Toxocara vitulorum infection in a cohort of beef calves in Iowa.

Toxocara vitulorum, an ascarid that infects bovines, is largely considered a parasite of tropical and sub-tropical areas of the world. Infections in more temperate climates have been reported but little is known about T. vitulorum transmission in North America. Herein, we detail an investigation of an Iowa beef farm where necropsy of a 20 day old beef calf revealed a mass of large ascarid nematodes occluding the small intestine. Gross histopathological, and molecular features of nematodes recovered from the calf were consistent with T. vitulorum. Fecal samples obtained from calves in the herd revealed 14 of 34 (40%) were shedding T. vitulorum eggs. Calves continued to shed eggs following a single dose of a topical moxidectin product. These results suggest that T. vitulorum may be more widespread in the United States than previously recognized. Due to the pathogenic nature of this parasite, further investigation into the prevalence and transmission of T. vitulorum in North America is warranted.