Toxocara spp

From Cat
Adult Toxocara cati nematode

Toxacara cati is a common parasitic Ascarid nematode of cats worldwide.

In heavy infestations, it can cause ill-thrift and fading kitten syndrome, but otherwise is asymptomatic[1]. T. canis and T. malaysiensis[2] have also been reported in cats.

Eggs contains a second-stage larva which infects the cat by accidental ingestion, where the larvae migrate through the gut wall, pass through the liver to the lungs. In the lungs the larvae breakout into the air spaces, are carried up the trachea and are swallowed. They develop through the 3rd and 4th stages to the adults, which live in the small intestinal lumen. The prepatent period for this route of transmission is 56 days, although the adult worms are present in the small intestine by day 28[3].

A second route of infection for cats is via a paratenic host. If a mouse eats an infective egg the larva hatches and migrates to the tissues (liver) where it arrests. When the cat eats the mouse the larvae are freed and develop in the gut to adults. There is no extra-intestinal migration in this case.

The final route of infection is trans-mammary. The second stage larvae acquired in the milk by the nursing kitten develop in the intestine to adults. Like the case with a paratenic host, no extra-intestinal migration takes place after trans-mammary transmission. The prepatent period is about 3 weeks when the trans-mammary or paratenic host routes are utilized[4].

In adult cats, infection is usually asymptomatic, but trans-pulmonary migration can be responsible for verminous pneumonia.

A fading kitten syndrome is commonly seen in kittens that have not received regular anthelmintic therapy, or from Queens that have not been wormed during pregnancy. In affected kittens, weight loss, anaemia, diarrhoea, a pot-bellied appearance, and sudden death have been recorded.

Treatment is usually effective with fenbendazole or selamectin.


  1. Bowman, DD et al (2003) Feline clinical parasitology. Iowa University Press, Iowa. pp:274-281
  2. Gibbons LM et al (2001) Toxocara malaysiensis n. sp. (Nematoda: Ascaridoidea) from the domestic cat (Felis catus Linnaeus, 1758). J Parasitol 87(3):660-665
  3. Duarte A et al (2010) Survey of infectious and parasitic diseases in stray cats at the Lisbon Metropolitan Area, Portugal. J Feline Med Surg 12(6):441-446
  4. Lee AC et al (2010) Epidemiologic and zoonotic aspects of ascarid infections in dogs and cats. Trends Parasitol 26(4):155-161