First report of Toxocara vitulorum infection in a dairy calf in Tennessee

The ascarid nematode, Toxocara vitulorum, is a destructive parasite of ruminants with a world-wide distribution that causes mortality in calves, especially those with poor nutrition. Reports of T. vitulorum are scarce in the continental U.S. and Canada. A single gravid female T. vitulorum was discovered on the necropsy of a 2.5-month-old miniature Jersey calf from a dairy farm in Sparta, Tennessee. Genetic analysis of the 18S and COI genes revealed a 100 % match to T. vitulorum samples isolated from beef calves in Iowa and a 96.73 % match to T. vitulorum isolated from a yak in Austria. Although perforation of the small intestine was seen in the calf and is the typical cause of death in calves with high burdens of this worm, it is unknown if this single nematode infection contributed to the cause of death in this case. The source of the infection in this calf also remains unknown. Fecal centrifugal flotations on the rest of the herd (n = 8) did not produce any T. vitulorum eggs, even in the 2 calves that were under 6 months old on the farm. We were unable to obtain milk to test for T. vitulorum larvae from the calf's mother. This is the first report of T. vitulorum in Tennessee. Given the devastation caused by this parasite in cattle and bison herds in other countries, further studies to determine the prevalence and pathogenicity of this parasite in the U.S. are vital to prevent spread of this parasite to other vulnerable species and to prevent economic losses in the animal industry.