Prevention of microbial species introductions to the Arctic: The efficacy of footwear disinfection measures on cruise ships

Biosecurity measures are commonly used to prevent the introduction of non-native species to natural environments globally, yet the efficacy of practices is rarely tested under operational conditions. A voluntary biosecurity measure was trialled in the Norwegian high Arctic following concern that non-native species might be transferred to the region on the footwear of travellers. Passengers aboard an expedition cruise ship disinfected their footwear with the broad spectrum disinfectant Virkon S prior to and in-between landing at sites around the remote Svalbard archipelago. The authors evaluated the efficacy of simply stepping through a disinfectant foot bath, which is the most common practice of footwear disinfection aboard expedition cruise ships in the Arctic. This was compared to a more time consuming and little-used method involving drying disinfected footwear, as proposed by other studies. The two practices were evaluated by measuring microbial growth on paired footwear samples before and after disinfection under both conditions. Step-through disinfection did not substantially reduce microbial growth on the footwear. Allowing disinfected footwear to dry, however, reduced the microbial burden significantly to lower levels. Thus, the currently adopted procedures used aboard ships are ineffective at removing microbial burden and are only effective when footwear is given more time to dry than currently granted under operational conditions. These findings underscore results from empirical research performed elsewhere and suggest the need to better relay this information to practitioners. It is suggested that footwear should minimally be wiped dry after step-through disinfection as a reasonable compromise between biosecurity and practicability.