Case of the Week 449

The following object was found in a toilet and submitted to the parasitology lab. Identification? What is the significance of this finding? Images taken by my fabulous education specialist, Emily Fernholz.

Answer to Case 449

Answer: rat-tailed maggot, family Syrphidae

As nicely described by one of my readers, David Bruce Conn, "This is a rat-tailed maggot, larva of a hover fly belonging to the family Syrphidae. This one may be of the common genus Eristalis. They are not parasitic, but typically live in stagnant water and feed on organic material before pupating. They may incidentally live in toilets and latrines."

The larvae are very recognizable, a long "tail" that contains a breathing tube (respiratory siphon) that connects to the tracheal system and allows the larva to breath oxygen from the water surface. You can also make out antennae and prolegs.

I should note that there have been a few reports of facultative myiasis by this group, but in further investigating these references, I couldn't find any definitive evidence that this occurs (the specimens were all brought in by the patient after being found in the toilet.) Therefore, I think that unless definitely proven, all cases of rat-tailed maggots should be considered incidental findings due to environmental contamination.

Case of the Week 448

This week's beautiful case was donated by Florida Fan. These objects were identified during colonoscopy from a middle-aged man. No further history is available. Identification?

Answer to Case of the Week 448

Answer: Trichuris trichiura adults

The photos in this case show most of the characteristic identifying features of adult T. trichiura (a.k.a. whipworms) including the classic "whip" shape and eggs with bipolar plugs. The full adult shown is a male as evidenced by his reproductive structures and curled tail. Note that the skinny end is the anterior aspect and not the tail like many students of parasitology would initially assume. The full body of the female is not shown, but you can see characteristic eggs coming out of the uterus.

The stichosome is clearly visible in some of the photos; this prominent glandular organ is seen in trichurids such as Trichuria and Trichinella (as well as some other nematodes) and consists of a row of multiple unicellular cells called stichocytes. The stichosomeruns along the posterior aspect of the esophagus and is a key identifying feature in both intact and sectioned worms. The stichosome opens into the esophageal lumen and has both secretory and absorptive functions.

Case of the Week 447

This week's case is in honor of Memorial Day and was generously donated by Florida Fan. I've actually revived this from a previous case, since the colors (red, white and blue) are so beautiful with Florida Fan's rendition of the modified safranin stain. The red objects seen below were found in stool and measure approximately 10 micrometers in diameter.

Identification?

Answer to Case 447

Answer: Cyclospora cayetanensis oocysts

The beautiful red staining of these round oocysts is characteristic, whether using the standard modified acid fast stain or the modified safranin stain.

Case of the Week 446

This week's very timely case was donated by George at Memorial Sloan Kettering Cancer Center. The following objects were seen in a wet mount of a concentrated stool specimen. They measure less than 20 micrometers in dimension and do not have an apparent operculum.

Here is their appearance using iodine:

Identification?

Answer to Case 446

Answer: not a parasite; most consistent with mushroom spores.

In this case, the spores were noted in the stool of an individual who had consumed morel mushroom spores, and therefore we can be more specific about the identification.

Mushroom spores are a convincing mimic of parasite eggs. They can be differentiated by a few features, however:
1. Their size is smaller than Enterobius vermicularis eggs - one of their closest mimics.
2. Although in the size range for some of the smaller trematode eggs (e.g. Clonorchis, Metagonimus), they lack an operculum.

Again, special thanks to George who donated these images and reminded me that it is now morel mushroom season!

Case of the Week 445

This week's amazing case was donated by Mr. Boren Huot. This object was seen in a stool specimens from a patient in Cambodia.  Identification? (CLICK ON THE IMAGES TO ENLARGE)

Answer to Case 445

Answer: Capillaria philippinensis

This case shows an adult worm containing characteristic eggs of C. philippinensis. Note that each egg has a striated wall and bipolar plugs.

Thanks to the CDC DPDx for the photo of the egg shown in the upper right hand corner of the above image.

One reader asked how you could tell C. philippinensis apart from C. hepatica, since both can infect humans. The biggest clue in this case is that the worm was found in stool, whereas the adult worms of C. hepatica are only found in the liver. There are also subtle features of the adult worm and eggs that allow the 2 species to be differentiated.

Thanks again to Mr. Huot for donating a case that we don't get to see very often in the United States.