Taenia infection laboratory findings
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Laboratory Findings
Microscopic identification of eggs and proglottids in feces is diagnostic for taeniasis, but is not possible during the first 3 months following infection, prior to development of adult tapeworms. Repeated examination and concentration techniques will increase the likelihood of detecting light infections. Nevertheless, speciation of Taenia is impossible if solely based on microscopic examination of eggs, because all Taenia species produce eggs that are morphologically identical. Eggs of Taenia sp. are also indistinguishable from those produced by cestodes of the genus Echinococcus (tapeworms of dogs and other canid hosts). Microscopic identification of gravid proglottids (or, more rarely, examination of the scolex) allows species determination.
A, B: Taeniid eggs. The eggs of Taenia saginata and Taenia solium are indistinguishable morphologically (morphologic species identification will have to rely on the proglottids or scolices). The eggs are rounded, diameter 31 to 43 µm, with a thick radially striated brown shell. Inside each shell is an embryonated oncosphere with 6 hooks. The egg in Figure B still has the primary membrane that surrounds eggs in the proglottids.
C: Pollen artifact that could be mistaken for a taeniid egg; however, the shell is thinner, of nonuniform thickness, and no hooks are visible.
D, E, F, G: Gravid proglottids of Taenia saginata (Figures D and E) and Taenia solium (Figures F and G). Injection of India ink in the uterus allows visualization of the primary lateral branches. Their number allows differentiation between the two species: T. saginata has 15 to 20 branches on each side (Figure D and E), while Taenia solium has 7 to 13 (Figures F and G). Note the genital pores in mid-lateral position.