Wednesday, April 13, 2022

Case of the Week 679

Here is a beautiful tick for you all to identify from Florida Fan - something that is very timely for this season! You can use this TICK KEY to help you get it into the correct genus. What is the potential significance of this finding?

Tuesday, April 12, 2022

Answer to Case 679

 Answer to Parasite Case of the Week 679: Haemaphysalis sp. 

Congratulations to Blaine Mathison, Khaled Itani, Olugbenga Samuel Babatunde, Souti Prasad Sarkhel, Robyn Nadolny, Marc Couturier, @TickReport, and Alvaro Faccini-Martinez for the correct identification! 

It can be tricky to differentiate Haemaphysalis from from Rhipicephalus, so I created the following pictorial guide to help illustrate the key features. 

In the end, it all comes down to a difference of angles - in Haemaphysalis, the outward facing angle is from the palps, whereas with Rhipicephalus, it's from the basis capituli. Both of these ticks also have festoons and their mouthparts are as long as the basis capituli, so they otherwise have a very similar appearance. 

As Blaine points out, there are several members of this genus that are found in the United States, including the newly-invasive H. longicornis, or Asian longhorned tick. There arent' enough features shown in this case to get to the species level, but if you ever have a specimen in your laboratory, you can use this recently published KEY for assistance. Also, if you'd like to learn more about H. longicornis, the CDC has a brief overview HERE. The USDA also has a great site on H. longicornis that includes a regularly-updated map of the tick's distribution throughout the United States.

Thanks again to Florida Fan for donating this case!

Tuesday, April 5, 2022

Case of the Week 678

This week's fascinating and unusual case was donated by Dr. Vicki Schnadig at University of Texas Medical Branch. The patient is an elderly woman from rural Louisiana who presented with a subcutaneous thigh nodule. Dr. Schnadig's team first performed a fine needle aspirate of the lesion which showed the following laminated spherical structure, but no definitive pathogen:

Following this, the team noted a worm-like object protruding from the aspiration site and pulled it out:

The following are histologic sections of this object:


Sunday, April 3, 2022

Answer to Case 678

 Answer to the Parasite Case of the Week 678: Sparganosis - infection with the larval form (sparganum) of Spirometra sp.  Kudos to Dr. Francisco Bravo for getting the correct answer, and for the nice description from Florida Fan.

This was a fascinating case as sparganosis is a relatively rare parasitic infection in humans, and the way it was discovered following fine needle aspiration is very unique. It's possible that the laminated calcification seen on the aspirate smear is a calcareous corpuscle, but it's hard to know for sure. Therefore, it was a good thing that the sparganum began to extrude from the aspirate site and could be removed. It's macroscopic and microscopic appearance are diagnostic. Note the longitudinal smooth muscle fibers, loose stroma, and numerous calcareous corpuscles. The latter are seen in all cestodes, in both larval and adult forms. In this case, they mostly appear as empty oval-shaped structures, but can also calcify and appear dark purple on routine H&E stain.

Although removal is curative, this patient should be counseled to avoid eating undercooked fish, reptiles and frogs, to avoid acquiring another case of sparganosis in the future!