Atlas of livestock parasites
digitized collection of microscopical preparations

Atlas of Parasites Contents Information sources Glossary Administration

Toxocara canis (dog)



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"dog roundworm"

Distribution: Worldwide.   

Host: Small intestine of dogs (T. canis=In Czech: škrkavka psí) and cats (T. cati=In Czech: škrkavka ko?i?í) and foxes.

Life Cycle: Single-celled eggs pass from the host in the feces and develop to the infective stage in the environment (from soil or on fur). Dogs acquire infections of T. canis by transplacental (most important) and transmammary transmission or by the ingestion of larvated eggs or paratenic hosts (rodents). Cats acquire T. cati infection by ingestion of larvated eggs or paratenic hosts. Transmammary transmission may also occur in some circumstances. 

Pre-patent period is variable, typically 21 days after prenatal infection; 27-35 days after lactogenic infection; 32-39 days after ingestion of eggs.  Patent period 4-6 months except where immunity intervenes for example in pups.   

Diagnosis: Eggs are detected using centrifugal or simple fotation examination techniques. Toxocara eggs have a dark, round, single-celled embryo contained in a thick shell wall. Eggs of the two species are diffcult to differentiate. Toxocara canis tends to be subspherical, and T. cati tends to be elliptical in shape.     

Size: 85–90 × 75 µm   T. canis       

Size: 65 × 75µm T. cati             

Clinical features: Toxocara is an important pathogen in puppies and kittens. Stillbirths, neonatal deaths (T. canis), or chronic ill-thrift (T. canis, T. cati) can occur in infected animals. Adult dogs and cats are much less likely to have symptomatic infections. Low burden asymptomatic, higher burden may appear as cachexia and pot bellied appearance in pups.  Heavy infection can cause intestinal blockage or intussusception.  A low burden in older animals is unlikely to cause clinical signs.

Additionally, both species (especially T. canis) have zoonotic importance as causes of visceral and ocular larva migrans, particularly in children !    


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