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Lungworm. What is it ? How do we treat it? How can we prevent it?

What is lungworm?

Lungworm (Husk) is a parasite of the respiratory tract caused by Dictyocaulus viviparus. Lungworm is widespread in the UK but more common in wetter parts of the country such as the Southwest. Lungworm is picked up from cows eating Lungworm larvae from pasture.

What signs do I see?

Lungworm was traditionally seen more from August onwards but with the wetter summers of recent years we have been increasingly getting reports in July. Clinical signs for younger animals are widespread coughing, difficulty in breathing (dyspnoea) and death of severely affected animals. Adult dairy cows may cough in the milking parlour with reduced yields and occasional cases of secondary pneumonia. The severity of outbreaks in adult dairy cows will be related to the challenge and previous exposure/immunity of these cattle. First season grazing animals on permanent or semi-permanent pasture are the highest risk animals on most farms as the lungworm challenge overpowers their limited immunity. Disease mostly affects calves from dairy cows or autumn born suckler calves. Spring born suckled calves that graze with their mothers may experience some mild coughing but do not suffer as severely as they gradually develop immunity as the amount of grass in their diet increases. Lungworm life cycle. Source COWS (Control of Worms Sustainably 2014)

Lungworm larvae are susceptible to drying. In areas/seasons with higher average rainfall larvae may survive longer. Wet weather also promotes the release of Lungworm larvae from the dung pat. Wet summers and high stocking rates are therefore risk factors.

Treatment

Affected youngstock should be treated as early as possible because severely affected animals do not respond as well. Cattle can also look worse after treatment as dead or dying larvae block the airways of the lungs, increasing coughing and respiratory rate.

Calves with a secondary bacterial pneumonia will need antibiotics and Non-Steroidal Anti-Inflammatory treatment (NSAIDs). Treated cattle should be removed from infected pasture and transferred to clean pasture. If clean pasture is not available, you should speak to your vet regarding using a wormer which provides protection for an extended period.

Treatment of adult cows should be discussed with your vet on a case-by-case basis depending on the severity of the outbreak. Worming milking cows may stop them coughing but may stop them developing immunity and these cattle may require further treatment. In some herds it can be advisable to selectively treat individual animals or groups such as 1st lactation heifers.

Prevention

In herds with no history of Lungworm it is important that Lungworm is not bought into the herd with purchased cattle. Purchased cattle should be isolated and wormed as per your herd health plan (HHP). In herds with endemic Lungworm, it is worth discussing management at your HHP. The best way of preventing lungworm in first year calves is vaccination with the lungworm vaccine. Healthy animals should be vaccinated over 8 weeks. Two doses are given at an interval of 4 weeks and calves grazed two weeks after.

Long-acting wormers or regular worming can be effective in preventing Lungworm in first grazing animals. This is however not typically recommended as we can then get outbreaks of Lungworm at the end of the first grazing season, in second season grazing animals or adult cows that have built up no immunity.

Summary

Lungworm can be a severe problem on high-risk farms if not managed properly, this can result in a reduction in growth rates, milk drop or even deaths. A control plan should be tailored to your farm at the HHP with measures to ensure the sustainable use of wormers and that meat and milk withdrawal periods are followed correctly.