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).