Prevalence of heartworm, Sarconema eurycerca, Wehr, 1939 (Nematoda), in whistling swan, Cygnus columbianus columbianus

From 1973 to 1976, 795 whistling swans, Cygnus columbianus columbianus, were surveyed for microfilariae of the heartworm, Sarconema eurycerca, by blood test. Swans were captured on their east coast wintering grounds in Maryland and North Carolina, and on their breeding grounds on the North Slope, Alaska. Prevalence of heartworm in winter was 18, 9, 27, and 19% in 1973, 1974, 1975, and 1976, respectively. Prevalence was 32% in adults on the breeding grounds, 1974. Overall prevalence during 4 years was 20%; prevalence was 19% in adults and 24% in juveniles. Microfilariae were not found in cygnets 4 to 6 weeks of age on the breeding grounds.