Felis ISSN 2398-2950

Echinococcosis

Contributor(s): Maggie Fisher

Introduction

  • A serious zoonotic infection with adult tapeworms or the larval hydatid cysts of the genus Echinococcus.
  • Cause: dogs are more important than cats as the principal or occasional definitive host of all species of Echinococcus except Echinococcus oligarthrus where felids are the definitive hosts.
  • Cats (along with foxes and dogs) are definitive hosts for Echinococcus multilocularis and felids are the definitive hosts for Echinococcus oligarthrus (found in Central and South America). (This component will address feline infection with E. multilocularis.)
  • Signs: humans become infected with the metacestode stage resulting in the formation of hydatid cysts in various organs.
  • Cats infected with the adult tapeworm are unlikely to show any clinical signs.
  • Diagnosis: fecal examination using Coproantigen or coproPCR.
  • Treatment: praziquantel eliminates infection with adult worms in the cat.

Pathogenesis

Pathophysiology

Definitive host

  • Cats acquire infection by ingesting the metacestode stage containing infective proscolices in an intermediate host.
  • The pathogenic effect of adult tapeworms in the definitive host, including the cat, is low irrespective of challenge.

Intermediate hosts

  • Intermediate hosts, including man, are infected by ingestion of eggs passed in feces.
  • In intermediate hosts Echinococcus hatch in the lumen of the intestine, penetrate the intestinal wall   →   hepatic portal system   →   liver   →   form cysts. The liver is the primary predilection site.
  • With E. multilocularis undifferentiated germinal cells occasionally break free from the cyst and metastasize to other organs, especially the lungs and brain.
  • The cysts of E.multilocularis are not restricted by a fibrous capsule and thus progressively expand into surrounding host tissue through the growth of tubular processes.
  • Cysts develop slowly in the intermediate host (becoming infective in 2-4 years in the case of E granulosus and 40-60 days for E. multilocularis) but will eventually kill rodent intermediate hosts.

Timecourse

  • In suitable conditions the proscolices can survive for 1-2 weeks after the death of the intermediate host.
  • Onset of egg production begins about 28-35 days after infection with E. multilocularis.
  • Some adult E. multilocularis worms remain in the cat for up to approximately 3-4 months before they are eliminated.

Epidemiology

  • Eggs excreted by infected cats are fully embryonated and appear to be immediately infective for intermediate hosts. However transmission of infection to rodents from cats occurs poorly compared to dogs or foxes, so it appears that the cat is a poor host for E. multilocularis.
  • E. multilocularis eggs can remain infective in the environment for at least 6 months.
  • Insects, such as blowflies, and birds may be important in dispersing eggs from feces.
  • Foxes are most important definitive hosts and infection of intermediate hosts including humans may occur by accidental ingestion of vegetation, eg blackberries, dandelion leaves contaminated with eggs from fox feces in endemic areas.

Diagnosis

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Treatment

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Prevention

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Kapel C M, Torgerson P R, Thompson R C et al (2006) Reproductive potential of Echinococcus multilocularis in experimentally infected foxes, dogs, racoon dogs and cats. Int J Parasitol 36 (1), 79-86 PubMed.
  • Eckert J & Deplazes P (2004) Biological, epidemiological, and clinical aspects of echinococcosis, a zoonosis of increasing concern. Clin Microbiol Rev 17 (1), 107-135 PubMed.
  • Roberts M G & Aubert M F A (1995) A model for the control of Echinococcus multilocularis in France. Vet Parasitol 56 (1-3), 67-74 PubMed.

Other sources of information

  • www.esccap.org; website for European Scientific Counsel: Companion Animal Parasites, guidelines for worm control in cats and dogs.
  • Eckert J et al (2002) WHO/IE Manual on echinococcosis in humans and animals: a public health problem of global concern. Published by WHO and OIE, Paris.
  • Echert J (1998) Alveolar Echinococcosis (Echinococcus multilocularis) and other forms of Echinococcosis (Echinococcus vogeli and Echinococcus oligarthrus). In: Zoonoses. biology, clinical practice and public health control. Ed. S R Palmer, Lord Soulsby & D I H Simpson. Oxford University Press. pp 689-716.


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