Exotic venomous snakebites in Switzerland reported to the National Poisons Information Centre over 22 years

The private keeping of exotic venomous snakes is legally permitted in Switzerland. The aim of the present study was to characterise the epidemiological and clinical features of bites by exotic venomous snakes over a period of 22 years in Switzerland.

We included all calls related to exotic snakebites recorded at the Swiss National Poisons Information Centre (Tox Info Suisse) from 1997 to 2018. Exclusion criteria comprised indigenous snakes, non-venomous exotic snakes such boas or pythons, clinical courses incompatible with a snakebite or calls from abroad. Follow-up information was graded according to the Poisoning Severity Score.

Within the study period, 1,364 calls related to snakebites were recorded at Tox Info Suisse; 148 (11%) cases were attributed to exotic venomous snakes and fulfilled the study criteria. A total of 112 (98%) of 114 patients with medical follow-up information exhibited sufficient causality between exposure and clinical effects. Only adult patients were affected. The median age was 40 years (range 16-71) and the male gender was predominant (n = 136, 92%). Viperidae were involved in 87 (78%) and Elapidae in 25 (22%) patients. Overall, the main affected body part was the hand (89 patients, 79%). In the majority of the patients the clinical course was mild (46, 41%) or moderate (40, 36%), in a lower proportion asymptomatic (6, 5%) or with severe symptoms (20, 18%). No fatalities were reported in the study period. Severe symptoms were observed after elapid bites in six patients (24%) and after viper bites in 14 patients (16%). Besides local effects, neurological disorders after elapid bites and haematological disorders after viper bites were most frequently reported. Antivenom was administered in 24% (27 patients: 18 Viperidae, 21% and 9 Elapidae, 36%; 5 patients (4%) required multiple doses), overall, with good resolution of symptoms.

Exotic snakebite is a rare occurrence in Switzerland but has led to medically relevant morbidity, sometimes requiring antivenom treatment. Over half of the envenomed patients required symptomatic or specific treatment. No fatalities or bites in children were reported.