Cattle become resistant to the parasite, but a few adult worms are able to become established in cows. When young cattle are exposed to Haemonchus , especially when grazing irrigated summer pastures with high stocking rates, the results can be devastating. On permanent pastures, treating calves three and six weeks after the onset of warm-season forage growth will lower pasture contamination considerably. The lungworm, D. viviparus , can be one of the most devastating parasites of cattle. It is a parasite of the young as it stimulates an early immune response that protects adults against disease.
Parasitic bronchitis is a disease of livestock management.
Disease results when susceptible calves, such as dairy, stocker calves or cattle from areas which do not normally have Dictyocaulus , i.e., arid western ranges, are grazed in lush spring or autumn contaminated pastures. Conditions in pastures suitable for the propagation of mushrooms are similarly suitable for the transmission of Dictyocaulus . A dung-inhabiting fungus, Pilobolus, disseminates Dictyocaulus by propelling larvae through the air which have crawled onto sporangiophores. Most modern anthelmintics are effective in controlling lungworms in cattle. Calves treated after being infected exhibit resistance to infection.