ET Ben Strugnell, who specialises in livestock post mortems, addressed an evening meeting at Jameson’s feed merchants in Masham last month.

Mr Strugnell works alongside AHDB Beef and Lamb to investigate the causes of livestock losses in North-East England. He drew delegates’ attention to the topical issue of enzootic abortion in sheep, one of the most common causes of infectious abortion that he sees at his headquarters in Hamsterley, County Durham.

“Enzootic abortion can lead to lamb losses of 15 per cent-plus and if it occurs in the flock in one year, then it is highly likely that it will have spread by the following season,” said Mr Strugnell, of Farm Post Mortems.

“It is transmitted at lambing time, picked up by an uninfected ewe which comes into contact with a diseased placenta.”

Characterised by lambs which just fail to reach full term and on post mortem by a thickened, red placenta and custard-like discharge, enzootic abortion was easily preventable through the use of a reliable vaccine, he said. It cost approximately £2/head and would protect the ewe for her lifetime.

Aside from implementing a vaccination programme prior to tupping, flock keepers could minimise disease spread by the careful management of any lambs which were fostered on.

“Once the ewe has succumbed to enzootic abortion she will have immunity for subsequent lambings but her own lambs will have died. In the case of late abortions, infection may not affect her milk production and therefore there is a temptation to foster on a lamb from another ewe.

“If this decision is taken, then it is advisable to select a male lamb as a foster. Alternatively, a ewe lamb should be ear-notched to ensure that it is excluded from the future breeding flock.”

Toxoplasmosis was the second most prevalent disease diagnosed at the post-mortem centre and it was also preventable through vaccination. Dead lambs often exhibited mummification and examination at post mortem would show a series of small white spots on the cotyledons of the placenta.

Mr Strugnell stressed that the toxoplasmosis vaccine could also give lifetime disease protection, although he admitted that it was generally more expensive, compared with enzootic abortion.

Unlike enzootic abortion, it was safe to foster lambs on to infected ewes without the risk of disease transmission.

“Toxoplasmosis is caused by a parasite,” explained Mr Strugnell. “One of the most common routes of infection is through mice which host the disease and are then eaten by cats. The ewe will pick up toxoplasmosis through contact with faeces from these infected cats.

“In the same way that future immunity in the ewe is gained post-infection, older cats do not normally pass on the parasite; it is younger cats which pose the greatest risk on farms. However, it is virtually impossible to prevent cats from having access to farm yards.”

He assured producers that vaccination for both diseases associated with lambing time would produce a return on investment on most holdings in the long term and said it was essential to vaccinate all bought-in females.

The Schmallenberg virus is believed to have reached UK shores in 2012, having been transmitted by infected midges from abroad. Information on disease geography was limited, as confirmation relied on livestock producers opting to send in animals for post mortem, said Mr Strugnell.

It caused limb deformities in young lambs and in calves and foetuses carried to full term may require a caesarean. The disease was cyclical and it was possible that 2020 would be a high-risk year;

“About 30 cases of Schmallenberg were reported in 2017, but this figure may be the tip of the iceberg. Cattle in particular which succumbed to previous spikes in infection will be immune but their offspring will be vulnerable.

“There is a diagnostic test for Schmallenberg, but it is not straightforward. Another challenge is that the makers of the vaccine may not begin commercial production until numerous cases have been confirmed; by that stage it may be too late for farmers to take preventative action.

“The only precaution might be to graze breeding youngstock in areas near rivers or woodland, where midges are commonly found. If they are bitten by an infected insect, they will have experienced an immune response prior to mating.”

The closure in 2014 of eight out of the governmental 14 veterinary laboratories had been a blow to the industry in terms of disease control, he said.

“If a map showing the number of confirmed cases of the Schmallenberg virus was overlaid with a map of the remaining diagnostic centres, the disease incidence tends to be clustered around these areas,” said Mr Strugnell.

“This may indicate that cases are not being diagnosed in places where it is more difficult to access a post-mortem service.”