Dictyocaulus Parasitic Roundworms

Dictyocaulus is a genus of parasitic roundworms of major veterinary significance. Lungworms of the genus Dictyocaulus cause serious parasitic bronchitis (dictyocaulosis or "husk") in different domestic and wild ruminants (cattle and deer), particularly in young animals during their first grazing season. The clinical signs of dictyocaulosis vary from mild coughing to emphysema and pneumonia, and can result in death in severely affected animals. In some countries, lungworm-infected (seropositive) animals were found in approximately 80% of organic dairy herds examined in late autumn. The costs of outbreaks in such herds can be considerable.

In cattle Dictyocaulus viviparus causes verminous pneumonia, acute interstitial pneumonia and secondary bacterial pneumonia. The disease usually affects the calves who are raised indoors until four to five months of age. Affected animals develop abdominal respiration with an audible grunt. Caugh and eroded nares are also abserved. Treatment is usually with antibiotics and antihelminthic agents.

Dictyocaulus viviparus bovine lungworm lives in the bronchi and bronchioles of cattle. Eggs produced by females are coughed up, swallowed, and excreted in the feces as first-stage larvae which develop, under favorable environmental conditions, into third-stage larvae within 4–6 days. The cuticle from the second-stage larva is retained as a sheath around the third-stage larvae and protects this stage from adverse environmental conditions. Third-stage larvae are ingested by grazing cattle, penetrate the intestinal wall and migrate to the lymph nodes, where they molt to fourth-stage larvae. Fourth-stage larvae are then transported to the lungs, where they penetrate the alveoli and develop into adults (within 3–4 weeks).1 In the lungs, pathology develops due to the rapid increase in number and activation of eosinophils and mast cells that cause restriction of the airways and a collapse of the alveoli, resulting in swelling of the lung tissue and weakening and eventually rupture of air sacs (emphysema).




Dictyocaulus viviparus parasitic bovine lungworm
"Dictyocaulus-viviparus" de Alan R Walker

Cattle surviving the infection develop protective immunity lasting for up to one year. The control of Dictyocaulus infection and dictyocaulosis has been based on the prophylactic administration of an irradiated larval vaccine that induces a temporary protective immunity and prevents clinical disease. However, due to its high costs, limited shelf life and for ethical reasons, acceptance among veterinarians and farmers decreases nowadays. Therefore, control of the parasite relies primarily on anthelmintic treatment and pasture management.3

References

  • Deep insights into Dictyocaulus viviparus transcriptomes provides unique prospects for new drug targets and disease intervention Cinzia Cantacessi et al.
  • Antibodies Elicited by the Bovine Lungworm, Dictyocaulus viviparus, Cross-React with Platelet-Activating Factor. Frans N. et al.
  • Vaccination with recombinant paramyosin against the bovine lungworm Dictyocaulus viviparus considerably reduces worm burden and larvae shedding. Christina Strube et al.





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