''Metastrongylus'' is a genus of
nematodes of the family
Metastrongylidae, usually found as
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 t ...
s in
pigs 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 wo ...
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 bronchus. ...
. They are coughed up, swallowed, and passed out via the
feces. 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. T ...
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.
...
l stages over 10 days to become infective. The cycle is completed by the
pig 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 and migrate via the
lymph nodes and
blood vessel
The blood vessels are the components 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 ...
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