This week's case is a cool little finding from my lab, with videos by Emily F. Specimen type is urine (filtered through a Nuclepore (R) membrane), and the object shown measures approximately 150 micrometers in length.
Answer: Schistosoma haematobium egg containing a live miracidium.
The video in this case nicely shows the movement of the miracidium as it beats its circumferential cilia and retracts its apical papilla. Normally internal "flame" cells (protonephridium) can also been seen moving, but these cannot be appreciated in this video.
Answer: Strongyloides stercoralis adult female worms containing eggs and rhabditiform larvae. A possible filariform larva is also seen.
Adults worms are almost never seen in the stool of patients with strongyloidiasis, but when present, indicate a likely heavy infection. This case is remarkable because eggs and larvae are seen within the adult worms, illustrating how quickly the eggs hatch in the normal life cycle of this worm. The adult female usually lays the eggs directly in the intestinal mucosa where they quickly hatch to release rhabditiform larvae. This is why larvae, and not eggs, are found in the stool of patients with S. stercoralis infection.
Thanks again to Boren for donating this fascinating case.
This week's case is that of an elderly female with recent travel to a malaria-endemic area in South America. To evaluate the patient for malaria, venous blood was collected in tubes containing EDTA and thick and thin blood films were made immediately at the local hospital laboratory. These slides were stained and sent to my laboratory for examination, in addition to a tube of blood. Below are representative fields from those slides (images courtesy of Emily F.):
Two days later, we used the blood to make additional slides for teaching purposes. However, review of the new slides now revealed different forms than what was initially seen:
What is the likely cause of these different forms?
Answer: P. falciparum gametocytes with altered morphology due to prolonged storage in EDTA.
Careful review of the original slides revealed only P. falciparum parasites, and PCR testing for the 5 most commonly detected Plasmodium species revealed only P. falciparum DNA.
Also note that there are some hints that the rounded gametocytes are actually the same as the crescent/elliptical ones. Look at the image below which shows both forms. They are very similiar in appearance, despite the differences in overall shape. Therefore, you can see that a spectrum of morphologic changes occur overtime, with some gametocytes appearing more elliptical rather than round/oval.
This is an important pitfall that parasitologists need to be familiar with, and a good reminder for why blood smears need to be made as soon as possible after obtaining blood. Not only do the crescent-shaped gametocytes of P. falciparum tend to round up and look like gametocytes of P. falciparum with prolonged exposure to EDTA, but other changes can occur such as formation of 'applique' forms with P. vivax, maturation of gametocytes, exflagellation of microgametes, and rarely, formation of ookinetes (from fertilization of a macrogamete by a microgamete).
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. Enjoy!
The Fine Print: Please note that all opinions expressed here are mine and not my employer. Information provided here is for medical education only. It is not intended as and does not substitute for medical advice. I do not accept medical consults from patients.