Taeniasis vs cysticercosis infection routes

Maria Teresa Galán-Puchades

Department of Cell Biology and Parasitology， Faculty of Pharmacy， University of Valencia， Av. Vicent Andrés Estellés s/n， 46100 Burjassot-Valencia， Spain



Taeniasis vs cysticercosis infection routes

Maria Teresa Galán-Puchades*

Department of Cell Biology and Parasitology， Faculty of Pharmacy， University of Valencia， Av. Vicent Andrés Estellés s/n， 46100 Burjassot-Valencia， Spain

ARTICLE INFO ABSTRACT

Article history:

in revised form 16 March 2016 Accepted 15 April 2016

Available online 20 June 2016

Taeniasis

Cysticercosis

Infection routes

Although cysticercosis caused by Taenia solium （T. solium） is considered a neglected disease，its life cycle has been well known for more than two centuries. T. solium not only causes cysticercosis but also taeniasis in humans. These two diseases have totally different infection routes. To acquire taeniasis （the presence of the adult stage of T. solium in the intestine），humans have to ingest the larval stage （cysticercus） that infects a variety of organs and viscera in pigs， its intermediate hosts. Therefore， taeniasis is acquired when eating raw or undercooked infected pork. The adult stage in the human intestine release eggs that contain a hexacanth embryo， the oncosphere. If humans accidentally ingest the eggs of T. solium， the released oncospheres penetrate the intestine and become cysticerci. Therefore， cysticercosis is acquired by the ingestion of eggs that contaminate water， vegetables， hands etc. These facts should not be forgotten to avoid misinformation in scientific publications.

Dear Editor，

Rizvi et al. have recently published an article related to human neurocysticercosis （NCC）［1］， an infection of the central nervous system （CNS） caused by Taenia solium （T. solium）. According to the authors， NCC is considered a neglected disease. However，although cysticercosis is considered neglected， T. solium life cycle has been well known for more than two centuries. Humans are the only definitive host harbouring the intestinal adult stage of T. solium （taeniasis） （Figure 1）. The eggs shed in faeces contaminate the environment， as well as drinking water， vegetables， dirty hands etc. The eggs contain a larval stage， the oncosphere or hexacanth embryo， measuring approx. 20 μm. When pigs （the intermediate hosts） ingest the eggs， the released oncospheres penetrate the intestine and become cysticerci， a larval stage measuring approx. 1-2 cm， in various organs or viscera （cysticercosis）. When humans ingest raw or undercooked infected pork， the cysticerci turn into adults in the intestine causing taeniasis. Unfortunately， humans can also act as intermediate hosts when accidentally ingesting the eggs of T. solium in contaminated water， vegetables， on hands etc. The released oncospheres penetrate the intestine， become cysticerci and cause NCC when they are located in the CNS （Figure 1）. Therefore，taking this life cycle into account， I consider it essential to disabuse the authors who have provided some serious misinformation in their article:

Figure 1. Life cycle of T. solium in humans.GT， gastrointestinal tract； ES， extraintestinal sites； C， cysticercus； E， eggs； O，oncosphere； A， adult.

1. 'Epidemiologic studies have demonstrated tight clustering household or household contact with NCC patients have three times higher risk to have positive serology for cysticercosis compared with controls' （p. 100）.

Contact with NCC patients does not pose any risk of acquiring parasitation by T. solium since the cysticercus is enclosed in the CNS without the possibility of transmission to other people， ruling out， of course， cannibalism. The risk appears when people are in contact with patients suffering from taeniasis （the parasitation by the intestinal adult stage）， since these patients eliminate T. solium eggs，the origin of NCC.

2. 'The eggs hatch and release the larvae （cysticerci） into the intermediate host. The larvae penetrate the intestinal wall and spread through the blood stream to different organs in the body such as brain， striated muscles， liver and other tissues' （p. 102）.

The eggs release the oncospheres that penetrate the intestinal wall and then become cysticerci.

3. 'The cycle is complete when humans， the definitive host， ingest undercooked pork or untreated water containing the larvae. Once it gets into the human body， it attaches to the intestinal mucosa and grows to full length （p. 102 and Abstract）.

Taeniasis is acquired only by means of ingesting undercooked pork with cysticerci， which do not exist outside any intermediate host but only the eggs do. The ingestion of eggs leads to cysticercosis， not taeniasis.

4） 'The adult tapeworm releases cysticerci which can disseminate to different parts of the body' （p. 102）.

The adult tapeworms release eggs not cysticerci. The eggs abandon the host with faeces. Although internal autoinfection has been suggested， it is not clear that it really happens.

Conflict of interest statement

We declare that we have no conflict of interest statement.

References

［1］Rizvi SAA， Saleh AM， Frimpong H， Al Mohiy HM， Ahmed J， Edwards RD， et al. Neurocysticercosis: a case report and brief review. Asian Pac J Trop Med 2016； 9（1）: 100-102.

Document heading 10.1016/j.apjtm.2016.04.005

15 February 2016

*

Maria Teresa Galán-Puchades， Professor， Department of Cell Biology and Parasitology， Faculty of Pharmacy， University of Valencia， Av. Vicent Andrés Estellés s/n， 46100 Burjassot-Valencia， Spain.

Tel: +34 963544536

E-mail: mteresa.galan@uv.es