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Managing stomach and lungworm in calves

Managing stomach and lungworm in calves

Stomach worms and Lungworms or Hoose are the two main parasites that will affect calves at grass. Both are favoured by warm humid conditions. Patricia Lynch, Teagasc Westport emphasises the need to have a worm control plan in place, describes lungworm symptoms to watch out for and more here

In the absence of a control programme there is a steady build-up of stomach worm larvae on grazing pasture through the months of May, June and July as temperatures rise. Lungworm outbreaks occur later in the summer.

Stomach worms

Stomach worms in calves causes scouring, lack of thrive and in severe cases anaemia. July is the month when dosing will begin for many spring-born calves. Dairy-born calves will be much more susceptible to stomach worms than suckler calves because they have a higher intake of grass from an earlier age.  Spring-born suckler calves will be more at risk later in the grazing season as their grass intake increases around weaning.


Symptoms of lungworm are usually seen in young cattle in their first grazing season in the later part of the summer. The nature and severity of lungworm infections depends on the number of larvae that are ingested and on the response of the animal.

Clinical signs of lungworm infection include respiratory signs, panting and a harsh persistent cough which can be observed when moving stock or in severe cases even when stock are at rest. Performance can be hit and as seen in animals with severe infections, the onset of secondary pneumonia can develop with death ensuing quickly if left untreated.  Dung samples are not usually helpful in diagnosing lungworm infection as it takes some weeks for the immature larvae to develop into adults that produce eggs.

Having a good worming programme in place will limit the impact parasites will have on animal performance. Currently three Anthelmintic classes are available for parasitic worm control in cattle:

  • Benzimidazole (white)
  • Levamisole (yellow) and
  • Macrocyclic Lactone (clear)

Drug resistance - a growing concern

Drug resistance against worm populations has become a growing concern on many Irish farms. To prevent the build-up of drug resistance, calves should get the full recommended dose rate according to the animal’s weight, as per manufacturer’s instructions. Another suggestion is that the drug group type be changed each year. Each of these wormers are effective but differ between application type, persistency and withdrawal dates. Treat infected animals as early as possible because there may be varying degrees of infection in any one group. Levamisole and white drenches will take out what parasites are there on the day of treatment, but will have no residual affect. Macrocyclic Lactones such as ivermectins will give longer protection (28-120 days is typical).

Young calves can be vaccinated for lungworm after eight weeks of age with a double dose 4 weeks apart. These calves should not be exposed to any lungworm for at least two weeks after the 2nd dose. As a word of caution care needs to be taken when using long acting anthelminthics in the 1st grazing season because you may limit the animal’s exposure to lungworm larvae and cattle will remain susceptible to reinfection the following season due to not developing natural resistance. As with all animal health issues if you have any concerns contact your veterinary practitioner for advice.

Teagasc Advisors are regular contributors of articles to Teagasc Daily. You can contact any of our Teagasc offices using this link Teagasc Advisory Regions here