The VPIS regularly receives enquiries about animals that ingest fungi, particularly in the spring and autumn. Although the frequency of enquiries concerning fungi is high at these times, annually they comprise approximately 1% of enquiries. In the majority of cases the species of fungus is unknown.
In 2012 to 2013 the VPIS undertook a project with the Royal Botanic Gardens, Kew to identify fungi involved in cases of suspected poisoning. Out of a total of 17 cases completed with identification, a high incidence of Clitocybe ingestion by dogs was observed (see image above).
The principal toxin in Clitocybe species is muscarine, which is structurally similar to acetylcholine and competes for some acetylcholine receptor sites. Ingestion can cause rapid and dramatic onset of signs with hypersalivation, lacrimation, constricted pupils, vomiting and watery diarrhoea. In severe cases there can be collapse, bradycardia and hypotension. Prognosis is usually good in animals managed supportively with atropine therapy. Atropine, however, should not be used in ibotenic acid poisoning (eg, Amanita muscaria), as it has been shown to exacerbate clinical effects.
Clitocybe rivulosa is the commonest of the small whitish Clitocybe species found in Britain and the only one occurring in numbers on lawns. Other muscarine-containing fungi to be aware of are the Inocybe species, which mostly appear as small brownish toadstools.
For further reading on this topic, see the following letter published in the August issue of the Veterinary Record:
• Bates N, Edwards N, Dentinger BT, Ainsworth AM. 2014 Fungal ingestion in companion animals. Vet Rec 175:179-180.