Ergotism is a nationwide disease that affects livestock. It is one of the most important mycotoxins to be aware of.

The causative agent of this disease is known as Claviceps purpurea, which is a fungal parasite in rye, cereals and grasses.

It is most abundant during the summer months, where there has been a damp spring or where the local habitat is damp.

Stored infected feed can contaminate feed bins, which can become the source of infected feed.

The seed head is replaced with a black, elongated, hard structure known as the sclerotia and is about twice the size of the normal grain.

Within the sclerotia there is an ergot alkaloid mycotoxin, which primarily causes vasoconstriction (blood vessel narrowing) and/or hypoprolactinaemia (decreased prolactin hormone), which will ultimately result in agalactia at parturition.

Initial signs of disease occur a few weeks post-ingestion of ergotised feed.

Symptoms may include lameness in the hind limbs followed by forelimb lameness, an increase in body temperature and an increased respiratory rate.

The vasoconstriction primarily occurs in ruminants and results in diminished blood flow to the extremities, leading to a dry gangrene below the knee/hock, ear tips and/or tail.

Once dry gangrene sets in to the limbs, sensation is lost and there is a visible indented horizontal line demarcating dead tissue below the line and healthy tissue above the line. The affected area will harden and slough off, exposing raw underlying bleeding tissue with a foul odour.

Once dry gangrene has set in, there is no cure and slaughter is the most viable option. Antibiotics to prevent secondary infection, pain relief and Stockholm tar may be of some value if slaughter is not an option.

Some drugs have been successful in the early stages of the disease to try to reverse the vasoconstriction effect of the mycotoxin, but prevention is better than cure.

Prevention can be implemented by removing the flower heads of ergot-prone land, as even tiny amounts of the toxin can cause weight loss, poor fertility and potential interference with embryonic development.

Mark Duncan works at Clerkin Vets, Cootehill, Co Cavan. Clerkin Vets is part of XLVets, a group of progressive practices working together to achieve a better future for agriculture and veterinary in Ireland. Visit www.xlvet.ie.