Canis ISSN: 2398-2942

Ancylostoma caninum

Synonym(s): A. caninum

Contributor(s): Stephen Barr, Peter Irwin

Introduction

Classification

Taxonomy

  • Superfamily: Strongyloidea.
  • Genus: Ancylostoma.
  • Species: Caninum.

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Clinical Effects

Epidemiology

Habitat

  • Adults in small intestine.
  • Egg in environment.
  • L3 in environment; warm, moist/wet areas.
  • L3 persist in somatic tissues, mainly muscle.
  • L3 arrest in intestinal mucosa.
  • L3 in muscles of paratenic host, eg rodents.

Lifecycle

  • See lifecycle diagram Lifecycle Ancylostoma caninum - diagram.
    • Adult.
    • Egg.
    • 3rd stage larva.
    • Somatic 3rd stage larva.

Transmission

  • Only relatively limited transmission will occur in UK as the larvae need high temperatures for development.
  • In the US, transmission common in wet climates (south-eastern states).
  • In northern Australia, transmission occurs all year round.

Direct feco-oral transmission

  • Eggs passed in feces develop into infective L3 that are either ingested or penetrate the skin. Dogs can become heavily infected when they are put out on to grass or soil after warm, wet weather.

Maternal transmission

  • L3 are transferred from the bitch to her puppies, with virtually all the transmission taking place via the milk during weeks 1-3, but can be for as many as 5 weeks of lactation.
  • Transplacental transmission also occurs.

Paratenic hosts

  • Mice and some other animals have been shown to act as paratenic hosts, although their importance in the epidemiology of A. caninum is unknown.

Pathological effects

  • Protective immunity is evident in older dogs.
  • Hypersensitivity reaction to migrating larvae in older dogs can induce dermatitis.
  • Worms grasp plugs of mucosa in their buccal capsules and lacerates arterioles with their teeth.
  • Blood loss begins 8 days after infection.
  • Hemorrhagic anemia with loss of up to 0.1 ml blood/worm/day through blood sucking by worm, and hemorrhage from sites vacated as worms move several times a day.
  • Heavy infections produce acute anemia Ancylostoma caninum anemia (gum) in a puppy that may be accompanied by diarrhea in sucking pups and young dogs, with deaths of puppies 20-30 days after birth (sucking pups being particularly susceptible due to their low iron reserves) or young dogs 10-20 days after a large infection.
  • Heavy infection is more likely to cause diarrhea Diarrhea: parasitic or bloody diarrhea than similar number of Uncinaria spp. This may appear as frank or altered (black) blood.
  • Occasionally, respiratory distress due to trauma and hemorrhages from a very large bolus of larvae migrating though the lungs 1-5 days after infection of young puppies.
  • In lighter infections and in older animals, compensatory erythropoiesis maintains the animal with chronic anemia, dullness, reduced appetite, weight loss or reduced growth rates until eventually, acute iron deficiency anemia may intervene.
  • Eosinophilic hypersensitivity reaction to L3 penetrating the skin in sensitized animals can induce ulcerations and moist eczema, particularly on interdigital skin; this occurs in hot weather after rains when dogs are put out onto wet grass or soil.

Other Host Effects

  • Teeth cut into mucosa and L4 and adults feed on and use oxygen from blood and/or graze on mucosa, changing position and leaving bleeding points.
  • In the USA and Australia (especially tropical North) clinical disease is more common than in the UK, especially in late spring, summer and early autumn.
  • Rare report of occasional A. caninum adults in an indigenous dog in the UK.
  • Overwhelming infections seen in poorly managed kennels and pet shops or unpaved kennelling facilities.
  • Disease is unlikely to be seen in UK except in imported dogs.
  • Chronic anemia might be seen in an imported dog.
  • Maternal transmission and disease could be seen in puppies born to a bitch for possibly up to a year after she was imported.

Control

Control via animal

  • Anthelmintic treatment.
  • Remove from grass/soil runs.
  • The presence and later development of hypobiotic larvae in an imported dog is possible for perhaps up to a year.

Control via chemotherapies

Intestinal stages

Somatic larvae

Control via environment

  • Only very hot, dry conditions will kill the larvae.
  • Preventing neonatal disease requires cage sanitation and periodic anthelminthic medication of all adult dogs. Administer anthelminthic to pups from one week of age until weaning if anemia/weakness occurs and bi-weekly from weaning to 3 months of age in problem kennels.
  • Treat bitches that have lost litters with fenbendazole (50 mg/kg) given 4-9 days before whelping. Followup treatment 10 days later can prevent infection of pups from milk.

Public Health

  • Hookworms are a cause of cutaneous larva migrans (am) associated with L3 migration.
  • Initial infection in humans usually associated with larvae penetration of unprotected feet.
  • Infection can occur due to accidental ingestion of larvae and may lead to eosinophilic enteritis.
  • A. braziliense is the species most usually associated with zoonotic disease.
  • Feet, legs, buttocks and hands are the human body regions most commonly affected with CLM.

Vaccination

  • A vaccine comprising irradiated larvae for parenteral injection was marketed in the US but marketing was suspended.
  • No vaccine available in Australia.

Diagnosis

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Further Reading

Publications

Refereed papers

Other sources of information

  • Bowman D D (1999) Nematodes. In:Georgis' Parasitology for Veterinarians. Ed.: D D Bowman. 2nd edn. Philadelphia: W B Saunders. pp 178-184.
  • Bowman D D (1992) Hookworm parasites of dogs and cats. Comp Cont Ed Pract Vet 14, pp 585-594 (Review).
  • Miller T A (1971) Vaccination against the canine hookworm diseases. Advances in Parasitology 9, pp 180-183 (Review of life cycle, pathology and vaccination).

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