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Malignant edema is an acute, generally fatal toxemia of cattle, horses, sheep, goats, and pigs usually caused by
Clostridium
septicum
, often accompanied by other clostridial species. Other clostridia implicated in wound infections include
C
chauvoei
,
C
perfringens
,
C
novyi
, and
C
sordellii
. The disease occurs worldwide. A similar infection in humans is not uncommon. |
| Etiology: |
|
C
septicum
is found in soil and intestinal contents of animals (including humans) throughout the world. Infection ordinarily occurs through contamination of wounds containing devitalized tissue, soil, or some other tissue-debilitant. Wounds caused by accident, castration, docking, insanitary vaccination, and parturition may become infected. |
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| Clinical Findings: |
| General signs, such as anorexia, intoxication, and high fever, as well as local lesions, develop within a few hours to a few days after predisposing injury. The local lesions are soft swellings that pit on pressure and extend rapidly because of the formation of large quantities of exudate that infiltrates the subcutaneous and intramuscular connective tissue of the affected areas. The muscle in such areas is dark brown to black. Accumulations of gas are uncommon. Severe edema of
the head of rams develops after infection of wounds inflicted by fighting. Malignant edema associated with lacerations of the vulva at parturition is characterized by marked edema of the vulva, severe toxemia, and death in 24-48 hr. |
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| Diagnosis: |
| Similarity to blackleg (
Blackleg) is marked, and differentiation made on necropsy is unreliable; laboratory confirmation is the only certain procedure. Horses and pigs are susceptible to malignant edema but not to blackleg. (
C
septicum
also causes
braxy in sheep, a highly fatal infection characterized by toxemia and inflammation of the abomasal wall. This disease seems to be confined mostly to European sheep fed on “frosted” pasture.) |
| Diagnosis can be confirmed rapidly on the basis of fluorescent-antibody staining of
C
septicum
from a tissue smear. However,
C
septicum
is an extremely active postmortem invader from the intestine, and its presence in a specimen taken from an animal that has been dead for ≥24 hr is not significant. |
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| Control: |
| Bacterins are used for immunization.
C
septicum
usually is combined with
C
chauvoei
in a blackleg/malignant edema vaccine and is available in multicomponent vaccines. In endemic areas, animals should be vaccinated before they are castrated, dehorned, or docked. Calves should be vaccinated at ~2 mo of age. Two doses 2-3 wk apart generally give protection. In high-risk areas, annual vaccination is indicated, as is revaccination after severe trauma. |
| Treatment with high doses of penicillin or broad-spectrum antibiotics is indicated early in the disease. Although injection of penicillin directly into the periphery of the lesion may minimize spread of the lesion, usually the affected tissues still slough. |
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