Friesian cow in grass field

Wet late summer warning over lungworm larvae

Cattle lungworm is an unpredictable and potentially deadly parasite and cases are on the rise thanks to a warmer and wetter climate.

Cattle become infected with lungworm (Dictyocaulus viviparous) by ingesting larvae fromc ontaminated pasture. Hot and dry weather kills them off, but they thrive in the warm and wet conditions seen seen in recent years.

Larvae can also remain protected within the moist core of dung and sudden, heavy rain can lead to their release onto grass and potential outbreaks of parasitic bronchitis or husk.

Lungworm is highly pathogenic and a major productivity-limiting disease, causing severe losses in affected stock if untreated. Yet it can be difficult to diagnose at an early stage, often only spotted when there is a full-blown outbreak within the herd.

First-season grazing cattle are the most susceptible to disease, with no chance to acquire immunity before exposure. The impact on growth can be significant, with weight gains halved within 32 days following infection¹. It also leads to reduced milk yields and fertility rates, dead or culled animals and a large vets bill.

And climate change and wetter weather patterns mean the threat of lungworm in UK dairy herds is increasing.

During the past 40 years, data shows an increase in the number of reported cases. Outbreaks are now seen in spring and autumn, outside of the traditional window between July and August, particularly in the South West and Wales. Some cases have been reported as late as November.

To compound this, husk has moved from being a youngstock disease to a condition frequently seen in adult dairy cattle. They may have built up some immunity to lungworm infection as youngstock, either naturally or through vaccination, but this only lasts for six to 12 months.

Affected animals will also be more susceptible to other respiratory diseases. However, lungworm should always be considered first as a potential cause of coughing.

Farmers can address the specific risk of lungworm as part of a herd parasite control plan. Co-infections with gutworms such as ostertagia ostertagi and cooperia oncophora, which can result in higher lungworm burdens² highlights the importance of an integrated parasite control strategy.

Early signs of lungworm infection:

  • Milk drop - often the first sign, caused by increased resting time, reduced feeding and reduced drinking
  • Coughing - a deep, harsh cough, initially during periods of activity but progresses to coughing at rest with laboured breathing
  • Weight loss - the acute stages of lungworm cause rapid weight loss in animals
  • Altered stance - severely affected animals will typically stand with neck and head extended in an ‘air-hungry’ position


  1. Vercruysse, J. & Claerebout, E. (2001) Treatment vs non-treatment of helminth infections in cattle: defining the threshold. Veterinary Parasitology 98 ;195–214
  2. Kloosterman et al (1990) Vet Parasitol 36: 117-122.