Muellerius

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