On an imported case of Taenia saginata

Key words: Human taeniasis. Taenia saginata. Taenia asiatica.

Dear Editor,

I have read with interest the article by López-Cayela et al. recently published in your journal (1). I would like to contribute to this article with some comments about the human Taenia species. Humans act as definitive hosts not only for the two species the authors consider in the article, i.e. Taenia solium and T. saginata, but also for a third species, T. asiatica (2). According to the authors' information, the worm causing the imported case of human taeniasis to Spain was apparently identified only by the morphology of the gravid proglottids. They do not mention the precise number of uterine branches the tapeworm exhibited but I presume it should have more than 13 since they identified it as T. saginata and not T. solium. However, it should be noted that T. asiatica has the same gravid proglottid morphology as T. saginata, therefore presenting the same number of uterine branches. As a consequence of this similarity, the only way to distinguish between the two species is by means of molecular techniques. The patient supposedly got infected in the Ivory Coast, a country in which T. asiatica has not been found so far. However, the definite geographical distribution of T. asiatica, an originally Asian parasite, is still not known. Probably due to globalization, the species could be present worldwide since its definitive hosts (humans) as well as its intermediate ones (pigs) are both cosmopolitan. On the one hand, the fact that the two species have different sources of infection makes the distinction between T. saginata and T. asiatica so important. Humans have to ingest raw or undercooked beef containing the infective stage (cysticercus) to acquire T. saginata, whereas in the case of T. asiatica the source of human infection is not beef but pork, just the same as in the case of T. solium. On the other hand, T. saginata does not cause human cysticercosis, i.e. the infection with extraintestinal larvae or cysticercus, a sometimes fatal disease when the cysticerci are located in the central nervous system (neurocysticercosis). However, it is still not known whether T. asiatica is able to cause human cysticercosis just as T. solium does. It has been suggested that T. asiatica could mainly cause human liver cysticercosis due to the clear hepatic tropism that the cysticerci show in the pig, its natural intermediate host (3).

References

1. López-Cayela JF, Contreras SN, Martín-Rodrigo L. Taenia saginata: An imported case. Rev Esp Enferm Dig 2015;107:440-1.         [ Links ]

2. Eom KS, Rim HJ. Morphologic descriptions of Taenia asiatica sp. n. Korean J Parasitol 1993;31:1-6.         [ Links ]

3. Galán-Puchades MT, Fuentes MV. Taenia asiatica intermediate hosts. Lancet 2004;363:660.         [ Links ]