e. Dwarf Tapeworm (Hymenolepis nana). The development of this tapeworm
is unusual in that both the larval and adult stages are found in the human intestine.
Infective eggs are expelled by adult worms in the human intestine. Larvae hatch and
develop to maturity, still in the human intestine. No intermediate host is needed;
therefore, transmission can be from person to person.
f. Dwarf Tapeworm (Hymenolepis diminuta). This tapeworm is a parasite
common to rodents. Intermediate hosts are rat fleas, beetles, and cockroaches.
Humans become infected by accidentally swallowing infected arthropods (rat fleas,
beetles) which are in cereals or stored products. Children, especially, are likely to
swallow these arthropods in precooked cereals.
Generally, a person infected with dwarf tapeworms will have several.
However, a person infected with the larger tapeworms will rarely have more
than one or two worms.
SIGNS AND SYMPTOMS
Generally, adult tapeworms in the human intestine do not compete with the host
for food substances; therefore, the worms cause no symptoms. However, a heavy
tapeworm infection may cause diarrhea, abdominal pain, and anorexia. Approximately
1 to 2 percent of those having fish tapeworm may develop anemia. Persons infected by
the pork tapeworm sometimes have central nervous system involvement. In the central
nervous system, cysticerci (the larvae of the pork tapeworm) are usually located in the
meninges, cerebral cortex, ventricles, and occasionally the parenchyma. The
symptoms, occurring several years after the infection, are brought on by the death of
the larvae triggering inflammatory toxic reactions. The signs and symptoms are clear
and can resemble those for cerebral tumor, basal meningitis, encephalitis, intracranial
hypertension, and hysteria. The most prominent symptoms are those of recurrent
For all types of tapeworm, the drug of choice is niclosamide. An alternative drug
is paromomycin, less effective but available commercially. The best treatment is
prevention. First, be sure there is adequate sanitation. Prevent human feces from
contaminating soil, animal food, and water. Avoid irrigating pastures with sewage.
Secondly, cook beef, pork, and fish thoroughly. Finally, practice good hygiene.