Taenia species
Taenia multiceps, T. serialis (coenurosis)
Coenurosis is a rare infection with the larval (metacestode) stage of Taenia multiceps and T. serialis. The larva is called a coenurus. Histologically, the infection looks like cysticercosis but there are multiple protoscoleces within each bladder (fluid-filled sac).
Taenia saginata/Taenia asiatica, proglottid
Mature proglottids of Taenia solium, T. saginata and T. asiatica are longer than they are wide. Microscopic examination of the uterine branches is required for differentiation of the species; T. saginata and T. asiatica have 12 to 30 primary uterine branches on each side of the uterine stem, while T. solium has 7 to 13. Molecular testing is required for differentiation of T. saginata and T. asiatica. Examination of the uterine branches can often be accomplished by simply pressing a proglottid between 2 glass slides and examining it by light microscopy. However, this may not work for proglottids that are fixed in ethanol or formalin, requiring them to be cleared first using lactophenol or other chemical. India ink may be injected through the lateral genital pore to highlight the uterine branches, but this is a technically-challenging procedure. Alternatively, proglottids may be embedded in paraffin and histologically sectioned and stained; when embedded correctly, serial sections are often successful in revealing the number of primary uterine branches from the uterine stem. The images here show a fresh proglottid pressed between 2 slides (injected with India ink), and a hematoxylin and eosin-stained tissue section.
Taenia solium, cysticerci
Taenia species have two forms in nature: an adult tapeworm in the definitive host, and a larva (cysticercus) in the intermediate host. Taenia solium is unique in that humans can serve as both definitive and intermediate hosts for this parasite. In comparison, humans only serve as the definitive host for Taenia saginata and T. asiatica, and rarely, as the intermediate host for other Taenia species. Shown here are the cysticerci of Taenia solium. The specimens in the jar have been removed intact so that the cyst-like nature and internal scolex can be seen. This specimen is from the amazing Tulane collection that had been amassed by the great parasitologist, Dr. Thomas C. Orihel. You can see a brief video of this specimen HERE.
You can view whole slide images of Taenia species:
Cysticercus in a muscle HERE.
Racemose cysticercosis HERE.
Cysticercus in an eye HERE.
Taenia solium, scolex
This is the characteristic scolex with "armed" rostellum of Taenia solium. Rostellum is the diminutive form of the Latin word rostrum meaning snout; "armed" refers to the double row of anterior hooklets which aid in attachment. Both Taenia solium (the pork tapeworm) and Taenia saginata (the beef tapeworm) have 4 suckers, but of the two, only Taenia solium has an armed rostellum. Therefore, the scolex morphology can be used to differentiate these two adult tapeworms.
Taenia species, adult worm
The adult worm of the human intestinal Taenia species (T. solium, T. saginata, T. asiatica) are comprised of repeating segments called proglottids. When mature, the proglottids are longer than they are wide. Microscopic examination of the uterine branches is required for differentiation of the species; T. saginata and T. asiatica have 12 to 30 primary uterine branches on each side of the uterine stem, while T. solium has 7 to 13. Molecular testing is required for differentiation of T. saginata and T. asiatica.
Taenia species, eggs
These are the characteristic eggs of Taenia species. Note the thick outer striated shell and internal hooked onchosphere. They are among the smaller of the eggs found in human stool specimens, measuring just 30 to 35 micrometers in diameter. The eggs of the human-infecting intestinal Taenia, T. solium, T. saginata, and T. asiatica, are morphologically similar and cannot be differentiated by microscopy alone. Some images provided by Phong Duong.
