Hoose- Lungworm in Cattle

Date published: 23 July 2025

Parasitic pneumonia in cattle colloquially known as Husk or Hoose is caused by lungworm, Dictyocaulus viviparus. AFBI has detected two cases of lungworm in carcasses submitted respectively to both Omagh and Stormont postmortem labs in the last 2 weeks. The cattle were aged between 12 and 15 months, and both were out at grass. One was a case of sudden death while the other was treated for pneumonia.

The most common clinical signs of lungworm infection are a ‘husk’ like cough and increased respiratory rate with or without temperature, depending on the involvement of secondary infection. However, with a heavy infestation acute respiratory distress and rapid death can occur. Other signs of lungworm infection include weight loss, drop in milk yield and anorexia. 

Cattle are infected with lungworm by ingesting larvae from pasture, with the severity of disease affected by the number of larvae ingested and the response of the animal. The larvae invade across the intestinal wall, and move in the blood stream to the lungs, where they develop into adults. The adults then produce larvae, which are coughed up, swallowed, and passed in the faeces. Fully developed larvae survive on pasture for a relatively short time and are advantaged by wetter summers. The rainfall in NI in June was above the monthly average, which could lead to increased numbers of larvae remaining on pasture.

When an animal has been exposed to lungworm, it can develop immunity hence lungworm is generally seen in first grazing season calves in late summer or autumn. Adult cattle can become infected if they have never been exposed, had rigorous anthelmintic control as calves or lacked re-exposure to maintain their protective immunity. Re-infection syndrome can occur in older cattle that have a partial immunity to lungworm, leading to a hypersensitivity-type reaction. 

Parasitic pneumonia is suspected based on clinical signs and grazing history. However, it should still be a differential in housed cattle, particularly those not treated for lungworm following grazing or those being zero grazed. Confirmation of patent lungworm infection relies on detection of larvae in faeces hence the standard faecal worm egg count will not identify lungworm. If an earlier infection or reinfection syndrome (i.e. the infection is not producing larvae) is suspected, examination of the mucous retrieved by bronchoalveolar or tracheal lavage may assist with diagnosis. Postmortem examination of any animal dying suddenly or from respiratory disease can also play a vital role in confirming the diagnosis.

Treatment

Lungworm can be treated effectively with appropriate use of anthelmintics, and choice will depend on severity of disease, ease of administration and duration of action. Once treated, animals should be moved onto clean pasture if a wormer with residual activity was not used. Clinically affected animals with a heavy lungworm burden must be monitored closely after anthelmintic use, as lungworms dying all at once can block the airways. Hence when treating these animals, it is best to seek veterinary advice regarding the most appropriate product to use.

Vaccination is available as a method to control infection and generally involves immunisation of young stock prior to exposure to lungworm. However, for vaccination to remain effective repeated exposure to lungworm is required to maintain immunity. 

Parasitic pneumonia cases are likely to increase in the coming months, so it is advisable to monitor cattle closely for signs of coughing and consider lungworm as a possible cause of respiratory signs in affected cattle.