This week's case was generously donated by Dr. Nazia Nagi in New Delhi, India. She saw these 'cute' little objects (around 15 micrometers long) during her rotation in the Diarrhoeal Laboratory. The patient is a young teenager with diarrhea lasting for 15-17 days. Identification?
Saline wet mounts:
Answer to the Parasite Case of the Week 724: Giardia duodenalis trophozoites and cysts.
Florida Fan eloquently described the characteristic motility pattern of Giardia trophozoites: "Beautiful autumn leaves falling in the wind in a sliding side to side motion." He also notes that "Giardia trophozoites and cysts can present a little challenge to parasitologists at times. Most of us are used to see the typical kite-shaped trophozoite with its nuclei, sucking disks and flowing flagella. When these trophozoites turn sideways, we may see only แบก leafy profile, and when they stand on their tails they will look like the kid next door poking his head over the privacy fence showing only the top of the head and the two eyes. The typical ovoid cysts can float on their ends and we may observe only a spherical object with a few discernible dots for nuclei. In my practicing days, I built models of both the trophozoite and the cyst and rotated them around to show the team the different morphology when viewed at different angles. Beautiful case indeed." Thank you for the great imagery, Florida Fan!
Most people are familiar with the classic morphology of the trophozoites (and less so of the cysts), but we have to remember that not all organisms have a 'textbook' appearance. Here are the lovely images from this case:
This week's case was donated by Dr. Nancy Wengenack and the Mycology lab at Mayo Clinic. These objects were found in a fungal culture for dermatophytes (lactophenol blue stain). What are they, and what is their significance?
Answer to the Parasite Case of the Week 723: mite, not scabies. Given that this mite was found in a fungal culture from skin scrapings, it could very well be a dust mite (Dermatophagoides sp.) as many of you suggested. However, mites are challenging to identify, so genus/species level identification is best left to the acarologists (people who study mites and ticks).
The biggest concern here is its location - on a fungal culture in the mycology laboratory. Mites are a terror in the mycology lab. They crawl from plate to plate, contaminating and destroying cultures from patient samples. In most cases, the culture plates need to be destroyed and the lab decontaminated. This is the reason why my colleague, Dr. Wengenack, was so upset to find these! However, she knew of my interest in mites and was kind enough to donate this case to the blog.
Some readers questioned if these were scabies mites. Fortunately scabies mites (Sarcoptes scabei) can be easily differentiated from most zoonotic and environmental mites by their rounded bodies and short legs:
This week's (rather disturbing) case was generously donated by Dr. Niels Olson. This is a parasite found in salmon throughout the world - sorry sushi lovers - no slight is meant against any commercial provider of salmon. Parasitism is a fact of life. What is the likely identification of this parasite? What would happen if it was ingested without cooking or freezing?
Answer to the Parasite Case of the Week 722: anisakid larvae, one of the members of the Anisakis simplex, Pseudoterranova decipiens, or Contracecum osculatum complex.
Humans can become transiently infected with the larvae when they are ingested in undercooked fish, such as this salmon. The larvae may embed in the gastric or intestinal mucosa, causing intense pain. Endoscopic removal is curative. In less severe cases, the larvae will migrate back up the esophagus and out the mouth - a much preferred (but disturbing!) alternative. They can also be passed in the stool. In these settings, the larvae have to be differentiated from immature Ascaris lumbricoides. This can be accomplished using a number of morphologic features.
To avoid anisakiasis, Chia-Yu Chiu wisely notes that the FDA recommends that salmon (and all fish) should be well-cooked or frozen prior to ingesting to kill the larvae. This case is a good example of how fish is not always frozen prior to sale - even in a well known grocery chain. Therefore, it is up to the consumer to freeze the fish prior to eating raw! The FDA recommends freezing for 7 days using a standard, consumer-grade freezer (-20℃). Restaurants usually freeze for 24 hours or less at -70℃.
On a final note, some people develop an allergy to anisakids, and therefore even freezing won't protect from allergic reactions following consumption. Individuals with severe anisakid allergies may have to avoid ocean fish indefinitely.
Happy American Independence day (July 4th) and a belated Canada day (July 1st)! As an American, this weeks case very appropriately has a lot of red, white, and (purple-ish)
blue. The following round objects were seen in a stool specimen on modified acid fast. The patient has had more than 1 week of profuse watery diarrhea and abdominal discomfort.
These objects were also highlighted with using calcofluor white fluorescence staining (arrow) along with stool flora.
What are these objects? Are they fungus or parasite?
Answer to the Parasite Case of the Week 721: Cryptosporidium sp. oocysts. These oocysts are a parasite, even though they stain with the non-specific calcofluor white fluorescent dye. Also, the abbreviation "crypto" is often used to refer to either Cryptosporidium (parasite) or Cryptococcus (fungus), so it's always good to make sure you audience know what you were talking about!
Cryptosporidium spp. oocysts are one of several intestinal parasites that stain red with the modified acid fast stain; Cyclospora spp. and Cystoisospora belli are the other two. Note that these 3 parasite genera are commonly referred to as coccidian parasites (i.e., member of teh Coccidia group). However, evidence now indicates that Cryptosporidium more closely related to the Gregarinasina group. I've purposely shown these 3 organisms in my last 3 cases for comparison. Here is a composite image of the 3 parasites together:
This week's case is generously donated by Dr. Nazia Nagi from Maulana Azad Medical College in New Delhi. The patient is a young, HIV-positive, adult male with diarrhea. The following structures were seen in a wet mount and modified Ziehl-Neelsen stained stool preparations. They measure approximately 35 micrometers long. Identification?
Answer to the Parasitology Case of the Week 720: Cystoisospora belli oocysts
These oocysts are easy to differentiate from Cyclospora and Cryptosporidium oocysts based on their large size and ovoid shape. Thanks again to Dr. Nazia Nagi for donating this classic case!
