Trematodes (flukes)
click to edit
Bilaterally symmetrical
Tough tegument – protect again digestive enzymes
They have two suckers for attachment to the host.
No real digestive system (will explain further in class)
Hermaphroditic
Pass through several different larval stages: miracidium, sporocyst, radia, cercaria and metacercaria.
Require one or more intermediate hosts, one of which is nearly always a mollusk (phylum)/gastropod (class). i.e., snail, slug
Eggs are operculated, contain a ciliated embryo called a miracidium.
Miracidia released when eggs are laid and come into contact with water.
Nanophyetus salmincola (salmon poisoning fluke)
DH cat, dog, other mammals
IMH: 1 - snail
2 - salmonoid fish
Very small, up to 3mm in length. One or two deep brown eggs in the uterus. Resides in small intestine
N. salmincola can transmit Neorickettsia helminthoeca, a type of bacteria that cause Salmon Poisoning Disease (SPD) in dogs and other canids. SPD is a severe and commonly fatal hemorrhagic gastroenteritis.
Gold eggs with operculum
Alaria spp. (intestinal fluke)
IMH snail then tadpole
PH Frogs, snakes, and mice (eat tadpoles)
2-4mm in length and fleshy. Two wing-like alae. Resides in small intestine.
5-6 weeks
eggs Oval, light brown, and fairly large (120 × 65 µm)
Paragonimus kellicotti (lung fluke)
IMH snail then crayfish
Adult: Reddish brown, oval, usually found in cysts, primarily in the lungs
5-6 weeks
Diagnosis
Fecal sedimentation
Tracheal wash
Radiographic changes (thoracic)