Monday, June 25, 2012

Case of the Week 213

The following were seen on a stool parasite examination (O&P) from a 4 year old child.  No travel history outside of the U.S. was reported. 

What is the preferred method of testing for this organism?


Sunday, June 24, 2012

Answer:  Pinworm (Enterobius vermicularis) eggs/ova.
Thank you to all of those who wrote in - you all got this one correct. 

Although pinworm eggs can be seen on a stool parasite exam, the optimal way for detecting this parasite is using the cellophane tape method, also known as "Scotch tape method" or "Sellotape method" (depending on what country you're from.  As mentioned by MericaDiagnogen "In this procedure, sticky cellophane tape applied to the anal area of the patient collects ova, which is then pressed onto a microscope slide and viewed."  Dr. Parker reminds us that this should be done first thing in the morning, (before the patient bathes or defecates). 

Most importantly, Eagleville mentions that "most 'cellophane' tape these days is frosted which makes the microscopic a bit more challenging. Specify "clear" tape to expedite the process."

Finally, Anonymous suggested the use of the SWUBE device (which simply stands for Swab in a Tube) in place of cellophane tape.  See an image HERE.  (I have no stock in this device or in the company that makes it.)

This device uses essentially the same technique as the cellophane tape method in that a transparent surface (in this case, a plastic paddle) has a sticky side that is applied to the peri-anal skin to capture the eggs and/or adult females.  The paddle has a handle that allows the person collecting the eggs to retrieve the sample with minimal skin contact.  The paddle is then place in the transport tube and sent to the lab where it can be placed directly under the microscope and examined.  I like this device because it's easier for parents or caregivers to use than cellophane tape and it eliminates the need for a glass slide.

Monday, June 18, 2012

Case of the Week 212

The following was received in clinical parasitology for identification.  The patient (a physician) was concerned because he found this arthropod attached to his thigh and wants to know what he should do.  It was attached for approximately 6 hours. After removing it, he put it in the first container he could find (hence the interesting submission container!)

What would be your advice to this physician?

Sunday, June 17, 2012

Answer to Case 212

Answer:  Ixodes scapularis tick (a.k.a. deer tick, black-legged tick), female, not engorged.  Mouthparts are intact. Congratulations to everyone who wrote in - you all had the correct answer.

The answer to the second question I posed, "What would be your advice to this physician?" is a bit trickier.  Thank you for all of the thoughtful responses to this post. 

In advising physicians about prophylaxis or treatment for tick borne illnesses, I refer to the Infectious Diseases Society of America (IDSA) guidelines (Wormser et al., CID 2006) which state that "for prevention of Lyme disease after a recognized tick bite, routine use of antimicrobial prophylaxis or serologic testing is not recommended."  Instead, a single dose of doxycycline may be given for prophylaxis in certain cases; cases should meet the following criteria:

1.  Patient is >/= 8 years of age
2.  The attached tick is identified as I. scapularis (hence the utility of laboratory identification)
3.  The tick is estimated to have been attached for >/= 36 hours (based on degree of engorgement or patient exposure history)
4.  Prophylaxis can be started within 72 h of the time that the tick was removed
5.  Ecologic information indicates that the local rate of infection of these ticks with B. burgdorferi >/= 20%
6.  Doxycycline is not contraindicated

Prophylaxis for other tick-borne diseases (e.g. anaplasmosis, babesiosis) is not recommended.

In this case, the tick is clearly not engorged and was reported to be atached for only 6 hours.  Therefore, I advised the patient (in this case, a physician) to not take any further steps at this point, but to watch for signs and symptoms of tick-borne illness such as rash, myalgias, headache and fever, and to see his physician if any of these arise.

Monday, June 11, 2012

Case of the Week 211

Dear viewers,
This week I promised my lead tech that I would not subject you to another histology image. Therefore, I've included a short video of a live arthropod that was recently submitted to my lab for identification.  I particularly like how you can see the gut contents moving.

(my apologies to B.A.M. for not including a close-up view of the pronotum)

Sunday, June 10, 2012

Answer to Case 211

Answer:  Cimex sp.

This is a nice example of blood movement within the gut of a bedbug.  Note the classic shape of this hard-to-eradicate pest.

The differential diagnosis in this case includes other Cimex species (e.g. bat bug); however, these can be ruled out by looking at the hairs on the pronotum.  Unfortunately I didn't have a nice photo to show you a close up of the pronotum so the furthest you could go from just this movie is "Cimex sp."

Monday, June 4, 2012

Case of the Week 210

The following biopsy is from the superior rectus muscle of a 70 year old woman with a retroorbital mass by CT and significant eye swelling.  She has never travelled outside of the United States and lives in the midwest.  Diagnosis? (CLICK ON IMAGES TO ENLARGE)

(H&E, 20x original magnification)

(H&E, 40x original magnification)

(H&E, 100x original magnification)

(H&E, 200x original magnification)

(H&E, 200x original magnification)

Sunday, June 3, 2012

Answer to Case 210

Answer:  Dirofilariasis

This was a tough case, with lots of different responses offered by viewers.  The presence of a worm cross-section in the superior rectus muscle rightly calls to mind diagnoses of trichinellosis and cysticercosis.  However, the round aspect of the worm supports the diagnosis of a nematode, while the relatively large size, lack of a nurse cell, surrounding necrosis, and worm morphology (including diagnostic internal cuticular ridges) are consistent with the diagnosis of Dirofilaria sp.  This filarial worm, commonly known as the dog heart worm, can cause a self-limited infection in humans with pulmonary and subcutaneous masses.  Infection is transmitted through the bite of a mosquito and is more common in the southeastern U.S., although a handful of cases are reported in the upper midwest each year.  Another reason to apply DEET and avoid mosquito bites this summer!

Internal cuticular ridges are shown by the arrows below.  Note the surrounding necrosis (top image) and necrotizing granuloma (bottomw image).