Table 7 is a reference for identifying the diagnostic stage of the common intestinal nematodes. The geographic location and means of infection are also listed.
Table 7. Nematodes Living in the Intestinal Tract.| Species and Description | Image of Diagnostic Stage | Geographic Location | Means of Infection |
| Ascaris lumbricoides egg ~45-75 µm long a. Fertilized corticated egg (bumpy coat surrounding the egg) b. Fertilized decorticated egg (no bumpy coat) | a.
(36) b.
(37) | Throughout tropical and subtropical regions, especially where sanitation is poor. Occasionally pig farms. | Consuming something that has soil contaminated with eggs on it. |
| Enterobius vermicularis a. egg 50-60x20-50 µm seen in tape prep b. adult 2.5 mm x 0.2mm (adults are seen in perianal folds and occ. in stool specimen | a.
(38) b.
(39) | Worldwide, even where sanitation is good | Consumed from contaminated hands or can be breathed in and swallowed. |
Hookworm: Necator americanus and Ancylostoma duodenale 60-75 x 35-40 µm
| 
(40) | Worldwide, especially in warmer climates where larvae in the soil can survive; certain species predominate in certain areas | Penetration of human skin by infective larvae living in the soil. |
| Strongyloides spp. primarily larvae are seen in the feces 180-380 µm long Arrow shows typical rhabditiform larva in stool specimen | 
(41) | Tropical and subtropical areas throughout the world | Direct penetration by infective filariform larvae from the soil. |
| Trichuris trichiura 50-55 x 20-25 µm note characteristic polar plugs. | 
(42) | Worldwide, especially in tropical areas and where there is poor sanitation. | Consuming substances contaminated with eggs. |
36. DPDx. "Ascariasis - Figure D: Fertilized egg of A. lumbricoides in an unstained wet mount of stool."CDC.gov, 19 Jul 2019, https://www.cdc.gov/dpdx/ascariasis/index.html
37. DPDx. "Ascariasis - Figure A: A. lumbricoides decorticated, fertile egg in wet mounts, 200x magnification." CDC.gov, 19 Jul 2019, https://www.cdc.gov/dpdx/ascariasis/index.html
38. DPDx. "Enterobiasis - Figure B: Eggs of E. vermicularis in a wet mount." CDC.gov, 5 Aug 2019, https://www.cdc.gov/dpdx/enterobiasis/index.html
39. DPDx. "Enterobiasis - Figure A: Adult male of E. vermicularis from a formalin-ethyl acetate (FEA) concentrated stool smear. The worm measured 1.4 mm in length. Image contributed by the Centre for Tropical Medicine and Imported Infectious Diseases, Bergen, Norway." CDC.gov, 5 Aug 2019, https://www.cdc.gov/dpdx/enterobiasis/index.html
40. DPDx. "Hookworm (Intestinal) - Figure B: Hookworm egg in an unstained wet mount, taken at 400x magnification." CDC.gov, 17 Sep 2019, https://www.cdc.gov/dpdx/hookworm/index.html
41. DPDx. "Strongyloidiasis - Figure D: Rhabditiform larva of S. stercoralis in an unstained wet mount of stool. Note the short buccal canal and the genital primordium (red arrow)." CDC.gov, 30 Jul 2019, https://www.cdc.gov/dpdx/strongyloidiasis/index.html
42. DPDx. "Trichuriasis - Figure B: Egg of T. trichiura in an unstained wet mount." CDC.gov, 19 Dec 2017, https://www.cdc.gov/dpdx/trichuriasis/index.html
