What is Hymenolepis diminuta (HDC)?

Hymenolepis diminuta is one of the most widely studied organisms which colonizes the guts of vertebrates (Arai, 1980). It causes little or no adverse symptoms in its usual primary hosts (common rodents such as laboratory rats and pet hamsters) (Arai, 1980), and colonization of humans is rare and generally without any adverse symptoms, even in developing countries where the organism is very common (Wiwanitkit, 2004). Thus, by definition, the species is not a parasite. At the same time, the organisms efficiently supplement the biome.

Hymenolepis diminuta cystercercoids (HDCs) offer the following advantages over other organisms (nematodes that are generally cultivated in either pigs or in humans) that are currently being used to enrich the fauna in humans.

(a) The low cost of cultivation facilitates its use for biome supplementation by the population as a whole.

(b) No transmission from human-to-human is possible, since (1) the organism does not effectively colonize humans, and (2) an intermediate host is required for the life-cycle of the organism to be complete.

(c) HDCs are taken orally, like other organisms currently found in food (e.g., probiotics and yeast for brewing beer and culturing yogurt).

(d) The distribution of the HDCs in the human body is strictly limited to the lumen (inside) of the gut, unlike nematodes currently in use (hookworms and whipworms) which breach the barrier of the gut.

(e) For the purposes of egg production, the organisms are housed in laboratory rodents, which are easily kept cleaner than other vertebrates for which the meat is routinely consumed raw by humans (e.g., fish, cattle).

(f) For consumption by clients, the HDCs are raised in grain beetles (Tenebrio molitor), which are normally found in the human food supply as a harmless contaminant in a wide variety of grains. The grain beetles, in turn, subsist strictly on materials prepared for human consumption (oatmeal). Thus, all potential contaminants accompanying the cultivation and isolation of HDCs from grain beetles are those products already consumed by humans in post-industrial culture. In stark contrast, other helminths currently in use (including those approved by the US Food and Drug Administration for clinical trials) must be isolated directly from the actual feces of humans or pigs prior to use.

(g) In general, cestodes (such as Hymenolepis diminuta) are very well adapted to (compatible with) their primary hosts, or those hosts in which they are carried during the adult stage of their life.


1. Arai H.P. 1980 Biology of the tapeworm Hymenolepis diminuta. Academic Press, New York, p 733.
2. Wiwanitkit V. (2004) Overview of hymenolepis diminuta infection among Thai patients. MedGenMed, 6(issue), 7.

More on biome restoration and HDCs

Having a healthy biome should be a basic human right. We believe people should have access to healthy fauna, just as much as they should have access to food and water.

Hymenolepis diminuta colonizes rodents; it does not infect rodents. (Infection indicates disease.) HDCs do not even colonize humans, although they probably persist for a brief period that amounts to a very small fraction of their potential lifespan.

HDCs are NOT parasites. Parasites, by definition, harm the host. In this ecological context, humans and Hymenolepis diminuta are mutualists, which means that both species benefit. In a social context, Hymenolepis diminuta would be considered domesticated, since we control its reproduction for our own benefit.

HDCs are NOT the same as Hymenolepis diminuta (rat tapeworm). The HDCs are only one life stage of Hymenolepis diminuta. Thus, we are not actually facilitating the addition of worms, per se, into the human biome. We do know that the development of Hymenolepis diminuta is almost always arrested in humans sometime before an adult worm is formed, so we can only say that people are using HDCs, NOT an actual tapeworm, for supplementing or maintaining their biome.