Lungworm Diagnosis and Prevention in Goats

The parasite and disease

Lungworm causes inflammatory disease of the lower respiratory tract, also known as verminous bronchitis or verminous pneumonia. Lungworms in goats cause significant disease in Australia and can occasionally lead to death. Infection is commonly seen in goats which may already be debilitated by other parasitic diseases and sub-optimal nutrition.

There are three species of lungworm that occur in goats in Australia. They are the large lungworm, Dictyocaulus filaria, and the small lungworms, Muellerius capillaris and Protostrongylus rufescens. The small lungworms prefer cool conditions and require an intermediate host (slugs and snails) for their development. This restricts these lungworms to cooler southern regions of Australia. The large lungworm, D. filaria, has a wider distribution including the Darling Downs in Queensland.

For more information about the individual life cycles of the lungworm species click here.

Symptoms

Clinical signs of lungworm include lethargy, chronic fever, coughing, thick nasal discharge, increased respiratory rate, poor appetite, and weight loss. The main symptom in goats tend to be coughing as the lungworm irritates the lining of the goat’s airways. Lungworm infection in the lower respiratory tract can result in pneumonia or bronchitis. At post -mortem examination white thread like worms can be visible in the airways (large lungworms) and nodular lesions can be detected in the lungs containing either worms or pus (small lungworms, see Image 1).

Diagnosis

Diagnosis is not always easy and is based on clinical signs, post-mortem findings and laboratory testing using a sedimentation test or Baermann apparatus (detecting lung worm larvae in faeces). Larvae may also be found in nasal secretions.

Treatment

All broad-spectrum drenches will remove lungworms. No drench resistance has been reported. However, Muellerius infection in goats is difficult to clear and may require prolonged treatment programs.
As with all treatments for parasitic infection, prevention is better than the cure. Like other parasites, reinfection occurs when larval stages of lungworm survive on pasture from one season to the next. This highlights the importance of correct grazing management. As an intermediate host is necessary to complete the lifecycle of lungworms, preventing contact with snails and slugs will be helpful. On small holdings, geese and ducks can be used to eat snails. Fencing off wet areas and using troughs for watering stock will minimise the likelihood of goats consuming the intermediate host.