Endoparasitism in dogs: 21,583 cases (1981-1990).

Prevalence of endoparasites (particularly ascarids) in dogs examined at the Oklahoma State University veterinary medical teaching hospital during 1981 to 1990 was determined by fecal and blood examinations. Approximately 1,250 fecal and 900 blood specimens were examined each year. In 1981, 55% of dogs harbored 1 or more parasites, compared with 36% in 1990. Percentages of all endoparasitic species decreased, except Giardia spp, which increased. The greatest decrease in prevalence was for Ancylostoma spp, which changed from 39% in 1981 to 15% in 1990. Prevalence of Toxocara spp and Trichuris spp also significantly decreased from 1981 (8% and 12%, respectively) through 1990 (4% and 9%, respectively). Although there appeared to be a downward trend in these ascarid infections, considerable environmental contamination probably existed and continues to exist because of high fecundity and long survival of eggs in the environment. Prevalence of Dipetalonema spp had a downward trend from a high of 4% in 1981 to < 1% by 1991. Prevalence of Dirofilaria spp decreased from 12% in 1982 to 6% in 1985, but by 1990, it was 11%.