Heartworm in dogs in Canada in 1987.

In late November 1987, 1246 institutional veterinarians and small and mixed animal clinics across Canada were sent a questionnaire in order to assess the status of Dirofilaria immitis in Canada in 1987, and 50% of them responded. Veterinarians reported that 165,428 dogs were blood tested for heartworm disease and 511 dogs were found with D. immitis microfilariae. Another 78 dogs were amicrofilaremic but diagnosed with heartworm disease to give the total number of cases diagnosed in 1987 as 589 (0.35%).Heartworm was reported from British Columbia, Manitoba, Newfoundland, Ontario and Quebec, but most (478) of the cases were from Ontario. South-western Ontario continued to be the primary focus of the infection in Canada. There were 82 cases reported from Quebec, mostly from and around Montreal, and 23 from Manitoba, mostly from Winnipeg, Selkirk, and surrounding areas. Heartworm was found most frequently in companion dogs over three years of age maintained mainly outdoors in rural areas. About 29% of the cases were observed with clinical signs of heartworm disease and 81% had a history of not having left Canada.