Parasitic worms in the cat & dog can be defined as tapeworms ( cestodes ) & roundworms ( nemotodes ).

Adult tapeworms live in the intestines of the primary host animal, releasing segments ( proglottids ) containing eggs that may be seen in the faeces or adherent to the coat & skin around the back passage. They resemble a flattened grain of rice & are mobile when first passed. These eggs must be ingested by a different species of animal, the secondary host to develop further into the larval stage. Infection with tapeworm is caused by the ingestion of a secondary host carrying the larval stage of the parasite.

The most common tapeworm found in the cat & dog is Dipylidium caninum. Eggs shed in the faeces are ingested by fleas & develop into larvae within the flea. Cats & dogs are then infected by ingesting fleas during grooming. Young children & babies may also be infected following the accidental ingestion of fleas.

The very small tapeworm, Echinococcus granulosus is far less common, but represents a serious risk to humans. The dog is the primary host & mammals such as sheep & humans are the secondary hosts. Eggs from this tapeworm will infect humans producing large hydatid cysts, whereas dogs pick up the larval form in uncooked meats or by mouthing dead animals. Eggs shed by infected dogs can remain in the soil for 12 months & may contaminate vegetables for human consumption.

Roundworms are yellowish-white worms, 2 to 3 inches in length & pointed at each end. When passed with the stool, they are are easily seen. The eggs, however, are microscopic & can only be diagnosed by laboratory analysis.

The common intestinal worm is called Toxocara canis in the dog & Toxocara cati in the cat. Female worms produce thousands of eggs each day. Pets are infected when they ingest the eggs of the appropriate species of roundworm. Other modes of transmission include movement across the placenta during pregnancy & into the milk during lactation. Puppies are commonly infected in this way. If humans accidentally ingest infective eggs of this parasite the resultant larvae migrate into the tissues of the body. Once in the body these larvae often migrate to the eye & brain & may lead to blindness & epilepsy. This process, which is called visceral larval migrans is difficult to detect & may have very serious consequences.

Another form of roundworm seen in the cat & dog is the hookworm.This parasite invades the skin of cats & dogs & migrates to the intestine where it attaches & sucks blood. If humans contact the eggs passed, the larvae migrate into the skin causing a severe inflammatory reaction, cutaneous larval migrans.

For further information, click on the pictures: