Lungworm

Lungworms are parasitic nematode worms of the order Strongylida that infest the lungs of vertebrates. The name is used for a variety of different groups of nematodes, some of which also have other common names; what they have in common is that they migrate to their hosts' lungs or respiratory tracts, and cause bronchitis or pneumonia. The lungworm will gradually damage the airways or lung tissue by inciting an inflammatory reaction inside the tissue. Ultimately, the parasites survive and reproduce in the respiratory tissues. The category is thus more a descriptive than a precisely taxonomic one.

The most common lungworms belong to one of two groups, the superfamily Trichostrongyloidea or the superfamily Metastrongyloidea, but not all the species in these superfamilies are lungworms.

The lungworms in the superfamily Trichostrongyloidea include several species in the genus Dictyocaulus which infest hoofed animals, including most common domestic species. Different species are found in cattle and deer (D. viviparus), donkeys and horses (D. arnfeldi), and sheep and goats (D. filaria). These animals have direct life-cycles. The lungworms in the superfamily Metastrongyloidea include species that infest a wider range of mammals, including sheep, goats and pigs but also cats and dogs.

These include Metastrongylus elongatus (apri), found in pigs; Oslerus osleri found in dogs; and Aelurostrongylus abstrusus found in cats. Some of these have indirect, and complex, life-cycles; several of them involve slugs or snails as intermediate hosts, where the habit of sniffing at slug trails, or even licking them, causes the parasite egg to enter the dog's respiratory tract. In the case of A. abstrusus the cat is normally infected by eating a bird or rodent that has itself eaten the original host.

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