Welcome back to all of my US readers from the Thanksgiving holiday. Here is a fun case with the answer embedded - just listen to the audio with the video. Or if you'd prefer, keep the volume down and give your best guess on what you think this is!
This case is donated by Dr. Jessica Lin and her colleague who is field physician in Tanzania. The patient is a 4 year old boy with anal pruritus and history of passing worms from his anus. Several white-tan worms measuring ~5mm long were examined:
The following objects were seen in fluid aspirated from a cyst in the liver. Identification?
Answer to the Parasite Case of the Week 731: Echinococcus sp. protoscolex. Hopefully you all got to look at it moving! Given that this is a single liver cyst, it would fit with E. granulosus. Correlation with radiologic and epidemiologic features would be helpful for confirmation.
Here are some of the key diagnostic features:
This week's case is generously donated by Idzi Potters and the Institute of Tropical Medicine, Antwerp.
The following were seen in used contact lens solution from a young woman with complaints of eye pain and blurry vision. The first two images are taken with light microscopy, and the third with phase-contrast microscopy. What is your diagnosis? Please describe the forms you are seeing.
Answer to the Parasite Case of the Week 730: Acanthamoeba keratitis.
As noted by Anonymous, the pictures are a perfect rendition of the “thorny” Acanthamoeba trophozoite and its polygonal cyst (acanth is New Latin, from Greek akanthos, from akantha thorn, spine). Cysts have 2 layers: a wrinkled outer layer (ectocyst) and inner layer (endocyst) that can be polygonal, spherical, hexagonal, or star-shaped.
Dr. Satishkumar Krishnam further described the trophozoite as "characterized by spine like pseudopodia (acanthopodia)." Chuck Blend noted that it looks like the first few seconds of a new proto-universe forming!
This week's case was generously donated by Drs. Jacob Rattin, Anisha Misra, and Hannah Wang, and originally identified by Marissa Roberts. The following objects were seen on a trichrome-stained stool specimen and measure approximately 15 micrometers in length. What is your identification?
Answer to the Parasite Case of the Week 729: Trophozoites of Chilomastix mesnili
Below is an answer written by Dr. Jacob Rattin (@EternalStudying):
This non-pathogenic flagellate has pear-shaped trophozoites that are 6 – 24 μm long with a longitudinal spiral groove running along the body (not seen in this specimen). If visualized in a fresh prep, the motility may allow the spiral groove to be seen as the organism turns (see Case 475). The trophozoite has one nucleus (arrowhead), usually at the anterior end, with an eccentric karyosome and a cytostome (oral groove) close by. The posterior end tapers to a point (arrow).
Differentiating C. mesnili trophozoites from other non-pathogenic flagellates such as Enteromonas hominis, Pentatrichomonas hominis, and Retortamonas intestinalis can be quite difficult. Thankfully, these organisms are non-pathogenic. However, the following features may be useful in teasing apart these fun flagellates!
Enteromonas hominis trophozoites measure 5 – 7 µm long with one nucleus and three anterior flagella and one posterior flagellum. It has a single nucleus with a large karyosome. There is no cytostome which helps to differentiate it from C. mesnili.
Retortamonas intestinalis are 4 – 10 µm long with an ovoid trophozoite form with a cytostome at the anterior half that is bordered by a fibril. The single nucleus is at the anterior end and has a small karyosome.
Pentatrichomonas hominis. The trophozoites are pyriform in shape, measuring 6 – 20 µm long. They have five flagella, with four directed anteriorly and a fifth directed posteriorly. The fifth flagellum forms the outer edge of an undulating membrane and projects beyond the posterior. A single nucleus is at the anterior end and contains a small karyosome.
Thanks again to Dr. Rattin for taking on the non-pathogenic flagellates! I'm sure you'll agree that he did an excellent job. Thanks also to the laboratory technologist, Marissa Roberts, who took these photos, and to Dr. Anisha Misra at the Cleveland Clinic for her scientific oversight.
This week's case was donated by Drs. Meredith Kavalier, Megan Shaughnessy, and David Cartwright. The patient has a history of treated urothelial cell carcinoma and remote travel to Asia. The cytopathologist was concerned by the presence of the following structures seen in a routine screening urine sample. How would you interpret these findings?
Answer to the Parasite Case of the Week 728: Not a parasite egg; uric acid crystals.
Uric acid crystals are a very convincing mimic of Schistosoma haematobium eggs! They are both found in urine, and they both have a terminal spine. However, there are a number of features that can be used to easily differentiate the two:
his week's case was generously donated by Dr. Richard Bradbury. The following structure was seen in a concentrated wet prep of stool. It measures approximately 80 micrometers in diameter. Check out the video to see this structure in multiple planes. Identification?
Answer to the Parasite Case of the Week 727: Hymenolepis diminuta
As noted by Lamia Gala on LinkedIn, "The distance between the outer and the inner shell is large with no polar filaments" which is consistent with H. diminuta. This is in contrast to Rodentolepis (formerly Hymenolepis) nana, which does have polar filaments between the outer and inner shell. H. diminuta is also slightly larger than R. nana, measuring 70-85 micrometers in greatest dimension (compared to 30-50 for R. nana). Florida Fan provided the helpful memory aid that the word "diminuta" is larger in size than "nana", which also applies to their eggs (thanks FF!). Here are some of the key morphologic features:
This weeks case features the following small, oval-shaped, red-staining objects seen in a bronchoalveolar specimen from an immunocompromised patient. The objects measure approximately 2 micrometers long. The stain is a strong trichrome (chromatrope 2R method). Identification? What is the significance of this finding? (CLICK ON IMAGES TO ENLARGE)
Answer to the Parasite Case of the Week 726: Microsporidia spores; genus and species not determined
These small spores stain deep red with the chromotrope 2R method and its modifications. They are oval shaped and often have a darker-staining equatorial band in the middle of the spore. Spores of Enterocytozoon bieneusi are very small (0.8 to 1.4 micrometers long), whereas other species such as Encephalitozoon spp., Vittaforma cornea, and Anncaliia algerae are a little larger. Some (e.g., Anncaliia) are up to 4 micrometers long and may be mistaken for small years such as Histoplasma capsulatum (especially because they are focally GMS positive!)
This week's interesting case is generously donated by Dr. Justin Juskewitch. Hopefully all of you have been able to avoid this so far this summer!
The patient is a young girl who developed this very itchy rash about 30 minutes after a swim in a fresh water lake in Maine (Northeastern United States). The rash developed to what is shown below over a period of several hours.
Her two siblings had a similar presentation. All three children had resolution of itching with benadryl, corticosteroid cream, and oatmeal body wash baths over the next few hours, but the rash lasted for 5-7 days.
What is the most likely diagnosis? Is any additional therapy recommended?
Answer to Parasite Case of the Week 725: Swimmer's itch
As noted by Florida Fan, this is "typical swimmer’s itch, also known by other names depending on the activity of the patient like 'clam digger’s itch' or 'duck itch'." (Also called Pelican itch in Australia) "All are caused by [zoonotic] cercariae in most freshwater bodies of water frequented by ducks and/or water birds. The cercariae penetrate the skin and cause a cercarial dermatitis. This summer is so hot even in the Northern most states that a quick plunge into the lake is certainly very appealing. We may expect to see more cases like this one."
Indeed, this is a distressing result from what would otherwise be a lovely dip in a cool lake!
An anonymous reader elaborated that "Swimmer's itch is an allergic condition that occurs when trematode cercariae, the motile and infectious stage of avian schistosomes (eg, Trichobilharzia spp.), penetrate the skin of humans. They utilize a variety of different species of birds as definitive hosts (humans are not suitable hosts), and rely on different snail species as intermediate hosts. If any, only symptomatic therapy is needed (anti-itch lotions, antihistamine), the cercariae die quickly without causing a severe trematode infection."
Marc Couturier noted "Growing up in Maine, we just called that...the result of swimming in Maine". Yikes! It's also common in northern Minnesota and Wisconsin in the United States.
I had to laugh at the Twitter (X) response from That Packer Girl 🏈 (@thatpackergirl) - "*sideyes the mergansers and snails at the family cabin*"
In the United States, swimmer's itch 'season' is mid summer. According to a post from Anoka County, Minnesota, Parks and Recreation, you can "Reduce your chances of getting severe swimmers’ itch by following these simple guidelines. Dry off as soon as you leave the water. Rub skin briskly to remove water drops before they evaporate. Be sure to dry underneath waistbands and around leg openings. Encourage children to dry off thoroughly each time they leave the water. Shower with soap and fresh water or change into dry clothes as soon as possible. Don’t wade or play in shallow water. Swimming from a raft or pontoon minimizes your exposure. Don’t feed geese and ducks near your beach. Waterfowl are an important adult host for the parasites."
I hope you all enjoy the rest of the summer!
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 ạ 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?
