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Sat 21 Nov 2009

Lungworms (Dictyocaulus spp.)

Although many species of worm parasites are harbored in the gastrointestinal and respiratory tracts of cattle and sheep, only a few species cause significant health and economic damage. One of these is the lungworm (Dictyocaulus spp.).It affects both cattle and sheep worldwide.

Life Cycle

 
Young cattle eat contaminated grass

Infective larvae pass into small intestine



Once they reach the lungs, the larvae leave the blood and develop into adults in the air passages. The irritation caused by the worms which are about 7.5 cm long stimulates the lungs to produce great quantities of mucus. This mucus becomes foamy and blocks the air passages when the calf tries to force air into its lungs.

A calf showing symptoms of lungworms (husk)

 Larvae penetrate intestine wall and migrate to the lungs in the blood.
larvae develop into adults in the larger air spaces in the lungs, and are ready to start breeding about 28 days after ingestion.
The Dictyocaulus spp. eggs hatch in the lungs. Thousands of microscopic larvae may be coughed up and swallowed by the animal.
Immature larvae move through the gut passing out in the dung onto pasture, where they develop through two larval stages in a few days.
The final stage larvae, now infective, may crawl up foliage ready to be eaten. Some larvae may be spread on pasture by fungal sporulation of Pilobolus spp., which grows out of dung pats.
Young cattle eat contaminated grass
Larvae are vulnerable to adverse weather conditions, but in warm, moist, shaded conditions may live for over a year.

Treating a Lungworm Problem
It is very important to test your sheep or cattle for possible lungworm infection before starting a prevention routine.

Symptoms: Sheep (Dictyocaulus filaria)

  • Initially no apparent signs of infection apart from coughing, until the disease becomes severe.
  • Clinical symptoms include verminous pneumonia leading to viral and bacterial pneumonia, with labored breathing and anxiety evident.
  • Depressed performance is an additional symptom.
    If you suspect your sheep has a problem, consult a veterinarian.

Symtoms: Cattle (Dictyocaulus viviparus)

  • Increased respiratory rate to possibly twice normal
  • Coughing - especially noticable when chased
  • Loss of condition, becoming more rapid
  • A fatal pneumonia may develop, characterised by gasping for air
  • Some infected calves may develop a hypersensitivity to the lungworm that may cause acute respiratory problems or sudden death. Calves experiencing an acute syndrome show considerable distress in trying to breathe in enough oxygen, with the mouth open and frothing, and the tongue extended.

    Why Lungworms Are a Problem

    Pneumonia in animals, as in humans, can lead to death. When breathing is troubled, the mood, activity and performance of the animal all exhibit downturns that, in turn, can lead to lower resistance, and eventually, other infections.

    Prevention
    Immunity to lungworm slowly develops as animals mature.

    Management practices:
    Breaking the Cycle - Clean Grazing

      Anthelmintic Treatments and Conventional Control

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Last modified: Thursday 18th of December 2003 04:32:14 PM