How to protect your flock from clostridial diseases and pasteurella

Clostridial diseases and pasteurella pose a serious threat to unvaccinated sheep.

Below we outline what causes each disease and how to spot it, with the help of MSD vet adviser Stephanie Small. 

Few of these diseases are treatable, with most causing rapid death, so prevention in the form of a well-planned flock vaccination programme is essential.

Clostridial diseases

The group of bacteria known as clostridia are organisms commonly found in soil, where they can survive for a long period of time.

Most of these organisms occur naturally in the gut of healthy animals and pass in manure and subsequently contaminate the soil.

A stressful event, such as a change in weather, diet or an endoparasite infection, is required to trigger clinical infection.

There are eight main types of clostridial disease that affect sheep.

Scroll further down to find out more about how they caused, the symptoms they present and how to prevent them. 

Lamb dysentery

Caused by toxins released by the organism Clostridium perfringens type B and causes infection of the intestine.

See also: 7 key lambing diseases: How to prevent and treat them


  • Bloody diarrhoea (dysentery)
  • Sudden death

Age it usually occurs

  • Under two weeks of age

Pulpy kidney

Caused by the toxins released by Clostridium perfringens type D when it is absorbed into the intestinal tract.

It usually exists in small numbers in the gut of healthy animals, but if the intestine favours bacterial growth caused by a sudden diet change or the movement to new or better pasture, it can produce fatal toxins.


  • Sudden death
  • Post-mortems will show destruction of kidneys, but this is not the only diagnosis where this occurs

Age it usually occurs

  • Two to three months


Caused by the toxins of the bacterium Clostridium chauvoei. Bacterial spores are ingested from pasture and then enter the bloodstream and lodge in the muscles, where they can remain dormant until a wound is created as a result of tail-docking, shearing or injury.


  • Dull
  • No appetite
  • Fever of 42C (107F) or more
  • Sudden onset of severe lameness caused by the inflammation of muscle
  • Rapid death

Age it usually occurs

  • Mostly youngstock between six months and two years, with most cases occurring at grass

Black disease

Caused by the organism Clostridium novyiand and is associated with liver fluke infestation. It invades the liver and produces a fatal toxin. It occurs after the liver becomes damaged by fluke migrating in large numbers from the intestine to the liver.  


  • Rapid death

Age it usually occurs

  • Usually in the autumn or early winter when fluke migrate in their largest numbers from the intestine to the liver, although timing will vary depending on weather events and fluke risk

Tetanus (lock jaw)

Caused by Clostridium tetani, which penetrates puncture wounds. Once healed, the organism multiplies rapidly without the presence of oxygen and produces a deadly toxin.


  • Symptoms can take four days to three weeks to occur after infection
  • Muscle spasms
  • Animal will go down and all four limbs will go stiff
  • Death caused by paralysis and asphyxiation

Age it usually occurs

  • Any


Caused by Clostridium botulinum (type C and D) when animals have access to decaying matter, particularly poultry litter.


  • Sudden death
  • Can present as hindlimb weakness which progresses to affect the front limbs
  • Lack of muscle tone and tongue protrusion

Age it usually occurs

  • Any


Caused by C septicum, which is normally found in gut and soil.

The disease generally occurs in the winter when sheep eat frosted root crops. The frozen feed damages the lining of the abomasum (fourth stomach), which allows the organism to enter.


  • There is a sudden onset of illness with segregation from the group
  • Complete anorexia
  • Depression
  • A high fever 42C (107F) or more
  • The abdomen may be distended with gas, and there may be signs of abdominal pain
  • The sheep becomes recumbent, comatose and dies within a few hours of first becoming ill

Age it usually occurs 

Weaned yearlings

Malignant oedema

Caused by C septicum (or occasionally C chauvoei) which is found in gut and soil. Occurs following traumatic injury with deep-penetrating wounds becoming infected with the bacterium.


  • Marked fever
  • Depression
  • Toxicity
  • Swelling at site of infection
  • Death within 24-48 hours

Age it usually occurs


Prevention of clostridial diseases

  • Breeding ewes require a primary course of two injections of an appropriate clostridial vaccine given four to six weeks apart followed by an annual booster four to six weeks before lambing (no longer than twelve months apart).
  • Immunity will be transferred to the lamb providing they have had adequate colostrum (lambs should receive 10% of their bodyweight in colostrum within 24 hours and half of this amount within four to eight hours).
  • Passive immunity runs out after a few weeks. Therefore, lambs should be vaccinated from three weeks of age and a second dose should be given four to six weeks later.


Caused by three types of pathogens: Mannheimia haemolytica, Bibersteinia trehalosi and Pasteurella multocida.

They are commonly found in the tonsils and throat of healthy animals, but under stress the animal’s immune systems becomes suppressed and these bacteria multiply and invade the lungs, causing septicaemia and pneumonia.

It can be triggered by stress arising from weaning or castration, for example, or if air quality in sheds is poor or humid.


  • Septicaemia (generally caused by Bibersteinia trehalosi) results in sudden death. Case fatality is higher than with other organisms.
  • Pneumonia causes symptoms such as fever, laboured breathing, nasal discharge, conjunctivitis, loss of appetite and reduced growth rates

Age it usually occurs

  • Pasteurellosis can affect very young lambs and is also common in weaned lambs aged four to 10 months 
  • Most common cause of sudden death between August and December
  • Adult sheep are also at risk


  • Antibiotics may be prescribed in conjunction with your veterinary surgeon, but losses may continue


  • Lambs should be vaccinated with an appropriate pasteurella vaccine from three weeks of age with a second dose given four to six weeks later
  • Lambs that received two doses in the spring may require a booster where the risk is high in the late summer/early autumn period. Speak to your vet or animal health adviser.