This week's case is by Florida Fan, and represents a nearly 'picture perfect' representation of a particular filarial species in a peripheral blood smear. What is your identification? For students, residents, and fellows - this is a classic, and definitely fair game on exams!
Answer to the Parasite Case of the Week 804: Brugia sp. microfilaria, favor B. malayi
As noted by Idzi and others, this is a textbook example of Brugia sp. microfilaria, with beautiful terminal and sub-terminal nuclei and a characteristic long cephalic space. However, Idzi rightly recommends caution in committing to a species since B. malayi and B. timori can have a very similar appearance. He notes that "to decide which one, either geographical information is needed (B. timori is more restricted to the Lesser Sunda Islands of the Indonesian archipelago - from Bali over Timor to the Tanimbar Islands - while B. malayi is more widespread in South-East Asia), or information about the stain for the blood film (both Brugia species have a sheath in fact, but if the smear is stained with Giemsa, the sheath of B. timori is usually not visible).
While we don't have an exposure history in this case, the stain is Giemsa, which points us to B. malayi. However, I consider the sheath staining to be a soft diagnostic feature, as I've seen this type of faint pink staining with Wuchereria, and not all B. malayi sheaths stain with Giemsa.
Since the sheath staining is not reliable, we must use the other criteria for differentiating B. malayi and B. timori as follows:
The CDC DPDX also has some nice examples of B. malayi and B. timori.
Thanks again to Florida Fan for donating this beautiful case.
For this week's case, we have a worm submitted from an otherwise asymptomatic teenager. No further history was provided. What is your identification, and how would you sign this case out?
Answer to the Parasite Case of the Week 803: Toxocara species, adult female. Humans are NOT a host for this life cycle stage of the parasite. Therefore, as Philip, Anastasia, Anatoly, HCLM Fan, and others mentioned, the most likely scenario is that this worm came from a family pet instead of the teenager. Less likely, the teenager could have swallowed the worm and its finding in stool represents spurious passage. Unfortunately, we were not able to get any additional history in this case. Hopefully this result was reassuring and helpful to the patient and family.
Although this worm resembles the large human intestinal worm, Ascaris lumbricoides, it can be differentiated in this case by two main features:
First, this worm has pronounced lateral alae, which are not found in Ascaris lumbricoides. (Lateral alae are found in Enterobius vermicularis, but that worm is much smaller and can therefore be excluded).
Apologies everyone for the delay in posting a case. I've been travelling a lot and just returned from South Korea. While I was there, I was offered the following dish consisting of raw crab. If I had chosen to eat it (which I didn't), which parasites could I have acquired?
Answer to the Parasite Case of the Week 802: No significant parasite risk.
But wait, you may say, what about paragonimiasis???
As noted by Anatoly, Kim Tae Yun, and others, these are marine crabs rather than fresh water - an important distinction! Eating undercooked freshwater or estuarine (brackish) crabs could indeed lead to paragonimiasis, and this was historically an endemic infection in Korea. However, the risk from eating undercooked marine crabs is relatively low. According to Kim Tae Yun, "Most Korean people enjoy the food so called GEJANG (crab soaked in soy sauce)...And the GEJANG in the photo looks very delicious."
What do you think?
Anisakiasis and gnathostomiasis are hypothetical risks from eating freshwater crabs as well, but highly unlikely as crabs are not the typical hosts for the associated parasites.
I must admit that I chose not to eat this dish for two reasons: first, I was uncertain about the type of crab offered, and second, I'm not a huge fan of raw seafood. However, the food I did eat, including a crab hotpot and kimchi pancake, were absolutely delicious.
Thank you all for sharing your own experiences.
This week's case was an interesting finding from microscopic examination of skin scrapings. What is your diagnosis? And what forms are you seeing?
Answer to the Parasite Case of the Week 801: Sarcoptes scabei, adult and juvenile mites, eggs, and feces (scybala).
Florida Fan so nicely described the findings here as follows: "Boy, this should give the host quite an itch. We find the feces or scybala, the egg, the premature or developing stage before eclosion and finally the mother mite itself. Sarcoptes scabiei and its family members not only infest humans as itch mites but also infest other warm blooded animals as mange as well. Hopefully the Easter bunnies are spared from its cuniculi species."
Here is a closer view of two eggs (arrows) and numerous fecal pellets (the small, oval, granular structures):
Welcome to our 800th case! Given the occasion, I thought we deserved something spectacular, and these images from Heather Morris definitely fit the bill. These worms measure ~1 cm long. What is your diagnosis?
Answer to the Parasite Case of the Week 800: Enterobius vermicularis (pinworm), numerous adult females seen, with eggs in the background.
There was a lot of great discussion in this case! Florida Fan noted the lateral alae, which are one of the characteristic features of this worm. They are most prominent as cephalic inflations, but they continue along the length of the worm. Other classic features include the pin-shaped tail of the female worms, size, and location. We can't make out the eggs in these images, but Florida Fan noted that they would be flat on one side, and curved on the other (i.e., planoconvex).
Thank you for celebrating the 800th Case with me!
This week's case was donated by Drs. Jacob Rattin and Akeesha Shah. The patient is an elderly male with a history of bladder cancer, status post cystectomy, who was undergoing screening urine cytology. The specimen was collected from a urostomy bag from an ileal conduit. The following forms were seen on the Thin Prep specimen. They measure 50 to >120 micrometers long. What is your diagnosis?
Answer to Parasite Case of the Week 799: Not a parasite; plant material consistent with guar gum.
Guar gum (a.k.a. guaran) is a galactomannan polysaccharide extracted from guar beans. It has thickening and stabilizing properties that are useful for food, feed, and industrial applications. In medicine, it is often used as an adhesive to keep ostomy bags attached to the skin. This is how it likely got into the specimen from this patient.
Some readers queried if this plant material could have originated from the intestinal tract, given that the patient has an ileal conduit. However, in looking into the way an ileal conduit is created, we can see that it is disconnected from the GI tract and therefore would not contain food material.
For fun, I decided to investigate the microscopic appearance of guar gum using common parasitology stains. Below are my results using a simple wet prep, modified trichrome (Ecostain) stain, and Giemsa stain. Note that it is birefringent with polarized light, as is most plant material.
This interesting finding has been reported before by Nomani et al. Thanks again to Drs. Rattin and Shah for donating this interesting case!
It's the first Monday of the month and time for our case from the Institute of Tropical Medicine in Antwerp! This case is donated by Idzi Potters, as well as Ms. Loranne Lambregts, a new ITM friend and very promising parasitologist!
The following objects were recovered from a patient's scalp. They measure about 2-4 mm and are very motile. What is your identification?
Answer to the Parasite Case of the Week 798: Insect larva; specifically, a flea larva
As noted by Anatoly, this object has the features of a flea larva: "legless, segmented body (13), setae, head capsule, size". The location on the scalp is also supportive of a flea larva - likely from a household pet. Flea larvae are photophobic and are often found deep in animal and pet nests/bedding, carpets, and floor cracks. They are not parasitic on the host, and do not take a blood meal, unlike adult fleas.
Some of you suggested that this could be myiasis, which is caused by dipteran fly larvae. However, fly larvae lack clear body segmentation as seen in this case, as well as a true head capsule and long bristles (setae). Although not shown in this case, flea larvae also lack spiracular plates as seen in dipteran larvae.
In comparison to beetle larvae - another consideration in this case - flea larvae lack legs.
HERE is a nice resource from Animal Patient for additional information (and a rather disturbing video of flea larvae in carpet fibers 😯). The CDC has additional information on fleas, including the diseases that the adult fleas carry and how to get rid of them.
Here is a labelled diagram with some of the key diagnostic features seen in this case:
Thanks again to Loranne Lambregts and Idzi Potters for donating this interesting case!
