Ileitis: A disease worth preventing (part I)

Wide scope of problem demands planning

Why prevention?

Making perhaps the best case for prevention, rather than just control, is the pervasiveness of ileitis and its negative financial impact on an operation. Research shows that virtually all farms are at risk for the disease, leaving farmers to wonder not if ileitis will strike, but when. Using the National Animal Health Monitoring System (NAHMS) serum bank, researchers found the causative agent of ileitis, Lawsonia intracellularis, in 96.2% of all U.S. swine herds.⁽¹⁾ This represents up to 77.2 million pigs affected by ileitis annually, translating to an approximate annual loss of as much as US$1.7 billion, depending on disease severity, duration, mortality and culls.⁽²⁾

Not all animals within a group will experience the same degree of sickness at the same time. Typically, a few pigs break with ileitis, while the majority are still incubating with no apparent signs (although ileitis is already hurting performance).

So how did ileitis become so widespread? Researchers think L. intracellularis is transmitted via the fecal-oral route between infected and non-infected pigs. Transmission can also occur from sow to pig, pig to pig or through replacement breeding stock. Other disease-carrying vectors may include boots, birds and rodents.

Acute ileitis, which can cause sudden pig mortality, appears to be even more unpredictable than the chronic form of the disease. Acute ileitis, sometimes referred to as porcine hemorrhagic enteropathy (PHE), can appear in closed populations with high biosecurity. This alone warrants prevention strategies, as PHE can lead to costly outbreaks in expensive breeding stock. Unfortunately, PHE is only half the story. Chronic ileitis is the more common and costly form. However, this form often goes undetected until records show the disease's negative effect on feed efficiency, average daily gain and days to market weight-or lightweight pigs at barn closeout. This clearly presents the bigger threat to the nation's grow-finish pig population.

The case for disease prevention

Farmers and veterinarians continually face new health management challenges. Larger sow herds, multisourcing and new management techn- iques often impact disease prevalence and present- ation within herds.(4) Researchers continue to discover new disease interactions that affect healthcare decisions. For all these reasons, efficient farmers often choose to minimize production losses up front by focusing on disease prevention.

Three disease situations

Ileitis often "sneaks up" on farmers. To understand how this occurs, experts place pigs in one of three disease status categories: naïve, chronic/inapparent or breaking. (See graphic.) Naïve animals have simply not been infected with L. intracellularis, but are susceptible. After infection takes place, chronic ileitis may appear in incubating pigs showing subclinical signs such as reduced average daily gain. As the disease progresses, more outward signs such as diarrhea may occur. Finally, in the worst cases, an ileitis break can manifest in the acute form, causing pig death.

The bottom line: ileitis is a concern in any phase, making prevention a top priority.

One approved choice

In a recent study, 88% of swine practitioners said they were very likely or extremely likely to recommend a feed-additive program to prevent ileitis.3 The U.S. Food & Drug Administration has approved only one product to do this-Tylan® Premix.

Ileitis: A disease worth preventing (part II)

Unlike the days when most producers and veterinarians were simply acting like swine-health firefighters, today's industry is focused on preventing disease challenges rather than treating after they strike. Why? Because it makes good economic sense.

Stop the profit drain

"Prevention makes more sense than treatment because money has already been lost when you see clinical signs of ileitis," says Dr. David Bane, a US veterinarian. "When pork producers use prevention strategies for ileitis, they're going to be dollars ahead."

Preventing ileitis is critical to maintain profit margins because ileitis can worsen key production variables such as average daily gain, feed efficiency, days to market and even pig flow. (See table.) Studies show that average daily gain can decrease by as much as 35% ⁽⁵⁾ and feed efficiency can worsen by as much as 20%.⁽⁶⁾ Fortunately, more producers are now aware of the magnitude of this pervasive disease and are finding ways to prevent it before it causes economic harm.

Pathogen plays dirty

Since Lawsonia intracellularis, the causative agent of ileitis, is present in 96.2% of U.S. herds ⁽⁷⁾, preventing an ileitis outbreak is the goal of most producers. Unfortunately, fighting this widespread disease with typical biosecurity tactics alone isn't very successful.

"Lawsonia intracellularis lives in swine feces for one to two weeks," says Dr. Steven McOrist, a veterinary pathologist and leading ileitis researcher from Australia. "It only takes a small amount of feces containing about 1 million bacteria per gram to infect a pig. And the average pig feces has 10 million bacteria per gram, so Lawsonia is very infectious."

Dr. McOrist says the spread of ileitis via pig feces is particularly difficult to control since manure can cling to floor slats even when powerwashed. "Once a single pig becomes infected, dozens more can get the infection by pig-to-pig contact."

Since L. intracellularis is so easily spread, Dr. Bane says producers should consider using Tylan® Premix at 100ppm for 21 days to prevent and control ileitis. "This can stop the shedding of Lawsonia and keep other pigs from becoming infected. This is a low-risk strategy because preventing even a small loss from ileitis covers the cost of medication.⁽⁸⁾"

Profit bottleneck

Since ileitis-infected pigs suffer with poor performance, an increase in lightweight pigs is almost inevitable. Simply marketing these poor-doers outside a packer's preferred weight range is not an economically sound decision.

Holding sick pigs back to allow them to reach acceptable market weight is an option, but it can potentially compromise today's high-health, all-in/all-out units.

Keeping pigs healthy and growing is the only way to ensure barns keep flowing and production schedules are met. While there is no cure for ileitis, producers can turn to Tylan Premix to prevent and control ileitis. Tylan is the only product approved in the United States to prevent and control ileitis.

Cost of poor performance
Feed conversion loss Cost per pig 5% US$1.98 10% US$3.96 15% US$5.94 20% US$7.92	Average daily gain reduction Cost per pig 5% US$1.68 10% US$3.36 15% US$5.04 20% US$6.72
Assumptions: 22.68-68.04 kg pig growth, feed cost US$150 per ton, FCR = 2.42, ADG = .73kg

Performance-related losses can mount quickly when ileitis spreads through a herd.

Tylan® is a trademark for Elanco's brand of tylosin.

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Footnotes:
¹ Bane, D., Norby, B., Gardner, I., Roof, M., Knittel, J., Bush, E., Prevalence and management risk factors associated with Lawsonia intracellularis seropositivity in the U.S. swine herd, 1997.
² Veenhuizen, M., Elam, T., Soenksen, N., The potential economic impact of porcine proliferative enteropathy on the U.S. swine industry, 1998.
³ Independent market research, 1999.
⁴ Halbur, P., Porcine Respiratory Disease Complex, Iowa State University, 1997.
⁵ 14th IPVS Proceedings, 1996.
⁶ Porcine Proliferative Enteropathies, McOrist, S., Gebhart, C.J., Diseases of Swine, 8th Edition.
⁷ Prevalence and Management Risk Factors Associated with Lawsonia intracellularis Seropositivity in the U.S. Swine Herd. David Bane, DVM, Ph.D., Elanco Animal Health; Bo Norby, University of California-David; Ian Gardner, BVSc., Ph.D., University of California-Davis; Mike Roof, NOBL Laboratories; Jeff Knittel, NOBL Laboratories; and Eric Bush, USDA-APHIS.
⁸ Elanco data on file.

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