Muellerius capillaris: Hair lungworm.

General Description: Thread like nematode, 12 to 23mm in length. Posterior end of male is spirally coiled.

Life Cycle: Indirect, with snail or slug intermediate host. Adults in lungs lay eggs which develop to first-stage larvae. These are passed in faeces 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.

Location: Alveoli and tissue surrounding them.

Geographical Distribution: Worldwide.

Significance: Although the significance is not well known, it may contribute to pneumonia.

Effect on Host: Adults in lung tissue produce greyish nodules up to 2cm 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.

Diagnostic Information: Larvae appear in faeces.

Control: Most anthelmintics have not been shown to be effective.