Lungworm – the key questions
Lungworm infection or hoose is one of the most important respiratory diseases of cattle in Ireland, Catherine Egan, Teagasc Beef Specialist, explains.
Outbreaks can be widespread and unpredictable, resulting in reduced animal performance and in severe cases animal losses. Infection can also be more severe when a long, dry period is followed by heavy rain, which leads to a large hatch; this is particularly relevant now.
What is it?
Lungworm is a roundworm parasite, similar to gut worms, that completes its life cycle in the lungs. It is caused by a parasitic larvae ingested by animals off grass. It is most commonly seen in the second half of the grazing season, when large numbers of lungworm larvae have built up on pastures. Young dairy-bred calves and autumn-born suckler calves are in the biggest danger bracket, as they are consuming more grass than spring suckler calves on milk and they have little or no resistance. It becomes more important later in the season in spring-born calves, as they consume more grass. Lungworm can also be seen in older cattle who have failed to develop or maintain immunity in the first grazing season.
How does it spread?
Larvae need to move out of the dung pats and onto grass. The two main pathways are:
- Rain – the droplets splash the larvae out of the dung and it attaches itself to the grass;
- The fungus Pilobolus has a mechanism where it “explodes”. This pushes the larvae up into the air and can spread the larvae up to 3m.
What to look out for?
The clinical signs of disease include:
- Intermittent coughing, particularly after moving stock.
- Moderately affected animals will have coughing bouts even when they are resting and may show signs of increased difficulty in breathing.
- Heavily affected animals suffering from respiratory disease have an increased breathing rate accompanied with opened mouth breathing with head and neck outstretched. The tongue will also appear as they try to cough. The cough will be the harsh deep ‘husk’ cough. Cattle can lose condition rapidly.
- The nature and severity of lungworm infection depends on the number of larvae that are present.
How do you treat it?
The three major groups of anthelmintics are all effective against lungworm. If coughing is detected in a group of cattle at grass and hoose is suspected, all cattle in the group should be dosed. Cattle should be moved to a ‘clean’ pasture or an anthelmintic with persistent action may be used to prevent re-infection. Calves that were heavily infected need to be closely observed in the 1-2 days post treatment.
What do I need to be aware of?
It is important to note that faecal sampling is not relevant in the case of lungworm, as by the time eggs reach the dung, the damage is already done. Care needs to be taken when using-long acting anthelmintics in the first grazing season because you may limit the animals’ exposure to lungworm larvae and cattle will remain susceptible to re-infection the following season due to not developing natural resistance.
Further information on lungworm is available in the Animal Health Ireland website and always talk to your vet.