Trichuris trichiura: Barrel-Shaped Egg with Bipolar Plugs
Original bench-card visuals for recognizing Trichuris trichiura (whipworm) eggs in stool: barrel-shaped brown shell with hyaline bipolar plugs at each end - one of the most visually distinctive helminth eggs.
Trichuris trichiura egg: barrel shape and bipolar plugs
Barrel-shaped (football-shaped), golden-brown shell, 50-55 x 22-24 um. Hyaline (colorless) plugs protrude from both poles. Unsegmented single cell inside when freshly passed. Eggs float with zinc sulfate but not with formalin-ethy...
50-55 x 22-24 um. Barrel (football) shape is pathognomonic among intestinal helminth eggs. Golden-brown thick shell. Hyaline (colorless, refractile) plugs protrude from both poles. Interior contains a single unsegmented cell in freshly passed stool. Light infections may be missed - use concentration methods.
In older or soil-derived specimens, the single cell develops into a fully formed larva. Bipolar plugs remain intact. The barrel outline and plug morphology are unchanged regardless of internal development stage - shape alone identifies this egg. Embryonated eggs are infective; handle with standard precautions.
50-55 x 22-24 um. Barrel (football) shape is pathognomonic among intestinal helminth eggs. Golden-brown thick shell. Hyaline (colorless, refractile) plugs protrude f...
In older or soil-derived specimens, the single cell develops into a fully formed larva. Bipolar plugs remain intact. The barrel outline and plug morphology are uncha...
What to look for in stool
| Visual clue | Meaning | Student shorthand |
|---|---|---|
| Barrel (football) shape | Trichuris trichiura | Pathognomonic among intestinal helminths - no other common egg has this symmetric barrel outline |
| Bipolar hyaline plugs | T. trichiura - confirm | Colorless, refractile plugs at each pole; if absent, reconsider ID; plugs persist regardless of internal development stage |
| Golden-brown thick shell | T. trichiura | Shell color and thickness distinguish from thin-shelled hookworm; Ascaris has similar thickness but different shape |
| Single cell inside (fresh) | Unsegmented T. trichiura egg | No morula - unlike hookworm (2-8 cells); fully developed larva = older specimen or soil-derived |
| 50-55 um length | T. trichiura | Size eliminates most mimics; Capillaria hepatica and C. philippinensis have similar plugged eggs but different clinical context |
Trichuris trichiura egg identification guide
| Pattern | What to call it | How to think about it |
|---|---|---|
| Barrel shape, bipolar plugs, golden-brown shell | Trichuris trichiura - positive | Report with approximate burden estimate (few, moderate, many eggs per low-power field) |
| Similar shape, pitted shell, different size | Capillaria spp. - rule out | Use clinical history (hepatic mass vs. intestinal symptoms vs. fish ingestion) and morphologic detail to differentiate |
| Barrel outline, no internal detail visible | T. trichiura - acceptable ID | Bipolar plugs alone are sufficient for positive report; internal cell stage does not affect ID |
- Barrel shape + bipolar hyaline plugs = Trichuris trichiura - one of the most morphologically distinctive helminth eggs.
- Bipolar plugs are retained in all developmental stages - use shape + plugs regardless of internal content.
- Capillaria spp. are the primary mimic; differentiate using plug texture, size, and clinical context.
Barrel shape + bipolar plugs = Trichuris. No other common intestinal egg looks like this.