1. Larvae ........ Go to: 4 & 5
2. Ova .......... Go to: 8, 9, & 10
3. Adult Worms .......... Go to: 17, 18, 19, & 20

4. Larvae in blood ........ Dirofilaria immitis
5. Larvae in mucus, sputum, or feces .......... Go to: 6 & 7

6. Larvae in mucus, sputum, or feces. Larvae with a S-shaped spine at the end of the tail ........ Aelurostrongylus abstrusus
7. Larvae in feces. Larvae with a straight conical tail, without an S-shaped spine ........ Strongyloides stercoralis

8. Ova in feces ........ Go to: 11 & 12
9. Ova in urine (with bipolar plugs)........ Capillaria plica or Capillaria feliscati
10. Ova in sputum, or nasal discharge (with bipolar plugs)........ Capillaria aerophilus

11. Ova in feces with bipolar plugs ........ Capillaria aerophilus
12. Ova in feces without bipolar plugs ........ Go to: 13 & 14

13. Ova with a rough coat around the shell ........ Toxocara cati
14. Ova with a smooth shell .......... Go to: 15 & 16

15. Ova ellipsoid, with morula stage filling much of the shell ........ Hookworm (Ancylostoma sp. or Uncinaria sp.)
16. Ova oval, with single-cell stage pulled away from the interior shell wall ........ Toxascaris leonina

17. Adult nematode found in a Subcutaneous nodule ........ Dracunculus insignis
18. Adult nematode in vomitus .......... Go to: 20 & 21
19. Adult nematodes in feces .......... Go to: 22 & 23

20. Anterior end is bunt with a cuticular collar ........ Physaloptera sp.
21. Anterior end is rounded with large lips and cervical alae ........ Go to: 22 & 23

22. The tail of the male worm is finger-like ........ Toxocara cati
23. The tail of the male worm is triangular and NOT finger-like .......... Toxascaris leonina