Case of the Week 432

This week's case was generously donated by Dr. Nicole Hubbard. Small white motile objects were seen in a infant's stool specimen by the mother and a stool ova and parasite exam was ordered. The results of the stool exam were negative however, and objects continued to be seen; therefore representative objects were placed in formalin and sent to the laboratory for identification. They measured approximately 12 mm in greatest dimension. By manipulating the objects with forceps, the following structures were identified:

4x objective

10x objective

 40x objective

Identification?

Answer to Case 432

Answer: Dipylidium caninum egg packets

Thank you to all of my readers who wrote in with the answer - you all recognized the very characteristic appearance of the eggs within packets. This appearance, along with the case presentation and description, is classic for infection with D. caninum. 

Because the proglottids of D. caninum are so small (resembling grains of rice), they can be difficult to definitively identify in the parasitology lab. To make matters worse, they are often dried out or partially mangled when they arrive. Therefore, we will rehydrate the specimen in saline when needed, and then view them under the dissecting microscope. With some gentle manipulation using forceps, we can usually express egg packets out of the proglottids. This is what we did in this case and explains why the eggs packets are slightly immature appearing, without clearly visible internal hooklets. Here are some images from this case with further detail.

If that fails, proglottids can also be cleared using lactophenol and mounted on a slide.

Case of the Week 431

This week's case is an arthropod which was found on a sandy beach in South America. It is approximately 1 mm in greatest dimension.

Identification?

Answer to Case 431

Answer: Tunga penetrans adult flea

This was a tricky case because this flea is rarely seen outside of the human host. When it comes to clinical attention, it is usually because the female has embedded in the skin and has enlarged (with eggs), causing a painful lesion on the host.

When seen, this flea can be differentiated from other common human-biting fleas by a few characteristic features, including a shorter, rounder body, long serrated mouthparts, and compressed thoracic region. It does not have genal or pronotal combs. I've shown a Ctenocephalides adult below for comparison.

Florida Fan invited us to walk on his beautiful Florida beaches where he guarantees we will NOT encounter Tunga penetrans!

Case of the Week 430

This week's case is from an elderly institutionalized patient with diffuse thickened skin on her arms and back. A crust from skin was submitted for examination, and scrapings showed the following:

Many were hard to photograph because they kept moving! Identification?

Answer to Case 430

Answer: Sarcoptes scabei, the scabies or human itch mite. The presence of thick skin crusts is consistent with crusted or 'Norwegian' scabies.

This case demonstrates adult mites (with 8 legs) and nymphs and larvae (with 6 legs). Eggs with clearly-visible internal larvae are also seen:

Here are some fun facts about Sarcoptes scabei. They are arachnids, rather than insects (related to ticks and spiders). Also they undergo incomplete metamorphosis between life cycle stages (i.e. they are hemimetabolus). That means that the immature forms such as larvae and nymphs look very similar to the adults. That is quite different from holometabolus arthropods where the larvae look completely different from the adult (a good example is the flea which has a worm-like larval stage).

Here is a fun little poem from Florida Fan to go with this case:

Itchy, itchy little buggy.

Wherever cramped and unsanitary

You spread, from one fellow inmate than another,

You itch, I scratch then the bacteria follow to bother.

From the spaces between the knuckles,

To where there is a skin fold you dwell

For the poor souls, you terrorize you inflict just hell.

Itchy, itchy little buggy,

Sarcoptes scabiei you're not funny.

Case of the Week 429

This week's case was generously donated by Dan Rhoads at the Cleveland Clinic. The following video and images were taken from a corneal culture. What are the objects seen here?

Pay particular attention to the object denoted by the arrows and arrow head:

If you watch the video closely, you can see some motion in the object outlined by the arrows above (enlarge the video to view using your full screen):

Answer to Case 429

Answer: Acanthamoeba sp.
Shown here is a characteristic double-walled cyst and 2 less-easily visualized trophozoites. You can also see the background bacteria (Escherichia coli) which had been plated on the agar as a food source for the amebae. Florida Fan suggested that some creative editing would allow the trophozoite to be more easily seen, so here is my best shot:

Now that you know what to look for, I would encourage you to go back and look at the video again. If you watch closely, you can see subtle movements inside of the trophozoite with opening and closing of the contractile vacuole. Geeky parasite fun!

Case of the Week 428

Happy New Years! I have 2 announcements to make with this post. First, we will be "opening" 2017 with a beautiful case from Florida Fan (see below). Second, I want to announce that I have a new website: http://parasitewonders.com.  This website will serve as a repository for the cases that I post on my blog (in an easy-to-search A through Z format). The website also contains a flashcards feature where you can test your knowledge of common and uncommon parasites. I will continue to populate the image bank and flashcards as I post new cases, so I \encourage you to bookmark this page and check back often.

So now, on to the case:
This object was identified in a concentrate stool specimen. The photograph was taken at 400x, and the object measures just over 150 micrometers in length. No further history is available. Identification?

Answer to Case 428

Answer: Fasciola hepatica/Fasciolopsis buski egg.

As some of you pointed out, the characteristic features of this egg are:
1. It's large size
2. The presence of an operculum
3. The thin clear wall and internal undifferentiated embryo

I love this particular egg because it is 'opening' for the new year!