Monday, November 25, 2019

Case of the Week 570

This week's case was generously donated by Dave Neitzel at the Minnesota Department of Health. A mutant headless tick! Wouldn't it be great if they were all this way?

Can anyone identify the genus of this tick?

Sunday, November 24, 2019

Answer to Case 570

Answer to Parasite Case of the Week 570: Ixodes scapularis adult female with a missing external capitulum and mouthparts. Or as Blaine noted, "A headless tick:  Ichabod scapularis!"

The image below shows these parts where they are normally located on the accompanying female tick (white oval):
Examination of the ventral aspect shows an "inverted-U" shaped anal groove, allowing this tick to be identified to the Ixodes genus. One reader had queried if the genital pore was also absent on our mutant tick, but re-examination by Dave Neitzel indicated that it IS there; it is just obscured by the glare of the light.

So how did this happen? Well, Dave and some of our readers rightly indicated that the tick must have taken 2 prior blood meals in order to molt from larva to nymph, and then nymph to adult; thus it must have had functional mouthparts during those previous stages. However, as Dave noted, "something went horribly wrong during the last mold from nymph to adult. Given the radical changes that occur during a molt, I am surprised that we don't see more obvious mutations!" He also shared that he has seen several 7-legged ticks from his regular field collections in Minnesota, but surprisingly, no other mutants. He hypothesized that the capitulum and mouthparts are still present, but that they are inverted and therefore not externally-facing. The lack of of the visible capitulum and mouthparts has shifted the position of the legs, thus making them look longer. Finally, he commented on the "sclerotic structure" noted between the first pair of the legs by Makrone.  He also had seen this and speculated that it might be some of the residual tissue from the inverted mouthparts/capitulum.

Thanks to Dave for the fascinating case! As Sam mentioned, Ixodes scapularis is the vector for Babesia microti, as well as several bacterial pathogens and Powassan virus. Wouldn't it be great if they were all 'headless'?

Monday, November 18, 2019

Case of the Week 569

This week's case was captured by my awesome Parasitology Education Specialist, Felicity Norrie, MLS(ASCP). The following were identified from skin scrapings from a resident of a skilled nursing facility. Identification?

Sunday, November 17, 2019

Answer to Case 569

Answer to Parasite Case of the Week 569: Sarcoptes scabei eggs, larva and adult. Fecal pellets (scybala) are also seen. I love how you can see the larval mite emerging from the egg in this photo:

As several readers mention, scabies is infectious to others, and thus the residents and health care workers in this skilled nursing facility must be evaluated for infection and treated if need be. Anonymous also mentioned that "scabies is not a problem of lack of hygiene but of overcrowding and wherever close person-to person contact is common. Scabies spreads quickly especially in nursing/care homes if no skilled GP or dermatologist is available to diagnose the index Patient, even in highly developed countries." This comments brings up the important point that infection does NOT reflect poor hygiene of the infected individuals. The mite infects all ages, ethnicities and social strata.

Monday, November 11, 2019

Case of the Week 568

This week's case is from Old One - illustrated by him and animated by his son. It features an arthropod that measures a few millimeters in length.
See it in action HERE!

Sunday, November 10, 2019

Answer to Case 568

Answer to Parasite Case of the Week 568: Pseudoscorpion or false scorporion, not a human parasite.

This fun little arthropod is occasionally submitted to the clinical laboratory for identification, and may be mistaken as a true scorpion. While both scorpions and pseudoscorpions are arachnids, pseudoscorpions are very small (1 cm or less in length) and lack a tail with a stinger. As sylvie g and Santiago note, pseudoscorpions can occasionally be found in the house, but they don't bite or sting humans, and instead feed on other small arthropods such as booklice.

Thanks again to Old One and his son for the donation of the cool animated illustration.

Tuesday, November 5, 2019

Case of the Week 567

This week's case is from Idzi Potters and the Institute of Tropical Medicine, Antwerp. The following object was seen in a concentrated stool specimen from a 3-year-old toddler with diarrhea (40x objective). It measures 45 micrometers in greatest dimension. Identification?

Monday, November 4, 2019

Answer to Case 567

Answer: Hymenolepis nana egg.
As many of you pointed out, this eggs beautifully demonstrates the filaments arising from the 2 poles of the inner membrane (arrow heads, below image). You can't make it out here, but there are 4-8 of these filaments arising from each pole. You can also nicely see the hooks of the 6-hooked oncosphere:
Some of you may know that humans become infected with this parasite when they ingest infected arthropods. As Sam mentioned, children are a common host - likely due to their tendency to put things in their mouth. Adults can also become infected as Blaine reminds us in his poem:
There once was a chap from Indiana
who with his cereal enjoyed a banana
but with the cereal he did eat
he received an unexpected treat
The cestode known as Hymenolepis nana!

If you do an internet search for "oatmeal" and "bugs," you will find multiple consumer complaints (and some nice YouTube videos) to explain the cereal reference.

Importantly, infection via ingestion of eggs shed in stool (autoinfection or from another person) is also possible, making this a common intestinal cestode infection worldwide.