Lecture 2: Trematodes

Question 1

Subclasses of trematodes

Answer 1

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

Question 2

Morphology of flukes part 1

Answer 2

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

Question 3

morphology of flukes part 2

Answer 3

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

Question 4

Schistosomes

Answer 4

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

Question 5

schistosoma hematobium
schistosoma mansoni
schistosoma japonicum
schistosoma bovis
heterobilharzia americana

Answer 5

urinary
mesenteric vein
portal and mesenteric vein
ruminant
canine blood

Question 6

lifecycle of fluke

Answer 6

operculated egg-miracidium-sporocyst-redia-cercaria-metacercaria-adult

Question 7

operculated egg in life cycle

Answer 7

produced by adult, has an operculum (opening) on one end of egg (pole). egg contains embryonic fluke

Question 8

miracidium in life cycle

Answer 8

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.

Question 9

sporocyst in life cycle

Answer 9

miracidium loses its ciliated coat and develops into sporocyst. undifferentiated mass of cells, develops into sac. develops entirely within snail.

Question 10

rediae in life cycle

Answer 10

within sporocyst germinal cells multiply and become rediae. has oral sucker, pharynx, intestine, birth pore. found entirely within snail.

Question 11

cercariae in life cycle

Answer 11

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.

1. penetrate or ingested by 2nd IH
2. attach to vegetation and become encysted
3. penetrate the DH directly

Question 12

encysted in life cycle

Answer 12

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.

Question 13

fasciola hepatica

Answer 13

the liver fluke

cattle, sheep, goats, ruminants. rabbits. need lymnaeid snail IH

Habitat: bile ducts

life cycle 5 months

Question 14

ID fasciola hepatica

Answer 14

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

Question 15

life cycle of fasciola hepatica

Answer 15

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.

Question 16

life cycle fasciola hepatica 2

Answer 16

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.

Question 17

pathogenicity of fasciola hepatica

Answer 17

dependent on number of metacercaria ingested
no damage from passage of juvenile flukes through intestine or peritoneum. primary lesions on liver or bile duct.

1. acute fascioliasis
2. chronic fascioliasis

Question 18

acute fascioliasis

Answer 18

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

Question 19

black disease

Answer 19

complication of acute fascioliasis caused by clostridium novyi. proliferates in migratory lesions of juvenile flukes. sheep 2-4 yrs

Question 20

clincial signs of acute fascioliasis

Answer 20

sudden death, blood-stained froth at nostrils, blood discharge from anus

Question 21

chronic fascioliasis

Answer 21

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.

Question 22

hyperplastic cholangitis

Answer 22

adult flukes in bile ducts.
epithelium of bile ducts hyerplasia
eggs lodge in smaller ducts. hypoalbuminemia and hypoproteinemia

Question 23

pipestem liver

Answer 23

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.

Question 24

clinical signs of chronic fascioliasis

Answer 24

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

Question 25

Diagnosis of flukes

Answer 25

fecal sedimentation, recover operculated eggs from feces, yellow shell, indistinct operculum

Question 26

Platynosomum fastosum

Answer 26

lizard poisoning fluke
host: cats (florida)
ID: adults- small, testes parallel
eggs: brown, operculated

Question 27

Lifecycle of platynosomum fastosum

Answer 27

asults in bile ducts of cat. operculated eggs enter bile and leave with feces.
eggs with miracidium ingested by terrestrial snail
cercariae within daughter sporocysts
cercariae encyst in anolis lizards. toads geckos skinks too
cercariae shed tail and produce transparent cyst wall. encystment. metacercarial stage.
metacercariae in bile duct of lizard. ingested by kitty
excyst and juvenile flukes to bile duct and gall bladder where mature

Question 28

pathology of platynosomum fastosum

Answer 28

not severe disease. clinical: inappetence, hepatic dysfunction
lizard poisoning: weight loss, emaciation, diarrhea, vomiting, jaundice, death

Question 29

diagnose platynosomum fastosum

Answer 29

fecal sedimentation, recover eggs. if bile ducts occluded eggs not able to make way to feces.
necropsy.

Question 30

Heterobilharzia americana

Answer 30

canine blood fluke
host: dog, bobcat, racoon, gulf coast, louisiana, mississippi
mesenteric and hepatic veins
ID adults dioecious males: gynecophoric canal, females, slendereggs, no lateral spine, miracidium

Question 31

lifecycle of heterobilharzia americana

Answer 31

adults in mesenteric and hepatic veins. eggs passed in feces.
eggs make contact with water. release miracidium. penetrates aquatic snail.
cercariae penetrate DH
migrate to lungs, liver, mesenteric veins. pair up sexually.
eggs throgh intestinal lumen

Question 32

clincial signs of heterobilharzia americana

Answer 32

asymptomatic
site of penetration- possible rash. eggs in lumen- inflammation
possible: diarrhea, vomit, weight loss, lethargy, hemoperitoneum

Question 33

diagnose heterobilharzia americana

Answer 33

eggs in feces, often sedimentation