1. Clostridial Diseases

2. Clostridia are relatively large, anaerobic, sporeforming, rod-shaped organisms. The spores are oval, sometimes spherical, and are central, subterminal, or terminal in position.
Clostridium spp, Gram's stain, high power. Note the characteristic spore in this large gram-positive rod. Courtesy of Dr. John Prescott

3. Clostridial diseases can be divided into 2 categories:
1) those in which the organisms actively invade and reproduce in the tissues of the host, with the production of toxins that enhance the spread of infection and are responsible for death (sometimes referred to as the gas-gangrene group)
2) those characterized by toxemia resulting from the absorption of toxins produced by organisms within the digestive system (the enterotoxemias), in devitalized tissue (tetanus), or in food or carrion outside the body (botulism).

4. Clostridial diseases Systems affected Spore formingGI
Musculo-skeletal
Nervous
Spore forming
Natural inhabitants
Soil
Intestinal tracts
Affects numerous species

5. Black leg
Blackleg is an acute, febrile disease of cattle and sheep caused by Clostridium chauvoei (feseri) characterized by emphysematous swelling, usually in the heavy muscles. It is found worldwide.
It can affect cattle and sheep; cattle 6 to 18 months old are most commonly affected.

6. Etiology
C chauvoei is a Gram+ found naturally in the intestinal tract of animals. It probably can remain viable in the soil for many years, although it does not actively grow there. Contaminated pasture appears to be a source of organisms.
Outbreaks of blackleg have occurred in cattle on farms in which recent excavations have occurred, which suggests that disturbance of soil may activate latent spores.
Lesions develop without any history of wounds, although bruising or excessive exercise may precipitate some cases

7. Clinical Findings and Lesions:
Usually, onset is sudden, and a few cattle may be found dead without premonitory signs.
Acute lameness and marked depression are common. Initially, there is a fever but, by the time clinical signs are obvious, body temperature may be normal or subnormal.
Characteristic edematous and crepitant swellings develop in the hip, shoulder, chest, back, neck, or elsewhere. At first, the swelling is small, hot, and painful.
Blackleg, muscle of a cow. Note the characteristic black color and the dry appearance of the necrotic muscle, with tiny gas bubbles just visible in the tissue. Courtesy of the Department of Pathobiology, University of Guelph

8. Diagnosis
A rapidly fatal, febrile disease in well-nourished young cattle, particularly of the beef breeds, with crepitant swellings of the heavy muscles suggests blackleg.
The affected muscle is dark red to black and dry and spongy; it has a sweetish odor and is infiltrated with small bubbles but with little edema.
The lesions may be in any muscle, even in the tongue or diaphragm. In sheep, because the lesions of the spontaneously occurring type are often small and deep, they may be overlooked

9. Control
A bacterin containing C chauvoei and C septicum is safe and reliable for both cattle and sheep.
Calves should be vaccinated twice, 2 wk apart, at 2-6 mo of age; in high-risk areas, revaccination may be necessary at 1 yr and every 5 yr thereafter.
When outbreaks are encountered, all susceptible cattle should be vaccinated and treated prophylactically with penicillin to prevent new cases, which may develop for up to 10 days, at which the bacterin provides protection.

10. Malignant Edema

11. Malignant edema
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

12. 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.

13. 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.

14. Diagnosis
Similarity to blackleg is marked, and differentiation made on necropsy is unreliable; laboratory confirmation is the only certain procedure.
Diagnosis can be confirmed rapidly on the basis of fluorescent-antibody staining of C septicum from a tissue smear.

15. 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.