Eukaryotic Parasites

Question 1

What are examples of ectoparasites?

Answer 1

lice, mites, ticks

Question 2

What are examples of protozoal parasites?

Answer 2

entamoeba histolytica, giardia intestinalis, toxoplasma gondii

Question 3

Ectoparasites

Answer 3

• get metabolic input from interaction with a cutaneous surface
• insects and arachnids

Question 4

Protozoa

Answer 4

• unicellular
• mainly non-parasitic (can live outside of hosts for part of life cycle)
• two forms:
  
  • trophozoite - active, invasive
  • cyst - inactive but resistant to destruction
• eg malaria, amoebiasis, giardiasis, toxoplasmosis, trypanosmiasis
• pathogenicity varies with host factors (immunocompromise)

Question 5

What are the 3 major types of helminths?

Answer 5

• roundworms
• tapeworms
• flukes

Question 6

Helminths

Answer 6

• multicellular
• limited organ systems (respiration via skin)
• realtively common sexual cycle - egg to adult worm
  
  • do not complete maturity cycle within a single host
  • eggs mus tbe developed outside human hosts (animals, soil, plants)
    
    • exception to this is strongyloides

Question 7

Roundworms (nematodes)

Answer 7

• major pathogens of humans and livestock
• tube-like, covered with cuticle
• most are free-living

Question 8

Ascaris lumbricoides infection can cause

Answer 8

• GI obstruction
• cholecystitis

Question 9

What is the life cycle of ascaris?

Answer 9

• eggs produced in jeunum are excreted in faeces
• contaminate and mature in soil
• ingested via contaminated water or uncooked plants
• larvae hatch in intestine
• into lungs via intestinal walls and hepatic circulation
• cross alveolar spaces to trachea
• swallowed

Question 10

What is Gram negative hyperinfection?

Answer 10

• as strongyloides stercoralis penetrates into gut and circulation it can bring GN organisms with it
• significant risk for GN sepsis
• much more likely in immunosuppression

Question 11

Flukes (trematodes)

Answer 11

• all are parasitic
  
  • cannot live outside host for long
• ‘figure 8’ life cycle - human phase and animal resivoir phase
• non-segmented
• blind gut
• organs in parenchyma
• surface tegument

Question 12

What is unique about the life cycle of schistosoma?

Answer 12

• transmitted by freshwater snails
• larvae infect humans where they mature in the portal veins and reproduce in the gut
• eggs shed in stools into water sources where larve infect snails

Question 13

Tapeworms

Answer 13

• all are parasitic
  
  • sit in duct and consume host nutrients
• segmented body
• surface tegument
• no gut
• organs in parenchyma