Pentastomida shares features with both Arthropoda and Annelida, but is usually regarded as its own phylum. Within Pentastomida are two orders: Porocephalida and Cephalobaenida. Porocephalida includes two families of medical interest: Porocephalidae and Linguatulidae (tongue worms.)
Six species are known to infect humans:
- Armillifer armillatus
- Linguatula serrata
- Armillifer moniliformis
- Armillifer grandis
- Leiperia cincinnalis
- Raillietiella hemidactyli
- and possibly a new one: Porocephalus taiwana (11)
A. armillatus and L. serrata make up more than 99% of all reported cases of pentastomiasis.
The Discovery of Pentastomida:
1765: Wrisberg reported three worms in the frontal sinuses of a dog (as described in 12).
1787: The French veterinary surgeon P. Chabert (1737-1814), Director of the Veterinary College in Alfort, found a pentastomid ‘worm’ in the nasal passages of dogs and horses. He called this Taenia lanceolata.
1789: Fröhlich, a German, found the same parasite in the lung of a hare and gave it named it Linguata serrata.
1847: Pentastomiasis was first described in humans by Pruner, in Cairo. While performing autopsies, he found encysted parasites in the liver, bowel, and mesentery. He described them incorrectly as nematodes or insect larvae. They were reexamined by Bilharz a few years later, and he recognized them as Pentastomum. (6)
1848: Beneden classified Pentastomum within the phylum of Arthopeda.
1860: Leuckart classified pentastomes in the class Arachnida.
Disagreement surrounding the classification of pentastomes continues today, but most researchers are happy to designate Pentastomida as its own phylum.