An unusual neurological presentation after exposure to snails.

The reviewer (Dr Marion Woods, Royal Brisbane and Women’s Hospital, Australia) commented:

“The case of Angiostrongylus cantonensis infection with the clinical manifestations of eosinophilic meningo-encephalitis and myeloradiculitis that caused lower limb weakness and bladder dysfunction described in this issue of the journal is the likely consequence of ingestion of a very high worm burden of the L3 infectious larval forms of this rat nematode. The L3 larval content of slugs and snails varies considerably with some snails, such as the African giant land snail, Achotina fulica, containing up to 90,000 L3 larvae (a likely lethal dose). [1] The syndrome of myeloradiculitis with lower limb weakness and bladder dysfunction is a common manifestation of canine Angiostrongylus cantonensis infection in Australia with ingestion of snails and slugs the likely source of infection. [2] Treatment directed at reducing inflammation (corticosteroids) produces better outcomes than treatments directed at killing adult worms in the central nervous system. Our practice is to use a tapering dose of corticosteroids (60 mg/day prednisone for 5-7 days).

For clinicians who have the rare opportunity to intervene after snail or slug ingestion but prior to neurological symptoms, animal studies have shown that drugs such as albendazole (human dose 10 mg/kg/day if > 60 kg, 15 mg/kg/day if < 60 kg) can effectively kill L3 larval stages before they reach the central nervous system. [3] Usually the occurrence of eosinophilic meningitis prompts the question about slug and snail ingestion. Snails and slugs that are infected constantly exude L3 larvae in their wake onto salad vegetables and other raw foods stuffs that may be ingested by unwary future patients. In humans, the median incubation time between ingestion and meningitis symptoms is 11 days with a range of 6-31 days. [4] In animal models, up to half of the ingested L3 larvae are found in the brain as soon as 3 days post ingestion with the majority of L3 larvae found in the brain by day 7 post ingestion. By 30 days nearly all of the worms have migrated from the brain to the pulmonary arteries to become adults. [5]

[1] Wallace GD, Rosen L. Studies on eosinophilic meningitis. V. Molluscan hosts of Angiostrongylus cantonensis on Pacific Islands. The American journal of tropical medicine and hygiene. 1969 Mar;18(2):206-16.

[2] Mason KV. Canine neural angiostrongylosis: the clinical and therapeutic features of 55 natural cases. Australian veterinary journal. 1987 Jul;64(7):201-3.

[3] Lan KP, Wang CJ, Lai SC, Chen KM, Lee SS, Hsu JD, et al. The efficacy of therapy with albendazole in mice with parasitic meningitis caused by Angiostrongylus cantonensis. Parasitology research. 2004 Jul;93(4):311-7.

[4] Slom TJ, Cortese MM, Gerber SI, Jones RC, Holtz TH, Lopez AS, et al. An outbreak of eosinophilic meningitis caused by Angiostrongylus cantonensis in travelers returning from the Caribbean. The New England journal of medicine. 2002 Feb 28;346(9):668-75.

[5] Wallace GD, Rosen L. Studies on eosinophilic meningitis. VI. Experimental infection of rats and other homoiothermic vertebrates with Angiostrongylus cantonensis. American journal of epidemiology. 1969 Mar;89(3):331-44. “