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!
