Fighting lungworm in cattle

LUNGWORM infection, or hoose as it is often referred to, can be widespread, and infection this year may be more severe with the spell of heavier rain that followed the long dry spell.

Lungworm infection is one of the most notable respiratory diseases of cattle in Ireland. Outbreaks can be 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 of larvae.

It is caused by a parasitic larvae ingested by animals off grass and 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 at the greatest risk as they are eating more grass than springborn suckler calves. They also have little or no resistance built up. It becomes more important later in the season in springborn 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.

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 open-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 present.

The three major groups of worm doses or anthelmintics are all effective against lungworm. The three classes of wormers are Benzimidazoles (white wormer), Levamisoles (orange wormer) and Macrocyclic Lactones (clear wormer) such as Ivermectins.

Benzimidazoles are oral drenches. They are fast acting and have no persistent activity, which means they will not give any cover to new infections post dosing.

Levamisoles can be either oral, injectable or pour-ons. They are also fast acting, with no long term cover. The Macrocyclic Lactones are either injectable or pour ons. They do not act as quickly, but they do give long term cover against new infections.

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 one or two days post-treatment.

Dung 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 anthelminthics in the first grazing season because you may limit the animals’ exposure to lungworm larvae, and cattle will remain susceptible to reinfection the following season due to not developing natural resistance.

When deciding on a suitable treatment programme and products, you should consult with your vet.