Vet: 'Iceberg diseases' are cutting sheep flock productivity
Sheep veterinarian Phillipa Page says hidden "iceberg" diseases significantly reduce flock productivity, especially when ewe mortality exceeds 3% a year. She urges farmers to set targets and make small annual improvements across several management areas.
Hard-to-spot conditions known as "iceberg diseases" are significantly reducing the productivity of sheep flocks, particularly when annual ewe mortality rises above 3%. That was the message from veterinarian Phillipa Page, a former president of the Sheep Veterinary Society in the UK, who spoke at the AgriSearch Flock Focus 2026 event in Co. Tyrone, Northern Ireland. AgriSearch is an agricultural research organisation.
Targets and iceberg diseases
According to Page, sustainable sheep production depends on setting targets. One is keeping lameness below 1% a year; another is holding ewe mortality under 3%.
The Cotswolds-based vet described iceberg diseases as conditions that add to the impact of other health problems such as lameness and poor body condition scores. They include Maedi Visna, caseous lymphadenitis (CLA), Johne's disease and Border disease virus. She said these are mostly bought-in diseases that can be screened for. Marginal yearly improvements across a range of management areas can, over time, make a very significant difference.
Lameness
Page named foot rot and Contagious Ovine Digital Dermatitis (CODD) among the significant contributing factors. She said lameness must be tackled promptly, using antibiotics if needed, but that the long-term aim must be prevention.
The vet believes foot bathing should not be used to treat foot rot, particularly in older ewes, because gathering animals in one place speeds the spread of disease. Lame animals should be kept away from the rest of the flock where possible. She said the active chemicals in footbaths should be regarded purely as disinfectants.
Faecal egg counting and teeth
Page also highlighted faecal egg counting after sheep have been drenched for worms, which lets a flock owner gauge the level of wormer resistance. As a rule of thumb, older ewes should have a built-in resistance to worm burdens, raising the question of whether they need drenching at all.
She also stressed checking animals' molar teeth, since sheep with properly functioning molars can grind down forage and other feeds effectively.
