Muellerius

  • Common, although not major pathogens; little economic importance.

Life-Cycles

    • Indirect life-cycle involving mollusc intermediate hosts
    • L1 passed in faeces, penetrate foot of mollusc, develop to L3 in 2-3 weeks
    • Infected mollusc ingested with grass
    • L3 released by digestion and travel to lungs by lymphatic route
    • Adults found in alveoli/parenchyma (Muellerius) or small bronchioles (Protostrongylus)
    • Prepatent period 6-10 weeks (Muellerius), 5-6 weeks (Protostrongylus)

Epidemiology

    • High prevalence because of wide range of intermediate hosts, prolonged survival of larvae in faeces, long periods of patency (>2 years) and poor host immunity

Muellerius capillaris

  • Muellerius capillaris common parasite of sheep and goats in respiratory infections
  • Common in sheep and goats
  • Rarely any clinical significance
  • Grossly:
    • Multifocal interstitial pneumonia grossly evident as firm "lead-shot" nodules throughout the parenchyma, often with enveloping granulomatous response
    • Early stages are reddish in colour, turning later to greyish green, may calcify
    • Mostly in dorsal region of caudal lung lobes
  • Histologically:
    • Damaged alveolar septa with mild fibrous thickening and lymphocytic infiltrate
    • In more developed host resistance, foci of eosinophils around larvae, hyperplastic epithelium, macrophages, giant cells
    • May be some calcification