Figure 1

Figure 1. . . . Calgary and Edmonton, Alberta, Canada, census metropolitan areas in which 91 coyote carcasses were collected during 2009–2011 and tested for Echinococcus multilocularis. Reference maps (2006) were obtained from...

Ninety-one hunted or road-killed coyotes were collected during October 2009–July 2011. Most (n = 83) of the carcasses were from the Calgary census metropolitan area (CMA) (Figure 1). The remainder (n = 8) were opportunistically collected from the Edmonton CMA. Of those from the Calgary CMA, the exact location of collection was known for 60 animals: 27 were from Calgary and 33 were from the rural fringe, including 2 near Strathmore. Of the carcasses from the Edmonton CMA, 7 were from Edmonton and 1 was from a periurban site. Sex and age of 90 of the coyotes were recorded.

Before necropsy, all carcasses were stored at −20°C. Gastrointestinal tracts collected at necropsy were refrozen at −80°C for 3–5 days to inactivate Echinococcus spp. eggs. Once thawed and dissected, intestinal contents were washed, cleared of debris, and passed through a sieve (500-µm pores), and the material in the sieve was examined for Echinococcus spp.

Figure 2

Figure 2. . . . Differential interference contrast micrograph of a representative Echinococcus multilocularis isolate from a coyote carcass in Alberta, Canada, October 2009–July 2011. The parasite was 2,059.72 μm long, as measured...

Adult tapeworms were counted and identified as E. multilocularis on the basis of morphologic features (Figure 2). To confirm morphologic identification, PCR was performed by using species-specific primers (11). Briefly, a representative adult worm from each positive animal was lysed in 50 μL of DNA extraction buffer (500 mmol/L KCl, 100 mmol/L Tris-HCl, pH 8.3, 15 mmol/L MgCl₂, 10 mol/L dithiothreitol, and 4.5% Tween 20) containing 2 μL of proteinase K. This lysate was further diluted (1:20 in double-distilled water), and 2 μL was used for PCR. Amplicons of an expected 395 bp confirmed infection with E. multilocularis.

E. multilocularis was identified in 23 (25.3%) of 91 coyotes by using morphologic and molecular identification. Among positive animals, 18 (20.5%) of 83 were from the Calgary CMA and 5 (62.5%) of 8 were from the Edmonton CMA. In the Calgary CMA, 4 (14.8%) of 27 positive animals were found in the city and 9 (27.3%) of 33 were found in the rural fringe (Figure 1). Five (21.73%) of 23 coyotes for which the location was not recorded were also positive.

E. multilocularis intensity (number of cestodes per host) ranged from 1 to 1,400 (median 20.5). The frequency of infection was significantly higher in male coyotes (n = 44, 34.19%) than in female coyotes (n = 46, 15.2%; χ² 4.337, df 1, P_exact = 0.05) (Table). No difference was detected between 43 juvenile coyotes and 47 adult coyotes (Table).

We demonstrated that E. multilocularis is common in coyotes of metropolitan areas of Calgary and Edmonton, Alberta, Canada, including their urban cores. This finding might indicate an emerging phenomenon similar to that observed in Europe with infiltration of urban centers by E. multilocularis caused by an increase in red foxes in cities such as Copenhagen, Geneva, and Zurich (2). In Alberta, this phenomenon may be caused by coyotes occupying the urban landscape or by city sprawl invading the natural habitats of coyotes.

Our data suggest that E. multilocularis is enzootic in coyotes in Alberta and that perpetuation of the wild animal cycle of E. multilocularis within cities and surroundings and potential infection of domestic dogs may pose a zoonotic risk, as documented on Saint Lawrence Island, Alaska, and in China (2,12). With a considerable increase in domestic dog population of Calgary (32.1% increase since 2001, a total of 122,325 dogs in 2010; Animal and Bylaw Services Survey 2010, www.calgary.ca/CSPS/ABS/Pages/home.aspx) and substantial human population growth (32.9% increase in Calgary since 1999; Statistics Canada, 2009, www.statcan.gc.ca/start-debut-eng.html), awareness is needed of potential transmission risks associated with changing city landscapes and E. multilocularis in the urban environment.

In Canada, only 1 autochthonous human case of alveolar echinococcosis has been reported in Manitoba (13). However, imported cases have been described. In Alberta, there are no known reports of alveolar echinococcosis. This finding may be caused by the long incubation time required for clinical manifestation in humans (12) or a strain of E. multilocularis with a low zoonotic potential. Although there is little evidence of human risk from the strain of E. multilocularis in central North America (14), a human case caused by this strain has been confirmed (15).

Our finding of E. multilocularis in coyotes in urban regions in Alberta suggests that surveillance for this parasite should be increased in North America. Although removal of this parasite from domestic dogs and cats is effective, eradication from free-ranging definitive hosts may be unfeasible (2,12). Interventions other than improving public awareness about prevention and transmission risk are probably unnecessary, and public health messages should target veterinarians and dog owners because domestic dogs probably represent the main infection route for humans in North America (2,12). Genetic characterization of E. multilocularis and spatially explicit transmission models should also be developed to better assess risks of this emerging zoonosis in North America and worldwide.