Echinococcus multilocularis, a tapeworm of wild canids, is one of the causative agents of echinococcosis, a lethal and increasingly important zoonosis. Infection in canids is often subclinical. Eggs shed in feces are ingested by intermediate hosts, typically small rodents, but large mammals (including humans) can become infected. Larval stages invade the intermediate host’s liver, causing proliferation of locular cysts that are locally invasive and can metastasize to other internal organs. Infection in humans resembles neoplasia, is challenging to treat, and is potentially fatal.
Range and incidence of echinococcosis are increasing throughout Europe and advancing in the U.S. The UK is currently free of E multilocularis; however, increased pet travel into the UK since introduction of the PET Travel Scheme threatens this status. Dogs may harbor the infection subclinically, and definitive diagnosis can be made only on necropsy, making routine screening problematic. A single dose of praziquantel is highly efficacious in treating infected dogs, and monthly treatment is an effective preventive. The current PET Travel Scheme (ie, requiring 1-time treatment of praziquantel given 1–5 days before importation) has thus far been effective in preventing echinococcosis from entering the UK. Political factions within the European Union seek to standardize border control and eliminate the protections afforded by the PET Travel Scheme.
