Parasite Case of the Week 10

Welcome to the Parasite C.O.W.
Every Monday I will post a new case, as well as the answer to the previous case (you will find it below the corresponding case). Please feel free to leave a comment or your thoughts regarding the diagnosis. Enjoy!

The following egg identified from soil near a community center. As you focus up and down, you notice the egg has a thick pitted shell (Click on the images to enlarge).












Questions:
Identification?
Most likely host(s)?
Could eggs from this organism pose a risk to humans?

Answer to Case 10

Congratulations to everyone who had written in. This is indeed a Toxocara egg.
Most likely host(s)? Dog or cat
Could eggs from this organism pose a risk to humans? Yes, if ingested (usually by children), it can cause a condition called visceral larva migrans. The worm cannot mature to an adult in humans, but instead, remains in the larval stage and wanders around the body.

Parasite Case of the Week 9

Welcome to the Parasite C.O.W.
Every Monday I will post a new case, as well as the answer to the previous case (you will find it below the corresponding case). Please feel free to leave a comment or your thoughts regarding the diagnosis. Enjoy!

These worms were expelled from a patient after treatment with Albendazole and Piperazine. The longest among them are 40 cm in length. Click on images to enlarge.










Questions:
Most likely diagnosis?
How are these worm acquired?

Answer to Case 9

Most likely diagnosis? Ascaris lumbricoides

Without being able to examine the worms more closely, you can still make a preliminary diagnosis based on the size and shape of the worms - A. lumbricoides is the largest roundworm (Nematode) that parasitizes humans. I'm guessing that this fact (and their resemblance to a bowl of noodles) prompted Patty to write "Nothing gives me the gag reflex quite like ascaris worms".

The sheer number is also consistent with the diagnosis - Ascaris adults can number in the 100's or even 1000's in infected individuals! Since they live in the small intestine, it's easy to see how intestinal obstruction can occur with heavy infections.

How are these worm acquired? Through ingestion of eggs in contaminated food and water.

Parasite Case of the Week 8

Welcome to the Parasite C.O.W.
Every Monday I will post a new case, as well as the answer to the previous case (you will find it below the corresponding case). Please feel free to leave a comment or your thoughts regarding the diagnosis. Enjoy!

The below Wright-Giemsa stained blood film is from a patient with no reported travel outside of the United States. Click on the images to enlarge.











Diagnosis?

Answer to Case 8

Diagnosis: Babesiosis
I can tell from the responses (both on the web and off) that this case was far too easy for my U.S. friends, and a bit challenging for my U.K. friends. That's to be expected given that cases of Babesiosis are rare Great Britian, but common in parts of the the U.S.

Babesiosis must always be kept in the differential diagnosis with this microscopic picture and lack of travel to malaria-endemic areas. It is caused by over 100 species, but is mainly due to infection with B. microti and B. divergens.

In this case, your main differential diagnosis would be P. falciparum malaria caused by so-called "airport" malaria (malaria transmitted by mosquitoes that have stowed away on a plane from an endemic area). This is usually seen in patients who live near an international airport.

Babesia spp. and P. falciparum share the following features:
1. They have small, similar appearing ring forms
2. Multiple parasites per red blood cell are common

The main features that allow you differentiate Babesia spp. from P. falciparum are:
1. Babesia ring forms are irregular
2. No schizonts or gametocytes are present with Babesia spp.
3. Extracellular merozoites are commonly seen in Babesia infection (none shown in this case)
4. Babesia merozoites classically form a tetrad or "maltese cross", although it is actually rare to see this. Here is an image of how this would look (click on image to enlarge):

http://www.med.univ-angers.fr/discipline/lab_hema/morphogrweb/33.jpg
Shown with permission from Dr. Zandecki, Faculte de Medecine d'Angers

Parasite Case of the Week 6

Welcome to the Parasite C.O.W.
Every Monday I will post a new case. Please feel free to leave a comment or your thoughts regarding the diagnosis. Click on the images to enlarge. Enjoy!

The following cyst was found in a section of skeletal muscle and was submitted for hematoxylin and eosin stained-sections after formalin fixation and paraffin embedding.










Image 1 (top) - 100 times original magnification.
Image 2 (bottom) - 400 times original magnification.
Click on images to enlarge.




Questions:
Name of disease caused by this parasite?
Causative agent?
How is this organism acquired?

Answer to Case 6

Name of disease caused by this parasite? Cysticercosis
Causative agent? Taenia solium
How is this organism acquired? Through ingestion of EGGS. The adult worm is acquired through ingestion of larvae. This is a favorite test question.

Differential diagnosis

First, you can tell this is a cestode due to the presence of calcaneous corpuscles (small calcified bodies) which are unique to cestodes (arrows).










The presence of a single hooked protoscolex within the small folded cyst tissue is characteristic of T. solium. However, you should also consider the following when looking at a larval cestode in tissue. All can be found in muscle, as in this case.

1. Echinococcus species - expect to see multiple cysts. In E. granulosus, each cyst contains multiple hooked protoscoleces. (Note that T. solium cysticeri only have only one hooked scolex per cyst) Protoscolex formation is rare in E. multilocularis, whose cysts are usually sterile in humans.

2. Spirometra species - do not form protoscoleces, so no hooks or suckers will be seen. The larva is solid-bodied and is not surrounded by a bladder.

3. Taenia multiceps and Taenia serialis (coenurus) - Like E. granulosus, cysts contain multiple protoscoleces with typical hooks and suckers, but are surrounded by a thin wall without a laminated membrane.

Parasite Case of the Week 5

Many of you will be happy to see that there is NO arthropod in this week's case. Instead I have something a bit unusual - some movies. These are short films of what you might see in a "hot stool" - that is, one that comes fresh from the patient without any fixative. This method is commonly used in the tropics for diagnosis. Furthermore, you're bound to see questions regarding characteristic motility on Board exams and the like, so it's good to be familiar with the classic patterns.

The first movie shows the classic motion. The second movie is to demonstrate morphology. The organism in question has finally slowed down enough to allow a closer look.

Questions:
1. Identify the organism
2. State the significance of finding this organism in a stool sample.



Movie showing characteristic motion


Movie showing morphology

Answer to Case 5

Congratulations to Heather who correctly identified this organism! This is indeed Trichomonas hominis; a non-pathogenic flagellate from a stool specimen. It has now been renamed as Pentatrichomonas hominis.

Here is her description which I include because it so perfectly describes the motion of the Trichomonads:

"This is more what I call the "Night at the Roxbury Guys" movement--you know, the head-side-twitch to the beat of the music thing. (Don't know what I mean? Check it out here:

Watch the YouTube video

This is characteristic motility of Trichomonas species. If in stool, then, this would be Trichomonas hominis, and in a genital source would be Trichomonas vaginalis. T. hominis is a commensal and considered nonpathogenic, while T. vaginalis is, of course, a problem."

Go and watch the youtube video (you don't have to watch the whole thing - just the first 5 seconds and you'll get the idea), and then check out the following. Alex from Rip and Read (also my husband) made this for me. Fun!