Introduction to Diagnostic Medical Parasitology
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  • Exercises for helminth eggs
    • How big is the egg (maximal length)?
      • Smaller than 35 micrometer
        • Has the egg an operculum and the following characteristics?
          • Egg has a marked shouldering and a broad and round posterior end
          • Egg is more elongated, has no shouldering and has a small terminal knob
      • 35-110 micrometer
        • How do the poles of the egg look like?
          • The egg has a plug at each pole
            • How is the shape of the plugs?
              • The plugs are clearly protruding
              • The plugs are less prominent, shell is striated
          • The egg has no plug at the poles
            • Does the egg have an operculum?
              • An operculum is present (needs careful observations!)
                • What is the size of the egg and what is the shape of the operculum?
                  • Egg is small (approx. 40 µm) round oval, flattened operculum, no shoulder, embryonated eggs brown, unembryonated eggs light yellow(Be aware that eggs can be temporarily found after a meal; parasitized liver!)
                  • Egg has medium size (approx. 60 -70 µm), operculum oval, golden yellow egg not embryonated, sometimes a small knob at the abopercular end
                  • Egg is rather big (approx. 70-110 µm) oval, flattened operculum, golden brown egg is not embryonated (eggs mainly found in the sputum) (For the differential diagnosis of Paragonimus eggs a specialist is needed)
              • The egg has no operculum
                • How does the egg-shell look like?
                  • Shell is thin and smooth
                    • What is the developmental stage of the egg?
                      • Egg with miracidium, minute lateral spine (often not visible)
                      • Round oval egg with 2-8 blastomers (in freshly fixed stool)
                      • Elongated oval egg with more than 8 blastomers
                  • Shell is thick
                    • What is the aspect of the thick shell?
                      • Thick shell has a rough surface
                        • What is the shape of the egg?
                          • The egg is broadly oval,fertilized
                          • The egg is elongated oval,unfertilized (longer than fertilized eggs)
                      • Thick shell is smooth
                        • What is the shape of the egg?
                          • Egg is asymmetrical (one side convex, one side flattened
                          • Egg is round
                            • Which characteristics can be seen?
                              • Egg has a pale yellow to brown embryophore and a striated shell
                              • Egg has no embryophore but polar filaments, and is colourless
                              • Egg has no embryophore and no polar filaments and is pale yellow brown
                          • Egg is oval (Fertilized and unfertilized eggs without a rough shell can sometimes be found)
      • larger than 110 micrometer
        • Does the egg have an operculum (may be difficult to see)?
          • Operculum present; Egg is really big (125 -145 µm!) with a thin shell
          • No operculum; Egg has a spine
            • Where is the spine located?
              • Spine is lateral
              • Spine is terminal, anterior end of egg rounded (eggs mainly in urine, rarely found in stool)
              • Spine is terminal, anterior end of egg tapered (gives aspect)