According to data from the Wales Veterinary Science Centre (WVSC), sheep abortion submissions have increased this year, with diagnostic rates reaching their highest level since 2020.
Enzootic Abortion of Ewes (EAE), caused by Chlamydia abortus, was the most common cause of ovine abortion, accounting for 72% of diagnosed cases at WVSC.
The findings come despite the availability of effective vaccines such as Toxovax and Enzovax.
Interim results from the 2026 FlockCheck diagnostic scheme, run by MSD Animal Health, show similarly high exposure levels, with 75% of 421 samples testing positive for toxoplasmosis and nearly 30% of 212 samples returning positive results for EAE.
MSD veterinary adviser Dr Kat Baxter-Smith said the data highlights a persistent gap in disease prevention. “These are preventable diseases that can cause devastating losses, yet many farmers don’t realise there’s a problem because losses often go unrecorded or unexplained,” she said.
She urged farmers to take a risk-based vaccination approach this summer, particularly where replacements are being introduced or flocks have experienced higher barren rates or lamb losses.
“Unless barren and abortion rates are below 2%, or the flock is fully closed, ewe vaccination should be considered. Both are NOAH Category 1 diseases, meaning vaccination should be standard practice,” she said.
“If disease is present, or stock is being bought in from flocks of unknown status, the cost of vaccination is easily offset by reducing future losses.”
Dr Baxter-Smith said non-pregnant ewes can be vaccinated at least four weeks before tupping, but stressed summer as the ideal window for action.
Protection from both vaccines is long-lasting, with Enzovax typically boosted every three to four years and Toxovax lasting at least two lambing seasons. “Once control is established, long-term management is straightforward,” she said.
However, Dr Baxter Smith cautioned that infection is not always obvious. “Enzootic abortion doesn’t always cause abortion storms. Subtle signs such as lower scanning rates, weak lambs or poorer survival can still indicate significant disease impact.”
Toxoplasmosis, caused by Toxoplasma gondii, is also a major driver of barren ewes and weak lambs, with infection occurring through ingestion of oocysts shed in cat faeces, making control difficult.
“The parasite’s eggs are extremely resilient and can survive for over a year in the environment, so the risk is constant,” she said.
Dr Baxter-Smith added: “The data clearly highlight persistent levels of disease exposure, with enzootic abortion and toxoplasmosis remaining entrenched in UK sheep flocks despite both being fully preventable through vaccination. These are not isolated issues, and the evidence shows they continue to contribute to significant reproductive losses across flocks.
“Now is the time to review 2026 lambing performance and abortion losses, and work with your vet to put prevention strategies in place ahead of the 2027 breeding season.”
