Answer to Case 723

Answer to the Parasite Case of the Week 723: mite, not scabies. Given that this mite was found in a fungal culture from skin scrapings, it could very well be a dust mite (Dermatophagoides sp.) as many of you suggested. However, mites are challenging to identify, so genus/species level identification is best left to the acarologists (people who study mites and ticks). 

The biggest concern here is its location - on a fungal culture in the mycology laboratory. Mites are a terror in the mycology lab. They crawl from plate to plate, contaminating and destroying cultures from patient samples. In most cases, the culture plates need to be destroyed and the lab decontaminated. This is the reason why my colleague, Dr. Wengenack, was so upset to find these! However, she knew of my interest in mites and was kind enough to donate this case to the blog.

Some readers questioned if these were scabies mites. Fortunately scabies mites (Sarcoptes scabei) can be easily differentiated from most zoonotic and environmental mites by their rounded bodies and short legs:

Case of the Week 722

 This week's (rather disturbing) case was generously donated by Dr. Niels Olson. This is a parasite found in salmon throughout the world - sorry sushi lovers - no slight is meant against any commercial provider of salmon. Parasitism is a fact of life. What is the likely identification of this parasite? What would happen if it was ingested without cooking or freezing?

Answer to Case 722

Answer to the Parasite Case of the Week 722: anisakid larvae, one of the members of the Anisakis simplex, Pseudoterranova decipiens, or Contracecum osculatum complex. 

Humans can become transiently infected with the larvae when they are ingested in undercooked fish, such as this salmon. The larvae may embed in the gastric or intestinal mucosa, causing intense pain. Endoscopic removal is curative. In less severe cases, the larvae will migrate back up the esophagus and out the mouth - a much preferred (but disturbing!) alternative. They can also be passed in the stool. In these settings, the larvae have to be differentiated from immature Ascaris lumbricoides. This can be accomplished using a number of morphologic features. 

To avoid anisakiasis, Chia-Yu Chiu wisely notes that the FDA recommends that salmon (and all fish) should be well-cooked or frozen prior to ingesting to kill the larvae.  This case is a good example of how fish is not always frozen prior to sale - even in a well known grocery chain. Therefore, it is up to the consumer to freeze the fish prior to eating raw! The FDA recommends freezing for 7 days using a standard, consumer-grade freezer (-20℃). Restaurants usually freeze for 24 hours or less at -70℃. 

On a final note, some people develop an allergy to anisakids, and therefore even freezing won't protect from allergic reactions following consumption. Individuals with severe anisakid allergies may have to avoid ocean fish indefinitely.

Case of the Week 721

 Happy American Independence day (July 4th) and a belated Canada day (July 1st)! As an American, this weeks case very appropriately has a lot of red, white, and (purple-ish)
blue. The following round objects were seen in a stool specimen on modified acid fast. The patient has had more than 1 week of profuse watery diarrhea and abdominal discomfort.

These objects were also highlighted with using calcofluor white fluorescence staining (arrow) along with stool flora.

What are these objects? Are they fungus or parasite?

Answer to Case 721

 Answer to the Parasite Case of the Week 721: Cryptosporidium sp. oocysts. These oocysts are a parasite, even though they stain with the non-specific calcofluor white fluorescent dye. Also, the abbreviation "crypto" is often used to refer to either Cryptosporidium (parasite) or Cryptococcus (fungus), so it's always good to make sure you audience know what you were talking about!

Cryptosporidium spp. oocysts are one of several intestinal parasites that stain red with the modified acid fast stain; Cyclospora spp. and Cystoisospora belli are the other two. Note that these 3 parasite genera are commonly referred to as coccidian parasites (i.e., member of teh Coccidia group). However, evidence now indicates that Cryptosporidium more closely related to the Gregarinasina group. I've purposely shown these 3 organisms in my last 3 cases for comparison. Here is a composite image of the 3 parasites together:

Thanks again to Dr. Nazia Nagi for donating the C. belli case.

Case of the Week 720

This week's case is generously donated by Dr. Nazia Nagi from Maulana Azad Medical College in New Delhi. The patient is a young, HIV-positive, adult male with diarrhea. The following structures were seen in a wet mount and modified Ziehl-Neelsen stained stool preparations. They measure approximately 35 micrometers long. Identification?

Answer to Case 720

 Answer to the Parasitology Case of the Week 720: Cystoisospora belli oocysts

These oocysts are easy to differentiate from Cyclospora and Cryptosporidium oocysts based on their large size and ovoid shape. Thanks again to Dr. Nazia Nagi for donating this classic case!

Case of the Week 719

This week's case is very timely! The following objects were seen on a modified safranin-stained stool specimen. They measure approximately 8 to 10 micrometers in diameter. Identification?

40x objective:

100x objective:

Answer to Case 719

 Answer to the Parasite of the Week 719: Cyclospora sp. oocysts. 

While Cryptosporidium spp. oocysts have a similar appearance, they are smaller than Cyclospora oocysts, measuring only 4-6 micrometers in diameter. 

Note that Cyclospora oocysts do not stain uniformly with either the modified acid fast or modified safranin methods, although there tends to be fewer unstained oocysts with the latter. The microwave modification of the safranin stain will also improve the staining uniformity (see the CDC procedure HERE).

As Dr. Marc Couturier pointed out on Twitter, there are now three morphologically-identical species of Cyclospora known to cause human infection: C. cayetanensis, C. ashfordi, and C henanensis. Therefore it is best to report this finding out as "Cyclospora species."

Lastly, Idzi discussed in the blog comment sections why this finding is so timely. Every year now in the past decade, the U.S. has seen summer outbreaks of cyclosporiasis linked to imported produce (e.g., cilantro, basil, snap peas, lettuce, raspberries) from Latin America. Infection is transmitted to humans through ingestion of fecally-contaminated food and water. Therefore, infection originates from regions where there is poor sanitation and lack of access to clean water.

 

  

Case of the Week 718

Welcome back to our first case of the month, with a special case from Idzi Potters and the Institute of Tropical Medicine, Antwerp.  The following structures were found in a bronchoalveolar lavage from a middle-aged Belgian patient with asthma who presented with increased shortness of breath. He reports no travel out-of-country and works as an administrator at an insurance company. He recently reported an insect infestation in his home.Video credits are for Monique Vatlet (CHU Ambroise Paré, Mons, Belgium).

Identification?