Farmers are urged to be on high alert as fatal cases of ‘hoose’ have already been diagnosed in cattle in Northern Ireland this grazing season despite one of the driest summers on record.
The Agri-Food and Biosciences Institute (AFBI) said its laboratories already confirmed several cases of the parasite in cattle submitted for post-mortem examination.
It’s warning farmers to be vigilant as the UK and Ireland enter the ‘high-risk period’ for parasitic pneumonia.
Parasitic pneumonia
Parasitic pneumonia, also known as ‘hoose’ or ‘husk’, is an economically important disease in cattle caused by the lungworm Dictyocaulus viviparus.
Lungworm can result in severe financial losses due to a loss of performance and fatalities in growing cattle and drop in milk yield and fatalities in lactating cows.
Outbreaks of parasitic pneumonia are usually observed from July to October with occasional outbreaks occurring either earlier in the summer or after October.
Whilst warm and moist conditions are required for a build-up of lungworm contamination on pasture, cases are occurring despite this summer’s dry conditions and lungworm should be considered as a possible reason for cattle coughing.
With recent rain in a number of areas, lungworm burdens on pasture are expected to increase further.
How infection occurs
Lungworm infection is acquired by the ingestion of larvae from pasture and calves in their first grazing season – dairy calves and autumn-born suckler calves are most at risk of being affected.
Animals exposed to infection develop a degree of immunity which provides a level of resistance to re-infection in previously exposed animals.
The persistence of this immunity is, however, dependent on further exposure, otherwise, immunity wanes over time.
Current long-acting anthelmintics – which are used to prevent or treat parasitic gastroenteritis – are highly-effective, but can have the effect of reducing the exposure of young animals to low levels of lungworm infection, which is required to ensure the development of protective immunity.
Cases of parasitic pneumonia are now commonly diagnosed by AFBI in older calves and in adult cattle in which immunity to lungworm has waned due to a lack of exposure in the intervening period, or in animals which were not exposed to lungworm in previous seasons.
Symptoms
Clinical signs of lungworm infection include respiratory signs, panting and harsh persistent cough. Growth rates may be affected.
Severe infections result in difficulty in breathing and death. Faecal testing for lungworm larvae is also a useful diagnostic aid, but negative results are possible, particularly in early infections.
Effective treatment options are available involving the administration of anthelmintic products. Veterinary advice and treatment should be sought for affected animals.
