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?