Monday, December 31, 2018

Case of the Week 525

This week's case is an 'oldy but goody' - a case donated to me by Dr. Eric Rosenbaum years ago that I just re-discovered. The history is particularly fun, and a great way to end 2018.

Dr. Rosenbaum was made aware of this case when he was paged by a neurosurgeon. As a clinical pathologist, he was quite surprised to be asked to come to the operating room; however, he soon understood the request when he saw what was incidentally noted on the patient's skin during brain surgery:


This little arthropod was quite active and rather hard to catch (!) The patient is from the southeastern United States. Identification?

10 comments:

Anonymous said...

Pretty sure that it's a hard tick from the genus Amblyomma; the distribution fits for where it was found. I can't definitively speciate, but could guess it to be a male A. americanum.
Frankly, I'd like to know how freaked out the neurosurgeon had been.

Anonymous said...

Amblyomma americanum. I think a male.
BW in Vt

MDeLeon said...

What a great story, and great photos :) This looks like a juvenile female Amblyomma sp. tick to me. The scutum only covers the upper part of the back of female ticks, while the scutum covers the entire back of male ticks. The body shape and transparency of the exoskeleton make me think this is a juvenile. Also, I think the measurement must have been in mm, not cm. I cannot imagine seeing a 1.5 cm long tick, AHHHH!

Joe Camp said...

I also think this is a female tick with the lack of a complete scutum covering the dorsum as would be the case for a male tick.

Anonymous said...

Quite an intriguing clinical presentation. I have not known any eight legged tumor. However, from the pictures we can gather the following clues:
1. There are eight legs, this is an adult tick (from a previous case).
2. The anal groove is posterior to the anus, this eliminate Ixodes spp.
3. The basi capitulum does not have lateral projections, ruling out Rhipicephalus spp.
4. There is no lateral projections on the palpi, this eliminates Haemaphysalis spp.
5. The second segment of the palpi,thought not very clear is longer than the basi capitulum, this eliminates Dermacentor spp. and makes it compatible with Amblyoma spp.
6. There are two clear eyes at the corners of the scutum, another characteristic of Amblyoma spp.
7. There is no "star" on the dorsal side at the bottom of the scutum, this make the tick not americanum.
Overall, this tick is morphologically most compatible with an adult female (scutum not covering the entire back) Amblyoma spp. from America not americanum.
This is as far as I can go, will leave the species to the real entomologists.
Florida Fan

William Sears said...

Would say amblyomma species as I can't make out a clear anal groove and I think I see festoons although it is hard to tell with partial engorgement. The mouthparts are smaller than palps but maybe the hypostole was broken off upon removal. Being super active also points towards amblyomma species.

Old One said...

This tick has 8 legs, eye's, a partial scutum, broken mouth parts, apparent festoons (obscured by focus), did not see porose area or genital aperture.

The porose area(PA) is a nice diagnostic feature in that is found only on females. It's used to cover each of the eggs with water resistant barrier. This is accomplished with the help of 2 inflatable arms (gene's organ) which can be seen only during the egg laying process. These arms help in moving the egg from the genital aperture (GA) over the capitulum and roll them around on the PA. With 8 legs but without PA and GA I would say this tick is a nymph.

The broken hypostome and chelicera hints at the possibility that this tick has long mouthparts that were cemented deep in the hosts tissue. Ticks with shorter mouth parts (Dermacentor) cement at the surface of the skin. often leaving a skirt of cement attached to the capitulum (often confused as host skin) and often retain their mouthparts.

The high activity level of this tick is a characteristic seen in Amblyomma and even more so in its cousin Hyalomma. They are sometimes described as almost predatory. Literally one can hear them running through grass to get to their host (prey).

I would like to make a comment about the ticks sensory organs. The Haller's organ is found on the forearms of the first set of legs( in humans it would be the perfect spot on the wrist to place perfume). During the questing process the extended arms make it easier to hook the host but also serves to detect the host. Haller's contains a number detectors one of which is CO2 detection which is often used to trap ticks using dry ice as bait.

Based on my compadres findings as well as my own observations, I believe the tick to be Amblyomma americium nymph

Old One said...

Amblyomma americanum... at least I should spell it correctly.


The instructor placed a male Dermacentor variabilis on the edge of a large circle of filter paper. Then he placed a drop of pheromone at it's center. As if a gun shot, the race began full throttle. The tick put pedal to the metal as it rocketed across the paper. Missing it's mark, it ran past the drop and made a speedy U turn. I swear I could hear 8 little tick feet "spinning rubber"as it made haste to the scent.

Some people like a flea circus, but give me a tick race any day.

Blaine A. Mathison said...

This is an Amblyomma americanum nymph. A couple things to remember:

1. Amblyomma species usually do not possess their white maculae in the nymphal stage. The mouthparts here (palps) are long, but the presence of eyes immediately rules-out Ixodes.

2. I see a lot of people guessing the gender. You cannot put the gender on a hard tick nymph, because all nymphs, regardless of gender, have a short dorsal shield.

Anonymous said...

Thank you Blaine, I will pass the info to my team.
Florida Fan.