''Metastrongylus'' is a genus of nematodes of the family Metastrongylidae, usually found as lungworms in

pig The pig (''Sus domesticus''), often called swine, hog, or domestic pig when distinguishing from other members of the genus ''Sus'', is an omnivorous, domesticated, even-toed, hoofed mammal. It is variously considered a subspecies of ''Sus ...

s and sometimes causing parasitic bronchitis. It causes a disease called metastrongylosis.

Species

*'' Metastrongylus elongatus'' (Dujardin, 1845) synonym '' Metastrongylus apri'' (Gmelin, 1780) *'' Metastrongylus pudendotectus'' (Wostokow, 1905) *'' Metastrongylus salmi'' (Gedoelst, 1823) *'' Metastrongylus confusus'' (Jansen, 1964) *'' Metastrongylus asymmetricus'' (Noda, 1973)

Life cycle

The lifecycle is indirect. The

eggs Humans and human ancestors have scavenged and eaten animal eggs for millions of years. Humans in Southeast Asia had domesticated chickens and harvested their eggs for food by 1,500 BCE. The most widely consumed eggs are those of fowl, especial ...

are laid by the adult

worm Worms are many different distantly related bilateral animals that typically have a long cylindrical tube-like body, no limbs, and no eyes (though not always). Worms vary in size from microscopic to over in length for marine polychaete worm ...

in the

bronchi A bronchus is a passage or airway in the lower respiratory tract that conducts air into the lungs. The first or primary bronchi pronounced (BRAN-KAI) to branch from the trachea at the carina are the right main bronchus and the left main bronch ...

. They are coughed up, swallowed, and passed out via the

feces Feces ( or faeces), known colloquially and in slang as poo and poop, are the solid or semi-solid remains of food that was not digested in the small intestine, and has been broken down by bacteria in the large intestine. Feces contain a rela ...

. The eggs are then eaten by

earthworm An earthworm is a terrestrial invertebrate that belongs to the phylum Annelida. They exhibit a tube-within-a-tube body plan; they are externally segmented with corresponding internal segmentation; and they usually have setae on all segments. ...

s in which they develop through three

larva A larva (; plural larvae ) is a distinct juvenile form many animals undergo before metamorphosis into adults. Animals with indirect development such as insects, amphibians, or cnidarians typically have a larval phase of their life cycle. Th ...

l stages over 10 days to become infective. The cycle is completed by the

eating the earthworm. Infection, therefore, only occurs where pigs have access to earthworms, for example, in outdoor production. The larvae from the earthworm penetrate the

intestine The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organs of the digestive system, in humans a ...

and migrate via the

lymph node A lymph node, or lymph gland, is a kidney-shaped organ of the lymphatic system and the adaptive immune system. A large number of lymph nodes are linked throughout the body by the lymphatic vessels. They are major sites of lymphocytes that inc ...

s and

blood vessel Blood vessels are the structures of the circulatory system that transport blood throughout the human body. These vessels transport blood cells, nutrients, and oxygen to the tissues of the body. They also take waste and carbon dioxide away from ...

s to the lungs, undergoing two more larval stages in the process. The prepatent period is 3-4 weeks.

References

Strongylida Swine diseases Veterinary helminthology Parasitic nematodes of mammals Rhabditida genera {{Rhabditida-stub