Sunday, February 24, 2008

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.

Sunday, February 17, 2008

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.

Sunday, February 10, 2008

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?

Saturday, February 9, 2008

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