Answer: Hard tick (Ixodidae) nymph emerging from the larval exuvia. The inverted "U-shaped" anal groove on the ventral surface (photo below) allows us to identify this as an Ixodes species.
The gender is not possible to discern in nymphs, but as mentioned by Anon, it can be determined in adults by examining the scutum and basis capituli. The scutum (dorsal shield) of the female only covers a portion of the dorsal surface, compared to the male in which it covers nearly the entire dorsal surface. In the nymphal stage, both males and females have a similar-appearing scutum. Also, only females have porose areas whereas males do not. The porose areas are located on either side of the basis capituli and produce antioxidants which are combined with waxy secretions from the Gene's organ. This substance is applied to eggs right after they are laid and serves as a protective coating. The porose areas also lubricate the Gene's organ, allowing it to expand and retract more easily.
Thanks again to Dr. Graham Hickling for donating this fascinating video. Thank you also to Dr. Robyn Nadolny for the additional information about the function of porose areas and Gene's organ. If you'd like to see the Gene's organ in action (and tick eggs being laid), check out this other amazing video by Graham.
The following parasites were discovered in a man's peritoneal tissue during an inguinoscrotal hernia repair. The resided in Benin, Africa. Here is the resected section of peritoneum along with the attached parasites (CLICK ON IMAGE TO ENLARGE):
Answer: Pentostomiasis; most consistent with Armillifer species. William Sears also suggested that Raillietiella sp. is also in the differential, which Idzi confirms. Both are found in African countries and associated with consumption of raw snake meat. Identification is accomplished morphologically by counting the annuli. You can also use molecular studies, although these are not widely available.
Idzi also provided me with the following beautiful (and very creepy) photos from his Institute's specimen archives which show an adult and larval Armillifer armillatus:
Idzi and his group published this case, so you can read more about it HERE. Fascinating case!
Answer: Enterobius vermicularis (or E. gregorii); a.k.a. pinworm.
Several of you noted the classic features of the female pinworm shown in this case: the prominent anterior cervical alae, classic eggs (in and outside of the worm), and the slender "pin-like" tail that gives this worm its common name. Males also prominent cervical alae but lack the pointy tail; instead they have a blunt, often curved, posterior end with a single spicule.
As mentioned by Florida Fan, infected patients typically experience nocturnal anal pruritus, and the worm may be observed crawling on the surface of the stool. Ali Mokbel also noted that each work lays approximately 10,000 eggs each day. Importantly, these eggs are fully infectious within 4-6 hours of being laid, and this is one of the most important reasons why this worm is common in the United States and other resource-rich temperate climates. The eggs of most other intestinal nematodes require an incubation period in the soil before becoming infectious, and therefore infection can be prevented with proper sanitation measures, including waste treatment.
Thank you again to Dr. Kadkhoda for donating this classic case!
This is a special post to wish a very happy Thanksgiving to all of my American readers. Can you all see the turkey head in the following blood smear? (you may need to use your imagination a bit).
The image is courtesy of my awesome lab education specialist Emily Fernholz. Can you tell what Plasmodium species is shown here?
The answer to Case of the Week 469 will be posted tomorrow.
The below was seen on a stool agar culture after incubation at room temperature for several days. The patient is a 62-year-old woman from the Philippines. The images are by my awesome lead tech, Heather Rose, while the video is by Emily Fernholz, Education Specialist extraordinare.
The following were seen in the concentrated wet preparation of the stool specimen :
Answer: Strongyloides stercoralis. Note the characteristic morphology and the impressive larval load in the stool agar culture! It's been a while since I've seen such a heavily loaded specimen. We immediately contacted the clinical team in this case since we were concerned about potential hyperinfection syndrome - a life-threatening condition - to ensure that the patient was treated immediately.
As mentioned by Florida Fan, Ali, William and Idzi, a rhabditiform larva with a short buccal cavity is clearly shown, allowing us to confirm the identification of S. stercoralis.
Idzi also astutely noted that there are eggs and different stages of larvae present. There were also rare adults in the specimen (not shown). I didn't highlight them in my original post since their morphology is less than optimal, but here are closer views:
Strongyloides stercoralis adults and eggs are not usually seen in stool specimens, but can be seen in very heavy infections like this one.
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.