Lecture 2 1/23/24 Flashcards
What are the distinguishing characteristics of the Platyhelminthes phylum?
-no external cuticle/molting
-earliest bilateral/triploblastic animal
-nerve ganglion in anterior end
-dorsoventrally flattened
-acoelomate/no body cavity
-hermaphroditic
Which classes fall into the Platyhelminthes phylum?
-Turbellaria
-Trematoda
-Cestoda
What are the morphologic/biologic characteristics of Trematoda?
-leaf-shaped
-no segmentation
-incomplete alimentary canal w/ no anus
-sucks for attachment
-all species are parasitic
What are the characteristics of the Trematoda subclass Digenea?
-indirect life cycle
-first intermediate host is always a mollusc
-hermaphroditic
-produce operculated eggs
-contain all fluke species
What are the key points of the general trematode life cycle?
-miracidium must reach snail
-asexual generations (sporocyst, redia) occur within snail
-cercaria leaves snail and encysts in new host or environment as metacercaria
What are the potential methods for the infective stage of Trematoda to reach the definitive host?
-passive ingestion
-predation
-skin penetration
How does host specificity vary between the mature and immature stages of Trematoda?
-immature stages are very host specific
-mature stages are often not as host specific
What are the characteristics of Fasciola hepatica?
-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
What is the distribution of Fasciola hepatica?
-south-central US
-Florida
-northwest US
What is the pathophysiology of Fasciola hepatica?
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
What is the acute disease seen with Fasciola hepatica infection?
hemorrhagic hepatitis
What chronic diseases/states are seen with Fasciola hepatica infection?
-anemia
-hypoalbuminemia
-decreased production
-liver fibrosis
-hyperplasia and calcification of bile ducts
-black disease/necrotic hepatitis
How is Fasciola hepatica diagnosed?
-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
What control steps can be taken with Fasciola hepatica?
-controlling access to wet areas
-molluscicides
-anthelmintic administration
What are the characteristics of Fascioloides magna?
-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
Where is Fascioloides magna found within the deer?
lives within a cyst with a duct that enters the bile duct
Why are Fascioloides magna flukes dangerous in goats, sheep, and cervids?
the immature flukes wander instead of forming cysts, causing damage to the liver
What is the geographical distribution of Fascioloides magna?
-northern US
-Canada
How can Fasciola hepatica and Fascioloides magna be distinguished?
-Fasciola hepatica has a distinguished anterior “beak”
-Fascioloides magna is typically larger, but not always
What are the characteristics of Platynosomum fastosum/concinnum?
-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
What is the geographic distribution of Platynosomum?
-southeastern US
-Caribbean
What clinical signs are seen with a Platynosomum infection?
-vomiting
-diarrhea
-icterus
-hepatomegaly
What are the characteristics of Paragonimus spp.?
-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
If adult lung flukes are in the lungs, how do the eggs end up passing in the feces?
the eggs are laid in the lungs, coughed up, and swallowed
How are Paragonimus spp. adults found in the lungs?
in pairs within lung cysts
What are the clinical signs of Paragonimus spp.?
-resp. problems
-cough
-lethargy
-pneumothorax
Which Paragonimus spp. is of most zoonotic significance?
Paragonimus westermani
What are the characteristics of Schistosomes/Blood Flukes?
-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.
What are the characteristics of Heterobilharzia americana?
-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
What is the geographic distribution of Heterobilharzia americana?
Florida to Texas, and north to Kansas
How is Heterobilharzia americana diagnosed?
finding eggs on sedimentation
Which drugs are used to treat Heterobilharzia americana?
-fenbendazole for eggs
-praziquantel for adults
