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 π (@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 αΊ‘ 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.
