Lecture 2 1/23/24

Question 1

What are the distinguishing characteristics of the Platyhelminthes phylum?

Answer 1

-no external cuticle/molting
-earliest bilateral/triploblastic animal
-nerve ganglion in anterior end
-dorsoventrally flattened
-acoelomate/no body cavity
-hermaphroditic

Question 2

Which classes fall into the Platyhelminthes phylum?

Answer 2

-Turbellaria
-Trematoda
-Cestoda

Question 3

What are the morphologic/biologic characteristics of Trematoda?

Answer 3

-leaf-shaped
-no segmentation
-incomplete alimentary canal w/ no anus
-sucks for attachment
-all species are parasitic

Question 4

What are the characteristics of the Trematoda subclass Digenea?

Answer 4

-indirect life cycle
-first intermediate host is always a mollusc
-hermaphroditic
-produce operculated eggs
-contain all fluke species

Question 5

What are the key points of the general trematode life cycle?

Answer 5

-miracidium must reach snail
-asexual generations (sporocyst, redia) occur within snail
-cercaria leaves snail and encysts in new host or environment as metacercaria

Question 6

What are the potential methods for the infective stage of Trematoda to reach the definitive host?

Answer 6

-passive ingestion
-predation
-skin penetration

Question 7

How does host specificity vary between the mature and immature stages of Trematoda?

Answer 7

-immature stages are very host specific
-mature stages are often not as host specific

Question 8

What are the characteristics of Fasciola hepatica?

Answer 8

-aka Common (Sheep) Liver Fluke
-DH is ruminants, humans, and other mammals
-1st IH is amphibious snail
-no 2nd IH
-pre-patent period of 2-3 months
-operculated eggs 130x75 um
-adults 2-3x1 cm
-migrate in liver
-adults found in bile ducts

Question 9

What is the distribution of Fasciola hepatica?

Answer 9

-south-central US
-Florida
-northwest US

Question 10

What is the pathophysiology of Fasciola hepatica?

Answer 10

Acute:
-migration of larvae in abdominal cavity and liver
Chronic:
-hyperplasia and fibrosis of bile ducts
-thickened duct walls that are more permeable to plasma proteins
-anemia and hypoalbuminemia

Question 11

What is the acute disease seen with Fasciola hepatica infection?

Answer 11

hemorrhagic hepatitis

Question 12

What chronic diseases/states are seen with Fasciola hepatica infection?

Answer 12

-anemia
-hypoalbuminemia
-decreased production
-liver fibrosis
-hyperplasia and calcification of bile ducts
-black disease/necrotic hepatitis

Question 13

How is Fasciola hepatica diagnosed?

Answer 13

-considering geographic location and patient transport history
-finding eggs on fecal sedimentation
-clinical signs/imaging/hepatomegaly
-history of access to water/wet pastures
-adult morphology on necropsy

Question 14

What control steps can be taken with Fasciola hepatica?

Answer 14

-controlling access to wet areas
-molluscicides
-anthelmintic administration

Question 15

What are the characteristics of Fascioloides magna?

Answer 15

-aka Deer Fluke
-1st IH is amphibious snail
-no 2nd IH
-DH is white-tailed deer
-abnormal hosts include sheep, goats, cattle, camelids, moose, and elk
-adults are 30-100x20-30 mm
-eggs are 110-170x75-96 um
-pre-patent period is 7-9 months

Question 16

Where is Fascioloides magna found within the deer?

Answer 16

lives within a cyst with a duct that enters the bile duct

Question 17

Why are Fascioloides magna flukes dangerous in goats, sheep, and cervids?

Answer 17

the immature flukes wander instead of forming cysts, causing damage to the liver

Question 18

What is the geographical distribution of Fascioloides magna?

Answer 18

-northern US
-Canada

Question 19

How can Fasciola hepatica and Fascioloides magna be distinguished?

Answer 19

-Fasciola hepatica has a distinguished anterior “beak”
-Fascioloides magna is typically larger, but not always

Question 20

What are the characteristics of Platynosomum fastosum/concinnum?

Answer 20

-aka Lizard Poisoning Fluke
-1st IH is terrestrial snail
-2nd IH is pill bugs
-lizards and amphibians serve as paratenic hosts
-DH is felids
-pre-patent period is 2-3 months
-eggs are 34-50x20-35 um
-found in bile ducts/gall bladder

Question 21

What is the geographic distribution of Platynosomum?

Answer 21

-southeastern US
-Caribbean

Question 22

What clinical signs are seen with a Platynosomum infection?

Answer 22

-vomiting
-diarrhea
-icterus
-hepatomegaly

Question 23

What are the characteristics of Paragonimus spp.?

Answer 23

-aka Lung Flukes
-1st IH is aquatic snail
-2nd IH is crayfish/crabs
-DH is mammals
-pre-patent period is 1-2 months
-adults are 7-12x4-6 mm
-eggs are 75-118x48-65 um
-diagnosed through sedimentation/sugar float

Question 24

If adult lung flukes are in the lungs, how do the eggs end up passing in the feces?

Answer 24

the eggs are laid in the lungs, coughed up, and swallowed

Question 25

How are Paragonimus spp. adults found in the lungs?

Answer 25

in pairs within lung cysts

Question 26

What are the clinical signs of Paragonimus spp.?

Answer 26

-resp. problems
-cough
-lethargy
-pneumothorax

Question 27

Which Paragonimus spp. is of most zoonotic significance?

Answer 27

Paragonimus westermani

Question 28

What are the characteristics of Schistosomes/Blood Flukes?

Answer 28

-dioecious/separate male and female forms
-live in portal and mesenteric vasculature
-cercariae penetrate host skin
-eggs migrate through tissue to lumen of GI or bladder
-eggs are NOT operculated
-major pathology from granulomatous inflammation around eggs
-dermatitis from cercarial penetration of non-human spp.

Question 29

What are the characteristics of Heterobilharzia americana?

Answer 29

-1st IH is snail
-no second IH
-no metacercaria
-DH is dog, raccoon, bobcat, opossum, rabbit, horse
-pre-patent period is 2 months
-cercaria penetrate skin and enter lungs and liver
-adults ~4mm and found in copula in mesenteric veins
-eggs 88x74 um

Question 30

What is the geographic distribution of Heterobilharzia americana?

Answer 30

Florida to Texas, and north to Kansas

Question 31

How is Heterobilharzia americana diagnosed?

Answer 31

finding eggs on sedimentation

Question 32

Which drugs are used to treat Heterobilharzia americana?

Answer 32

-fenbendazole for eggs
-praziquantel for adults