Canine Alveolar Echinococcosis: An Emerging and Costly Introduced Problem in North America

Alveolar echinococcosis (AE), caused by the metacestode of Echinococcus multilocularis, is emerging in both dogs and people in North America. Here, we review 27 cases of canine AE opportunistically reported since the index case was described in 2009 in Western Canada. We describe clinical presentation, diagnosis, treatment, outcome, and source of canine infection, based on genetics of the parasite isolated from some canine cases. Diagnosis of AE was by histopathology and/or PCR on DNA extracted from metacestodes. The median age of dogs at diagnosis was 4 years (range 1-12), which is low compared to neoplasia, the most common differential diagnosis. There was no sex predilection and different breeds were involved, but there were a disproportionate number of boxers and beagles relative to their representation in the general canine population. The most common potential risk factors included contact with wildlife and visits to off leash areas. Abdominal distension was the most common clinical sign at presentation, and medical imaging generally revealed an abdominal mass. On histopathology, protoscoleces were observed in 7 out of 14 dogs. In 7 cases, DNA sequences were most similar to European (versus North American) haplotypes, identical to those recently reported in coyotes as definitive hosts in North America, and different between eastern and western North America, implying multiple introduction events. Dogs that were not treated (n = 6) had 16% survival in the first 100 days in comparison with 82% survival of treated dogs (n = 11). Direct costs to the owner of treating canine AE ranged from 1,317 to 12,655 CAD depending on the situation at the onset of treatment. This study provides important clinical, epidemiological, and economic information for veterinary practitioners and regulators for importation of dogs, and for public health, as dogs with AE may serve as indicators of parasite range expansion and risk to humans.