Summary: Parasitology

Read the summary and the most important questions on Parasitology

• 1 Lectures

• 1.1 Introduction

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• What are facultative and obligate hosts?

  Fucultative is when the parasite may exist in an free living stage, ibligate is when the parasite cannot survive without its host.

• 1.2 Diagnostic challenges

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• How do protozoa replicate?

  Through schizogony/sporogony or binary fission

• What does ASSURED stand for?

  Affordaple, sensitive, specific, user-friendly, rapid&robust, equipment free, deliverable

• What are limitations of ASSURED?

  It is focused on test& treat and remote areas, but in other settings other requirements may be as important (eg reproducibitity for research, counting for helminths, large throughput)

• What are cons of microscopy?

  Less sensitive (3 samples of 3 days), species distinction may be difficult, time consuming, requires training, observer dependent, multiple procedures with one sample

• How can entamoeba histolytica, giardia lamblia and cryptosporidium parvum be diagnosed? And what are the pro's and cons?

  1. Microscopy
  Pro: available, affordable, mostly specific
  Con: more samples, staining procedures
  
  2. Antibody detection
  Pro: fast, sensitive
  Con: invasive
  
  3. Antigen detection (like pregnancy test)
  Pro: fast, sensitive, less training required, reproducible
  Con: Only crypto+giardia, relatively expensive, miss other parasites
  
  4. PCR, NAAT
  Pro: fast, sensitive, specific, multiplex, high throughput, quality control options, reproducible
  Con: need molecular set-up laboratory

• How can malaria be diagnosed and what are pros and cons?

  1. Microscopy (thick smear with lysed blood, thin smear with fixed and stained blood)
  + Sensitive (thick), species differentiation (thin), quantification, fast
  
  - detection limit, observer&procedure dependent, not fast enough, labourous
  
  2. Antibody detection (serology)
  - it takes time to develop antibodies so you might be dead
  
  3. Antigen detection (RDT's used in many areas, fingerprick stick)
  + fast, species differentiation for vivax and falciparum, no training, sensitive when high parasite loed, widely available, inexpensive
  - less sensitive for non-falciparum, no counting, deletions in target antigen reported
  
  4 PCR
  + sensitive, specific, quantify, large throughput
  - costly, not so fast, availability (now changing)

• How is schistosoma diagnosed and what are pros and cons?

  1. Microscopy (reference test, look at eggs as other half stuck in tissue, kato-kats to look at intensity eggs per mg/ml)
  + specific, quantification, available, affordable
  - low sensitivity, fluctuation of egg secretion
  
  2. Serology/antibodies (chronic so you stay positive)
  + specific, sensitive, no cross-reactivity with other helminths
  - no intensity of infection, not for evaluation of treatment
  
  
  3. Antigen detection 
  + non-invasive
  - POC-CCA only mansoni and 20 mins reading, UCP-LF CAA laboratory based

• What are 3 requirements for a new diagnostic tool for schistosoma?

  1. Highly field applicable and user friendly
  2. Highly sensitive: case detection for monitoring intervention
  3. Detecting active infection (worm load)

• What are CCA and CAA?

  These are circulating antigens excreted from the parasite gut. They can be found in blood and urine and they are unique for schistosoma.