Strategies To Control Enteric Pathogens

Many managment and control efforts for enteric disease are remarkably similar to strategies of the past.

Over the last decade, pig production has changed dramatically. But enteric pathogens continue to have a major impact on modern swine production.

Some of the more prevalent pathogens of the past, such as swine dysentery, have been replaced with diseases such as F18 Escherichia coli (E. coli), salmonella and porcine proliferative enteritis (ileitis).

Yet many of the old diseases are still very common, including Transmissible gastroenteritis (TGE), rotavirus and coccidiosis.

Whether designing new pig production systems or learning how to operate existing units, many of the management and control efforts for enteric disease are remarkably similar to strategies of the past.

Pig Flow

For pig flow, the main goals are to put pigs of similar health status together, limit age spread on site and use all-out pig flow before repopulating a site.

Similar health is best achieved by limiting the number of sow farm sources per site. A balance between how fast a site is filled and the number of sources is also important. Porcine reproductive and respiratory syndrome (PRRS) has taught us to follow good pig flow rules. But that's also very true for many enteric diseases.

If it's not possible to keep pigs of the same health status together, try to equalize pig immune status before commingling with vaccines such as salmonella, E. coli and ileitis.

When flowing pigs out to the nursery/finish site, make sure sites are flowed with pigs of the same health status as the previous turn.


With enteric disease, it is critical that a stringent sanitation protocol is followed so when all the pigs are removed from the site, the disease agents are also removed.

Enteric pathogens are fairly hardy organisms. Under the right circumstances, many can live for months outside the pig (Table 1). Therefore, as a general rule, pork producers need to work harder on sanitation to rid the environment of enteric pathogens than they would for respiratory pathogens.

Heat and dryness are the two factors that kill enteric pathogens. Clearly, this is why many enteric pathogens seem to spread more easily in the cool, damp times of the year.

If you are having problems with enteric pathogens on your farm, reevaluate sanitation between groups of pigs. Sanitation fails when we fail to remove all of the manure and organic matter from a site prior to new pigs arriving.

Table 1. Pathogen Potential Survival Times
E. coli three months
Salmonella >nine months (if cool/damp)
TGE > one year (if cold)
Swine Dysentery 60 days (mice up to one year)
Roundworm Eggs several years

The first step to ensure that sanitation is done correctly is presoaking. Many producers have automatic soakers in the barns set on timers, which allow good soaking action and loosening of organic material without filling the pit with more water.

In addition, it is helpful to use detergents or soaps prior to pressure washing to help loosen organic material. This can be done with foam applicators or by wetting the barn down with soap prior to washing.

Next comes the most important job of thoroughly washing the barn and removing all organic material with the high-pressure sprayer. Focus on areas where you know it is difficult to remove all the manure. After this is done and the barn is allowed to dry, inspect the area using a flashlight and chalk (Table 2). Look for problem areas where you can typically see manure, such as under feeder lips and water cups, on the bottom of gate rods and in the joints between slats and stem walls. A stem wall is a concrete wall poured 6-12 in. from the floor up. Then a wood wall is constructed on top. This keeps moisture away from the wood wall. In wean-to-finish facilities, creep mats are especially important. In general, the mats are hard to wash and are the most frequent areas of contamination for new pigs entering the facility. In cases of F18 E. coli outbreaks in nurseries or wean-to-finish barns, the mats are often set out for an entire turn, and disposable mats (a 4 × 8 sheet of ¼-in. plywood) are used. After the turn, burn the plywood sheets.

Then rewash the problem areas found on the inspection, allow the barn to dry again and apply disinfectant.

Also, make sure that the loading chute and the non-pig areas of the barn (office, entryway) are clean and free from any organic matter.


Disinfectants are the final step to provide insurance that all the pathogens are dead prior to new pigs arriving.

Since drying is a very effective strategy for killing pathogens, ensure the barn dries both after the wash and the disinfectant application before pigs are allowed entry.

Disinfectants can be applied in many ways. A hose end applicator set at the correct dilution ratio is an effective strategy for applying disinfectant at the correct concentration. Another option is applying the disinfectant with a suction apparatus at the end of the high-pressure sprayer wand. This method needs to be calibrated so the right concentration is applied. Read the label of each product so the correct dilution is used. If your sprayer puts out 4 gal./minute and it takes 30 minutes to wet all surfaces, a total of 120 gal. needs to be used. If the correct dilution ratio is ½ oz. of product/gal. of water, a total of 60 oz., or nearly ½ gal. of disinfectant needs to be used.

Table 2. Barn Sanitation Checklist
• Inside feeder lip
• Bottom side, bottom gate rod
• Bottom side and inside water cup
• Creep mats
• Slat joints/grout lines
• Sides of slats
• Stem walls — sides and top
• Edge of barn next to stem wall
• Loading chute
• Office and barn entry area
• Supplies — boots, coveralls, gloves, panels, prods, syringes
Look closely at these problem spots. Use a flashlight and mark areas to be rewashed with chalk. Must not see any visible manure.

Also, disinfectants can be applied through foggers that fill the entire barn with a fog of the disinfectant. I like to rotate disinfectants on a quarterly basis and use a different class of disinfectant for each quarter (Table 3, page 32).


Enteric disease in pigs is actually a complex interaction between the number of “bugs” present in the environment, immunity levels of the pigs and concurrent stresses occurring within the pigs' environment.

We must be aware of the environmental stresses and deal with them on a daily basis. We can manage environmental stress by controlling the pigs' environment to the best of our ability.

One of the most common errors I see in nursery and finish facilities is a lack of understanding of the ventilation controller. It is critical to know how the controller works and if the settings are correct to provide pig comfort. Understand each stage of ventilation, the number of fans operating during that stage, the temperature each stage comes on and goes off, and how fast each stage ramps to 100%.

Table 4 on page 33 provides temperature recommendations by age of pig.

Follow these “Golden Rules” to keep pigs healthy and happy:

  • Keep pigs dry;
  • Keep pigs warm;
  • Keep pigs draft-free; and
  • Make sure pigs have fresh feed and fresh water.

I know it sounds too simple — but it's amazing how often these basic rules are broken and how much enteric disease is present because of these errors.

Keep Pigs Dry

In general, enteric pathogens cause diarrhea. When we have more diarrhea on top of the slats, we have more humidity in the barn. As stated earlier, drying kills many of these enteric pathogens. Therefore, it is critical that we keep humidity levels in the barn between 50-65%. Measure the relative humidity with a humidistat reader to get a feel for the correct humidity level.

Humidity levels are controlled in finishing barns by ventilation rates. If humidity levels are too high, the minimum ventilation rate is too low.

Table 3. Disinfectant Comparison
Chlorhexidine Chlorine Quaternary Ammonium Phenolic Cleaner Iodophors Formaldehyde Potassium Peroxymono-sulfate
Primary Products Nolvasan Bleach Rocal Annihilator Vetphene; Environ One Stroke Premise Cleaner Gentle Iodine Betadine DC&R Virkon S
Effective Against Viruses Yes Yes Yes Fair Yes Yes Yes
Speed of Kill Fast Moderate Moderate Moderate Moderate Slow Fast
Effective Against Fungus Yes Yes Yes Yes Yes
Sporicidal at Room Temperature No No No No Yes Yes
Effects of Hard Matter None None (unless alkaline) Reduced Speed of Kill None None (unless alkaline)
Effective with Cold Water Yes Yes Yes Warm Best Yes
Compatible With Anionic Surfactant (Soaps) No Yes No Yes Yes
Compatible With Non-Ionic Detergents Yes Yes Yes No Yes
Effectiveness in Presence of Organic Matter Good Very Poor Good Excellent Poor to Fair Good to Excellent
Detrimental Effects of Heat No Inactivated at >110° F. No No Inactivated at >110° F.
Most Effective pH Range Alkaline Acid Alkaline Neutral Neutral
Any Residue Action Yes Hypochlorites - No Chloramines - Yes Yes Yes Yes
Skin Irritation Properties Mild Moderate Mild Harsh Mild Non-irritating
Disadvantages - Inactive By Organic Debris Incompatible with Soaps, Limited Spectrum Strong Odor w/Coal & Wood Tar Distillate Expensive, Inactivated by Organic Debris Unreliable at Temperatures <65° F.

Keep Pigs Warm

Cold stress is a real stress on pigs. Observing how pigs are laying and behaving in their environment will help you understand if set points are correct. Normally, in nurseries and wean-to-finish barns, we provide mats in the zone heating area. This allows us to have the room a few degrees cooler. It is important that the pigs lie in the zone heating area. The creep mats are provided so a pig can utilize an area of the room with no updraft from the pit. The mats also provide a large feeding surface for the pigs the first week after weaning. Provide adequate mat space (.3-.5 sq. ft./pig) so all pigs can lie on it.

Table 4. Air Temperature (Varies by Pig Size, Pig Health & Season)
Week Temperature (degrees F)
1 84°
2 82°
3 80°
4 78°
5 76°
6 74°
7 72°
8 70°
Week Temperature (degrees F)
1 72°
2 71°
3 70°
4 69°
5 68°
6 67°
7 66°
8 65°
9 64°
10 64°
11 64°
12 64°
13 64°
Week Temperature (degrees F)
1 84°
2 82°
3 80°
4 78°
5 76°
6 74°
7 72°
8 70°
9 69°
10 68°
11 67°
12 67°
13 66°
14 66°
15 65°
16 65°
17 64°

Keep Pigs Draft-Free

Keeping pigs draft-free is accomplished by providing the right air inlet speed so incoming air gets mixed with room air before falling onto the pigs. The standard goal is 700-800 ft./min. out of the inlets. This should be measured with a high-speed air meter to make sure inlets are set properly.

Other ways that pigs can be exposed to drafts is for air to come into the facility through curtain holes, door leaks or broken inlets, or having minimum ventilation rates set too high on the controller.

Keep Pigs Hydrated

Keeping pigs hydrated with fresh, clear and cool water to drink on a daily basis is extremely important. Warm water is a common problem that I see in the early nursery phase. Flushing the water lines several times a day for the first several days until pigs are drinking well is important to maintain water freshness and keep water cool.

Check the flow rates and make sure that pigs have easy access to water. Flow rate should be ½ to 1 qt./min. and water pressure in the lines should allow the weaned pig to depress the nipple easily without getting splashed in the face with high-pressure water.

Water smell and taste is a problem in many nurseries, too — especially where antibiotics have been used routinely for water medication. Clean the lines before pigs are brought in. Adding bleach or organic acids to the water lines can work well. Many of the organic acids can be used even with pigs in the facility.

The only way to know if water is a problem is by getting in the pen and checking the temperature, flow rate, smell and taste early in the turn to make sure there are no complications that will stress the pig. Water should be tested for coliforms by sending a sample to a lab to make sure your well has not been contaminated. Review the adjacent environmental checklist in Table 5 for guidelines.


Biosecurity centers around the principle that you want to keep diseases out that you don't already have.

Figure 1 on page 34 provides a schematic drawing of potential sources of enteric pathogens on the hog farm.

The first obvious rule is to never allow pigs from outside the system in without a thorough health history and specific tests to prove that they carry no new disease.

Keep people out of the barns that do not belong there. And, make sure those who do enter the barns have been away from pigs at least overnight, and have nothing with them or on them that could carry enteric pathogens.

Require outside people and chore personnel to have specific farm boots and coveralls that are only worn in the barns. Service people will need to come to the barns for repairs on occasion. Make sure that they meet the downtime and biosecurity rules for your farm. They should be away from pigs at least overnight. Do not let them bring equipment that has been in other barns. If repair equipment is needed, make sure all items are cleaned, wiped down with a disinfectant and allowed to dry before entering the barns.

Table 5. Environmental Checklist
Humidity level:
50-65% relative humidity
Zone Heating:
Provide .3-.5 sq. ft./pig of mat space
90° F first 7-14 days
Inlet speed:
700-800 ft./min.
Feed quality:
Fresh — check bins and feeders
Quality — grind or pellet
Water Quality:
Pressure — nursery & w/f = 8-10 lbs./sq. in.
Flow — ½ - 1 qt./min.
Taste and smell

A recent study by Sandy Amass, DVM, Purdue University, clearly demonstrated how easily enteric pathogens such as F18 E. coli are moved site to site by people. Simply washing hands or both changing clothes and washing hands did not stop the spread of F18 E. coli from infected pigs to non-infected pigs. Only a complete shower followed by a change of clothes stopped the E. coli.

We often see F18 E. coli in flows of pigs with no history of F18 E. coli in the facility or flow. Never underestimate people as vectors for this disease.

Keep birds, rodents and dogs and cats out of the barn. A bird screen must be maintained. A mouse baiting program must stay current.

In addition, feed spills and bin pads should be kept clean to avoid attracting birds and rodents. This is very important in the TGE season.

Trucking biosecurity needs to be reviewed often. Make sure you understand where your trucks are being washed, the standard operating procedures of that truck wash and the status of the last pigs hauled on the truck.

Also, be certain the driver is wearing clean boots and coveralls; store on the truck in a clean area. The cab of the truck should be inspected for cleanliness. It is not uncommon in the winter months to get TGE on a nursery or finish site about five days after pig entry due to truck contamination.

The rendering box area is key to biosecurity because it connects pig farms with dead pigs from the same geographic area. It is important that all farm workers follow procedures for using the rendering box. Develop a written protocol to include these rules:

  • Only go to the dead box at the end of the day;

  • Wear disposable boots if possible or wear specific boots that do not go back into the barn. All coveralls should be laundered after going to the dead box. The equipment to remove dead pigs from the barn should not go to the dead box area; and

  • There should be a line at the dead box that the barn and the rendering truck do not cross. The rendering driver should enter on one side and pigs should be delivered to the other side.


If you suspect that your pigs have an enteric pathogen, seek veterinary assistance and get an accurate diagnosis so treatment can be targeted to the specific disease present.

Treatments revolve around killing the pathogen, keeping the pigs hydrated and creating an environment in the gastrointestinal tract that makes it difficult for the pathogen to multiply. Remember when pigs are acutely ill, their ability to eat feed or drink water containing antibiotics is limited.

Therefore, individual animal injections are important. But it is often difficult to spot every pig with diarrhea. Do a walk-through and count the number of loose stools per pen as a guide to decide if oral antibiotics should be administered.

In general, if there are greater than 3-5 loose stools per pen of 25-50 animals, water medication is probably advised.

Oral antibiotics for enteric diseases fall into two categories:

  1. Antibiotics that are in the gut and absorbed into the body, and

  2. Antibiotics that stay within the gut.

Review this information with your veterinarian, as some enteric diseases are confined to the intestinal tract only (ileitis), while others start in the gut but end up in the entire body (salmonella). Therefore, when treating with antibiotics, select those that are absorbed into the bloodstream. I often see enteric disease being treated with an antibiotic of little benefit to the condition.

Consult your veterinarian about specific drug choices for treatment of enteric disease. In general, good injectable choices include ceftiofur, tylosin and lincomycin. Good oral choices include neomycin, gentamicin and tiamulin. For viral enteric diseases (TGE, rotavirus), antibiotics will be ineffective unless there is a secondary bacterial infection. Often electrolytes help keep the pigs hydrated.

As with any infectious process in pigs, early detection and treatment are the keys. Nothing is more important than being with the pigs twice a day, and walking the barn in a manner that allows you to see every pig.


Prevention centers on feed-grade products and oral vaccines to help control enteric infections in swine. Feed-grade products such as high levels of zinc, probiotics, immune products and acidifiers have all been used to decrease the organisms' abilities to multiply within the gastrointestinal tract. Feed-grade antibiotics fed at specific time frames in the grow-finish period have also been beneficial at reducing clinical disease. Oral vaccination with non-pathogenic live organisms has been very successful in reducing clinical disease for salmonella, E. coli and ileitis.


Management and control strategies for enteric diseases in swine involve basic principles that are not very complex. It is important to recognize management of pig flow, sanitation, environment and biosecurity as well as strategic vaccination and medication. All can play a huge role in the health of the pig in the nursery and grow-finish systems.

But it is the ability to actually implement these tools on a daily basis by discussing them, and having written protocols, that sets many farms apart from others, and allows them to be more profitable and enjoyable to work in.