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.