Trematodes (Flukes)
Small, flat, leaf-like worms, flattened dorso-ventrally with no body cavity
Body mass consists of: mesodermal parenchyma, where internal organs are embedded
Oral and ventral suckers that help attach to the host
Infest various organs of the human host
e.g. intestinal veins, urinary bladder, liver, lung
Use freshwater snails as an intermediate host
Domain: Eukaryote
Kingdom: Animalia
Phylum: Platyhelminthes (flatworms)
Class: Trematodes (flukes)
Hermaphrodite: organism that has both kinds of reproductive organs and can produce both gametes associated with male and female sexes
Life cycle beginning: hermaphroditic adult fluke produces eggs in the human (definitive host)
eggs are excreted into the environment
first larval stage (miracidium) develops inside the eggs
the larvae seek out and infect suitable snail species (first intermediate host)
asexual reproduction occurs in the snail
several intermediate development forms can be distinguished (sporocyst, redia) and the final larval stage (cercaria)
leave the snail and seek out second intermediate host
a fish or crustacean
in the second intermediate host, the cercaria form cysts called metacercaria excysts
if the infected raw or under-cooked fish or crustacean is eaten by a human, the metacercaria excysts, and the fluke invades tissues (such as the lung or liver) and begins producing eggs
called “blood flukes”
have separate distinct sexes
similar life cycle to hermaphroditic flukes
only one intermediate host (snail)
acquired by: schistosome cercaria directly penetrating the skin in contaminated rivers and lakes
adult schistosomes take up residence in various abdominal veins
in fresh water, the organisms infect snails (in which they multiply)
cercaria are released into the fresh water
Hepatic/liver flukes
Fasciola hepatica
Intestinal flukes
Fasciolopsis buski
Heterophyes heterophyes
Lung flukes
Paragonimus westermani
Blood flukes
Schistosoma haematobium
Schistosoma mansoni
Small, flat, leaf-like worms, flattened dorso-ventrally with no body cavity
Body mass consists of: mesodermal parenchyma, where internal organs are embedded
Oral and ventral suckers that help attach to the host
Infest various organs of the human host
e.g. intestinal veins, urinary bladder, liver, lung
Use freshwater snails as an intermediate host
Domain: Eukaryote
Kingdom: Animalia
Phylum: Platyhelminthes (flatworms)
Class: Trematodes (flukes)
Hermaphrodite: organism that has both kinds of reproductive organs and can produce both gametes associated with male and female sexes
Life cycle beginning: hermaphroditic adult fluke produces eggs in the human (definitive host)
eggs are excreted into the environment
first larval stage (miracidium) develops inside the eggs
the larvae seek out and infect suitable snail species (first intermediate host)
asexual reproduction occurs in the snail
several intermediate development forms can be distinguished (sporocyst, redia) and the final larval stage (cercaria)
leave the snail and seek out second intermediate host
a fish or crustacean
in the second intermediate host, the cercaria form cysts called metacercaria excysts
if the infected raw or under-cooked fish or crustacean is eaten by a human, the metacercaria excysts, and the fluke invades tissues (such as the lung or liver) and begins producing eggs
called “blood flukes”
have separate distinct sexes
similar life cycle to hermaphroditic flukes
only one intermediate host (snail)
acquired by: schistosome cercaria directly penetrating the skin in contaminated rivers and lakes
adult schistosomes take up residence in various abdominal veins
in fresh water, the organisms infect snails (in which they multiply)
cercaria are released into the fresh water
Hepatic/liver flukes
Fasciola hepatica
Intestinal flukes
Fasciolopsis buski
Heterophyes heterophyes
Lung flukes
Paragonimus westermani
Blood flukes
Schistosoma haematobium
Schistosoma mansoni
