results
You tell Charlie what you think is going on. You explain how F18 E. coli causes disease. He looks at you, maybe a little unimpressed, and asks, “So what do I do? What do I give them? They can’t keep on dying like this, Doc!”
Before you leave the farm, you consider your relationship with this farmer. Your role here is most definitely that of “problem solver” and you have been made acutely aware of the situation at hand. However, you know that there are times when the veterinarian is not as in touch as they should be, and in these situations, the farmer is making disease and treatment decisions that they shouldn't. You know that a valid VCPR is key to proper diagnosis and responsible treatment of disease. You run through the tenets of a valid VCPR.
For more information on the veterinarian/client/patient relationship, please see “Additional Resources” at the end of this module.
You walk to your truck and start filling your cooler with tissue samples from three acutely infected pigs. You think you know what the lab results will say, but you’ve been fooled before. That’s why you’ve taken a comprehensive tissue sampling from each pig (both fresh and fixed samples)—you don’t want to miss the bug if it’s there.
Now: what tests do you want the lab to run? There are a lot to choose from. Some make sense in this situation and some do not. Different diagnostic labs charge differently for their workups, but regardless of this, it's important to review your diagnostic options and consider the usefulness of each.
For more information on the diagnostic sampling, please see “Additional Resources” at the end of this module.
Diagnostic Results Review
You leave the farm after going over the treatment protocol with Charlie. He is understandably worried, but you manage to sell him on the idea that you can do some things to prevent this problem from happening in his next groups placed. You ask him to call you in four days with a progress report, and you tell him that the diagnostic results will be back at about the same time.
When the lab results are in, you see that you were right: it looks like F18. The jejunal epithelium was covered by rod-shaped bacteria. The lab cultured predominant hemolytic E. coli. Genetic analysis showed it to be a toxin-producing F18 strain (Shiga toxin IIe and Stable Toxin A). A Strep infection would have shown some distinct lesions in the brain, but they weren’t there. The tissues were negative for PRRS and swine influenza. F18 is now the definitive diagnosis.
You examine the antibiotic susceptibility profile. Looks like you picked the right drugs. You knew that with F18, antibiotic resistance could develop quickly in a population or at a site. However, just because gentamicin worked this time, it won’t necessarily work next time. You run through the list of antimicrobial agents this lab screens for susceptibility to.
The diagnostic lab has given you a table of antimicrobial agent resistance profiles from ß-hemolytic E. coli isolations over the years. This table gives you some confidence in the agents you might want to use.
|Resistant||Susceptible||Grand Total||% of isolates susceptible|
On more than one occasion, you've seen profiles come back showing no effective antibiotics against F18 E. coli. You recall the Animal Medicinal Drug Use Clarification Act (AMDUCA): when the approved swine drugs are not effective according to the algorithm, the law allows for a veterinarian to make appropriate use of this decision-making flow chart. You review the AMDUCA requirements (see link on next page).
- General guidelines on AMDUCA
- Guidelines specific to antibiotic use in swine
- List of Prohibited Drugs in Food Animals
- FDA Center for Veterinary Medicine
Follow-Up and Prevention
One Week Later: You haven’t heard from Charlie yet, so you have no idea how the pigs are doing. You dial him up while scanning over the diagnostic lab report. Charlie answers and you ask how things turned out. “Well, I injected 'em all and ran that stuff in the water. They stopped dying within two days, but Doc, they look rough. I still see a little scouring and the cough is gone, but man, they look rough. Like they’re stunted.”
You pause to consider what he’s said. Yes, this has played out like a very typical F18 outbreak. Rapid onset, high mortality, and then large numbers of crummy-looking pigs that take a long time to recover. You tell him, “The lab found F18 and that fits with what you’re describing, Charlie. The drugs you used were a good choice, but it can take a while to recover from the damage from an outbreak like this. Those rough pigs won’t snap back immediately. How’s the west barn?”
“Oh, they look great. I guess it’s just a problem with the east barn, huh?”
You know that the west barn had dodged a bullet. Maybe it was a contaminated trailer that happened to haul pigs to the east barn, maybe it came with the pigs from the sow farm, and there was enough pathogen-load in the east barn pigs to ramp up the problem. Maybe the pigs were stressed… Was the east barn’s feed mixed correctly, or maybe the pigs were all chilled and loaded into a damp barn? There are a lot of questions, but you know that wishful thinking will not keep the west barn safe. You and Charlie need to do some preventive planning.
Prevention Plan Created
What do you do to get ahead of this thing? It’s two days later and you drive up to Charlie’s house.
Charlie greets you with a cup of coffee. “That east barn still looks a little rough, but they’re coming around. Wish we could have avoided that. We won’t be able to do any better than 25% mortality on that group now. That’s a lot of dead pigs.”
You sit down at the kitchen table and look for a blank piece of paper. “Charlie, I don’t know how the bug got into that barn, but it’s there now and it’s probably going to make its way over to the other barn on the next turn. I’ve seen this many times, and I’ll tell you everything I know to control it.” You get your pen out. “Let’s draw this thing out so we can see what our options are.”
Before you get any further, Charlie interrupts, “I think we’ve got the answer. Why don’t I just hit them hard with those same drugs, just earlier so they never get sick?”
What a teachable moment! You take Charlie through your experience with other E. coli strains that developed resistance very quickly. You bring up the concept of ‘judicious use of antimicrobial agents’ and the increased cost of having to rely on antimicrobial agents to control disease when other strategies would be less expensive and more effective.
A bottle of Escherichia coli avirulent live culture vaccine, brand name Edema Vac 500.
There are a lot of things to try:
- Vaccinate for F18 E. coli
- Improve the sanitation
- Improve the ventilation
- Install nonhumid zone heating
- Carefully use antimicrobial agents
- Sustain the zinc level in the feed longer
- Treat any concurrent disease (e.g., PRRS, Salmonella, Rotavirus)
- Ensure water quality
- Use disposable-compostable floor mats
- Try specialty feed additives (for example, antibodies from eggs)
A heat lamp installed and hanging from ceiling.
A bag of Zinc Methionine Complex, brand name Zinpro 100.
A group of pigs huddled together on a disposable-compostable floor mat.
Pails of specialty feed additive Eggstend F18.
What Will We Do Going Forward, and What Would the Result Likely Be?
You know that this producer has tried some of these interventions in the past to control his enteric disease. The current situation is much more severe than previously, so you push for implementing several of these measures simultaneously. Each step should help to knock the problem down to a more manageable level and maybe eliminate it altogether.
- Diagnostic lab results from necropsy tissue samples confirmed F-18 E. coli, specifically in jejunal epithelium.
- Antibiotic susceptibility testing showed resistance to several antibiotics as well as susceptibility to several other antibiotics.
- The Animal Medicinal Drug Use Clarification Act (AMDUCA) allows for a veterinarian to make appropriate use of the decision-making flowchart when approved swine drugs are not effective based on antimicrobial susceptibility testing.
- Prevention plans are important for disease control, especially F-18 E. coli.
- Examples of prevention plan measures include vaccination for F-18 E. coli, improving sanitation and ventilation, installing nonhumid zone heating, careful use of antimicrobial agents, sustain the zinc level in the feed, treat any concurrent disease (e.g., PRRS, Salmonella, Rotavirus), ensure high water quality, use disposable-compostable floor mats, and try appropriate specialty feed additives.
There are no references used for this section.