Case of the Week 424

The following are Giemsa-stained peripheral blood smears from a young girl who was recently treated for malaria. What is the material inside of the white blood cells?

Answer to Case 424

Answer: hemozoin pigment

This pigment is formed as the infecting Plasmodium species feeds on the host's hemoglobin in the red blood cells. This young girl had previously been diagnosed with a heavy Plasmodium falciparum infection (3.5% parasitemia). Here are some images of her previous thick and thin blood films.

Fortunately, she made a full recovery. Thank you again to Emily F. for these beautiful photos.

Case of the Week 423

The following objects were observed in an aspirate of liver cyst fluid (carmine stain). Identification?

40x

100x

200x

400x

Answer to Case 423

Answer: Echinococcus sp. protoscoleces

Each protoscolex has an internal row of hooklets that will evert one inside of the canine definitive host and become the head of the adult tapeworm.

A couple of readers asked me about the Carmine stain. It's unfortunately not one that we perform in the lab anymore although there are instructions and recipes in many major parasitology texts and online. It's really a beautiful way to highlight the structures of various worms, but just not something that we usually need for diagnostic purposes. I try to show photos of these 'older' stains from time to time to hopefully inspire others who want to revive them for teaching purposes.

Case of the Week 422

Here is another lovely photograph from Florida Fan - a straight forward ID for those of you studying for boards or your Trop Med exam.

This object was observed in a stool specimen from a middle-aged man from India. It measures approximately 30 microns in diameter.

Identification?

Answer to Case 422

Answer: Taenia species, egg

As Deepak described, the characteristic features include the small size, yellow-brown color and thick radially striated shell. Note the presence of a six-hooked embryo (oncosphere) inside.

Unfortunately you can't tell the different Taenia species (i.e. Taenia solium, T. saginata, T. asiatica) apart from the egg alone. This would require molecular testing and/or examination of the scolex or proglottid morphology.

Thanks again to Florida Fan for donating this classic example of a Taenia eggs.

Case of the Week 421

This week's beautiful photographs came from Florida Fan. The specimen came from a middle-aged male.

By spinning down the 70% ethanol that the specimen had been transported in, the following objects were seen. They measured approximately 60 micrometers in length.

Identification?

Answer to Case 421

Answer: Diphyllobothrium species
There are several characteristic morphologic features shown in these nice images from Florida Fan. First, we have a long segment of a relatively large tapeworm, with proglottids that are wider than they are long. Immature proglottids of Taenia solium and T. saginata can also be wider than they are long, but the fact that we could get eggs from the proglottids means that they are mature. Therefore, we can exclude Taenia based on the shape of the proglottids. We can also exclude the other human tapeworms since none are this large.

Another feature that I find to be helpful for identifying Diphyllobothrium is that the uterine structures are clearly visible in the center of each proglottid - even without staining or microscopic examination:

Finally, the eggs that were found in the accompanying fluid leave no doubt as to the identification, having the classic shape and features of Diphyllobothrium, including an operculum and abopercular knob.

As Anon pointed out, species identification would require epidemiological information, and ultimately molecular testing. Therefore, we report this out as "Diphyllobothrium species" in my lab.