Toxocara canis is the causative agent of both ocular and visceral larva migrans in its paratenic human hosts, representing a serious global public health threat. In addition, toxocariasis is the most common helminth infection in the U.S. The primary mode of transmission in humans is contact with contaminated soil; however, the recent identification of T canis eggs on dog hair has initiated questions regarding the risk for toxocariasis through direct contact with pet dogs. Several conflicting papers with varying results have recently examined the prevalence of T canis eggs (both embryonated and nonembryonated) on the hair of dogs. In this study, the rate of contamination in pet dogs was examined. Hair samples were collected from the head, neck, back, and perianal area of 182 animals presented to veterinary clinics, grooming centers, and boarding kennels in Dublin, Ireland. A total of 16 dogs had contaminated haircoats, and 26 eggs were quantified in total (2 nonviable, 23 unembryonated, and 1 embryonating). The prevalence of T canis contamination was 8.8%, and on average 4.24 eggs were identified per gram of hair. There were no significant differences in egg numbers from the head, neck, back, or perianal area samples; older dogs were significantly more likely to carry eggs on their hair than dogs less than 1 year of age. Study supported by Bayer Animal Health

Commentary: This study suggested that pet dogs whose owners practice proper care and husbandry pose a very low risk for T canis transmission to human contacts. The dogs in this study were likely treated with prophylactic antiparasite medications and were regularly groomed, contributing to low T canis prevalence. One point to consider in this study is that dogs with T canis eggs on their backs may have picked up eggs by rolling in soil and grass. Clinicians may advise concerned pet owners to limit this behavior in public parks to reduce the risk for hair contamination.—Carly Jordan, PhD candidate

Contamination of the hair of owned dogs with the eggs of Toxocara spp. Keegan JD, Holland CV. VET PARASITOL 173:161-164, 2010.