1. Nematode Larva .......... Go to: 4 & 5
2. Helminth Egg or Protozoal Cyst .......... Go to: 6 & 7
3. Worms / Segments in feces / vomitus .......... Go to: Gross Worm Key
4. Larvae in blood ..........
Dirofilaria immitis
5. Larvae in feces, with rhabditiform esophagus & conical pointed tail
.......... Strongyloides stercoralis
6. Large packet of 2 or more spherical eggs.
.......... Dipylidium caninum
7. Single egg or cyst .......... Go to: 8 & 9
8. Eggs or cysts with smooth non-ornate shells. ...... Go to: 10 & 11
9. Eggs with ornate (plugs, operculum, striations, rough) shells.
.......... Go to: 12 & 13
10. Small protozoan oocyst with thin shell and a single cell embryo.
.......... Cystoisospora sp.
11. Morulated egg. .......... Hook-worm egg
12. Spherical to oval eggs with striated or rough shell.
.......... Go to: 14 & 15
13. Oval to Elongate eggs with operculum or bi-polar plugs.
.......... Go to: 16 & 17
14. Small spherical egg w/ striated shell & embryo w/ hooklets.
.......... Taenia sp.
15. Large round to oval egg w/ rough pitted shell & single cell embryo.
.......... Toxocara sp.
16. Eggs with bipolar plugs. .......... Go to: 18 & 19
17. Eggs with a single operculum. .......... Go to: 20 & 21
18. Bi-polar plugs with a smooth shell surface.
....... Trichuris vulpis
19. Bi-polar plugs with fine pits on the shell surface.
.......... Capillaria boehmi
20. Large egg with a rim around the operculum.
.......... Paragonimus kellicotti
21. Smaller egg without a rim around the operculum.
.......... Spirometra sp.
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