Lecture 2: Trematodes Flashcards
Subclasses of trematodes
monogenea: ectoparasite, amphibs, reptiles, fishies
digenea: (digenetic flukes)
endoparasitic, domestic and wild animals, humans. require more than one (usually two) hosts. FIRST INTERMEDIATE HOST FOR ANY DIGENETIC FLUKE IS USUALLY A SNAIL
Morphology of flukes part 1
dorsoventrally flattened. can be long and narrow; leaf shaped; thick fleshy body. schistosomes are long and thin like nematodes
have a tegument that may be smooth or covered with spines
2 attachment organs: anterior feeding sucker called oral sucker
ventral attachement called acetabulum
morphology of flukes part 2
digestive system begins with mouth surrounded by oral sucker, muscular pharynx, esophagus- two blind ceca. branched or unbranched (dendritic)
excretory and nervous system
hermaphrodites besides schistosomes
males: two testes, vas deferens, seminal vesicle, prostatic portion, cirrus (penis), cirrus sac and genital pore. testes either tandem (one before other) or parallel (side by side)
female: one ovary, seminal vesicle, vitelline or yolk glands, vitelline duct, ootype (eggs formed), mehlis’ gland (surrounds ootype) uterus and genital pore
Schistosomes
split bodied flukes- the weirdo flukes
inhabit blood vessels
not hermaphrodites
resemble nematodes/round worms
female very slender. male carry female in groove in his body called gynecophoric canal
eggs are thin shelled and have no operculum. some have lateral or terminal spine
parasite of humans
schistosoma hematobium schistosoma mansoni schistosoma japonicum schistosoma bovis heterobilharzia americana
urinary mesenteric vein portal and mesenteric vein ruminant canine blood
lifecycle of fluke
operculated egg-miracidium-sporocyst-redia-cercaria-metacercaria-adult
operculated egg in life cycle
produced by adult, has an operculum (opening) on one end of egg (pole). egg contains embryonic fluke
miracidium in life cycle
emerges from egg, squeezing through operculum. triangular and broad anterior end. tiny cilia. spine on anterior end used to puncture into first intermediate host- SNAIL.
sporocyst in life cycle
miracidium loses its ciliated coat and develops into sporocyst. undifferentiated mass of cells, develops into sac. develops entirely within snail.
rediae in life cycle
within sporocyst germinal cells multiply and become rediae. has oral sucker, pharynx, intestine, birth pore. found entirely within snail.
cercariae in life cycle
many cercariae develop in rediae. emerge through snail’s skin and escape into environment. oral and ventral sucker, intestine, excretory and nervous system. tail for propelling.
- penetrate or ingested by 2nd IH
- attach to vegetation and become encysted
- penetrate the DH directly
encysted in life cycle
drop tail, thick wall. encysted. metacercaria. infective stage. must reach DH to finish life cycle. no metacercaria if directly to DH. excysts in intestine of host and migrates to predilection site and develops into adult.
fasciola hepatica
the liver fluke
cattle, sheep, goats, ruminants. rabbits. need lymnaeid snail IH
Habitat: bile ducts
life cycle 5 months
ID fasciola hepatica
adults- skin covered with spines, leaf shaped, broaded anterior. cone shaped projection on head. prominent shoulders.
clouded internal morphology- highly branched internal organs, intestinal ceca. mutilobulated testes, branched ovary, lateral vitelline glands, uterus anterior to testes. eggs operculated
life cycle of fasciola hepatica
adults found in bile ducts of ruminants, operculated eggs enter the duodenum with bile and leave with feces
on contact with water, eggs hatch and miracidium emerges from operculated egg
miracidium swims around, penetrates aquatic snail lynmaea sp.
within snail, develop sporocyst, 5-8 rediae
cercariae
settle on vegetation below water or bottom of pond
produce transparent cell wall. metacercaria
swallowed by ruminant when host eats vegetations or drinks them.
life cycle fasciola hepatica 2
metacercariae encyst in duodenum. juvenile flukes. immediately penetrate intestinal wall enter abdominal cavity and migrate over abdominal viscera until make contact with capsule of liver.
penetrate liver and migrate through parenchyma (2 months). feed and grow. enter bile ducts and mature within 1 month, begin producing eggs 1 month later.
pathogenicity of fasciola hepatica
dependent on number of metacercaria ingested
no damage from passage of juvenile flukes through intestine or peritoneum. primary lesions on liver or bile duct.
- acute fascioliasis
- chronic fascioliasis
acute fascioliasis
occurs in sheep.
traumatic hepatitis. migration of large numbers of juvenile flukes (10,000+)
extensive destruction of liver parenchyma
marked hemorrhage, rupture of liver capsul, enlarged and pale
less acute: liver covered with migratory tracks infiltration of wbc. early fibrosis.
death rapid or after several days. decline to move, anorexia, painful abdomen
black disease
complication of acute fascioliasis caused by clostridium novyi. proliferates in migratory lesions of juvenile flukes. sheep 2-4 yrs
clincial signs of acute fascioliasis
sudden death, blood-stained froth at nostrils, blood discharge from anus
chronic fascioliasis
occurs in both sheep and cattle most common form
characterized as hepatic fibrosis. migration of juvenile flukes produces characteristic tracks in liver. parenchyma destruction. hemhorrage. necrosis. thrombus in hepatic vein and liver. ischemic coagulative necrosis.
healing of lesions begins- collagen laid down, fibrosis occurs- scar tissue contracts and contorts liver.
hyperplastic cholangitis
adult flukes in bile ducts.
epithelium of bile ducts hyerplasia
eggs lodge in smaller ducts. hypoalbuminemia and hypoproteinemia
pipestem liver
cattle. calcification of fibrotic lesions in bile duct develops and complete casts of the bile duct formed. walls of duct completely calcified and protude markedly from durface.
clinical signs of chronic fascioliasis
sheep: lack vigor, diminshed apetite, mucous membranes pale, edema, wool dry and falls out, debilitated, emaciated, depressed
BOTTLE JAW
cattle: digestive disturbances, constipated, diarrhea, emaciated dull weak
