Toxascaris Leonina: Dog and cat roundworm

General Description: Typical roundworm; males up to 7cm long, females up to 10cm. The eggs are oval with thick smooth coat.

Life Cycle: This roundworm infects dogs, cats, foxes and wild animals such as wolves. Toxascaris leonina has a simple, direct life cycle. The infective second-stage larva develops inside the egg 3 to 6 days after leaving the host. Larvae hatch after being ingested. The larvae burrow into the wall of the intestine, moult and return to the intestinal lumen to mature. The prepatent period is 6 weeks. Mice serve as transport hosts. Unlike Toxocara canis larvae, the larvae of this species do not migrate through body tissues or infect puppies before birth.

Location: Small intestine.

Significance: Damage occurs only in young dogs, producing poor general condition and possibly death if uncommonly large infections are present.

Effect on Host: Infected puppies have potbellied appearance and intermittent diarrhoea and show poor general condition. Intestinal obstruction can be caused if large numbers of worms are present.

Diagnostic Information: Characteristic eggs can be identified in the faeces of infected dogs.

Control: Infected dogs can be treated with appropriate drugs. Faeces removal is important in controlling canine ascarids.

Tangled mass of ascarids		T.leonina – scanning electron microscope photo of mouth parts
Eggs – T. leonina in dog faeces		T. leonina – egg enlarged