Pasteurellosis vaccines in sheep

Pasteurellosis is one of the most common causes of death in growing lambs in Great Britain (GB), despite there being effective vaccines that offer protection against disease. 

Bacteria previously identified as being Pasteurella species have been reclassified; the main species causing disease in sheep are now called Mannheimia haemolytica, and Bibersteinia trehalosi. M. haemolytica commonly causes either septicaemia in young lambs or pneumonia in all ages of sheep. B. trehalosi is most commonly associated with septicaemia in older lambs.

The cost: £7–15m per year of acute enzootic pneumonia to the GB national flock in 2005 (Bennett R. 2005).

Most vaccines marketed in the UK for the control of pneumonic or systemic pasteurellosis are in combination with vaccines for clostridial diseases. 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.

The following pasteurellosis vaccines have been marketed in the UK:

• Heptavac P Plus is a multivalent clostridial vaccine for sheep that can also aid in the control of pneumonic and systemic pasteurellosis
• Ovipast Plus is a vaccine for the active immunisation of sheep as an aid in the control of pasteurellosis caused by M. haemolytica and B. trehalosi
• Ovivac P Plus is a multivalent clostridial vaccine for sheep that can also aid in the control of pneumonic and systemic pasteurellosis

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.

Denominator: The common industry recommendation for farms on which pasteurellosis is an issue is to vaccinate lambs with a primary course of pasteurella vaccine, unless they are destined for slaughter before 10 weeks of age, or their mother was given a booster vaccine in late pregnancy. On such farms, it is recommended that all adult sheep should be given a primary course and receive an annual booster. The total number of vaccine doses that would be required to protect the national UK flock from pasteurellosis has been estimated based on the assumption that all lambs in flocks in June should receive two doses of vaccine and that the total breeding flock, as well as all rams, should get one annual booster vaccination.

Vaccination uptake

The uptake of vaccines to provide protection to sheep from pasteurellosis follows a similar trend to that of clostridial vaccines. This is not surprising, given that the main vaccines used are combination clostridia–pasteurellosis vaccines. Pasteurella vaccine uptake has been reasonably steady over the past seven years, with close to half of all sheep being vaccinated (46–52%).