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CLOSTRIDIAL DISEASE

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Clostridial Disease

Preventable infectious diseases can have a severe economic and welfare impact on a sheep flock. When the obvious visible symptoms appear, the infectious disease is established, losses are to be expected and treatment effectiveness is variable. Prevention is more cost effective and economically efficient when the sub-clinical and chronic losses are accounted for.

Clostridial diseases are caused by a group of bacteria that have the ability to form resistant spores. Spores can concentrate in areas of high sheep usage e.g. around yards, sheds and troughs. They are resistant to extremes in temperature and can survive in soil for many years. Disease occurs only when the spore is present in damaged body tissue which provides the right conditions for the bacteria to germinate and to produce toxins. The signs of disease are caused by the toxins produced by these bacteria, not the bacteria themselves.

The primary preventable clostridial diseases are:

TETANUS

Clostridium tetani

  • Tetanus is a naturally occurring bacteria that is found in the soil, NZ wide.
  • Tetanus spores enter the body via a wound due to husbandry procedures (e.g. docking) and accidental wounds.
  • Tetanus bacteria produces a neurotoxin that causes prolonged muscle spasms, resulting in death due to the paralysis of the breathing muscles.
  • Sudden death is the usual result.
  • Tetanus can be effectively controlled by vaccination.
Tetanus sheep

ENTEROTOXAEMIA (PULPY KIDNEY)

Clostridium perfringens type D

  • Pulpy Kidney disease is caused by a naturally occurring bacteria that is found in the gut of healthy animals as well as in the soil and faeces.
  • The Pulpy Kidney organism is triggered to develop by a modification in the rumen conditions due to a sudden feed change, resulting in a rapid multiplication of these bacteria and production of the Epsilon toxin that is absorbed into the blood.
  • Multiplication results in an overwhelming toxin level.
  • Sudden death is the result.
  • The disease is often seen around weaning or when stock are suddenly put on highly digestible crops.
  • There is no treatment for pulpy kidney, so prevention by vaccination and dietary management is important.
Pulpy kidney

BLACK DISEASE

Clostridium novyi type B

  • Clostridium novyi is a naturally occurring bacteria that is found in soil and gastrointestinal systems.
  • Its spores enter the body after ingestion, pass through the gastrointestinal wall and deposit in liver and other tissues.
  • Black Disease occurs when the liver is damaged, which provides ideal conditions for the spores to germinate, multiply, secrete toxin and produce signs of the disease.
  • Liver fluke larvae migrating through the liver are a common cause of the liver damage.
  • Sudden death is the result.
  • Control of black disease requires vaccination as well as strategic flukicide treatments in known fluke areas.
Black disease

BLACK LEG

Clostridium chauvoei

  • Clostridium chauvoei is a naturally occurring bacteria that is found in soil NZ wide.
  • The spore is ingested by animals whilst grazing, can live in the gastrointestinal tract, or can enter the bloodstream then lie dormant in the muscle.
  • Bruising, trauma or wounds trigger the spores to germinate, multiply, secrete toxin and produce signs of the disease.
  • The toxins affect local tissues with death of tissue with gaseous, gangrenous presentation and toxic death of organ tissue.
  • Sudden death is the usual result.
  • Management of the disease is aimed at prevention through vaccination. Most cases occur in flocks where the clostridial vaccination program is inadequate.
  • In sheep severe losses can occur following yarding, and vaccinating lambs with contaminated equipment.
Black leg

MALIGNANT OEDEMA

Clostridium septicum

  • Clostridium septicum is a naturally occurring bacteria that is found in soil NZ wide.
  • Its spores enter the body from the soil contamination of open wounds.
  • Wounds that may develop Malignant Oedema, include those at routine operations such as shearing, mulesing, castration and lamb marking. Fighting wounds and damage to the reproductive tract during a difficult birth are also risk factors.
  • The spores germinate in the wounds, multiply, secrete toxins and produce signs of the disease.
  • Sudden death is the result.
  • Prevention is achieved by vaccination. Hygiene and the use of low contamination areas (eg. temporary yards) are also important in reducing exposure to infective spores.
Malignant Oedema

SUDDEN DEATH

Clostridium sordellii

  • Clostridium sordellii is a naturally occurring bacteria that is found in the soil NZ wide, and gut of healthy animals.
  • Disease is triggered by a modification in the rumen conditions due to a sudden feed change, resulting in a rapid multiplication of these bacteria and production of the lethal toxin that is absorbed into the blood.
  • Animals are found dead with a bloated gas filled abdomen that has a putrid smell. It is very difficult to diagnose but is another potential cause of death if a robust 5in1 programme is followed and predisposing factors are in place.

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