ISSN 2398-2950      

Ascaridosis

ffelis
Contributor(s):

Ian Wright

Synonym(s): Ascarid infection; Toxocarosis; Toxascarosis; Roundworm


Introduction

  • Cause: ascaridosis includes infection with Toxocara cati and Toxascaris leonina.
  • T. cati is the ascarid most implicated as a zoonosis - a cause of visceral larva migrans, ocular larva migrans and covert toxocarosis in humans.
  • Signs: most likely in young kittens with a heavy T. cati infection   →   pot-belly, thin. Occasional intestinal obstruction with heavy burdens.
  • Intestinal ascarid burdens may be present in older cats. Unlikely to be associated with acute clinical signs but may be links with infection to feline bronchitis and asthma. 
  • Diagnosis: signs, fecal egg counts.
  • Treatment: anthelmintic.
  • Prognosis: good if appropriate treatment.

Pathogenesis

Etiology

  • Large intestinal burden of T. cati in the small intestine of kittens.
  • Migrating larvae leading to lung pathology.

Predisposing factors

General

  • Poor worm control Worm control.
  • Endemic high level of T. cati infection.

Pathophysiology

  • See Toxocara cati life cycle   Lifecycle: Toxocara cati - diagram  .
  • 2 main sources of infection for young kittens:
    • Transmammary transmission of larvae that have been resting in the queen's tissues as somatic larvae.
    • Embryonated eggs containing L3 larvae (previously considered to be L2) in the nest/run environment.
  • T. catilarvae carry out hepatotracheal migration in kittens.
  • Rapidly develop to adult worms in the small intestine.
  • First worms mature by approximately 3 weeks of age.
  • Small number of worms well-tolerated.
  • Presence associated with villous atrophy, malabsorption, increased thickness of intestinal muscle layers.
  • Larger worm burden: pot-bellied appearance and more marked malabsorption, etc.
  • The larger the worm burden the higher the risk of intestinal obstruction or death.
  • Villous atrophy within the small intestine leading to malabsorption Malabsorption.
  • T.cati migration can induce significant pulmonary and interstitial lung disease with severe lung parenchymal disease having been found in naturally infected cats.

Timecourse

  • Acute signs may be seen in kittens from the time that substantial numbers of T. cati enter and mature in the intestine.
  • The higher the burden the earlier clinical signs will be seen.
  • Normally unweaned kittens (3-8 weeks approximately).
  • Ill-thrift may be seen in kittens particularly in this age range.

Epidemiology

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Dillon A R, Tillson D M, Hathcock J 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 (4), 423-426 PubMed.
  • Wright I & Wolfe A (2007) Prevalence of zoonotic nematode species in dogs in Lancashire. Vet Rec 161 (23), 790 PubMed.
  • Fisher M (2003) Toxocara cati: an underestimated zoonotic agent. Trends in Parasitology 19 (4), 167-170 PubMed.
  • Wolfe A, Hogan S, Maguire D et al (2001) Red foxes (Vulpes vulpes) in Ireland as hosts for parasites of potential zoonotic and veterinary significance. Vet Rec 149 (25), 759-763 PubMed.
  • Carter C N (1980) Worms also kill. Vet Rec 106 (10), 233 PubMed.

Other sources of information

  • Deplazes P & Fisher M (2013) ESCCAP -Toxocara 2012. Vet Parasitol Special Issue 193/4.
  • Holland CV & Smith H V (2006) Toxocara the enigmatic parasite. CABI Publishing, Wallingford, UK. ISBN 1-84593-026-6.
  • Lewis J W & Maizels R M (1993) Toxocara and toxocariasis - Clinical, epidemiological and molecular perspectives. British Society for Parasitology and the Institute of Biology ISBN 0-900490-30-6.

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