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Toxocara canis ( T. canis, also known as dog roundworm) is a worldwide-distributed helminth parasite that primarily infects dogs and other , but can also infect other animals including humans. The name is derived from the Greek word toxon 'bow, quiver' and the Latin word caro 'flesh'.Bassert, J., & Thomas, J. (2014). McCurnin's Clinical Textbook for Veterinary Technicians. (8th ed.). St. Louis, MO: Elsevier T. canis live in the small intestine of the definitive host. This parasite is very common in puppies and somewhat less common in adult dogs. In adult dogs, infection is usually asymptomatic but may be characterized by diarrhea. By contrast, untreated infection with Toxocara canis can be fatal in puppies, causing diarrhea, vomiting, pneumonia, enlarged abdomen, flatulence, poor growth rate, and other complications.
As paratenic hosts, a number of , including humans, and some invertebrates can become infected. Humans are infected, like other paratenic hosts, by ingestion of embryonated T. canis eggs. The disease (toxocariasis) caused by migrating T. canis larvae results in two syndromes: visceral larva migrans and ocular larva migrans. Owing to transmission of the infection from the mother to her puppies, preventive anthelmintic treatment of newborn puppies is strongly recommended. Several anthelmintic drugs are effective against adult worms, for example fenbendazole, Milbemycin oxime, moxidectin, piperazine, pyrantel, and selamectin.
Both males and females have three prominent lips. Each lip has a dentigerous ridge on. The lateral hypodermal chords are visible with the naked eye. No gubernaculum is present. In both sexes there are prominent cervical alae. The adult T. canis has a round body with spiky cranial and caudal parts, covered by yellow cuticula. Toxocara canis is Gonochorism. The cranial part of the body contains two lateral alae (length 2 to 3.5 mm, width 0.1 mm). The eggs are brownish and almost spherical. T. canis eggs have oval or spherical shapes with granulated surfaces, are thick-walled, and measure from 72 to 85 μm. The eggs are very resistant to various weather and chemical conditions typically found in soil.
Another possible route of infection is the ingestion of paratenic hosts that contain encysted larvae from egg consumption, allowing the parasite to escape from the paratenic host and grow to adulthood within the small intestine of its definitive host, the dog.
Four modes of infection are associated with this species. These modes of infection include direct transmission, prenatal transmission, paratenic transmission, and transmammary transmission.Johnstone, Colin Dr. "Parasites and Parasitic Diseases of Domestic Animals." University of Pennsylvania, 24 Jan. 2000. http://cal.vet.upenn.edu/projects/merial/ascarids/asc_05a.html . 22 Apr. 2014.
Transmammary transmission occurs when the suckling pup becomes infected by the presence of L3 larvae in the milk during the first three weeks of lactation. There is no migration in the pup via this route.
L2 larvae may also be ingested by a variety of animals like mice or rabbits, where they stay in a dormant stage inside the animals' tissue until the intermediate host has been eaten by a dog, where subsequent development is confined to the gastrointestinal tract."Toxocariasis."
22 Apr. 2016.Veterinary parasitology 2nd edition G M Urqhart, J Armour, J L Duncen, A M Dunn F W Jennings Blackwell Science publishing 1996.
Toxocariasis can result in complications such as hepatomegaly, myocarditis, respiratory failure and vision problems, depending on where the larvae are deposited in the body.. Updated 16 Feb. 2016. In humans, this parasite can infect organs including the lungs, liver, and the back of the eye (which can result in blindness).
Anthelminthic drugs are used to treat infections in dogs and puppies for adult worms. Treatment protocol will vary based on the dog's age, production level and activity level. There are different treatment paths for puppies, pregnant bitches, lactating bitches, dogs with increased risk of infection, professional dogs, and dogs sharing homes with young children or immunocompromised individuals.
Puppies: from the age of two weeks, then every 14 days up to two weeks after weaning with fenbendazole/febantel, flubendazole, pyrantel, or nitroscanate, followed by monthly treatments for up to six months of age.
Pregnant bitches: to prevent transmission to the puppies, pregnant females can be given macrocyclic lactones on the 40th and 55th day of pregnancy or genbendazole daily from the 40th day of pregnancy continuing until the 14th day postpartum.
Lactating bitches: should be treated concurrently with the first treatment of puppies.
Dogs with increased risk of infection: i.e. those used in sports, competitions, shows, or those kept in kennels can be given two treatments 4 weeks before and 2–4 weeks after the event.
Professional dogs: i.e. therapy, rescue, or police dogs: 12 times a year, if excretion of worm eggs is to be excluded.
Dogs sharing homes with young children or immunocompromised individuals: 12 times a year, if excretion of worm eggs is to be excluded. ESCCAP. (2017). “Worm Control in Dogs and Cats”. European Scientific Counsel Companion Animal Parasites.
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