Bailey & Scott's Diagnostic Microbiology: Tissue Nematodes Flashcards


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1

intestinal nematodes

five stages; transmitted by skin puncture, free living soil, and ingestion of raw freshwater fish

2

tissue nematodes

five stages; transmitted by blood feeding arthropods, ingestion of freshwater crustaceans, and ingestion of contaminated meat

3

Trichinella spiralis

humans are accidental host which became infected by eating contaminated raw or undercooked meat; infections worldwide; infected mammal definitive host for transmission to humans-domestic pig most important, also bears, walrus, wild game; pseudospiralis and britovi are other species

4

Trichinella spiralis

encysted larvae ingested from undercooked meat; larvae deposit in striated muscle; adults remain in intestine

5

Trichinella spiralis clinical presentation

mild sub-clinical to severe illness dependent on parasite burden; nausea, vomiting, abdominal pain, and diarrhea; systemic illness leads to fever, facial edema around eyes, myalgia, marked eosinophilia, larval migration may occur affecting brain and meninges resulting in neurological symptoms, and myocarditis, arrhythmias, and sudden death

6

Trichinosis

distributed worldwide-most commonly in parts of Europe and the US; encysted larvae cause disease of muscle; adults reside in intestine; larvae will not encyst in brain or heart tissue

7

Trichinosis lab diagnosis

diagnosed with muscle biopsy, nucleic acid based testing, and serology

8

Toxocara spp.

zoonotic disease with worldwide distribution; persists months to years; humans accidentally ingest eggs; larvae released in small intestine, penetrate and migrate to other tissues (liver and lungs); adults unable to mature in human host; canis-dogs, cati-cats; no eggs in human illness

9

Toxocara spp. clinical presentation

most infections are subclinical with mild disease; severe forms visceral larva migrans (liver, heart, lungs, kidneys, muscle), ocular larval migrans, covert or common toxocariasis (nonspecific), and neurotaxocariasis (brain and CSF)

10

Toxocara spp. lab diagnosis

direct examination-stool specimens not useful since there are no eggs; other helminth eggs may be present (risk factor); definitive surgical histopathology of migrating larvae; serology useful, eosinophilia

11

Dracunculus medinensis

guinea worm acquired from ingestion of infected copepods in freshwater ponds; larvae released form copepods and migrate through thoracic musculature; mating occurs in peritoneal space (male dies, female migrates to surface to lay eggs); dracunculiasis

12

Dracunculus medinensis clinical presentation

well known presentation, no lab ID; rural, isolated areas of African countries; worms are attached to a stick and slowly retract from host by turning the stick

13

Ancylostoma spp.

common hookworms of dogs and cats; braziliense and caninum; found in southeastern US; infective larvae penetrate skin of human and migrate through subcutaneous tissue forming tracks; not intestinal; diagnosis made by track evidence

14

Parastrongylus cantonensis

rat lungworm endemic in SE Asia; rodents shed larvae that infect mollusks (IH) which are consumed by paratenic hosts (shrimp, fish, crabs, frogs) which humans then ingest; larvae migrate to CNS or eye; diagnosis based on histologic exam of adult female

15

Parastrongylus costaricensis

found in cotton or black rat endemic in Central and South America; cause abdominal angiostrongyliasis- inflammatory bowel lesions, appendicitis symptoms; associated with ingested salad contaminated with infected slugs or snails; diagnosed based on larvae or egg presence in tissue

16

Gnathostoma spinigerum

gastric spirurid nematode (dogs and cats); larvae hatch in water and infect copepods and humans accidentally ingest larvae from contaminated fish; worms cannot mature in humans and migrate in tissue; diagnosis based off of larvae found in tissue, head contains four rows of cephalic hooklets, and body is covered with transverse rows of spines