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Edema (Oedema) Disease

Pathogenesis of Edema (Oedema) Disease (ED)

Clinical signs of Edema (Oedema) Disease (ED)

ED mostly occurs in recently weaned pigs, although cases may be observed in later production stages as well. The disease may be sporadic and may affect only individual animals, but occasionally an entire batch of pigs is affected.

The subacute/ acute outbreak often is recognized as sudden death without previous signs of sickness. Pigs dead of ED are mostly in good condition. Some affected pigs become anorexic, 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 (figure 3). Few pigs survive the acute disease, but those that do remain runts (i.e. show stunted growth).

ΗThe course of the disease can also be prolonged. Clinical signs then reoccur in the same batch of pigs, especially after further change of feed, removal of zinc oxide (ZnO) or antimicrobials from the feed or another stress factor.

Piglets lateral rowingFigure 3: Nervous signs (lateral position, paddling limbs) in a pig with Edema (Oedema) disease, source: Ceva

Subclinical ED may also occur, where pigs are clinically normal but develop microvascular lesions and may have a decreased growth rate. These herds may show inhomogeneous groups of pigs in the different production stages.
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Chronic ED occurs in a low proportion of pigs recovering from acute disease or in herds where chimeric E.coli, which produce the heat labile (LT) and heat stabile (ST) toxins that cause post-weaning diarrhea (PWD) 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. In these cases subcutaneous edema is rare.
(Source: Diseases of Swine, Tenth Edition, Edited by J.J. Zimmerman et al., John Wiley & Sons, Inc. Published 2012)