Being a vet, my eyes and ears tend to be tuned to sights and sounds that others might not notice.

On holidays in west Clare this week, I couldn’t help but hear a herd of dairy cows in a roadside field let out an occasional cough as I strolled past. While the rest of the country baked in blue skies and warm sunshine, up here we had a sea fog interspersed with occasional warm showers – perfect weather for lungworm.

The year 2015 provided a watershed summer in changing our understanding of the life cycle and pathophysiology of lungworm, particularly in adult dairy cows. That year we saw an apparent epidemic of coughing dairy cows. Clusters falling off during milking due to the severity of the cough was a common theme.

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As vets, we had always relied on the supposed lifelong immunity to this parasite once initial infection had occurred in the calf.

Better understanding

We now understand better that, yes, while there can be lifelong immunity to the adult worm, which is killed by the cow’s white blood cells as soon as it reaches maturity in the air pockets of the lungs, there is no such immunity to the larval stage.

These larvae migrate through the lung tissue as they mature, causing damage which leads to a cough.

That summer, faecal samples were clear, and any amount of herds were checked for IBR, RSV and other such pathogens, with results, in most cases, proving negative. The only way to truly diagnose lungworm is by Broncoalveolar Lavage or a ‘lung wash’. These days we take it that coughing animals of any age in July probably have lungworm.

Addressing the problem

Treatment is easy, and products with nil milk withdrawal mean that dairy herds can be treated safely.

My preference is to treat coughing animals only, if possible, to prevent unnecessary use of anthelmintics. Very often it is the younger cows, particularly first year milkers, that are worst affected and they may be the only cows needing treatment.

Kieran O’Mahony

XLVets, Glen Vets, Tipperary