Atlas of livestock parasites
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Muellerius capillaris



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Nematodes (order Strongylida) 

"hair lungworm"

Distribution: worldwide.

Host: Lung parenchyma of sheep, goats, and some deer. Alveoli and tissue surrounding them (Muellerius spp. and Protostrongylus spp.

Life Cycle:  Indirect, with snail or slug intermediate host. Adults in lungs lay eggs which develop to first-stage larvae. These are passed in feces and penetrate a snail or slug where they grow to become infective third-stage larvae. Sheep eat the snails.
Digestion releases the infective larvae, which penetrate the intestinal wall and travel in the blood to the lungs, where they mature.  

Clinical features:  Although the significance is not well-known, it may contribute to pneumonia. Adults in lung tissue produce grayish nodules up to 2 cm in diameter. Smaller nodules form around eggs in the lung. Tissue which normally could be used for respiration is obstructed by the nodules. In heavy infections, lungs are weakened, and bacterial superinfections may occur. Most cases are asymptomatic. Heavy infections may cause clinical disease,  especially in goats infected with Muellerius.      

Diagnosis: Thread-like nematode, 12 to 23 mm in length. Posterior end of male is spirally coiled.  Larvae appear in feces. The Baermann test is used for detection of frst-stage larvae. Muellerius has a kinked tail with an accessory spine, in contrast to the plain tail of Protostrongylus.            

Size:  300–320µm Muellerius    

Size:  340–400µm  Protostrongylus    

Emetine hydrochloride appears to be the only effective anthelmintic.


M.capillaris 1
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M.capillaris tail
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