Biomedical Engineering Reference
In-Depth Information
secondary hosts. In this case, humans are used as the second intermediate
host, and are infected by the plerocercoid larvae (the same role held by fish
in the life cycle of Diphylobothrium latum, see above). Humans are a dead-
end host. The plerocercoid larvae migrate to subcutaneous tissues and vari-
ous organs, producing an inflammatory response. The resulting diseases is
called sparganosis. Clinical symptoms vary with the location of the larvae.
Only a few hundred cases of sparganosis have been reported. The primary
hosts vary and include dogs and birds. The first intermediate host is cope-
pods. The natural second intermediate hosts are usually birds, reptiles, or
amphibians. Humans usually contract the disease by consuming the raw flesh
of one of the natural intermediate hosts or, more likely, drinking copepods,
an animal small enough to go unnoticed in a glass of water.
Platyhelminthes
Trematoda (flukes)
Digenea
Echinostomida
Fasciolidae
*Fasciola
*Fasciolopsis
Opisthorchiida
Heterophyidae
*Metagonimus
Opisthorchiidae
*Clonorchis
*Opisthorchis
Plagiorchiida
Dicrocoeliidae
*Dicrocoelium
Paragonimidae
*Paragonimus
Strigeatida
Schistosomatidae
*Schistosoma
*Trichobilharzia
*Schistosomatidae species
Trematodes (flukes) are shaped like flattened worms. All of the flukes that
infect humans are members of Class Digenea. Members of Class Digenea,
like all trematodes, have a sucker at one end (the mouth) and a second, ven-
tral, sucker on its underside. A distinctive anatomic feature of species in
Class Digenea is its outer coat, wherein the junctions between cells disap-
pear, forming a cytoplasmic syncytium. The flukes in Class Digenea have a
life cycle that requires a minimum of two hosts (from Latin “di”, meaning
two and “ginus”, meaning type).
In several cases,
intermediate stages
Search WWH ::




Custom Search