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Spring poisoning hazards

02 March 2021
11 mins read
Volume 5 · Issue 2
Figure 5. The main toxin compound in Helleborous species (hellebore) is protoanemonin.
Figure 5. The main toxin compound in Helleborous species (hellebore) is protoanemonin.

Abstract

Poisoning can be seasonal. Potential toxic hazards in the spring include adders, which emerge from hibernation as the weather warms. Adders may not be seen to bite a horse, but envenomation should be considered in a horse with localised limb swelling that spreads up the leg. There are several spring-flowering plants which contain toxic compounds such as cardiogenic glycosides (foxglove, lily of the valley, oleander), protoanemonin (Hellebore) and grayanotoxins (Pieris and Rhododendron). Saplings of sycamore are a spring source of hypoglycin A which causes atypical myopathy in horses. Treating plant poisoning in horses generally involves removing the plant, providing good quality food and giving supportive care. Managing the effects of adder bite is supportive, centring around administration of specific antivenom.

As the weather warms in the spring, horses may be at risk of envenomation from adders emerging from hibernation or poisoning from grazing on the fresh spring growth of plants. Also, if the winter has been harsh and other forage is unavailable, horses may eat plants they would normally avoid. Plant poisoning can also occur if horses escape from their enclosure or if cuttings from spring-pruned plants or felled trees are left within their reach.

There is limited information on the incidence of poisoning in horses and it likely that cases are under-reported. In Europe, most cases of poisoning reported in horses involve plants and pesticides (Guitart et al, 2010; Bates, 2017; McFarland et al, 2017). If required, cases can be discussed with a poisons information service and can be reported retrospectively to the UK's Veterinary Poisons Information Service (VPIS) via its website (https://www.vpisglobalcom/report-a-case/ ).

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