Lungworm in cattle

LUNGWORM or hoose is caused by a parasitic worm and although normally associated with being a problem in calves in their first grazing season it can, under certain circumstances, be a problem in subsequent grazing seasons.

Outbreaks can be widespread, unpredictable and of economic significance resulting in reduced animal performance, milk yield and in severe cases animal losses.

Symptoms are usually seen in young cattle in their first grazing season in the later part of the summer.

The nature and severity of lungworm infection depends on the number of larvae that are ingested and on the response of the animal.

Lungworm can have both direct and indirect effects.

The indirect effects are mainly a result of inflammatory responses where the lungworm reproduces and begins egg production.

Individual animals will differ with regard to the severity of the symptoms.

If left untreated parasitic bronchitis is the main issue in previously naïve cattle which is usually (but not always) animals in their first grazing season.

In Irish conditions we normally see outbreaks in the period from August to October but this can vary year on year depending on grazing conditions, weather etc.

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. Yearling & adult cattle can be affected if they fail to develop adequate immunity as calves.

The lifecycle of lungworm alternates between a number of life stages and is highly dependent on climatic conditions.

As regards treatment and control most available anthelminthics are effective against larval & adult lungworms. Treat infected cattle 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 and but will have no residual affect.

Macrocyclic Lactones such as ivermectins will give longer protection (28-120 days is typical).

The product used will have a bearing on subsequent grazing management post treatment.

Calves that were heavily infected need to be closely observe in the 1-2 days post treatment. The disease is highly unpredictable and so it is virtually impossible to control using a clean grazing strategy.

Young calves can be vaccinated 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 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.

As with all animal health issues if you have any concerns please contact your veterinary practitioner.