Toxocariasis in a Dog: A Case-Based Approach to Diagnosis and Treatment

Toxocariasis is an important gastrointestinal parasitic infection in dogs caused by Toxocara canis, an ascarid nematode that localizes in the small intestine. The infection occurs worldwide and is particularly relevant in young dogs, where clinical disease can be more evident. Dogs may acquire infection through ingestion of food contaminated with Toxocara spp. ova, as well as through transplacental, transmammary, and cutaneous routes¹. Paratenic hosts include different species of mammals and birds. 

The clinical presentation can range from subclinical infection to significant gastrointestinal disease. Larvae 2 (L2) are responsible for visceral and ocular larval migration in paratenic hosts². Clinical disease is most frequently encountered in dogs younger than 6 months, while adult dogs may show few or no clinical signs and can act as reservoirs of infection³. 

Case Presentation² 

A 2.5-month-old female Pomeranian pup was presented to the Department of Veterinary Clinical Complex, College of Veterinary and Animal Sciences, Meerut, Uttar Pradesh, with inappetence and vomiting for four days. 

On clinical examination, the pup was slightly lethargic and dull. Rectal temperature, heart rate and respiratory rate were apparently normal. However, the mucous membranes were pale, and the capillary refill time exceeded three seconds. Melena was observed, along with white-coloured worms expelled in the faeces. 

The combination of gastrointestinal signs, pallor and visible worms warranted immediate parasitological examination. 

Diagnostic Approach 

Faecal material and the expelled worms were collected for examination and identification. Direct faecal smear examination demonstrated a large number of brownish, spherical, unembryonated eggs of Toxocara spp. 

Microscopic morphological examination of the adult parasites identified them as Toxocara canis. The male worm showed a curved posterior end, whereas the female worms had straight tails. Cephalic alae were also observed at the anterior end. 

Based on the clinical findings, identification of parasitic ova and morphological characterisation of the adult worms, the pup was diagnosed with toxocariasis. Coproscopy is described as a rapid diagnostic method for toxocariasis². 

Treatment and Clinical Outcome 

The pup was treated with pyrantel pamoate at 5 mg/kg body weight orally for three days. Supportive therapy included inj. ranitidine at 0.5 mg/kg body weight intramuscularly once daily for three days and syrup aRBCe pet at 2 ml orally twice daily for 15 days. 

The pup showed marked recovery after seven days of treatment. Treatment with pyrantel pamoate has also been associated with complete recovery in canine toxocariasis¹. 

Practical Clinical Insights 

For practicing veterinarians, this case highlights several points relevant to everyday clinical evaluation: 

• Age matters: Young pups, particularly those below six months, are more likely to develop clinical disease. 

• Do not overlook pallor: Anaemia may accompany significant parasitic infection and should be assessed alongside gastrointestinal signs. 

• Examine faeces carefully: Visible worms, melena and gastrointestinal abnormalities should prompt coproparasitological examination. 

• Confirm parasite identity: Identification of Toxocara spp. ova together with morphological examination of expelled adult worms supported the diagnosis in this case. 

• Consider the zoonotic relevance: Humans are accidental hosts, making appropriate antiparasitic management important for reducing the potential risk to pet owners. 

• Assess the clinical picture together: Clinical signs depend on the adult worm burden and immune status of the host¹. 

In this pup, the combination of vomiting, inappetence, pallor, melena and visible worms provided an important clinical indication, while faecal examination and parasite morphology helped establish the diagnosis. Early recognition and appropriate antiparasitic treatment, accompanied by supportive care when clinically indicated, can therefore be important in managing symptomatic canine toxocariasis. 

References 

1. Nijsse R, Mughini-Gras L, Wagenaar JA, Ploeger HW. Recurrent patent infections with Toxocara canis in household dogs older than six months: a prospective study. Parasites & vectors. 2016 Oct 4;9(1):531. https://link.springer.com/content/pdf/10.1186/s13071-016-1816-7.pdf 

2. Varun VK, Maurya PS, John JK, Jithin MV, Singh AK, Chandra N, Sarkar TK. Diagnosis and treatment of Toxocara canis infection in a dog-A case report. Indian Journal of Veterinary Medicine. 2021;41(2):66-8. https://isvm.org.in/backend/web/uploads/Paper14d.pdf 

3. Sager H, Moret CS, Grimm F, Deplazes P, Doherr MG, Gottstein B. Coprological study on intestinal helminths in Swiss dogs: temporal aspects of anthelminthic treatment. Parasitology research. 2006 Mar;98(4):333-8. https://boris-portal.unibe.ch/server/api/core/bitstreams/a4bdfd6a-02de-41ed-b606-e5d43545de01/content