Taenia spp. Egg and Gravid Proglottid
Bench-card visuals for Taenia species identification: the round radially-striated embryophore egg (morphologically identical between T. solium and T. saginata) and the gravid proglottid uterine branch count that separates the two clinically critical species.
Taenia egg (species indeterminate) + proglottid branch count for species ID
Taenia spp. egg: round, 30-45 um, thick radially striated embryophore, inner oncosphere with 3 hooklet pairs. T. solium vs. T. saginata: identical by egg - distinguish by gravid proglottid. T. saginata: >13 lateral uterine branche...
30-45 um. Nearly round. Thick outer embryophore with prominent radial striations (spoke-like pattern). Inner oncosphere: round with 3 pairs (6) of hooklets. Eggs of T. solium and T. saginata are morphologically identical. Also indistinguishable from Echinococcus granulosus eggs - clinical context is critical. When T. solium is possible, alert the clinician: cysticercosis risk to contacts who ingest eggs.
Gravid proglottid (excreted segment): inject with India ink through uterine pore to visualize lateral uterine branches. T. saginata: >13 lateral branches per side - dichotomously branching, thin. T. solium: 8-13 branches per side - fewer, thicker. Species distinction is critical: T. solium tapeworm carriers shed eggs that can cause cysticercosis (CNS, eye, muscle) in contacts and in the patient themselves via autoinfection.
30-45 um. Nearly round. Thick outer embryophore with prominent radial striations (spoke-like pattern). Inner oncosphere: round with 3 pairs (6) of hooklets. Eggs of...
Gravid proglottid (excreted segment): inject with India ink through uterine pore to visualize lateral uterine branches. T. saginata: >13 lateral branches per side -...
What to look for in stool
| Visual clue | Meaning | Student shorthand |
|---|---|---|
| Round, thick radially striated embryophore, 30-45 um | Taenia spp. egg - cannot determine species by egg alone | Also indistinguishable from Echinococcus granulosus eggs; clinical context is essential |
| Inner oncosphere with 3 hooklet pairs (6 hooklets) | Taenia or Echinococcus cestode egg feature | Hooklet pairs distinguish cestode eggs from other helminth eggs; clinical context separates Taenia from Echinococcus |
| >13 lateral uterine branches per side | T. saginata gravid proglottid | India ink injection to fill uterine branches; count from uterine stem to proglottid margin; dichotomous branching pattern |
| 8-13 lateral uterine branches per side | T. solium gravid proglottid | Fewer, thicker branches; immediately alert clinician - cysticercosis risk and public health implications |
| Scolex: 4 suckers + rostellum with hooks | T. solium scolex ("armed") | T. saginata scolex: 4 suckers, no rostellum ("unarmed"); rostellum with hooks confirms T. solium if scolex recovered |
Taenia species identification guide
| Pattern | What to call it | How to think about it |
|---|---|---|
| Taenia eggs in stool, no proglottid available | Taenia spp. - species indeterminate | Report as Taenia spp. eggs; alert clinician to T. solium possibility; request proglottid or scolex for species ID |
| Proglottid: >13 lateral uterine branches | Taenia saginata | Report as T. saginata; praziquantel or niclosamide; lower public health concern than T. solium |
| Proglottid: 8-13 lateral uterine branches | Taenia solium | Report as T. solium; urgent clinician notification; praziquantel; follow local public health protocols for cysticercosis risk |
- Taenia spp. egg: round, thick radially striated - species cannot be determined from the egg alone.
- Species determination requires gravid proglottid India ink branch count: >13 = T. saginata; 8-13 = T. solium.
- T. solium identification is a critical alert - immediate clinician communication for cysticercosis risk assessment.
Taenia egg = species indeterminate. Proglottid decides: >13 branches = T. saginata (beef). 8-13 branches = T. solium (pork, cysticercosis risk).