Giardia (Giant Microbes)

Today’s review was photographed on-site in the diagnostic parasitology lab I work in. In fact, I don’t own this figure (I don’t collect plush figures); it hangs on the white board in the lab. The figure I am referring to is that of the trophozoite stage of Giardia duodenalis (sometimes referred to by its synonyms as G. intestinalis or G. lamblia), part of the popular Giant Microbes line.

Giardia duodenalis is a cosmopolitan parasite of humans and other animals. Giardia has a very broad host range, including many species of wild and domestic mammals and birds. As the molecular epidemiology becomes better understood, there seems to be populations that have some host preference. Two genetic assemblages (A and B) have a broad host range and cause both human-to-human and zoonotic infections (infection from an animal source) in people. The other assemblages (C-H) have narrower host ranges to non-human animals; it is to be expected that at some point G. duodenalis will be split into multiple species. Giardia typically colonizes the duodenum and small intestine of its host. It has a simple life cycle alternating between the trophozoite stage, which is the feeding and replication stage, and the cyst stage, which is the environmentally-hard stage that causes infection in the next host. Both cysts and trophozoites are shed in stool/feces, but the next host becomes infected after ingesting cysts (only) in food, water, or fomites contaminated with feces. It is one of the most commonly-diagnosed parasitic diseases in the world.

The figure, when stretched out, would measure roughly 15 cm, which would put it in the 15,000:1-7,500:1 scale for a Giardia trophozoite. The figure is colored blue, which is appropriate, since the parasite can appear blue when stained with trichrome (the optimal stain for the microscopic detection of Giardia).

The figure has many of the hallmark features of Giardia, including two nuclei (and don’t let the stylized nature of the toy fool you; the nuclei of a Giardia troph do look like eyes staring back at you under the microscope!). The nuclei are surrounded by a frill, which represented the sucking disc (a structure the parasite uses for attaching to the host’s intestinal epithelium). Eight flagella (used for locomotion) are present, and they are in about the correct arrangement: two up top (anterior), four mid-body (two ventral and two lateral), and two posterior (caudal). Giardia has a very distinctive morphology, which makes it a great candidate for a toy such as this.

the Giant Microbe line has become very popular, especially among people in the medical and scientific fields, for offering a wide variety of plush toys of disease-causing agents (including everything from Ebola to the agents of gonorrhoea and malaria). Again, I don’t collect these, but I can understand the appreciate by people that do! I am unaware of any other figures of Giardia, except for museum-quality education models. If you like quirky toys of unusual organisms, check out the Giant Microbes line!