Biomedical Engineering Reference
In-Depth Information
The pentastome adult has the appearance of a worm. Unlike worms of
Classes Platyhelminthes or Nematoda, tongue worms display the typical
crustacean body type: fused segments all covered by a hard, chitinous cara-
pace. Tongue worms have five anterior appendages, leading to the class
name “Pentastomida”.
The primary hosts of tongue worms (i.e., the host that carries the adult
form of the organism) are vertebrate animals. Typically, the adult tongue
worm parasitizes the respiratory tract of these animals. Humans are the inter-
mediate host, carrying only the larval forms. Transmitted by food, pentasto-
mid eggs hatch in the intestines, and the larvae invade tissues to encyst
anywhere in the body. The nasopharynx is the most likely place to find the
cysts.
Typically, the cysts are walled off by an inflammatory reaction, and
eventually become calcified. With the exception of the obstructive effect
produced by the presence of a cyst, infections are often asymptomatic.
In areas where pentastomiasis is common, the cysts are often discovered as
incidental findings, at autopsy.
Pentastomiasis occurs most often in Africa, Malaysia, and the Middle
East. Less often, the disease may occur in China or South America. In the
Middle East, pentastomiasis is known as Halzoun.
Three genera of Class Pentastomida are involved: Linguatula, Armillifer,
and Porocephalus. One of the more confusing terms associated with pentas-
tomiasis is “porocephaliasis,” named for a pentastome genus, Porocephalus.
The genus “Porocephalus” and the infection “porocephaliasis” should not be
confused with “porocephaly,” a rare developmental disorder in which cysts
or cavities are found in the brains of infants.
Infectious species:
Linguatula serrata (pentastomiasis, marrara, Halzoun syndrome, tongue
worm disease, linguatulosis)
Armillifer armillatus (pentastomiasis, porocephaliasis)
Armillifer grandis (pentastomiasis, porocephaliasis)
Armillifer moniliformis (pentastomiasis, porocephaliasis)
Porocephalus crotali (pentastomiasis, porocephaliasis)
