Edema (Oedema) disease is a mostly acute, often fatal, enterotoxemia. The mainly affected production stages are recently weaned pigs, pigs during nursery and early finishers. It´s caused by Shigatoxin (Stx2e), which is produced by specific virotypes of Escherichia coli. The disease is often characterized by edema at specific sites, sudden unexpected death, and occasionally by neurologic signs related to lesions in the brain.
While the Shigatoxin (Stx2e) occurs worldwide, prevalence data from healthy herds are rarely available. Though a currently published longitudinal study in 3 healthy US farms observed a high prevalence (68.3%) of Shigatoxin-producing Escherichia coli (STEC) in pigs raised for pork production. The usual detection rate of Stx2e in suspected cases of post weaning disorder is around 20% up to 60%.
The causative agent of ED is Shigatoxin-2e. It´s encoded and produced by a specific virotype of Escherichia coli (EDEC) and occurs worldwide in diseased pig herds as well as in healthy herds. The primary habitat of E. coli in pigs is the gastrointestinal tract. Outside the intestine E. coli are found in fecal-contaminated feed, water, water from water pipes contaminated by biofilm, soil, and the environment of the pig barn. The infection happens via the oral route. When ingested in sufficient numbers, E. coli causing ED colonize and then proliferate rapidly to attain massive numbers. Colonization develops over 3-6 days and requires attachment of fimbrial adhesins to complementary receptors on the small intestinal epithelium or in the mucus coating in the distal jejunum and ileum. Stx2e is absorbed into the circulation and causes vascular damage in target organs.
Gelatinous edema show up at different locations, e.g. in the mesocolon (picture). Edematous swelling of eyelids, forehead, larynx and brain can be observed.
(Source: Disease of Swine, 10th edition)
Gelatinous edema in the mesocolon
EDEC or ETEC?
Differentiating E. coli virotypes complements the clinical examination and contributes to decision-making. Especially in the context of the reduction of antimicrobial use targeted disease prevention is essential.
For years IDT has been supporting with STEC-CHECK vouchers the diagnosis and differentiation of E. coli via biomolecular methods.
For more information about sampling and shipment, visit www.shigatoxin.com
IDT provides a Stec Check Kit for accurate sampling and shipment
The course can also be prolonged, if signs of the disease come up again, especially after further change of feed, removal of ZnO or antimicrobials from the diet or another stress factor.
ED mostly occurs in recently weaned pigs, although cases may be observed in later production stages up to finishers. The disease may be sporadic or may affect an entire herd.
The subacute/ acute outbreak often is recognized as sudden death without signs of sickness. Pigs dead of ED are mostly in good condition. Some affected pigs become inappetent, develop swelling of the eyelids and forehead. As a result of the laryngeal edema some pigs emit a peculiar squeal. Due to the edema in the brain pigs show convulsions, ataxia and lateral recumbency with paddling of limbs (picture). In most cases the number of runts are increased.
Nervous signs (lateral position, paddling limbs) in a pig with edema disease
Subclinical ED may occur, where pigs are clinically normal but develop microsvascular lesions and may have a decreased growth rate. These herds may show inhomogenous groups of pigs in the different production stages.
Chronic ED occurs in a low proportion of pigs recovering from acute disease or in herds where chimeric strains, which have the characteristic of ETEC – PWD strains but also produce Shigatoxin-2e, are detected. For periods varying from days to several weeks after intestinal infection, growth stops and sick pigs often show unilateral nervous disturbances such as circling movements, twisting of the head, or atrophy of limb muscles with progressive weakness. Subcutaneous edema is rare.
(Source: Disease of Swine, 10th edition)
The Shigatoxin-vaccination reduces the mortality and clinical signs of Edema (Oedema) disease into the fattening period. The single-dose of vaccination can be used from 4 days of age. Three weeks after the vaccination animals are protected by immunity, which persists at least until the 15th week of life.
The vaccination induces neutralizing antibodies. These antibodies neutralize the Shigatoxin and therefore prevent the development of acute or chronic clinical symptoms. However, the presence of Shigatoxin producing E. coli in the pigpen is not reduced by the vaccine because it does not act against the bacterium.
While the vaccination decreases the rate of losses and runts due to the Edema (Oedema) Disease, producer can reduce dramatically the use of antimicrobials like Colistin or Zinc oxide for controlling Shigatoxin-producing E. coli in rearing pigs. The Shigatoxin-vaccination helps minimizing the risk of developing resistant bacteria and thus actively contributes to consumer protection.
Visit www.shigatoxin.com for a case report from a 660 sow farm.
While Edema (Oedema) disease is a major economic problem in many pig herds, the Shigatoxin-vaccination provides a breakthrough solution. Nevertheless, many farm managers ask themselves: "Is vaccination against Shigatoxin in my farm worth it?"
The answer comes from the COIN calculator which is provided free of charge by IDT. COIN means “Calculate Online your Individual Netprofit”.
In addition to the psychological pressure from the large number of dead pigs, farms with moderate to severe outbreaks of Edema Disease also experience a financial disaster. Losses, decreased growth performance, inhomogeneity of groups as well as veterinary consultancy and treatment with antimicrobials contribute to the increased costs. Additionally an expensive diet feeding is required very often.
Though restrictive feeding to avoid the worst, the growth performance of piglets is impacted and the sales weight is decreased. Consequently, the rearing time is prolonged and the feed conversion deteriorates.
Every farm is unique. By entering your individual data in just a few steps you can calculate whether the Shigatoxin-vaccination will pay off. We recommend considering the cut rate of several months (of one year) when stating the loss rate so as not to cause bias by individual groups. The Edema (Oedema) Disease or the negative effects of Shigatoxin usually do not occur constantly rather being characterised by episodes.