Lungworm

(Dictyocaulus viviparus)

Dictyocaulus viviparus are long (40-80 mm), white worms that live in the air passages of the lungs of cattle.

Disease due to lungworm infection is uncommon in beef cattle in Australia, although a major problem in the northern hemisphere. Dairy calves 4-12 months of age and reared under cool, high rainfall conditions are most commonly affected although occasional outbreaks have occurred in warmer districts where pastures are prone to flooding.

Figure 1. Adult lungworms, Dictyocaulus-viviparus. Image courtesy of A.R. Walker Wikimedia Commons

Life cycle

Adult females in the lungs lay eggs containing a first stage larvae. Some of these eggs hatch in the lungs but most are mixed with the mucous exudate, are coughed up, swallowed, and then hatch during transit through the digestive system. First stage larvae (not eggs) are passed in the dung pat. Further development into the infective third stage takes about 4-5 days.

Infective larvae are very sluggish and do not actively migrate out of the dung pat. They may be carried by heavy rains, or when the crust of the pat is broken up by farm equipment or hoofs. Larval lungworms also gain access to clean grass using the spore structure of the fungus Pilobolus, which grows on cattle faeces. Larvae congregate on the sporangium (reproductive capsule) of the fungus and when it explodes, they can be propelled as far as three metres.

When eaten by grazing cattle, infective larvae move to the small intestine, penetrate the walls, moult to the pre-adult stage in the mesenteric lymph nodes, and travel via the mesenteric lymph system to the thoracic duct and blood system into the lungs.

Further ecological information on worms and their control:

  • Roundworm: lungworm life cycle and life stages
  • The lungworm life cycle is similar to that of the typical roundworm life cycle except that the first stage (L1) larvae is passed out with the dung and the fourth stage (L4) juvenile undergoes a migratory phase via the lymph to reach the lungs of cattle before maturing into the adult worms. The pre-patent period is about 22-28 days.
  • Climate factors contributing to paddock contamination with worms
  • Pasture management to reduce exposure to worms, alternate grazing and co-grazing
  • Cost of roundworms

Location in cattle

Dictyocaulus viviparus lives in the smaller bronchi and trachea of the lungs.

Figure 2. Calf bronchi with adult lungworms, Dictyocaulus viviparus. Image courtesy of A.R. Walker Wikimedia Commons

Signs

The main clinical signs of lungworm infection are dyspnoea (laboured breathing), coughing, nasal discharge and loss of weight. Coughing sounds like a dry, non-productive exhalation (‘husk’). Diarrhoea may also occur, but it is probably due to a concurrent infection with other gastrointestinal roundworms.

Signs of worms

 

Diagnosis

Clinical signs are suggestive of a parasitic bronchitis caused by the cattle lungworm. Eggs and first stage larvae may be found in the nasal discharge.

Laboratory analysis requires freshly passed faeces for recovery of first stage larvae using the sedimentation or Baermann technique.

At post mortem examination, tangled clumps of white worms are easily visible in the larger air passages of the lungs.

Figure 3. First-stage lungworm larva (arrow) recovered from bovine faeces. Image courtesy of the National Centre for Veterinary Parasitology, ncvetp.org

Treatment

All broad-spectrum drenches will remove lungworms. No drench resistance has been reported.

You can also review the chemical pages on this site to find out specific information about drenches, including their drench active, drench group, how they are administered, which worms they treat, resistance status, safety information and how they work.

The negative impact of this worm can also be reduced through using one of the integrated annual worm control programs that have been specifically developed for different regions across Australia.