Dear readers, I will soon be posting my 500th Case. Hooray!! To celebrate, I would like to recognize the creativity of my readers by displaying a photograph of your parasite-related artwork on my blog. I will then put the names of all of the individuals who submitted a photo of their art in a hat and pick 3 names to receive a special parasite prize ☺ If you would like to send me a photo that I can post on my blog on July 2nd, please send it to firstname.lastname@example.org
Now for this week's case - some beautiful eggs from my lab (images and video by Heather Rose):
Answer: Taenia sp. eggs. I forgot to mention that the stool specimen came from a human patient. Therefore, the main considerations are Taenia solium and Taenia saginata. If the patient acquired infection in Asia, then Taenia asiatica should also be considered. You cannot differentiate the 3 species based on the egg alone, instead, morphologic features of the adult worm (T. saginata/T. asiatica vs. T. solium) and molecular testing (T. saginata vs. T. asiatica) are needed. The photographs and video beautifully highlight the key diagnostic features:
As a side note, the eggs of Echinococcus species have a very similar appearance but would be found in the stool of infected dogs and other canids, and NOT in human stool.
Thanks again to Heather in my lab for the beautiful photos and video!
This week's case was generously donated by Florida Fan. The following bug were submitted by the physician of a 69-year-old woman. No further history is available. As Florida Fan says, "Here comes the summer, and with it comes the bugs."
Answer: Cimex species; bed bug
As Blaine mentioned: "B&B Bugs is back! Beautiful brown biting, blood-sucking bed bug! Boo-yeah!" William mentioned that the pronotal hairs are not long enough to be a bat bug - an important consideration since bat bugs can be found near human dwellings and may bite humans when their preferred (bat) host is not available.
The patient is a 65-year-old owner of a camel farm who presents to his primary care provider for a yearly check-up. As he has mild intestinal complaints, he submits a fecal sample to be checked for parasites. The following structures were observed, and measure approximately 85 x 45 microns. Diagnosis please?
Concentrated wet preparation, 400x
Concentrated wet preparation, 400x with Lugol's iodine
Answer: Trichostrongylus sp. egg
Congratulations to everyone who wrote in with the correct answer. Although this egg looks like those of the hookworms, Oesophagostomum spp., Ternidens spp., and Strongyloides stercoralis (latter only rarely seen in stool), the larger size (85 micrometers long) and tapered end points us towards Trichostrongylus.
This diagnosis is also supported by the history of camel exposure, as Trichostrongylus is primarily a parasite of ruminants. As Blaine mentioned, I should have posted this case on a Wednesday for 'hump' day!
William Sears also mentioned that the presence of eggs with well-developed larva indicates that the specimen likely sat for some time before being examined since the eggs are passed in human stool in an unembryonated state. Thanks again to Idzi Potters for donating this fascinating case.
This week's case was donated by Dr. Kamran Kadkhoda. It's a 'real life' case that I thought provided a fun challenge. The specimen was obtained from a 5 year old boy from Canada and submitted to the laboratory for identification. What do you all think?
Answer: Ixodes species tick (fragment), unengorged female
As Blaine, Idzi, Sheldon, Florida Fan, Richard, Agnes, and William nicely described, we can easily identify this tick fragment as an Ixodes species by its characteristic 'U-shaped' anal groove. Lack of festoons also supports the identification. One of our tick experts, Ellen, mentioned that the color is a good feature for determining sex, since female Ixodes are orange-brown while males are black and nymphs are transparent charcoal-grayish. Color can also be helpful for determining the degree of engorgement since adult females will become grayish-white once becoming engorged due to growth of new opisthosoma tissue. Thanks for the great description Ellen!
The tick is most likely I. scapularis, but could also be I. pacificus if it was from Western Canada. Dr. Kadkhoda (who donated this case) is in Manitoba, so I. scapularis would be most likely. Given the partial nature of this tick, we also need to consider other human-biting Ixodes species such as I. muris.
Answer: Malaria due to Plasmodium falciparum; >20% parasitemia
There were lots of great suggestions for what the lab should do after making this identification. The step of primary importance is to urgently contact the clinical team to relay the result and ensure they understand the importance of the diagnosis. In my laboratory we treat all malaria diagnoses as critical results. In this case, the causative agent (P. falciparum) and the high parasitemia (>2%) make this call even more urgent, since the patient is at very high risk of death from his infection and requires immediate treatment.
In addition to antimalarial treatment (e.g. IV quinidine or artesunate), red blood cell exchange may also be performed for patients with >10 % parasitemia. While the United States Centers for Disease Control and Prevention (CDC) no longer recommends red cell exchange for severe malaria, many other groups such as the American Society for Apheresis (ASA) feel that it is still warranted in life-threatening infections such as this one. You can read the arguments for red blood cell exchange for malaria with >10% parasitemia here:
Every week I will post a new Case, along with the answer to the previous case. Please feel free to write in with your answers, comments, and questions. Also check out my image archive website at http://parasitewonders.com. Enjoy!
The Fine Print: Please note that all opinions expressed here are mine and not my employer. Information provided here is for educational purposes only. It is not intended as and does not substitute for medical advice. I do not accept medical consults from patients.