You can place these mosquito larvae in the Culicinae subfamily due to the presence of respiratory siphons that allow them to hang below the water at an angle and breathe the oxygen above:
This is in contrast to anopheline mosquitoes (Anophelinae subfamily) who do not have a respiratory siphon and instead rest parallel to the surface of the water, breathing through their tail.
The Culicinae subfamily includes the genera Aedes, Culex, and Culiseta. Different species in these genera transmit a number of viruses and parasites, including yellow fever, dengue, West Nile virus, Eastern equine encephalomyelitis, Japanese encephalitis, and agents of lymphatic filariasis. Fortunately, most of these are not found in Minnesota where these larvae were found!
The following case was donated by Drs. Stephanie Slemp, Nicole Hubbard, Morgan McCoy, Ryan Relich, and Bryan Schmitt.
The following liver mass was resected from a 20 year old man. The man had recently immigrated to the U.S. from South America. Below is a cross-section of the lesion. While awaiting the histopathology, what is your differential diagnosis from the gross exam?
Note that you can make out the walls of several daughter cysts, which likely collapsed in vivo or during sectioning.
As some of you mentioned, other less likely options based on this gross appearance would be a non-infectious cystic lesion and an amebic liver abscess. The latter is unlikely given that the concents would be red-brown necrotic material classically referred to as "anchovy paste."
The definitive diagnosis is secured by microscopic examination of fluid obtained from the cyst or tissue sections of the cyst walls. In this case, tissue sections revealed thick laminated layers, consistent with E. granulosus:
Rare refractile hooklets were also seen within the degenerated granular cyst contents (1000x magnification below). No viable appearing protoscoloces were identified, as is sometimes the case in ruptured or degenerated hydatid cysts.
The following case was generously donated by Blaine Mathison. It is a photograph from a slide stained with a fluorescent antibody to a particular parasite. The green fluorescing objects measure approximately 4-6 micrometers in diameter. Diagnosis?
Lee suggested that this is the newly recognized species, Cryptosporidium enterprisium.
Florida Fan rightly points out that, although considered the gold standard test for Cryptosporidium, the DFA may not detect all species that infect humans. Therefore, another test that can be used to confirm the identification of spherical, 4-6 micron diameter objects on wet prep, would be an Acid Fast stain. As the new molecular multiplex panels become commercially available, they also may be used as an initial or confirmatory test.
Answer: Phthirus pubis, a.k.a. crab lice (3 to be exact).
Note their classic 'crab-shaped' claws - used for grasping on to the coarse hairs of the genital region and eyebrows/eyelashes. Also shown here is a classic nit of P. pubis, with the raised operculum that allows it to be differentiated from the flatter operculum of the body/head louse, Pediculus humanus. Here are the 2 nits shown side by side for comparison:
Every week I will post a new Case, along with the answer to the previous case. Please feel free to write in with your answers, comments, and questions. Also check out my image archive website at http://parasitewonders.com. Enjoy!
The Fine Print: Please note that all opinions expressed here are mine and not my employer. Information provided here is for medical education only. It is not intended as and does not substitute for medical advice. I do not accept medical consults from patients.