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.

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).