Equis ISSN 2398-2977

Habronema spp

Contributor(s): Timothy Nuttall, Gemma Pearson

Introduction

Classification

Taxonomy

  • Phylum: Nematoda.
  • Class: Secernetea.
  • Order: Spidurida.
  • Family: Habronematidae.
  • Genus:Habronema.
  • Species:muscae,majus(microstoma) andmegastoma(Draschiamegastoma).

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Clinical Effects

Epidemiology

Habitat

  • Worldwide distribution but infection prevalence increases with warmer climates.
  • Cutaneous lesions are often found in spring and summer due to increased activity of the intermediate hosts.

Lifecycle

  • Eggs/L1 are passed in feces from infected horses.
  • L1 are ingested by larval stages of intermediate hosts (house and stable flies).
  • L1 develop to L3 in synchrony with intermediate hosts development to maturity.
  • When the adult flies feed around the muzzle of horses the L3 larvae pass from its mouthparts and are swallowed.
  • L3 larvae burrow into the mucosa of the horses stomach forming nodules.
  • L3 larvae develop to mature adults after around 8 weeks in the nodules and produce eggs.

Transmission

  • Adult flies transmit larvae from feces to horses.

Pathological effects

  • Adult worms in stomach cause a (usually) clinically inapparent gastritis.
  • Larvae deposited on skin, open wounds or chronically wet areas on the horse can cause pruritic granulomatous lesions.
  • Ocular granulomatous lesions cause discharge and chronic conjunctivitis.
  • Larvae deposited around male genitalia may cause swelling and edema around the lesions, with occasionally massive lesions developing on male genitalia.
  • Lesions in lungs due to migrating larvae have also been reported.

Other Host Effects

  • No effects are seen on intermediate host.

Control

Control via animal

  • Glucocorticoids   Therapeutics: glucocorticoids   to control hypersensitivity reactions to the L3 larvae may be required as well as specific antiparasitic treatment.

Control via chemotherapies

Control via environment

  • The following may aid prevention:
    • Fly control via permethrin based fly sprays.
    • Insect proof rugs.
    • Housing during the day.
    • Turn out at night.

Diagnosis

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Amado S, Silveira A K, Vieira F D & Traversa D (2014) Habronemamuscae (Nematoda: Habronematidae) larvae: Developmental stages, migration route and morphological changes inMuscadomestica  (Diptera: Muscidae). Experamental Parasitology 136, 35-40 PubMed.
  • Rehbein S, Visser M & Winter R (2013) Prevalence, intensity and seasonality of gastrointestinal parasites in abattoir horses in Germany. Parasitology Research 112 (1), 407-413 PubMed.
  • Whitley D B, Rakestraw P C & Edwards J F (2011) Pathology in practice. Cutaneous habronemiasis.  JAVMA 238 (8), 993-995 PubMed.
  • Pusterla N, Watson J L, Wilson W D & Affolter V K (2003) Cutaneous and ocular habronemiasis in horses: 63 cases (1988-2002). JAVMA 222 (7), 978-982 PubMed.

Other sources of information

  • Reed S M, Bayly W M & Sellon D C (2010) Equine Internal Medicine. 3rd edn. Saunders. ISBN: 978-1-4160-5670-6.
  • Taylor M A, Coop R L & Wall R L (2007) Veterinary Parasitology. 3rd edn. Blackwell. ISBN: 978-1-4051-1964-1.

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