Dogs and cats harbor the enteric nematodes Toxocara canis and T cati, which can be transmitted to humans via the fecal-oral route; humans are infected by ingesting larvae in undercooked infected meat; infective eggs from garden soil, sandpits, and playgrounds; eating unwashed vegetables; and/or poor hand hygiene. Reported infection rates in dogs in Western Europe range from 3.5%–34% depending on environments (eg, pet, shelter animal, stray, rural/outdoor) and from 8%–76% in cats. Increases in urban small rodent populations also attract predators (eg, foxes) that can be a reservoir for Toxocara spp. Toxocariasis in humans can result in ocular or visceral larva migrans and overt toxocariasis. Infection in humans has also been associated with neurologic symptoms, chronic airway disorders, chronic pruritus, and eczema.
Diagnosis is typically achieved by identifying eggs in feces. Eggs are resistant to adverse environmental conditions and remain infective for years. Strategic treatment of dogs and cats should emphasize treatment of puppies, kittens, and nursing dogs and cats. Preventive recommendations include administration of anthelmintics ≥4 times yearly to prevent patent infections within a population. Regular treatment q4–6wk would prevent most patent infections; this can be achieved with monthly administration of macrocyclic lactones used for heartworm prevention. Deworming pregnant dogs and cats with the aim of reducing Toxocara spp is not generally advised, as current recommended doses of anthelmintics are not highly effective against the inhibited somatic larvae involved in intrauterine infection.
Environmental control of the ubiquitous roundworm can be difficult to regularly implement; however, monthly anthelmintic therapy virtually eliminates patent infections and significantly decreases risk to pet owners and other human contacts. The zoonotic and public health implications of roundworm infection and the ease and availability of monthly anthelmintics should urge the veterinarian to act in the interest of the greater public’s health and to emphasize the importance of preventive medicine.—Indu Mani, DVM, DSc
Veterinary and public health aspects of Toxocara species. Overgaauw PAM, van Knapen F. VET PARASITOL 193:395-406, 2013.