Felis ISSN 2398-2950

Toxocara cati

Synonym(s): T. cati, cat roundworm

Contributor(s): Peter Irwin, Sheelagh Lloyd, Grace Mulcahy, Ian Wright

Introduction

Classification

Taxonomy

  • Phylum: Nematoda.
  • Class: Secernentea.
  • Order: Ascaridida.
  • Family: Toxocaridae.
  • Genus: Toxocara.
  • Species:cati / syn mystax.

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Clinical Effects

Epidemiology

Habitat

  • L2 in tissues of any mammal or bird, including dog and mice, rats, rabbits, domestic farm animals, chickens.
  • Adult worms in small intestine of cats and felidae.
  • Eggs in environment.

Lifecycle

  • See Lifecycle diagram   Lifecycle: Toxocara cati - diagram  .
    • Adult male and female.
    • Egg.
    • L2.
    • Paratenic host.

Transmission

Infection in young kitten

Transmammary transfer of L2

  • L2 transfer via milk to kittens, develop in intestine without migration.
  • This transfer can continue through lactation.
Infection with eggs
  • L2 in infective eggs ingested by kittens undergo tracheal migration (via liver, lungs, trachea) to be swallowed and develop to adults with a prepatent period of about 2 months.
Infection of adult cat

Infection with eggs

  • Infection in the adult cat may result in hepatotracheal migration and development to adult worms in the intestine.

Infection with paratenic hosts

  • L2 in paratenic hosts, ingested by cats that hunt eg rodents, birds, or are fed raw meat, develop directly in intestine to adults.
  • It has been suggested that paratenic hosts do not represent the major source of infection for cats.

Pathological effects

Intestinal infection with adult parasites
  • Cats remain susceptible to direct development of L2 to adult in intestine.

Infection with tissue larvae

  • Presumably similar to the situation in older dogs infected with T. canis: L2 larvae can migrate in tissues.
  • L2 evade immune response very effectively, through repeated shedding of their surface antigens.

Activation of L2 in pregnancy and lactation

  • In dogs it is recognized that activation of L2 occurs from about last 20 days in pregnancy through lactation + direct transfer of L2 from ingested eggs to placenta or mammary gland at these times is coincident with a marked depression in lymphocyte responses for last 3-4 weeks of pregnancy and for 4-5 weeks into lactation .
  • Transplacental transmission does not occur in the cat but activation of larvae occurs and these pass through the mammary gland to the kittens in the milk.
AdultT. cati in the intestine
  • Histopathological effects of infection have not been investigated in the cat to the extent ofT. canisin the pup where light to moderate infections   →   malabsorption, villous atrophy, + increased thickness of intestinal muscle layers, the degree of change correlates directly with level of infection.
  • Heavy infections with T. cati  →   marked distension of anterior small intestine, pot belly, and possibly intestinal obstruction.

Other Host Effects

  • The inter-relationship between hormonal effects, directly, or indirectly via immune system, in relation to larval migration and development, is unknown.

Control

Control via animal

Treatment of kittens
  • Treatment is to minimize egg shedding and adult worm burdens.
  • Recommendations include treating kittens from 3 weeks of age at two weekly intervals until 2 weeks post weaning. Then monthly until 6 months of age.

Treatment of cats from 12 weeks to adulthood

  • Treatment recommended at 3 monthly intervals is thought to reduce egg shedding, extrapolating from T. canis data.
  • Monthly treatment will reduce egg shedding by over 90% and should be considered for hunting cats, those living with small children or immune compromised adults to minimize zoonotic risk.
  • No information available on reinfection following treatment.
  • Difficult to detect infected cats.
  • Infected cats will already be shedding eggs into the environment by the time they are detected, adding to environmental contamination.
  • Treatment with a broad-spectrum anthelmintic will control any cestode infection simultaneously.
  • No treatment available for treatment of quiescent or reactivated larvae in the queen.

Control via chemotherapies

Control via environment

  • Eggs are extremely resistant, survive several years.
  • Will even survive < 1 year when feces composted.
  • Desiccation in dry heat over many days lethal to eggs.
  • Sodium hypochlorite (concentrated) when in contact with eggs for some 10 minutes or more, strips off outer surface   →   eggs less sticky   →   wash away in drains. More prolonged contact with sodium hypochlorite dissolves shell to kill egg.
  • Covering of sandpits/boxes when not in use to prevent cats defecating in them.

Diagnosis

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Further Reading

Publications

Refereed papers

  • Recent references from VetMed Resource and PubMed.
  • Dillon A R, Tillson D M, Hathcock J, Brawner B, Woolridge A et al (2013) Lung histopathology, radiography, high-resolution computed tomography, and bronchio-alveolar lavage cytology are altered by Toxocara cati infection in cats and is independent of development of adult intestinal parasites. Vet Parasitol 193, 423-426 PubMed.
  • Overgaauw P A M & Van Knapen F (2013) Veterinary and public health aspects of Toxocara spp. Vet Parasitol 193, 398-403 PubMed.
  • Wright I & Wolfe A (2007) Prevalence of zoonotic nematode species in dogs in Lancashire. Vet Rec 161, 790-791 PubMed.
  • Fisher M (2003) Toxocara cati: an underestimated zoonotic agent. Trends in Parasitol 19, 167-170 PubMed.
  • Overgaauw P Aet al(1998)Anthelmintic efficacy of oxibendazole against some important nematodes in dogs and cats.Vet Q20(2) 69-72.
  • Overgaauw P A (1997)Aspects of Toxocara epidemiologiy - toxocarosis in dogs and cats.Crit Rev Microbiol23(3) 233-251.
  • Dubinksy Pet al(1995)Role of small mammals in the epidemiology of toxocariasis.Parasitology110(2) 187-193.

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