Australia’s gardens,slugs and snails: the risks of pica and rat-lungworm infection

Abstract

Dear Sir,

Ingestion of non-nutritive substances can be inherently dangerous, with effects ranging from heavy metal exposure (e.g. with lead), puncture or blockage of the gastrointestinal tract, to various parasitic helminth and nematode infections.¹ While oral exploration of almost anything within reach is part of expected development, in the first months and years of life, pica is a recognised mental health disorder, defined by persistent eating of non-nutritive substances.² Prevalence studies found pica in autistic and learning disabled institutionalised individuals occurs at a rate between 9.2%³ and 21.8%.⁴

Infection with Angiostrongylus cantonensis (commonly known as the rat-lungworm) may cause severe and long-lasting neurological impairment, as exemplified by a recent case in Sydney,⁵ but also often-fatal eosinophilic meningitis or encephalitis.⁶ Humans are accidentally infected when they ingest raw snails, slugs or vegetation covered with mollusc slime harbouring the larval form of the parasite. Rats are the main reservoir of infection, excreting infective larvae in faeces which subsequently penetrate or are ingested by the snail or slug intermediate host. The first Australian human case of this disease was reported in Brisbane in 1971,⁶ with a fatal report in 1999 in a child who ingested molluscs in a suburban Brisbane garden.⁷ Infection is thought to occur predominantly along the central east coast of Australia (southeast Queensland and northern New South Wales). In addition to the recent case,⁶ an adolescent “bravado case” was reported 10 years ago also in Sydney.⁸

A report of A. cantonensis infection in an adolescent in Taiwan with pica disorder was published in 2013, highlighting the potential risk of exposure to this parasite in patients with pica in other endemic areas.⁹ Since molluscs that carry A. cantonensis are endemic in even metropolitan areas of Australia, psychoeducation beyond the usual behavioural¹ and medical advice to parents, carers and clients with pica in Australia should include a warning regarding the risks associated with accidental ingestion of slugs and snails and their secretions.

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