Pasteurellosis – pneumonic and septicaemic form – is becoming more of an in issue in lambs from September through to November according to the latest disease diagnostic data for the last five years,

Information collected from post mortems on lambs with the disease, has shown that such lambs are dying either because they have not been vaccinated against it, or sometimes, because they have only received the first dose of vaccine and not the second dose four to six weeks later which is necessary to prime effective immunity.

Dr Katie Waine from the University of Nottingham, who collected the information, said the disease was the most common cause of death in lambs last year.

"Quite often, the dead lambs we have seen in the autumn also have high worm burdens or trace element deficiencies, which could have contributed to the pasteurellosis," she said.

According to vet, Ben Strugnell of Farm Post Mortems, pasteurellosis is an opportunistic disease that can be triggered by many factors, such as worm burdens, change of diet, border disease, trace element deficiency, adverse weather or overstocking.

“Autumn has always been a significant risk period for this disease because of the abundance of these different triggers. The disease diagnostic data clearly shows that this autumn peak of pasteurellosis is consistent and concerning and has important implications for effective control."

He added that if producers are keeping store lambs during this period they should talk to their vet or animal health provider about vaccinating them correctly.

“The key take-out message is that it is almost impossible to control the multiple, varied stress-related ‘trigger’ factors for pasteurellosis in lambs at this time of year, so the best advice to farmers is to make sure they have the best vaccination-induced immunity cover possible for the whole period that they are on the farm,” said Mr Strugnell.

In many cases this will mean giving store lambs, which have had two vaccination doses earlier in their lives, a third booster dose in August/September, so that they are fully immunised in advance of the autumn risk period.

“For those buying store lambs, it is advisable to try to establish that the incomers have had an initial vaccination course – two doses – and then give them a third one on arrival. However, this can often be difficult to determine.

“If an outbreak of pasteurellosis is encountered, it is important to assess the risk factors, so that disease can be prevented in the following year. This may involve blood sampling of lambs for trace element status and border disease antibodies, and/or egg counting for fluke and worms. Some assessment of dietary adequacy is also useful," concluded Mr Strugnell.