Canis ISSN: 2398-2942

Hookworm disease

Contributor(s): Maggie Fisher, Ken Harkin

Introduction

  • Cause: classical hookworm disease caused by Ancylostoma species, particularly A. caninum.
  • Rare in the UK and when present likely to be caused by the "northern hookworm" Uncinaria stenocephala. Common in the US and more southern parts of mainland Europe.
  • A. caninum now recognized as a zoonosis.
  • Signs: hookworm disease severity and clinical signs depend to a large extent on the species of hookworm:anemia (A. caninum), lethargy, inappetence, diarrhea (may be black and tar-like in A. caninum), dermatitis.
  • Diagnosis: signs, worms seen.
  • Treatment: anthelmintics and environmental control.
  • Prognosis: good with appropriate treatment.

Pathogenesis

Etiology

  • Hookworm disease is caused by infection with immature or adult hookworm population.

Predisposing factors

General
  • Access to grass runs.
  • Inadequate worm control.
  • Warm, wet weather (so disease maybe seasonal in incidence, eg may be seen in autumn after a warm wet summer).

Specific

  • Acute and peracute A. caninum infection associated with sudden infection with a large number of larvae (though 50 to 100 adult worms may be sufficient to kill a pup).
  • Disease may be seen before the worms reach adulthood, ie in the pre-patent period.
  • Chronic infection associated with prolonged exposure to a significant hookworm population.

Pathophysiology

  • Worms ingest blood and tissue fluid and damage small intestinal mucosa so that blood/fluid loss continues even when worm itself has moved to a new feeding site.
  • In acute or peracute A. caninum infection, severe anemia is caused and the animal has no time to compensate for the degree of blood loss.
  • In chronic A. caninum infection clinical signs may be seen if the rate of blood loss exceeds the animal's capacity for compensation.
  • A. caninum peracute infection where suckling pups receive a large infection of larvae from the dam in the milk.
  • Acute symptoms may also be seen in older pup that receives a sudden large challenge for the first time.
  • A. caninum Ancylostoma caninum are voracious blood suckers and possess teeth within their buccal capsules to slash the mucosa.
  • As worms move to fresh feeding locations they leave bleeding ulcers.
  • A. caninum worms can remove 0.1 ml blood per worm per day.
  • A.braziliense is less pathogenic removing only in the region of 0.008 ml blood per worm per day.
  • U.stenocephala worms damage the mucosa, resulting in protein losing enteropathy. Blood loss less severe.
  • Eggs passed in feces embryonate and hatch into infective larvae within a week in ideal conditions.
  • Dogs then reinfected when they ingest infective third stage larvae.
  • A.caninum infection may occur through the percutaneous route.
  • Main source of A. caninum infection for neonates is remobilization of resting L3 larvae from the somatic tissues of the bitch to the mammary gland.
  • Pass in the milk to the pups.
  • Transplacental transmission does not occur or not to any significant extent.

Timecourse

  • A. caninum larvae pass in the milk to pups from birth, clinical signs typically seen in second week after birth.
  • Pre-patent period approximately 16 days.

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.
  • Prociv P & Croese J (1996) Human enteric infection with A. caninum - hookworms reappraised in the light of a "new zoonosis". Acta Tropica 62 (1), 23-44 PubMed.
  • Schnieder T et al (1996) The efficacy of doramectin on arrested larvae of A. caninum in early pregnancy of bitches. J Vet Med 43 (6), 351-356 PubMed.
  • Kalkofen U P (1987) Hookworms of dogs and cats. Vet Clin N Am Small Anim Pract 17 (6), 1341-1354 PubMed.
  • Miller T A (1966) Blood loss during hookworm infection determined by erythrocyte labeling with radioactive 51 chromium. II. Pathogenesis of Ancylostoma braziliense infection in dogs and cats. J Parasitol 52 (5), 856-865 PubMed.

Other sources of information

  • Georgis' Parasitology for Veterinarians.(1995) 6th edn. Ed Bowman D D; W B Saunders ISBN 0-7216-5589-0.


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