Wednesday, June 19, 2024

Case of the Week 750

This week's case is an interesting challenge! It was donated by Drs. David Sullivan and Ted Nash. The patient is a young girl from Ethiopia with intermittent GI distress. Her parents said that she had passed several ovoid objects per rectum. One of these objects was submitted for histologic sectioning and revealed the following.

A stool parasite exam also revealed the following. 

Based on these findings, what is your diagnosis?

Wednesday, May 29, 2024

Case of the Week 749

This week's case features photos and videos from my lab, courtesy of Ms. Heather Morris and Felicity Norrie. The following object (which was still moving!) was submitted for identification. No history was provided, unfortunately. What do you think it is? (Be as specific as possible). What additional steps could you take to confirm your presumptive identification?

Tuesday, May 28, 2024

Answer to Case 749

 Answer to the Parasite Case of the Week 749: Adult tapeworm in the family Diphyllobothriidae (Diphyllobothrid), a.k.a., the broad fish tapeworm ๐ŸŸ. 

As astutely noted by Idzi Potters, "The proglottids of this tapeworm are gravid - the brown central points represent large numbers of dark eggs concentrated in a centrally positioned uterus. As the gravid proglottids are craspedote and wider than they are long, this points towards a Diphyllobothriid tapeworm (possibly Dibothriocephalus). An easy way to confirm this is to cut open a proglottid and expel some of the typical eggs. But for exact species determination, molecular tools should be deployed."

We didn't perform molecular testing to determine the exact genus and species, but we did confirm the worm's identity by expelling some of the eggs from the uterus. They looked something like the eggs from this previous case of the week.

Blaine and I described the current status of known Diphyllobothrids to infect humans in our chapter on Parasites of the Gastrointestinal Tract:

"The species implicated in human disease, and their current taxonomic status and broad geographic distributions, are Adenocephalus pacificus (southern South America, southern Asia), Dibothriocephalus latus (Holarctic), D. nihonkaiensis (Asian Pacific, eastern Russia, Pacific Northwest), D. dendriticus (Holarctic), D. dalliae (Alaska and Siberia), D. ursi (North America), Diphyllobothrium stemmacephalum (circumpolar), and D. balaenopterae (circumpolar). Two additional species implicated in human disease, “Diphyllobothriumcordatum and “D.lanceolatum, both circumpolar in distribution, are tentatively placed in Diphyllobothrium but will probably undergo generic transfer in the future (Kuchta et al., 2015; Waeschenbach et al., 2017)." As several of you have pointed out, Diphyllobothrium latum is now Dibothriocephalus latus ๐Ÿ˜Š.

Like most cases that we receive in our lab, we sadly didn't receive the travel history for the patient, and therefore we can't make any guesses as to the identity of this tapeworm based on known distributions. 

Sunday, May 19, 2024

Case of the Week 748

 We are now shifting gears from microfilariae to something completely different. These organisms were found in a small pond in Minnesota. What are they? Be as specific as possible.

Saturday, May 18, 2024

Answer to Case 748

Answer to Parasite Case of the Week 748: Culicine mosquito larvae and pupae.

The mosquito life cycle consists of four stages: egg, larva, pupa, and adult. Larvae and pupae are aquatic, so water source control is an important component of mosquito control programs. The larvae (commonly called wrigglers) feed on microorganisms such as plankton, algae, bacteria, and fungi; some even eat other mosquito larvae! 

Culicine larvae (including Culex and Aedes species) breathe oxygen through a respiratory siphon and may be seen 'hanging' from the surface of the water. Anopheline larvae (Anopheles species), in comparison, do not have siphons. They lie horizontally to the water surface and breathe through respiratory spiracles. 

You can further identify mosquito larvae using keys such as the CDC Pictorial keys for arthropods, reptiles, birds, and mammals of public health significance (page 138).

Mosquito pupae (commonly called tumblers) are also seen in this case. They do not eat and have a rapid tumbling motility which allows them to avoid predators. They breathe through two tubes from the surface of the water. 

If allowed to mature, the adult mosquito will emerge from the pupal case within a few days. Female mosquitoes from most species will seek out a blood meal to support egg production, and are capable of transmitting a variety of viruses and parasites to humans in the process.  Lymphatic filariasis and malaria are important parasitic diseases transmitted by mosquitoes.

Wednesday, May 1, 2024

Case of the Week 747

Welcome back to the very end of our microfilariae block with Idzi Potters and the Institute of Tropical Medicine, Antwerp! We are going to end with a very special and somewhat unusual case. The patient is an elderly man with recent travel to Senegal who had a 10-cm round worm removed from the conjunctiva of his left eye (!). Blood obtained around the same time revealed the following microfilariae measuring >200 micrometers long: 

What is your diagnosis?

Tuesday, April 30, 2024

Answer to Case 747

 Answer: Dirofilaria sp. microfilariae

This is the perfect challenge for the end of our microfilariae series! The history of finding a worm in the eye will usually make us think of Loa loa (indeed, this case was initially misdiagnosed as such), but the location of the patient (Senegal) and the unique features of the microfilariae are important clues to the actual diagnosis. You can read all about this cases HERE. I've seen a number of cases of nematodes removed from the eye - particularly from India - that were misdiagnosed as Loa loa but actually represented Dirofilaria. Adult worms from these parasites can be differentiated by size (Loa loa has a maximum length of ~7 cm, whereas Dirofilaria can be 10+ cm) and features of their cuticle. Case of the Week 513 shows the differences in cuticle nicely.  

Dirofilaria repens rarely releases microfilariae in humans, making this case particularly unique! Idzi and I both noted the interesting nuclear pattern within the microfilariae - being rather swirly with two elongated nuclei at the tip:

Thanks again to Idzi and ITM Antwerp for sharing this amazing series of cases. Next week we will move onto something entirely different ๐Ÿ˜Š.

Monday, April 22, 2024

Case of the Week 746

Welcome back to our microfilariae block from Idzi Potters and the Institute of Tropical Medicine, Antwerp! We are down to the last TWO specimens. This week's case is from a skin specimen - both skin samples AND a subcutaneous nodule (removed from the upper arm). The patient is a young man from Brazil.

Here is the nodule:

And here are the skin scarification specimens (read more about scarification vs. skin snips HERE):

Carazzi stain:

Giemsa stain:

The microfilariae are approximately 300 micrometers in length. What is your diagnosis?

Saturday, April 20, 2024

Answer to Case 746

Answer to the Parasite Case of the Week 746: Onchocerca volvulus microfilariae

This case nicely contrasts with Case 745 which shows the significantly smaller microfilariae of Mansonella perstans. Both are found in skin snips and skin scarification samples. Note that the nuclei do not go to the tail of O. volvulus as they do with M. streptocerca. 

Another great feature of this case is that Idzi included an image of a resected onchocercoma - the subcutaneous nodule containing the adult filariae:

Onchocerciasis, also known as river blindness, is a devastating disease found in parts of Sub-Saharan Africa and Latin America. It is classified as a neglected tropical disease by the World Health Organization. 

Monday, April 15, 2024

Case of the Week 745

We have moved onto microfilariae found in SKIN specimens - what fun! There are only a couple to choose from. Can you tell which one this is? The microfilariae are approximately 200 micrometers long.

Carazzi stain

Giemsa stain:

Sunday, April 14, 2024

Answer to Case 745

 Answer to the Parasite Case of the Week 745: Mansonella streptocerca microfilariae

Florida Fan and Anonymous pointed out the small size and the source of skin as key features for  diagnosing Mansonella streptocerca infection. Idzi also noted on LinkedIn that "A nice little detail is the etiology of the name “streptocerca”! It is derived from “strepto” meaning “twisted chain” and “cerca” meaning “tail”. The row of single round nuclei in its tail do resemble a chain (or necklace) in my opinion. The prefix “strepto” is also used for streptococcus - which indeed also forms “chains”…" What a fun insight!

Here is an image from this case that nicely highlights these features:

Thank you all for sticking with us for this fun series of microfilariae. We have TWO left for you, so stay tuned!

Monday, April 8, 2024

Case of the Week 744

 We are in the home stretch for the microfilariae! Can you believe that we have just a few more to go? (Unless I decide to repeat some ๐Ÿ˜‰)  This week's case shows microfilariae that are approximately 200 micrometers long. The patient is a resident of Brazil and has moderate peripheral eosinophilia. He is otherwise asymptomatic. 

Carazzi stain (Knott's concentration):

Giemsa stain (thick blood film):

Sunday, April 7, 2024

Answer to Case 744

 Answer to the Parasite Case of the Week 744: Mansonella perstans microfilariae.

As described by Florida Fan, "This is a rather small microfilaria, its width is only about half the diameter of the surrounding neutrophils. The Carrazi stain [a hematoxylin-based stain] did not show a sheath either. As such, we can definitely rule out all the sheathed and large microfilaria. We know that we are dealing with Mansonella species. The tail of this Mansonella is not curved , this allows us to eliminate Mansonella streptocerca (strepto = curved, cerca = tail) [and also the source is not tissue]. The tail is also not pointed, this rules out Mansonella ozzardi. We only have one left with a blunt tail: Mansonella perstans which persists." 

This image nicely shows all of these features:

You have all done a great job learning to differentiate the small, unsheathed blood microfilariae (i.e. Mansonella perstans and M. ozzardi) from the larger, sheathed microfilariae. 

Of course, co-infections can occur, and the following is a stunning photograph of M. perstans and Loa loa co-infection. I think we can all appreciated that the Loa loa microfilaria is the top based on its larger size and sheath. 

Thank you for these outstanding cases, Idzi!

Next week we will finish up with the tissue microfilariae. Will you be able to tell them apart?

Monday, April 1, 2024

Parasite Case of the Week 743

Welcome back for more microfilariae from Idzi Potters and the Institute of Tropical Medicine, Antwerp. The following microfilariae were seen in Giemsa-stained thick blood films from a man living on Alor Island, Indonesia. They measure approximately 305-315 micrometers in length. 

What is your identification? What is your primary differential?

Sunday, March 31, 2024

Answer to Case 743

 Answer to the Parasite Case of the Week 743: Brugia timori microfilariae. This was one of the tougher cases, but everyone did a great job narrowing the differential to Brugia. As noted by Florida Fan and Anonymous, we can immediately rule out Mansonella species based on the small size (length and diameter) of the microfilariae. Florida Fan also notes that the sheath is visible, confirming that we are dealing with Loa loa, Wuchereria bancrofti or the Brugia genus. 

He then details his method for coming to an exact diagnosis: "First the column of nuclei is so compact that we can rule out Wuchereria bancrofti, also the nuclei go to the end of the tail. Yet, the two terminal nuclei are distinctly separated from the nuclei column, this rules out any chance of being Loa loa. Now we have the Brugia genus left, but where is the pink sheath pertinent to Brugia malayi when stained with Giemsa stain? As such, we eliminate Brugia malayi. By the elimination process, we’re left with its cousin Brugia timori, the sheath of this one does not stain pink with Giemsa stain. Now let’s check the map of the lesser Sundae island, the Alor island is right North of Timor."

I will also point out that the head space is longer than that of B. malayi and there are a larger number of single-file nuclei going towards the tail. These features are more subtle and can be difficult to appreciate. I've done my best to point out some of them in the image below.

Thank you all for sticking with us on our microfilariae journey. The microfilariae can be very challenging to identify, and are rare in many parts of the world, so our lab staff may not have the opportunity to examine these organisms outside of their EQA/PT schema. 


Monday, March 25, 2024

Case of the Week 742

This week's case features another beautiful example of microfilariae in blood. The patient is from sub-Saharan Africa and presents with chronic swelling of his left leg. The microfilariae measure approximately 270 ยตm in length. 

Carazzi stain (Knott's concentration):

Giemsa Stain (thick blood film)

What is your identification? What time should blood be collected for this examination?

Sunday, March 24, 2024

Answer to Case 742

 Answer to the Parasite Case of the Week 742: Wuchereria bancrofti microfilariae.

I really enjoyed reading the comments on this case. FloridaFan provided this excellent description of his approach to microfilariae identification: "First the width of the worm is about the same as that of the surrounding neutrophils. Second, its length is greater than 200 micrometers. Third, it has a sheath. Now we know we are dealing with Loa loa, Wuchereria, or the Brugia ones, not with any little pesky Brugia. The next consideration is that the column of nuclei is continuous, the terminal nuclei are not separate from the immediate anterior nuclei. This eliminates the possibility of the Brugia malayi and timori, over that these are “far fetched” geographically. We are left with two candidates Loa loa and Wuchereria bancrofti. Though the tail is not so obvious, the Carrazi stain did show that the nuclei column terminates well short from the end of the tail. This rules out Loa loa. The only culprit left is Wuchereria bancrofti.

An anonymous commenter also noted that "Its nuclear column is relatively loose, and individual nuclei can be visualized throughout the column. The sheath is does not stain pink with Giemsa stain (as in Brugia malayi)."

These features can be nicely visualized in the photo of the Carazzi-stained Knott's concentration. Note that the Carazzi stain is a hematoxylin-based stain (rather than conventional Giemsa) that helps to demonstrate the sheath. It is a very useful stain to have!

Thanks again to Idzi Potters and the Institute of Tropical Medicine, Anwerp, for this beautiful case.

Monday, March 18, 2024

Case of the Week 741

Wow, we are already on our 3rd filarial case! The following lovely case from Idzi Potters and the Institute of Tropical Medicine, Antwerp, is another microfilaria found in blood. 

The patient is a middle aged male farmer from Central America who was noted to have mild eosinophilia on routine complete blood count. He is otherwise asymptomatic. The microfilariae measure approximately 175 micrometers in length. What is your identification?

Sunday, March 17, 2024

Answer to Case 741

 Answer to the Parasite Case of the Week 741: Mansonella ozzardi

As many of you noted, we can get to an identification of Mansonella sp. by the small size (length of just 175 micrometers, and the width less than the surrounding white blood cells). There is also no visible sheath, which is supportive of the diagnosis. 

So the next question is - which Mansonella is present?? As FloridaFan mentioned, the tip of the tail is pointed rather than blunt, which leads us away from M. perstans. Also, the source is not skin snips, so M. streptocerca is unlikely. That leaves M. ozzardi by default. 

To confirm this, we would look at the tail to see if the nuclei go to the tip (M. perstans) or not (M. ozzardi). It's a bit hard to tell in this case, but if you look closely, you can see that the nuclei DON'T go to the tip of the tail. So - Mansonella ozzardi, it is!

Congratulations to those of you who were able to get to Mansonella species. The microfilariae can be hard to identify, so this is definitely advanced  parasitology!

Monday, March 11, 2024

Case of the Week 740

Welcome to our next filarial case by Idzi Potters and the Institute of Tropical Medicine, Antwerp. This week features the following lovely microfilariae seen in a Giemsa-stained thick blood film. They measure approximately 220 micrometers in length. Identification?

Sunday, March 10, 2024

Answer to Case 740

Answer to the Parasite Case of the Week 741: Brugia malayi 

Thanks to everyone who wrote in. This is one of my favorite microfilariae! 

This case had 2 classic features that facilitated the identification: the pink sheath and separation of the 2 terminal nuclei in the tail (see arrows below). 

As I noted in the case last week, the sheath isn't always seen. Therefore, the larger length and tail nuclei configuration can allow for the identification, even when the sheath is absent. 

Sunday, March 3, 2024

It's Finally Here - Filariasis Month with Idzi Potters! Case of the Week 739

Dear Readers,

Welcome to Filariasis Month! We will actually have TWO months of filariae for you as there are so many to cover and so many beautiful cases by Idzi and the Institute of Tropical Medicine, Antwerp.

Idzi and I thought that we should start out with an 'easy' one. The following objects were seen on a blood smear from a patient living in Gabon. They are approximately 250 micrometers long. What is your identification? Bonus question: what additional laboratory test is important for guiding treatment?

Giemsa stained blood films:

Carazzi stain, Knott's concentration: