RANGE OF HEARTWORM (DIROFILARIA-IMMITIS) INFECTION IN MONTANA DOGS

The serological presence of heartworm in dogs of Montana was studied i n a 3-yr survey. Serum samples were provided by veterinary practitione rs throughout Montana or were submitted to the state diagnostic labora tory. Sem from 3,490 dogs were tested using an enzyme-linked immunosor bent assay (ELISA) for circulating adult heartworm antigen. Twenty-fou r serum samples were positive for heartworm antigen. Two were from dog s that had never been outside the state. Nineteen additional positive dogs, 7 of which presumably had never been out of the state, were repo rted through correspondence with veterinary practitioners. Because sui table vectors for Dirofilaria immitis exist in Montana, there is poten tial for propagation of heartworm.