Case of the Week 752

This week's case was generously donated by Brieanna Ray and Dr. Mike Mitchell. The following object was submitted for identification. It was removed from the skin and subcutis of a teenage girl living in the United States with no recent travel. What is the most likely diagnosis?

 

Answer to Case 752

 Answer to the Parasite Case of the Week 752: Botfly larva, likely Cuterebra species.

Thanks to Michele Calatri, Kate Geralt, Pablo David Jimenez Castro, Christina, and Josué Campos Camacho who wrote in with this answer. Cuterebra infection is not very common in humans but are known to occur occasionally. Unfortunately, we don't have the posterior spiracles to confirm the genus, and we don't have any further history about the patient. The good news is that the larva has been removed, which is curative.

This is how the larvae appear in their natural host:

Creepy Dreadful Wonderful Parasites: Case of the Week 130 (parasitewonders.blogspot.com

Case of the Week 751

 This week's case was generously donated by Dr. Karra Jones. A patient presented with intestinal intussusception, and the following was seen on histopathologic examination of the resected bowel. What is your diagnosis?

10x objective:

20x objective:

Answer to Case 751

 Answer to the Parasite Case of the Week 751: Anisakis species. 

Thanks to all who provided comments on this case! Idzi kicked us off with his comment: "The Y-shaped lateral chords tell me that this is patient has eaten raw (or undercooked) fish! 😉". Florida Fan then elaborated, "The cross sections tell us that this is a nematode. From online publications and Idzi's comment, the very tall musculature and Y-shaped lateral chords favor a diagnosis of anisakiasis."

Here is an annotated image showing some of the key features:

Note the eosinophilic tissue response surrounding the worm. 

Thanks again to Dr. Jones for donating this classic example of anisakiasis in tissue. 

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?

Answer to Case 750

 Answer to the Parasite Case of the Week 750: Bertiella sp. proglottids and egg.

Kudos to everyone who got this right! As noted by Idzi, "At first I thought this would be plant material, but the egg is quite typical for Bertiella sp. showing the typical pyriform apparatus inside. Secondly, in the third histology picture I think I see calcareous corpuscles, typical for and consistent with a cestode structure, together with an eosinophilic acellular tegument. So I'll follow Florida Fan with the diagnosis of Bertiella sp. infection.

Here is the characteristic egg with the pyriform apparatus inside:

Our previous case (565) shows this in greater detail, along with the short and wide proglottids (with a disturbing resemblance to bow tie pasta). 

When looking at the proglottids from cases 565, one can see how sectioning may reveal the 'interesting' histopathologic appearance that we see in this case.

Previous case:

Current case:

Sarah Sapp notes on X/Twitter that the preparation is...rather creative. Ideally, proglottids are sectioned so that we see them in coronal section. This appears to be a sagittal section. However, it can be very challenging to orient such a small object for histopathology sectioning, especially when the the type of material is not known. Fortunately, the acellular tegument and calcareous corpuscles allow for identification of this object as a cestode.

Thanks again to Drs. Sullivan and Nash for donating this interesting case!

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?

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 🐟. 

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, “Diphyllobothrium” cordatum 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 😊.

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. 

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.

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.

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?

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 😊.

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?

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. 

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:

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!
 

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 😉)  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):

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?

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?

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. 

 

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 µm 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?