Clostridial vaccines in sheep

Clostridial vaccines are cheap and highly effective multivalent vaccines, but deaths caused by clostridial diseases remain high, resulting in considerable losses to the sheep industry. 

Clostridial disease is the most common cause of sudden death for all ages of sheep in the UK. Examples of clostridial diseases include pulpy kidney disease (Clostridium perfringens type D), lamb dysentery (C. perfringens type B), struck (C. perfringens type C), braxy (C. septicum), black disease (C. novyi), and botulism (C. botulinum). With clostridial diseases, it is not the bacteria that cause disease but the toxins they produce.

The vaccines available have similar instructions: always check the packaging for specific doses and timings. The primary vaccination course is two doses of vaccine separated by a four- to six-week interval. A booster dose should be administered at intervals of no more than 12 months. If the dam has received a full primary vaccination course before pregnancy and receives a booster (check the products for timing) before parturition, she can provide the newborn lamb with passive immunity via the colostrum. This does not apply to Ovivac P, which doesn’t cover pregnancy clostridial diseases.

The following multivalent clostridial vaccines have been marketed in the UK:

• Bravoxin 10 is a multivalent clostridial vaccine for cattle and sheep
• Covexin 8 is a multivalent clostridial vaccine for cattle and sheep
• Covexin 10 is a multivalent clostridial vaccine for cattle and sheep
• Heptavac P Plus is a multivalent clostridial vaccine for sheep that can also aid in the control of pneumonic and systemic pasteurellosis
• Lambivac is a multivalent clostridial vaccine for sheep and pigs
• Ovivac P Plus is a multivalent clostridial vaccine for sheep that can also aid in the control of pneumonic and systemic pasteurellosis

Image courtesy and copyright of Chris Elkington.

Assumptions

Numerator: The number of doses of vaccine administered has been calculated by multiplying the number of packs sold by the number of doses per pack. For Covexin 8, a higher dose is used as the first dose in the primary vaccination course. It has been assumed that 20% of all doses of Covexin 8 are used in primary vaccination courses, and that half of these are administered at the higher dose level (i.e. it has been assumed that 10% of Covexin 8 doses used in sheep are 5 ml and the remainder are 2 ml). Bravoxin and Covexin 8 are also licensed for use in cattle. It has been assumed that 80% of the use of these vaccines is in sheep and the remainder in cattle. A small amount of clostridial vaccine is also used in pigs, but this is not considered significant.

Denominator: The common industry recommendation is to vaccinate lambs with a primary course of clostridial vaccine, unless they are destined for slaughter before 12 weeks of age, or their mother was given a booster vaccine in late pregnancy. It is recommended that all adult sheep should be given a primary course and receive an annual booster. The total number of clostridial vaccine doses that would be required by the national UK flock has been estimated based on the assumption that all lambs in flocks in June should receive two doses of clostridial vaccine and that the total breeding flock and all rams should get one annual booster vaccination.

Clostridial vaccine uptake steadily increased from 2013 to 2022. This then dropped from 65% in 2022 to 60% in 2023, likely due to supply chain issues.