Answer to Case 534

Answer to Parasite Case of the Week 534: Not a parasite; plant material. This is a neat finding since these structures (guard cells with stomatal pores) might be mistaken for parasite eggs such as Hymenolepis nana  due to their large size and morphologic features.

A quick biology review:
Guard cells are really neat. They are specialized cells in the epidermis of leaves and other parts of the plants that control gas exchange with the environment.They are produced in pairs and have a central opening called a stomatal pore. When a pair of guard cells are swollen (turgid) with water, the stomatal pore opens allowing carbon dioxide to flow in and oxygen (produced through photosynthesis) to flow out. While this gas exchange is essential to the plant, water is also lost through the stomatal pore; thus the plant has to balance the amount of CO2 absorbed from the environment with the amount of water lost through the pores.

Mary Parker kindly contributed the following image of stomata from the lower surface of an ash leaf and mentioned that "in a fresh sample as in the image, the plastids would contain greenish chlorophyll, but after gut transit, this would be lost."

Very cool! Thank you Mary!

Case of the Week 534

It's time for our fun monthly case from Idzi Potters and the Institute of Tropical Medicine, Antwerp. The following objects were seen in a stool specimen (direct wet prep) from a child with watery diarrhea. The objects measure approximately 40-45 µm in length. Identification?

Answer to Case 596

Answer to Parasite Case of the Week 596: Plant material; likely plant epidermis from leafy material. There appears to be a cuticle present, and part of an epidemal cell layer attached.

There are several nice images of dichotomous leaf epidemal structure HERE. Mary Parker, a botanist, noted that "in aqueous conditions, I  would expect an epidermal layer to curl with the cuticle inwards (which is the case in the images) as the cuticle is waterproof and doesn't swell, whereas the epidermal cells would be hydrated and expand forcing the layer into a spiral." Thank you Mary for your valuable input! Mary has also provided assistance with Case 534 in which we showed plant stomata, and Case 468 that showed banana material. Parasitologists and pathologists commonly see food material in fecal and intestinal specimens, as well as in cases of bowel rupture/fistula and food aspiration (i.e., in respiratory specimens). Therefore, it's helpful to have some basic familiarity with how plant material appears in routine preparations. 

Several writers asked if this could be Enterobius vermicularis or Trichuris trichiura. While the size and location may fit with either of these roundworms, the cuticle and attached cellular structure shows some subtle differences that are useful for excluding them. Specifically, the thick acellular roundworm cuticle is adjacent to a muscular layer, as shown in the images below. In comparison, the plant cuticle is adjacent to the boxy cells of the epidemis. I also highlighted some features that are useful for specifically identifying E. vermicularis and T. trichiura (i.e., lateral ala and bacillary band). 

One additional study that would have been helpful in this case would be to use a polarizer to see if the cuticle and cells are birefringent. Plant cell walls often are, whereas nematode cuticles are not.

Thanks again to Bobby Boyanton for donating this interesting case!

Answer to Case 643

 Answer to the Parasite Case of the Week 643: Not a parasite; plant material. 

As mentioned by Idzi, Bernardino, and Phil G-J, this beautiful structure is a peltate trichome, possibly from an olive (Olea) leaf. Bernardino Rocha provided a great link to this open access article and the photos look just like what we are seeing. 

To obtain further insight, I contacted our knowledgeable botanist reader, Dr. Mary Parker, and was pleased to hear that she agrees with our assessment! She commented that this structure is definitely a peltate trichome and could quite possibly be from the lower epidermis of a leaf of an olive tree. The trichome could have been a contaminant of olives or olive products (e.g., preserved olives, tapenade, unfiltered olive oil) and thus ingested to end up in our specimen. She also mentioned that herbs like mint have glandular peltate hairs on their leaves, but that there are usually fewer of the radiating head cells; therefore, Olea is a more likely source. She provided this striking photo of the lower epidermis of an ash leaf with a trichome. You can also see the guard cells of the epidermis - something we have featured before on this blog (Case of the Week 534 and answer)

We get to see so many fascinating things as parasitologists, and while it's not necessary for us to always know exactly what we're looking at, it's really fun when we can make an identification like this. Thanks again to our faithful contributor, Florida Fan, for donating this case.