vpg logo Parasite Diagnostic Key
Canine

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.

Cystoisospora sp. oocyst


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NC State College of Veterinary Medicine
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Raleigh, NC 27607