Clostridium tetani

26 أغسطس

Livestock health
Tetanus in sheep and goats

Ross Newman, DPI&F

Key points

  • Tetanus is a common, highly fatal disease in sheep and goats caused by a widespread bacterium.
  • Infection can be effectively and cheaply prevented through vaccination and good hygiene.

Infection

Tetanus is caused by spores of the bacteria Clostridium tetani . The spores have some important characteristics:
  • common in soil and faeces, remaining infectious for years
  • produce a potent toxin in a suitable, localised wound
  • not destroyed by most common disinfectants.
Infection normally occurs from a wound con­taminated by dirt, dust or faeces. Castration, ear-marking, tail-docking, mulesing, dehorning and debudding are all routine surgical procedures creating wounds that can be ideal growth sites for tetanus. Infection can also occur through non-surgical wounds eg dog bites, shearing cuts.
The incubation period is usually between three days and three weeks. In this period, the organism multiplies and produces its lethal toxin. The toxin penetrates the nerves around the wound and travels to the spinal cord and brain where it fixes to nerve cells to produce exaggerated and uncontrollable muscle spasms.

Signs

Signs seen in tetanus infection include muscle stiffness, lack of coordination, unusual walking, spasms, inability to eat or drink, protrusion of the third eyelid, bloat and overreaction to sudden noise or physical contact. Not all of these signs may be seen. Death usually occurs three to four days after the animal becomes sick. In a flock situation, a number of animals are often found dead without any sickness being observed.

Treatment

Treatment involves care of the local wound and correct administration of large doses of anti-toxin and penicillin. It is a complex procedure, so your veterinarian should be consulted as soon as tetanus is suspected. Response to treatment is usually poor and is quite expensive, so prevention is the best policy.

Prevention of tetanus

Cleanliness and vaccination are both essential in tetanus prevention.

Cleanliness

Because most disinfectants are ineffective against tetanus spores, cleanliness is essential when undertaking any husbandry or surgical procedure.
Any surgical instruments (eg ear-marking pliers, knives) should be thoroughly cleaned before and after use and be kept clean during the procedure. Yards should be watered to decrease dust. Using temporary yards in grassy areas will also help. When marking or mulesing, operators should make sure lambs and kids leave the cradle so they land on their feet and the wound is not contaminated by dirt.
Despite the best efforts, wound contamination is often a problem, so vaccination should also be used for prevention of tetanus.

Vaccination

Proper vaccination procedure involves giving two doses of vaccine at least four weeks apart. An annual booster dose is then recommended. This general procedure is necessary in all non-vaccinated animals. After the first dose, some temporary immunity will appear after 9 to 14 days, but this will quickly fade. Given that the incubation period can be as short as three days, it is obvious that a single vaccination will do very little to prevent the disease. Thus animals must have adequate immunity before any surgical procedure is undertaken, especially at marking – the most dangerous time for tetanus.
Protection at marking can be achieved in three ways:
  • Providing passive immunity to the lambs by giving ewes a booster vaccination a few weeks before lambing commences. A ewe which has been previously vaccinated will have a dramatic increase in immunity. This protection will be transmitted to the lamb in the colostrum. This method of providing immunity is demonstrated in Diagram 1. The immunity transmitted from the ewe will protect the lamb at marking. The lamb then receives its first vaccination and, with a booster at least four weeks later, will have continual protection. This is the best method of providing adequate tetanus protection for lambs at the potentially dangerous marking operation. It is very cost effective as 5-in-1 vaccine costs about 18c/dose and this vaccine will also protect against the other clostridial diseases eg pulpy kidney.
  • Giving tetanus anti-toxin, as well as vaccination at marking. Anti-toxin gives immediate protection and lasts two to three weeks, after which time some protection from the vaccination will appear. The animal still must be revaccinated after four weeks to produce lasting immunity. Anti-toxin costs about 45c/dose for a lamb (100 units), so this is an expensive method of providing such short-lived immunity.
  • Vaccinating lambs two weeks before marking and again no less than two weeks after. This method involves extra mustering and handling, with subsequent mismothering, so is a difficult procedure in most flock situations.
Note: Prices of vaccines and anti-toxins will vary greatly depending on pack size, quantity purchased and locality. The prices quoted are a guide only.

Tetanus in goats

The immunisation methods detailed for sheep can also be used for goats. However, as tetanus is much more common in goats than sheep:
  • All goats should be regularly revaccinated.
  • Tetanus anti-toxin should always be given to an unvaccinated animal when any surgical procedure or wound occurs.
  • Allergic reactions to vaccination sometimes occur in goats so it is advisable to vaccinate them only for pulpy kidney and tetanus rather than use a 5-in-1 for all five

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