Habronema and Draschia spp.

HABRONEMA and DRASCHIA SPECIES

General

• Spiruroids occurring in stomach:
  • Habronema microstoma - worldwide.
  • Draschia megastoma - tropical/sub-tropical climates.

Morphology

• 1.0-2.5cm long, slender white worms, flat spiral twist to male tail.

Life-Cycle

• Indirect LC, muscid fly intermediate hosts.
• Adults under layer of mucous in stomach (Habronema) or in large nodule (Draschia).
• Elongated embryonated eggs (50-60µm) passed in faeces.
• L1 ingested by fly larvae - develop to L3 as fly matures.
• L3 deposited on horse's lips as fly feeds - swallowed - mature to adult worms.
• Prepatent period = 2months.
• Larvae → "cutaneous habronemosis" or "summer sores":
  • larvae laid on skin wound → large granulomata
  • seasonal incidence
  • affected horses may be difficult to work.

The adult nematode lives in the stomach of the horse and produces eggs which are then passed in the faeces and hatch into larvae. The larvae are ingested by the house fly (Musca domestica) or stable fly (Stomoxys calcitrans) in their larval phase, and deposited on equine skin when they feed as adult flies.

Pathogenicity

• Adult worms:
  • Habronema - mild gastritis (no mucosal invasion)
  • Draschia - tumour-like nodules may impair pyloric function.

Control

• Regular anthelmintic treatment (adults - not required; larvae - ivermectin).
• Cover or turn over dung heaps (to prevent access of flies to breeding sites or kill by composting).

Cause Habronemiasis, Cutaneous