Canis ISSN: 2398-2942
Ascaridosis
Synonym(s): Ascaridosis; Toxocarosis; Toxascarosis; Roundworm
Contributor(s): Maggie Fisher, Ken Harkin, Peter Irwin
Introduction
- Cause: ascaridosis includes infection with Toxocara canis and Toxascaris leonina.
- T. canisis the ascarid most implicated as a zoonosis - cause of visceral larva migrans, ocular larva migrans and covert toxocarosis in humans.
- Signs: most likely in young pups with a heavy T. canis infection → pot-belly, thin.Occasional intestinal obstruction with heavy burdens.
- Intestinal ascarid burdens may be present in older dogs but unlikely to be associated with clinical signs.
- Diagnosis: signs, fecal egg counts.
- Treatment: anthelmintic.
- Prognosis: good if appropriate treatment.
Pathogenesis
Etiology
- Large intestinal burden ofT. canisin the small intestine of pups.
Predisposing factors
General
- Poor worm control.
- Endemic high level ofT. canisinfection in dogs and in the kennel environment.
Pathophysiology
- SeeToxocara canislife cycle
.
- 3 main sources of infection for young pups:
- Transmammary transmission of larvae that have been resting in the bitch's tissues as somatic larvae.
- Transmission in the milk - normally a minor route accounting for less than 5% of infection unless the bitch was infected in late pregnancy.
- Embryonated eggs containing L3 larvae (previously considered to be L2) in the nest/run environment.
- T. canislarvae carry out hepatotracheal migration in pups.
- Rapidly develop to adult worms in the small intestine.
- First worms mature by approximately 2.5 weeks of age.
- Small number of worms well-tolerated.
- Presence associated with villous atrophy, malabsorption, increased thickness of intestinal muscle layers Toxocara canis.
- 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.
Timecourse
- Acute signs may be seen in pups from the time that substantial numbers ofT. canisenter and mature in the intestine.
- The higher the burden the earlier clinical signs will be seen.
- Normally unweaned pups (3-8 weeks approximately).
- Ill-thrift may be seen in pups 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.
- Schnieder T, Laabs E M, Welz C (2011) Larval development of Toxocara canis in dogs. Vet Parasitol 175, 193-206 PubMed.
- Carter C N (1980) Worms also kill. Vet Rec 106 (10), 233 PubMed.
- Stoye M (1979) Ascarid and hookworm infections in the dog - biology, epizootology and control. Berl Munch Tierarztl Wochenschr 92 (23), 464-472 (Article in German) PubMed.
Other sources of information
- Deplazes P & Fisher M (2013)ESCCAP -Toxocara2012.Vet Parasitol Special Issue193/4.
- Holland CV & Smith H V (2006)Toxocarathe 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 BiologyISBN 0-900490-30-6.