Creepy Dreadful Wonderful Parasites

Case of the Week 194

2012-02-06T09:48:00.005-05:00

A corneal biopsy was obtained from a man with corneal opacities and painful erosions. He had not been able to wear his contact lenses for over 1 month due to the pain. (CLICK ON IMAGES TO ENLARGE)

H&E, 40 x original magnification

H&E, 100x original magnification

H&E, 400x original magnification

The corneal biopsy was also cultured in a peptone-
yeast extract-glucose broth and the following were identified.

Diagnosis?

Case of the Week 193

2012-01-29T15:18:00.004-05:00

The week's case is a tough one!

The following were found in the stool of animal handler with exposure to primates. The objects shown measure approximately 40 microns in diameter. Identification? (CLICK ON IMAGES TO ENLARGE)

(Unstained, 400x original magnification)

Answer to Case 193

2012-01-28T11:55:00.000-05:00

Answer: Bertiella sp. eggs

Great job everyone! I thought this would be a tough one, but received lots of correct answers. Bertiella is a genus of cestodes (tapeworms) that typically infect non-human primates, although humans are also occasionally infected.

The diagnosis can be made from the presence of the classic pyriform apparatus, an inner membrane with projections around a 6-hooked embryo.

Case of the Week 192

2012-01-22T12:28:00.005-05:00

The following hematoxylin and eosin (H&E) stained sections of brain are from a 1-year old child with fatal meningoencephalitis. The child was otherwise healthy and had not traveled outside of the U.S. (CLICK ON IMAGES TO ENLARGE)

Identification of this devastating infection?

20 x original magnification

100 x original magnification

400 x original magnification

400 x original magnification

400 x original magnification

400 x original magnification

Answer to Case 192

2012-01-21T15:03:00.002-05:00

Answer: Baylisascaris procyonis, the raccoon intestinal roundworm

Eggs of this nematode get into the environment and may be accidentally ingested by humans (typically young children) resulting in visceral larva migrans (VLM) as shown in this case. The larvae hatch from the ingested eggs and enter the blood stream to migrate readily throughout the body, with a predilection for the brain and spinal cord.

The diagnosis can be made by serology (available only at specialized centers) in association with a suggestive clinical presentation or through finding characteristic larvae in tissues. A peripheral eosinophilia and eosinophilic response in tissue sections is common.

The larvae are relatively large (50-60 microns in diameter) and have lateral alae (arrows below), and excretory columns (internal and adjacent to the alae). They also have multinucleated intestinal cells (not shown well here)

Not the presence of eosinophils and associated necrosis.

The differential diagnosis includes VLM due to Toxocara species which also have lateral alae and excretory columns, although these larvae are smaller in diameter (15-20 microns in diameter).

Case of the Week 191

2012-01-15T12:38:00.003-05:00

The following arthropods were found on a 50-year old man and were submitted for identification to the clinical parasitology laboratory. No further history was given. Identification?
Anyone have any idea what the 2 arthropods on the right are doing?

Answer to Case 191

2012-01-14T12:12:00.000-05:00

Answer: Pediculus humanus, body or head lice.

It is not possible to tell body lice and head lice apart morphologically, although as L.R. says, head lice are generally smaller than body lice. Furthermore, as Vanessa CH points out, body lice are hardier than head lice and are much more likely to remain alive after being separated for more than 24 hours from their host. These lice were definitely separated for more than 24 hours (probably more like 48-36 hours) and therefore are more likely to be body lice.

Now as for what the 2 on the right are doing, that's an interest question! Thank you for the guesses. Despite some interesting speculation (fighting? mating? feeding on each other?) I think that B.A.M. got it right by saying that they probably are just stuck together and are trying to get loose. Recall that lice are used to attaching to hairs and probably just got tangled up in this artificial environment.

Case of the Week 190

2012-01-02T13:10:00.003-05:00

The following was seen on skin biopsy within a hair follicle. How would you sign this case out? (CLICK ON IMAGE TO ENLARGE)

(Hematoxylin and Eosin, x1000)

Many thanks to Dr. Holkmann Olsen for donating this great case!

Answer to Case 190

2012-01-01T12:25:00.000-05:00

Answer: Demodex mite

These ubiquitous ectoparasites are found on most individuals in hair follicles (Demodex folliculorum) and sebaceous glands (D. brevis) and are considered to be normal skin flora. As such, they are commonly seen by dermatopathologists in skin biopsies.

I particularly like this photo because you can make out the appendages and mouthparts of this mite:

The intact organism can be seen on my previous CASE 58.

Case of the Week 189

2011-12-23T13:07:00.004-05:00

Dear Readership of Creepy Dreadful Wonderful Parasites,
May you have a wonderful holiday season with friends and family! Thank you for your continued support and comments.

Here is the 'case' for this week - a simple identification:

Answer to Case 189

2011-12-22T13:05:00.000-05:00

Answer: Phthirus pubis, a.k.a the crab louse, or as my readers said:
"the Yuletide pubic louse", "Pthirus barbae viridis: green bearded louse", "Pine-scented pubic louse", and "Louse found in Bad Santa's trousers"

Happy 2012!
Parasite gal

Case of the Week 188

2011-12-12T11:18:00.005-05:00

The following objects were found in the clothing of an 18 month old child. They measure approximately 3mm in length.

By manipulating them with a wooden applicator stick, the following was expressed out of these objects (CLICK ON IMAGES TO ENLARGE):

(100x original magnification)

(400x original magnification)

Thanks to Emily in my lab for these beautiful photos!

Answer to Case 188

2011-12-11T13:06:00.001-05:00

Answer: Proglottids and egg packets of Dipylidium caninum, the double-pored dog tape worm.

This small tape worm is acquired through ingestion of infected Ctenocephalides spp. fleas, prompting one of my readers to ask if the child got infected by ingesting the specimen from the previous case of the week! Another reader, MicrobeMan, had a similar inquiry "Was it merely coincidental that you posted Ctenocephalides last week? Regardless, it's very appropriate, seeing as that both adult C. canis and C. felis can carry the cysticercoid form of D. caninum to people."

To answer these questions - it was actually a complete coincidence that we happened to have a Ctenocephalides flea and D. caninum proglottids submitted to my lab in such a short time period of time, and I wasn't really considering the coincidence when posting these 2 cases. So good pick up for those of you who noticed!

I like this case because it has several classic features which allow for definitive identification. The small "rice grain" sized and shaped proglottids are classic, and the egg packets that were expressed from the proglottids are diagnostic, despite being immature. Note that the material surrounding the eggs is very granular, which is something I've seen frequently when eggs are prematurely expressed from the proglottids, rather than being released naturally. So don't let that deter you from making a diagnosis if the other characteristic features such as egg packets and hooklets inside of egg-like structures are present

Case of the Week 187

2011-12-05T15:51:00.004-05:00

Since I am at the ASTMH annual meeting at the moment, I will keep this case short and sweet:

The following was submitted for identification to the clinical parasitology laboratory. It was difficult to get it to hold still, since it was jumping between lids of a closed petri dish. It measures approximately 2 mm in length. (CLICK ON BOTTOM RIGHT OF MOVIE TO ENLARGE)

Identification?

Answer to Case 187

2011-12-04T09:05:00.000-05:00

Answer: Flea

Everyone who wrote in got this correct, despite the fact that the flea wasn't really staying still. We eventually took Blaine's advice and killed it (by placing it in ethanol). We then mounted it on a slide and got a much clearer picture of the flea, showing the genal and pronotal combs that are characteristic for Ctenocephalides species:

The dog and cat fleas (Ctenocephalides canis and C. felis respectively) can be further differentiated based on the shape of their head and "tooth" length of the genal comb.

Case of the Week 186

2011-11-28T15:28:00.003-05:00

The following was an incidental finding on pap smear. Identification? (CLICK ON IMAGES TO ENLARGE)

Pap stain, 400x original magnification

Pap stain, 1000x original magnification

Answer to Case 186

2011-11-27T15:45:00.000-05:00

Answer: Not a human parasite

I apologize to my readers that I don't know exactly WHAT this is. A consensus of knowledgeable parasitologists thought that this was not a human parasite, and possibly an artifact or fungal element. Meanwhile, my mycology colleagues did NOT think that this was a fungal element. Responses from the viewers also included Turbatrix aceti (vinegar eel) and hair.

The good news for this patient is that this is not a human pathogen and simply an incidental finding.

Thank you all for writing in with your interesting ideas!

Case of the Week 185

2011-11-18T22:06:00.003-05:00

The following was worm was seen emerging from a cricket:

Here are photos of the worm itself:

Identification?
Many thanks to Jason Pelletier who took the first photograph and Heidi Pierce who shared this cool case with me!

Answer to Case 185

2011-11-17T14:24:00.000-05:00

Answer: Horsehair worm, also known as the Gordian worm, in the group Nematomorpha.

Over 300 species in this group have been described. They are parasitic in their larval stage for various insects and crustaceans, and emerge from the host (as seen in this case) as free-living adults. The adults are typically found near or in water and are known to twist themselves into complex knots (resembling Gordian knots).

These worms superficially resemble nematodes and they are not uncommonly submitted to our lab for identification; however, they are not parasites of humans or other mammals.

Case of the Week 184

2011-11-14T09:43:00.005-05:00

The following images are from a Papanicolaou-stained bronchoalveolar lavage obtained from a 70 year old man with increasing respiratory distress. His medical history is significant for hemodialysis-dependent end-stage renal disease and vasculitis (treated with cytoxan).

Diagnosis? (CLICK ON IMAGES TO ENLARGE)
Any thoughts on what the last image represents?

x400 original magnification

x600 original magnification

Many thanks to Dr. Steven Goodman for donating this case!

Answer to Case 184

2011-11-13T11:18:00.003-05:00

Answer: Probable Strongyloides stercoralis larvae

Higher magnification would be needed to confirm the characteristic features of S. stercoralis filariform larvae (the stage that migrates to the lung during autoinfection). However, the overall appearance and clinical presentation is most consistent with strongyloidiasis hyperinfection.

To answer my question about the last photo - this does not represent a parasite, but might represent a fiber with proteinaceous debris. I was curious to see what others had to say, but no one commented.

Thanks to everyone for writing in!

Case of the Week 183

2011-11-07T09:35:00.003-05:00

The following were seen on Giemsa-stained peripheral blood films. The objects shown measure approximately 220 microns in length. Identification? (CLICK ON IMAGES TO ENLARGE)

x1000 original magnification

Answer to Case 183

2011-11-06T09:33:00.000-05:00

Answer: microfilaria of Brugia malayi

The diagnostic features of this case include the brightly staining pink sheath with routine Giemsa staining, relatively small size, and both terminal and subterminal nuclei (see below; click on image to enlarge).

Case of the Week 182

2011-10-31T08:31:00.002-05:00

For this week's case, I thought you might enjoy seeing a 'potpourri of parasites' from a stool concentrate wet preparation.

Which eggs are shown here?

Answer to Case 182

2011-10-30T09:31:00.001-05:00

Answer: Ova of Ascaris lumbricoides (upper center/right), Trichuris trichiura (left), and Taenia species (bottom, center/right). The eggs of Taenia solium and T. saginata cannot be differentiated by morphology, so Taenia species is an appropriate result.

Thank you for all of the responses on this case. They were all correct!

Case of the Week 181

2011-10-24T16:27:00.004-05:00

The following were incidental findings on seen on intestinal biopsies. Diagnosis? (CLICK ON IMAGES TO ENLARGE)
x20 original magnification

x40 original magnification

x100 original magnification

x200 original magnification

x400 original magnification

Answer to Case 181

2011-10-23T08:02:00.002-05:00

Answer: Whipworm (Trichuris trichiura)

Shown in this case are sections of a round worm in the colonic mucosa. The presence of cross-sections within the mucosa raise the possibility of several nematodes, including Strongyloides stercoralis, Capillaria philippinensis, and Trichuris trichiura, with the latter being supported by the presence of free-hanging sections of worm in the intestinal lumen (recall that the smaller head of Trichuris embeds itself into the colonic mucosa (arrows below), leaving the larger body hanging free in the lumen.) (CLICK ON IMAGE TO ENLARGE)

However, the defining feature of this case is the characteristic morphology of the eggs within the uterus demonstrating smooth walls and bipolar plugs.

Other features shown in this case are a nice example of a stichocyte with large nucleus and nucleolus and classic polymyarian musculature.

Thanks to everyone who wrote in for this case!

Case of the Week 180

2011-10-17T14:35:00.005-05:00

The below photographs are of H&E stained sections from an orchiectomy specimen. The patient is a Californian man with a complaint of "testicular mass." No further history is available. The questions that the referring pathologist has for you are:

1. Is this a worm or some type of artifact?
2. If it is a worm, could it be Strongyloides stercoralis or Toxocara spp.?

What do you think?

(x40 original magnification)

(x100 original magnification)

(x400 original magnification)

(x400 original magnification)

(x400 original magnification)

(x400 original magnification)

(x400 original magnification)

(x1000 original magnification)

(x1000 original magnification)

Answer to Case 180

2011-10-16T15:16:00.003-05:00

Answer: Adult filarial worm, female
Differential diagnosis includes Brugia and Wuchereria species, including zoonotic Brugia.

Additional history was received after the case was reviewed, which included a travel history to Central and South America. Therefore, W. bancrofti is a strong consideration, and serologic testing would be advised. Peripheral blood films could also be identified for microfilariae, although this particular worm does not appear to be gravid and is also somewhat degenerated, indicating that it is no longer viable. For W. bancrofti, blood for microfilariae examination should be obtained between 10 pm and 2 am when the microfilariae are released into the bloodstream.

Anonymous points out "In Pathoparasitology , the classic atlas by Michael Kenney, he says "except for W.bancrofti and aberrant eggs of schistosomes,no parasites are usually found in the testes". Thought this might help."

I agree - this is very helpful for formulating a differential diagnosis. The diagnosis microscopic features include:
1. coiled appearance on cross section with surrounding fibrosis
2. size/diameter
3. suggestion of a double uterus, consistent with an adult female filarial worm

Many times, microfilariae can also be seen within the uterus, although they were not present in this case.

I would like to thanks the excellent DPDx team who helped confirm my initial diagnosis and expand on the differential diagnosis. They have a very useful web site at http://www.dpd.cdc.gov/DPDx/

Case of the Week 179

2011-10-10T12:34:00.004-05:00

This week's case is somewhat challenging.

The following objects were seen on a peripheral blood film from a patient who recently immigrated from Africa. They measure 230-240 micrometers in length. No further history is available.
Identification? (CLICK ON IMAGES TO ENLARGE)

original magnification x 400

Original magnification x 1000

Answer to Case 179

2011-10-09T14:33:00.000-05:00

Answer: Loa loa

The key features shown in this case are the presence of a non-staining sheath (below), correct size range, and nuclei that extend to the tip of the tail.

Thanks to everyone who wrote in!

Case of the Week 178

2011-10-03T10:05:00.001-05:00

The following is a concentrated stool specimen stained with a modified acid fast stain. The patient had reported to his physician after a week-long bout of diarrhea. He had recently attended an event in which he and other guests had eaten fresh salad. Several of the other guests are also sick.

Objects shown measure 10 micrometers in diameter.
Identification?

Answer to Case 178

2011-10-02T12:17:00.002-05:00

Answer: Cyclospora cayetanesis oocysts

The size, history, and strong acid fast positivity are consistent with a diagnosis of cyclosporiasis. However, one viewer points out that the coccidians are inherently difficult to capture in a single photograph since the cellular features may not be well defined, and that fungal artifacts may still be in the differential. Therefore, I've also included the following wet-prep image showing an oocyst from this same case (CLICK ON IMAGE TO ENLARGE). From this image, the round shape and internal structures can be appreciated.

When examining modified acid fast stains, it is also important to note that the size of the stained objects is also important, since Cryptosporidium spp. oocysts have a very similar appearance, but are smaller (4-6 microns in diameter).

Case of the Week 177

2011-09-26T13:26:00.007-05:00

The following images are sections of a formalin-fixed paraffin-embedded gastric biopsy. No further history is available.
(CLICK ON IMAGES TO ENLARGE)

H&E 40 times original magnification

H&E 100 times original magnification

H&E 400 times original magnification

H&E 400 times original magnification

H&E 40 times original magnification

H&E 100 times original magnification

H&E, 400 times original magnification

Trichrome stain, 40 times original magnification

Trichrome stain, 200 times original magnification

Trichrome stain, 400 times original magnification

How would you sign this case out?

Answer to Case 177

2011-09-25T08:52:00.002-05:00

Answer: Worm causing anisakiasis; either Pseudoterranova decipiens or Contracaecum spp.

This diagnosis is based on:
1. The size of the worm (note the size compared to the glands in the gastric mucosa

2. The characteristic location (embedded in gastric or intestinal mucosa
3. The presence of Y-shaped lateral cords on a broad base (see image below). The broad base of the lateral cords excludes Anisakis spp., although this is in the initial differential diagnosis.

For images of what this worm looks like in fish flesh, take a look at the previous weeks' cases:
Frozen fish: Case 140
Cooked fish: Case 16

Also, here is a case where the worm was removed from the fish. This is what might get submitted to the microbiology lab for identification:
Case 157

Case of the Week 176

2011-09-19T10:18:00.004-05:00

The following objects were seen in cross-section in an appendix from a 14 year old girl with abdominal pain. Identification? (CLICK ON IMAGES TO ENLARGE)

(H&E, 40x original magnification)

(H&E, 100x original magnification)

(H&E, 200x original magnification)

(H&E, 40x original magnification)

(H&E, 100x original magnification)

(H&E, 200x original magnification)

Answer to Case 176

2011-09-18T12:21:00.001-05:00

Answer: Enterobius vermicularis (pinworm) cross-sections

This is a classic histologic appearance of E. vermicularis in cross-section. The diagnosis is made by identification of the lateral alae (singular=ala, from the Latin meaning "wing"). Indeed, you can see why these longitudinal ridges on either side of this roundworm's body have been likened to wings.

Other features include well-developed platymyarian-type musculature (Body musculature consisting of cells not protruding individually into Pseudocoelom), thick muscled esophagus, and thick nucleated intestine; features seen in many intestinal nematodes (round worms).

Some of these features are shown in Case of the Week 88

Thanks to everyone for writing in!

Case of the Week 175

2011-09-11T16:32:00.002-05:00

The following objects were seen in unstained fluid aspirated from a liver cyst and sent to microbiology. The beautiful images were taken by Heather A. Identification?

Answer to Case 175

2011-09-10T10:07:00.001-05:00

Answer: Echinococcus spp. protoscoleces

Shown here are multiple protoscoleces (larval tapeworms) of Echinococcus spp. The most common species to infect humans is Echinococcus granulosus, but E. multilocularis and less commonly, other species, may also cause human infection. Note that one larva has an everted protoscolex (below).

Based on the appearance of the everted protoscolex (above), you can see how this larval form will mature into the adult Echinococcus worm in the definitive canid host:

Adult Echinococcus granulosus worm

Higher magnification reveals the hooklets of the scolex, used to attach to the intestinal tract of the definitive host.

In echinococcosis, humans and herbivores are the intermediate host and are infected with the larval forms, whereas members of the Canidae such as wolves and domestic dogs are the definitive hosts and are infected with adult tapeworms.

Case of the Week 174

2011-08-29T09:44:00.002-05:00

The following were found in a vacant ski lodge which had not been occupied in several months. Identification? (CLICK ON IMAGE TO ENLARGE)

Answer to Case 174

2011-08-28T16:22:00.003-05:00

Answer: Bat bugs

Congratulations to all of my readers who got this right! I thought this might be a tricky case since bat bugs share many morphologic similarities with the ever-popular bed bugs. But most of you picked up on the subtle differences between the 2 arthropods.

As Blaine points out, "Given the length of the pronotal setae, they are bat bugs, Cimex sp. Cannot differentiate further without more geographic location (C. adjunctus in the east; C. pilosellus in the west)." Here are some web sites that highlight the important differences between these 2 bugs: BUGGUIDE and BADBEDBUGS

Case of the Week 173

2011-08-22T11:42:00.002-05:00

The following sections are from a skin biopsy of an itchy flank rash. Identification?

(H&E, 40x original magnification)

H&E, 400x original magnification

H&E, 400x original magnification

Answer to Case 173

2011-08-21T07:59:00.002-05:00

Answer: Scabies caused by the microscopic mite Sarcoptes scabiei.

This mite burrows into the superficial layers of the epidermis and deposits eggs and fecal pellets (scybala). The diagnostic features of this case are:
1. The location within the epidermis
2. Size of mite and presence of toothlike spines on its thin exoskeleton (see below).
3. Adult and egg forms (below)

The best way to diagnose scapies is via skin scrapings (rather than biopsy). Skin scrapings can be obtained through which will produce mites with the best morphology. To obtain skin scrapings, mineral oil can be applied to the possible skin tracts followed by vigorous scraping with a sterile scalpel blade or glass slide. The material obtained should be placed on glass slides and examined for the presence of mites, larvae, and fecal pellets.

Anonymous and Neuronurse mentioned that this parasite resembles Gnathostoma spp, which also have spines on their external surface. However, Gnathostoma are uncommon in the epidermis (usually seen in subcutaneous tissue and viscera) and the spines are much smaller than those seen on the scabies mite. Gnathostoma also has different internal structures including large lateral cords. Good thought!

Case of the Week 172

2011-08-15T08:43:00.002-05:00

A 35 year old immigrant from Sudan presents with fever. Images from a Giemsa-stained thin blood film are shown. Diagnosis? (CLICK ON IMAGES TO ENLARGE)

Answer to Case 172

2011-08-14T08:40:00.000-05:00

Answer: No blood parasites present; Howell-Jolly bodies, platelets, and a nucleated RBC present).

Great job everyone! Several respondents rightly raise the question of asplenia, given the Howell-Jolly bodies (nuclear remnants), nucleated RBCs, and RBC polymorphism with echinocytes (wrinkled RBCs with multiple spicules radiating from its circumference, resembling a sea urchin). These are common findings in a patient that does not have a functional spleen, since the spleen is responsible for removing RBCs that have not fully extruded their nucleus prior to entering the peripheral blood. We found out that this patient does NOT have a spleen which would explain the findings on this film.

This is a great example of a 'complicated' peripheral blood smear, in which
the exclusion of malaria or babesiosis can be quite difficult. The presence of Howell-Jolly does not exclude the presence of a blood parasite, so it is still important to examine these smears carefully. Anonymous raises the good point that PCR for malaria and babesiosis may be helpful when either of these infections are suspected. In this case, there was no evidence of blood parasites seen on thick and thin films, so we did not pursue PCR.

Other types of RBC "inclusions" include pappenheimer bodies (iron granules) and stain precipitate.

Finally, Anonymous mentions that the "tiny intraerythrocytic inclusions may be bacterial, like Bartonella. B. bacilliformis is the only one that's supposed to show up on peripheral smear, but no epidemiologic history to fit." This is a good thought, although as mentioned, it does not fit clinically. I would also expect the inclusions of B. bacilliformis to be more numerous and smaller than what is shown here.

Case of the Week 171

2011-08-07T11:00:00.003-05:00

The following were seen on a peripheral blood thick film from a recent African immigrant. Identification? (CLICK ON IMAGES TO ENLARGE)

Answer to Case 171

2011-08-06T21:25:00.001-05:00

Answer: microfilaria of Wuchereria bancrofti

The first step in identifying this microfilaria is to recognize the presence of a poorly-staining sheath. The sheath is nicely demonstrated in images 3 and 4 of this case. This narrows your diagnosis down to one of the 3 following sheathed microfilariae:
1. Wuchereria bancrofti
2. Brugia spp. (sheath typically stains deep pink on Giemsa)
3. Loa loa

The next step is to look at the tail nuclei to differentiate the 3 microfilariae. Note in the image below that the nuclei do not extend to the tip of the tail. Therefore, this is consistent with W. bancrofti. (CLICK ON IMAGE TO ENLARGE)

I did not give you the size of the organism, but that is also a helpful differentiating feature.

Thank you everyone for your responses!

Case of the week 170

2011-08-02T11:27:00.003-05:00

Multiple arthropods were submitted for identification to the Clinical Parasitology laboratory. No history was provided. A representative arthropod is shown below. How would you sign this case out?

Answer to Case 170

2011-08-01T08:08:00.000-05:00

Answer: Not a human parasite; insect larva

The presence of multiple 'hairs' or spines on this larva is not consistent with fly larvae that cause human myiasis.

Case of the Week 169

2011-07-25T12:10:00.006-05:00

I have a challenging case for you this week!
During routine colonoscopy for colon cancer screening, endoscopists noted the following worm-like objects in the cecum:

One of these objects was removed and sent to surgical pathology where it was fixed in formalin, paraffin embedded, and sectioned for staining with hematoxylin and eosin. Unfortunately, no intact objects were sent to microbiology for identification. The portion of the object shown measures 2.5 mm. (CLICK ON IMAGES TO ENLARGE - YOU'LL WANT TO SEE THE DETAILS ON THIS ONE!)

40x original magnification

100x original magnification

200x original magnification

1000x original magnification

Answer to Case 169

2011-07-24T11:15:00.001-05:00

Answer: Hymenolepis nana tapeworm

Shown here are classic proglottids and eggs (in utero) of Hymenolepis spp. The small size and probable presence of polar filaments is consistent with Hymenolepis nana (see images below).

As nicely stated by L.R., "adults only get to around 30-45 mm. The worm has an interesting life cycle flexibility - it can be transmitted via a direct transmission route from person to person as well as being transmitted by fleas which can serve as intermediate hosts/vectors."

As MicrobeMan correctly mentions, the eggs are somewhat distorted due to tissue fixation, processing and sectioning, and thus do not appear as spherical as would be expected in a stool preparation. They are also in utero, and some may be immature. An image of how the eggs typically look in stool can be seen at a previous post HERE.

Case of the Week 168

2011-07-11T07:19:00.002-05:00

The following is a Giemsa-stained peripheral blood thin film from a 5 year old girl with fever and a swollen eye. She has recently moved with her family from Argentina.
Diagnosis?

Answer to Case 168

2011-07-10T12:02:00.002-05:00

Answer: Trypanosoma cruzi trypomastigotes (flagellated forms)

Thanks to everyone who wrote in with the answer to this case - you were all correct!

EST2010points out that this organism "is transmitted through excrement from the Reduviid or 'kissing bug' found throughout S. America. Key differentiating features from African trypanosomes (T. brucei rhodesiense and T. brucei gambiense) include the very enlarged posterior kinetoplast, the curved 'C' shape and geography." Neuro_Nurse further notes that "the swollen eye is known as Romaña sign." So you all picked up on the clues that I gave you for this case.

Here is an image comparing the size of the kinetoplast between T. cruzi and T. brucei (the most important differentiating feature):

Although I've shown you the classic "C" shape of T. cruzi, note that this is not a reliable feature for identification, since T. brucei subspecies can also take on a "C" shape.

Case of the Week 167

2011-07-04T19:33:00.002-05:00

We will resume next week with the new Parasitology Case of the Week.

Answer to Case 167

2011-07-03T07:17:00.000-05:00

Answer: Giardia intestinalis (a.k.a. G. lamblia, G. duodenalis)
OR
As Tom writes "This looks like the rarely seen Giardia patrioticus, which is associated with outbursts of sometimes sulfrous emmisions, of which there is evidence in the background of the slide in this image."

Great Answer!

Case of the Week 166

2011-06-27T11:26:00.003-05:00

The following small intestinal biopsy was taken from an elderly woman with cough, abdominal pain, and diarrhea. She reports no travel history outside of the United States, and has lived in the southeastern U.S. most of her life. Diagnosis?

(CLICK ON IMAGES TO ENLARGE)
Hematoxylin and Eosin, 40 times original magnification

Hematoxylin and Eosin, 100 times original magnification

Hematoxylin and Eosin, 200 times original magnification

Hematoxylin and Eosin, 400 times original magnification

Answer to Case 166

2011-06-26T19:20:00.000-05:00

Answer: Strongyloides stercoralis larvae. This is a potentially serious infection, and can result in hyperinfection and death in immunocompromised hosts. It is endemic in regions of the world where human feces contaminates the soil, including some parts of the Southeastern United States where sanitation and waste treatment is inadquate.

Infection is acquired when infectious L3 larvae in soil penetrate intact human skin and enter the circulatory system to eventually reach the intestine.

Refer to the CDC DPDx web site for more information on the complicated life cycle of Strongyloides stercoralis.

Case of the Week 165

2011-06-20T11:20:00.005-05:00

I have a somewhat different case for all of your this week:

The following were seen on a Wright-Giemsa stained peripheral blood thin film from a 30 year old renal-transplant recipient with recurrent fevers. No travel history is available. (CLICK ON IMAGES TO ENLARGE)

Diagnosis?

Answer to Case 165

2011-06-19T10:02:00.001-05:00

Answer: Morulae (bacterial clusters) of Anaplasma phagocytophilum within neutrophils. As noted by Anonymous, the morulae of E. ewingii are also found within neutrophils and can look identical to Anaplasma morulae; thus the diagnosis should be confirmed by another method. In this case, real-time PCR confirmed the diagnosis of Anaplasma phagocytophilum. Serology can also be used, although there is cross-reactivity between Ehrlichia and Anaplasma and the titers for antibodies to both organisms should be examined to see which is higher (thus indicating the more likely cause of infection).

I decided to show this case, even though it isn't a parasite, since intra-leukocytic morulae can be seen on the same peripheral blood films that are made to look for malaria parasites, trypanosomes, and microfilariae. It is also possible to see (rarely) Borrelia spirochetes of relapsing fever. Therefore, it's important to look at all of the cells (and between them!) when examining a peripheral blood film - you never know what you'll find.

A word of caution - not all blood film preparations are suitable for visualizing morulae inside of leukocytes.The Giemsa-stained preparations in my laboratory have been optimized for detection of intra-erythrocytic parasites; they do not demonstrate leukocytes well. The morulae of this case were actually seen by my hematology colleagues on their Wright-Giemsa stained films. I examined blood from the same patient (same collection) by our Giemsa method and was unable to find any morulae.

Case of the Week 164

2011-06-13T08:43:00.004-05:00

The following was seen on a drop of unstained peripheral blood from a patient who traveled to Cameroon and Spain.

Here are some of these objects on Giemsa-stained concentrated blood (CLICK ON IMAGES TO ENLARGE). They measure approximately 240 - 300 micrometers in length.

Identification?

Answer to Case 164

2011-06-12T09:58:00.002-05:00

Answer: Loa loa microfilariae

The key features used to identify this case were:
1. Presence of a sheath (unstained, see below)
2. Internal nuclei that extend to the tip of the tail
3. Size in expected range for Loa loa.

In the image below, an empty-appearing space around the entire worm, as well as at the end of the tail (arrows) represents the unstained sheath.

As L. R. mentioned, "This would have been picked up in Cameroon not Spain I imagine as Loa Loa is the tropical African eye worm, contracted from a bite by the vector Chrysops spp. (mango or deer flies)."

Just a note: Most of the symptoms due to this worm are due to the migration of the adult, which brings it throughout the body, and sometimes across the bridge of the nose or surface of the eye (hence the name 'eye worm'). Although this can be very distressing to the patient (!), it does not typically harm the eye or cause any permanent change to the patient's vision. Loa loa should NOT be confused with Onchocerca volvulus which causes "African River Blindness." In the case of O. volvulus infection, ocular scarring and loss of vision is due to migration of the microfilariae (not the adults) through the eye, resulting in inflammation.

Loa loa also does not cause elephantiasis.

Thanks to everyone for writing in!

Case of the Week 163

2011-06-02T14:51:00.007-05:00

The patient is a 40 year old professor who had recently taken a trip to Brazil with 15 of his students. During his trip, he and his students took oral malaria prophylaxis, used an insecticide treated bednet while sleeping, and applied DEET to exposed skin during the day. However, one of the 15 students came down with "malaria" in March. The professor then presented with night sweats (but no fever) and the astute physician ordered a peripheral blood exam for parasites. The following are representative images from the blood films:

Identification?

Answer to Case 163

2011-06-01T13:02:00.001-05:00

Answer: Plasmodium vivax

Everyone who wrote in recognized these parasites correctly. As mentioned by Kanoot, there are multiple amoeboid trophozoites of P. vivax shown and a single gametocyte in image #2. Neuro_Nurse correctly mentions that failure to comply fully with malaria prophylaxis is one of the most common reasons for malaria in travelers. Although we don't know for sure, it is likely that this patient did not strictly adhere to the prescribed regimen.

After recognizing that a malaria parasite is present, it is then important to speciate the organisms and provide an estimation of percent parasitemia.
I use the following approach to determine the infecting species:

First, I look at the size of the infected red blood cell, in comparison to the uninfected neighboring cells. If the infected cells are consistently enlarged, then I narrow my identification down to either P. vivax or P. ovale. The presence of stippling (a.k.a. Schuffner's dots) as seen here helps to confirm this differential. I then look for characteristic features of the 2 species, such as amoeboid forms of P. vivax or a predominance of ovale-shaped infected red blood cells with fimbriated (jagged) edges that are associated with P. ovale infection. In this case, the enlarged amoeboid forms that fill most of the cytoplasm, and the irregular shaped infected red blood cells that seem to hug the contours of the neighboring cells allow for the diagnosis of P. vivax infection.

Back to our Patient:
Neuro_Nurse correctly states that the treating clinician should consider radical treatment with primaquine after ruling out G6PD deficiency in this patient. Primaquine is typically given in combination with other antimalarial treatment, since it has the most effect on the hypnozoite stages that remain dormant in the liver. This will prevent subsequent relapse due to activation of the hypnozoite forms. It is important to check for the inherited condition, G6PD (glucose-6-phosphate dehydrogenase) deficiency, before giving the patient primaquine, since it can lead to a serious, and even fatal, hemolytic anemia.

Case of the Week 162

2011-05-23T11:56:00.003-05:00

The following objects were identified in a concentrated fecal preparation from a 5 year old Kenyan adoptee. They range in size from 30 to 60 microns in length. Identification? (CLICK ON IMAGES TO ENLARGE)

Answer to Case 162

2011-05-22T16:40:00.000-05:00

Answer: Pollen, not a human parasite
Thank you to everyone who wrote in with your answer! Most recognized these objects a non-parasitic structures, based on their irregular size and shape, as well as lack of homology with known parasite eggs. Note the irregular contours in the images below which helped me determine that these weren't real eggs.

Case of the Week 161

2011-05-16T16:01:00.007-05:00

I have a real challenge for you this week! A 16 year old immigrant from Ethiopia presented with acute severe right upper quadrant pain, accompanied with fever and nausea. CT findings suggested a liver abscess and obstruction of the main hepatic duct. The patient's serum tested negative for Entamoeba histolytica antibodies. Stool parasite exam revealed eggs of several round worms and Giardia intestinalis cysts. Liver biopsy showed the following objects, measuring 60 to 80 microns in greatest dimension: (CLICK ON IMAGES TO ENLARGE)

(H&E, 200x original magnification)

(H&E, 200x original magnification)

(H&E, 400x original magnification)

(H&E, 400x original magnification)

(H&E, 400x original magnification)

(H&E, 400x original magnification)

Answer to Case 161

2011-05-15T11:45:00.003-05:00

Answer: Ascaris lumbricoides eggs (most appear unfertilized) surrounded by neutrophilic inflammation and necrosis.

This was definitely a challenging case, but the clues for diagnosis were as follows:
1. Size of eggs
2. Presence of external mammilations on the eggs, characteristic of Ascaris eggs
3. Presence of Ascaris eggs in the patient's stool, confirming the presence of intestinal ascariasis.
4. CT findings suggestive of bile duct obstruction (consistent with the presence of the adult Ascaris female worm in the bile duct - a rare but potentially serious complication.

Thanks to all of you that decided to take the plunge and submit an answer!

Case of the Week 160

2011-05-09T19:24:00.004-05:00

The following were seen in a Papanicoloau stained urine preparation. They vary in size from 40 to 60 microns in length. Identification?

Answer to Case 160

2011-05-08T08:02:00.001-05:00

Identification: Not a parasite; most likely uric acid crystals.
Congratulations to Dana who got this one right!

These crystals can cause quite a problem for the untrained cytopathologist, since they resemble parasite eggs and fungal conidia. However, as Luke points out, these are not parasite eggs because they have spines at BOTH ends, and not just one (as you would expect for Schistosoma hematobium eggs).

Other clues to tell us these are not parasite eggs are:
1. the cracked appearance of some of the crystals (parasite eggs may break open, but don't usually crack neatly in half)
2. Lack of internally staining structures (remember this is a pap stain, and true parasite eggs will typically stain)
3. Size variability and small size (smaller than what would be expected for S. hematobium eggs.

I've actually shown a picture a picture of these crystals before:
Click HERE to see the previous case.

Case of the Week 159

2011-05-02T10:14:00.005-05:00

A renal allograft recipient presents with increased serum creatinine and shortness of breath. The following objects measuring 2-3 microns in length were seen in the urine on Ryan's Trichrome Blue stain: (CLICK ON IMAGES TO ENLARGE)

Identification? Could this finding be related to her respiratory symptoms?

Answer to Case 159

2011-05-01T19:00:00.002-05:00

Answer: Microsporidia
Great comments for this case!
From Anonymous:
"The structures remind me of microsporidia. And because (a) trichrome staining of urine isn't typical, and (b) it's posted by a parisitologist, I'm guessing protist . . ."

Yes, good guess - although, as another anonymous commenter states: "this is another good 'parasite' that the mycologists stole." It's true - genomic evidence suggests that microsporidia are actually highly specialized fungi and NOT parasites. Alas.

Finally, Luke mentions "The use of the Ryan's blue modified Trichrome stain is usually specifically for detection of microsporidia spores. I think this is what this is. Given the increased serum creatinine levels, the patient evidently has renal dysfunction - the respiratory symptoms could be caused by the fungal microsporidia infecting mulitple organs - respiratory system has been involved in other cases but less frequently compared to small intestine, urinary tract and biliary tree, and most commonly seen in AIDS patients. The first documented case of an extra intestinal case of microsporidiosis in a renal transmplant patient was reported by Latib et al (2001) and can be found here".

So more on this case:
The modified or Ryan's trichrome blue stain is useful for staining the spores a bright red; while it's not specific (yeast can stain a fainter pink and other organisms may also be positive), it's helpful for identifying the spores of this small (2-5 micron) organism. The presence of a central bar (running perpendicular to the long axis of the spore) is a helpful feature for distinguishing microsporidia from various yeasts:

This patient ended up having renal involvement (diagnosed by renal biopsy) as well as lung involvement (diagnosed by BAL). By a lab-developed PCR assay, the BAL and urine were positive for Encephalitozoon cuniculi. This was also confirmed by electron microscopy of the the renal biopsy. This is consistent with infection with this species that commonly causes urinary and respiratory disease. So in the end, both this patients rising creatinine and respiratory symptoms could be attributed to a single infectious cause.

Thank you all for the great comments!

Case of the Week 158

2011-04-24T11:21:00.007-05:00

Please join me in recognizing World Malaria Day.

According to the World Health Organization (WHO) :

World Malaria Day is a day for recognizing the global effort to provide effective control of malaria. It is an opportunity:
- for countries in the affected regions to learn from each other's experiences and support each other's efforts;
- for new donors to join a global partnership against malaria;
- for research and academic institutions to flag their scientific advances to both experts and general public; and
- for international partners, companies and foundations to showcase their efforts and reflect on how to scale up what has worked.

I've chosen to recognize World Malaria Day with the following case:
The following are Giemsa-stained thin blood films from a 5 year boy living in Gambia (1000x times original magnification). (CLICK ON IMAGES TO ENLARGE)

Identification?

Answer to Case 158

2011-04-23T08:41:00.002-05:00

Answer: Plasmodium falciparum

Anonymous said it well:
"Rings galore, cells with multiple infections, applique forms, double chromatin dots - classic P. falciparum.

Also important in the diagnosis is the fact that the infected red blood cells (RBCs) are not enlarged in comparison to the neighboring uninfected cells and that no stippling is present. I've highlighted the important diagnostic features of P. falcipaum in the image below:

To answer LR's question on how to approach Plasmodium speciation:

The size of the infected cells and presence/absence of stippling are the first 2 things I tend to use to formulate my diagnosis. Enlarged RBCs (+/- stippling) supports the diagnosis of P. ovale/P. vivax. Normal sized or small RBCs with no stippling (possible clefts/dots) supports the diagnosis of P. falciparum/P. malariae/P. knowlesi. I then look at other features, such as size/shape of trophozoites, classic forms (e.g. "band" form of P. malariae or "head phone" form of P. falciparum), number of merozoites in schizonts, and presence of later stage forms (typically not seen in P. falciparum infection). The "classic forms" are characteristic but not definitive for the various species, and storage/transport conditions and anti-malarial treatment may cause variations in morphology; therefore, the diagnosis must be made taking the entire morphologic picture into consideration. Rapid antigen tests and PCR may be helpful with difficult cases.

Thanks to everyone who wrote in with comments on this case!

Case of the Week 157

2011-04-18T07:38:00.006-05:00

The following worm was found in a frozen cod fillet from the local chain grocery store. When first received, it had a red-brown color and was in a tight coil. It measures approximately 3cm in length.(CLICK ON IMAGES TO ENLARGE)

Posterior end:

Most likely identification?

If ingested, would this worm cause infection?

Answer to Case 157

2011-04-17T11:44:00.004-05:00

Answer: Anisakid larvae

Thanks to everyone who wrote in with the answer to this case. You all recognized this as one of the anasakid nematode (roundworm) larvae.

Anisakiasis is a zoonotic disease, with marine mammals (e.g. dolphins, seals) serving as the definitive hosts. Humans become accidental hosts after ingesting raw or undercooked seafood containing anisakid larvae. The larvae can't complete their life cycle in humans, but may attempt to embed in human gastric or intestinal mucosa, resulting in intense pain, and rarely, perforation. A chronic granulomatous response can also develop, mimicking inflammatory bowel disease. Alternatively, larvae may be "coughed up" or passed symptomatically in stool.

Luke Roberts reminds us that some individuals may experience gastroallergic reaction to anisakid antigens (in either alive or dead worms), resulting in urticaria (hives), erythema (redness), angioedema (swelling beneath the skin), bronchospasm (constriction of the airways), and even anaphylaxis (severe whole body reaction).

Human anisakiasis is most commonly caused by Anisakis simplex and Pseudoterranova decipiens (previously Phocanema decipiens).

Diagnosis can be made by identification of characteristic features of 2-cm anisakid larvae, including a posterior mucron or "spine" (when present) and 3 poorly formed anterior lips with a small boring tooth. Speciation is performed by examining the size, presence, and position of the intestinal cecum. B.A.M. comments that "A genus-level ID is not possible from these images, but there appears to be a hint of an anteriorly-directed intestinal cecum, which would support Pseudoterranova."

Anisakiasis is most common in places where people eat undercooked/uncooked saltwater fish or squid. Commonly infected fish include cod (Atlantic or Pacific), Pacific halibut, mackerel, salmon, and red snapper. Some studies have reported over 90% of examined fish to be infected. Fresh water fish may also be infected. The United States FDA and fishmongers/grocers try to mitigate the risk of anisakiasis by removing the worms prior to consumption. However, it's still easy to find these larvae. I can typically find at least 1 in a bag of 7 frozen cod fillets!

Fortunately, freezing kills the worm, and greatly decreases the risk of acute disease. However, as anonymous states "Freezing should render non-infectious, but I'll pass just the same."

According to the CDC, "adequately cooking fish (60° C) or freezing (-20° C for seven days or -35° C for 15 hours) before ingestion will kill anisakid helminths" and thus eliminate the risk for acute anisakisis.

Case of the Week 156

2011-04-11T10:36:00.003-05:00

A colon biopsy from a patient with dysentery is received. On endoscopy, multiple ulcers in the rectum are noticed. Diagnosis?

Modified phosphotungstic acid hematoxylin stain (PTAH), 400x original magnification
(note, this preparation stains RBC's black)

Modified phosphotungstic acid hematoxylin stain (PTAH), 1000x original magnification
(note, this preparation stains RBC's black; see arrows)

Answer to Case 156

2011-04-10T07:26:00.003-05:00

Answer: Amoebiasis, due to Entamoeba histolytica

The diagnosis can be made by identification of classic Entamoeba trophozoites with a "ring and dot" nucleus (see image) containing engulfed red blood cells (top 2 arrows).

This protozoan parasite only rarely invades the intestinal wall and causes symptomatic infection. Infection is most commonly asymptomatic. This organism is morphologically identical to the closely related human commensals E. dispar and E. moshkovskii, which may also be found in the human intestinal tract. Unless invasive disease or trophozoites containing ingested red blood cells are observed in biopsy or stool preparations, these amebae cannot be differentiated morphologically.

Case of the Week 155

2011-04-04T12:46:00.000-05:00

Welcome Mayo Clinic Medical Students to the Parasitology Case of the Week. Please look at the case below and answer the question using Blackboard.

Note to other viewers: This weeks case will be different from the others in that there will not be an option to write an answer on the blog. Please feel free to email me if you would like to add your comments/questions. I will then incorporate them into the answer next Monday.

The following worm was retrieved during a screening colonoscopy near the ileocecal valve: (CLICK ON IMAGES TO ENLARGE)

By gently 'prodding' the worm with an applicator stick, the following eggs were expressed:

Identification?

QUESTION: (Mayo Medical Students - Please answer on Blackboard)
Which of the following are true regarding this parasite?
1. It is a intestinal trematode (fluke)
2. Symptoms of infection tend to increase with worm burden
3. Ongoing autoinfection results in long lasting infection (decades)
4. Infection is acquired following ingestion of undercooked meat
5. Eggs are infectious within hours of being laid

Many thanks to Bill Pasculle who donated this interesting case and beautiful photographs!

Answer to Case 155

2011-04-03T08:44:00.004-05:00

Answer: Whipworm (Trichuris trichiura)
This is a classic example of a whipworm with its slender anterior portion (that will embed in the intestinal mucosa) and broader posterior end (that hangs in the intestinal lumen and deposits eggs).

The eggs shown here are also classic for whipworm, with a smooth thick wall and bipolar plugs.

http://www.blogger.com/img/blank.gif
A similar case was shown in a previous posting: Case 73

The answer to the multiple choice question (below) is #2

Which of the following are true regarding this parasite?
1. It is a intestinal trematode (fluke)
2. Symptoms of infection tend to increase with worm burden (correct answer)
3. Ongoing autoinfection results in long lasting infection (decades)
4. Infection is acquired following ingestion of undercooked meat
5. Eggs are infectious within hours of being laid

Thanks to the medical students for being such a great group, and to my wonderful regular readers who keep me on my toes!

Case of the Week 154

2011-03-21T08:31:00.004-05:00

A biopsy of the large intestine was performed on a 43 year old HIV positive male with chronic watery diarrhea. Hematoxylin and eosin stained sections are shown below, which reveal multiple small (5-7 micron diameter) objects that appear to sit on the mucosal surface.

Large intestine mucosal surface, 400x original magnification. Objects of interest shown by arrow heads.

1000x original magnification

Deep mucosal crypt in the large intestine, 400x original magnification

1000x original magnification

What additional tests could be performed for confirmation?

Answer to Case 154

2011-03-20T10:41:00.001-05:00

Answer: Cryptosporidium spp.
C. parvum and D. hominis are the 2 main species causing human disease.

As some of the commentors mentioned, this case demonstrates the classic site and morphology of this parasite - small, round, 5-7 micrometer diameter parasites with an intracellular, extra-cytoplasmic location in the intestine. As Alasdair mentioned, cryptosporidiosis can be fatal in HIV+ and is one of the most common infections associated with HIV/AIDS.

Additional tests that could be performed for confirmation include stool examination with modified acid fast or safranin stains, or antigen detection methods. The latter is typically the most sensitive method for detecting Cryptosporidium.

Case of the Week 153

2011-03-14T12:37:00.003-05:00

The following were found on Stool ova and parasite exam. No history is available. The objects vary in size from 5 to 10 micrometers in diameter.

Identification?

Answer to Case 153

2011-03-13T08:09:00.002-05:00

Answer: Blastocystis hominis

Anonymous said it well: "Blastocystis. There are different morphological forms of the organism and subtypes. Host specificity is poor. Many experts have dropped the "hominis".

I will look forward to further studies to determine if we keep the species designation. Meanwhile, I will continue to use the nomenclature used by the U.S. Centers for Disease Control and Prevention on their excellent Parasite web site, DPDx

Blastocystis can be identified in stool specimens by its characteristic cyst morphology, with central vacuole and peripheral nuclei (below).

Trichrome Stain, 1000x original magnification

This "thick-walled cyst" is thought to be the form of the organism that is transmitted to others. However, much is unknown about Blastocystis, including its life cycle and ability to cause disease. Recent phylogenetic studies have placed this organism in the informal group, the stramenopiles, which include water molds, diatoms, and brown algae. I'm sure there will be much more information to come on this fascinating protozoan parasite.

Case of the Week 152

2011-03-07T09:09:00.004-05:00

The following were found in a stool parasite exam from a 50 year old farmer with bloody diarrhea. Identification?

Unstained wet preparation, object measures approximately 100 micrometers in length

Unstained wet preparation, object measures approximately 100 micrometers in length

Trichrome stained preparation, object measures approximately 70 micrometers in diameter.

Answer to Case 152

2011-03-06T12:02:00.001-05:00

Answer: Balantidium coli trophozoites and cyst

This giant protozoan seems to inspire parasitologists everywhere by its size and unique features. As Tom said "It's like the over-sized mascot of the protozoan world. It is so big and fuzzy, it just makes you want to give it a hug." My predecessor, Dr. John Thompson, used to call it "the aircraft carrier of the fecal flotilla."

Perhaps the the folks at GIANTmicrobes WILL someday make a plush version. If you can get a plush bedbug to snuggle with, surely you could get a big furry protozoan? Until then, you will have to make do with the following image:

Case of the Week 151

2011-02-28T10:01:00.003-05:00

The following were seen microscopically (4x objective) on a non-nutrient agar plate containing stool. The patient was from Cambodia and presented with abdominal pain and eosinophilia.

Here is a macroscopic image of the agar plate with the stool specimen.

Diagnosis?

Answer to Case 151

2011-02-27T08:59:00.000-05:00

Answer: Probable infection with Strongyloides stercoralis. Other larvae, such as those of hookworm species, can have a similar appearance on agar culture, and thus it is important to correlate the laboratory findings with the clinical presentation. In this case, the patient had a long standing eosinophilia, consistent with ongoing autoinfection with S. stercoralis. Microscopic examination of the larvae can also confirm the identification.

MicrobeMan gave a great description in his comment to this post:
"The non-nutrient agar plate very nicely demonstrates the production of furrows left in the wake of the migrating larvae, which emanate away from the central "dollop" of feces. The bacteria are dragged along by the migrating worms and grow in the furrows, which acts as an indicator for larval migration. As a side note, this particular scenario can play out in vivo, as well. In the host, gut flora can be introduced outside of the intestinal lumen by larvae that have penetrated the intestine."

The last point above is very important; bacteria introduced into the blood stream by migrating larvae can cause bacterial sepsis and contribute to the morbidity and mortality of strongyloidiasis.

Case of the Week 150

2011-02-21T11:49:00.004-05:00

A 50 year old male from South America died suddenly and an autopsy was performed. show are hematoxylin and eosin stained tissue sections of myocardium (heart muscle). Diagnosis?
(CLICK ON IMAGES TO ENLARGE)

(100 times original magnification)

(400 times original magnification)

(1000 times original magnification)

(1000 times original magnification)

Answer to Case 150

2011-02-20T09:49:00.000-05:00

Answer: Trypanosoma cruzi amastigotes

congratulations to Josh, Alasdair, BW, and Anonymous who wrote in with the correct answer!

The diagnostic features of this case are:
1. Location in cardiac muscle
2. formation of "pseudo-cysts"

3. Amastigotes (non-motile forms) within pseudocysts, containing both a nucleus and rod-shaped kinetoplast

Case 149

2011-02-07T05:21:00.003-05:00

The following was identified in "perirectal abscess fluid."
It measures approximately 55 microns in length. Identification?
Photo courtesy of Heather A.

Answer to Case 149

2011-02-06T11:39:00.002-05:00

Answer: Enterobius vermicularis ovum (egg) surrounded by inflammatory cells. Thank you for all of the comments on this case!

All of you realized that this is a pinworm egg, due to the presence of characteristic features, including medium size (50-60 microns in length) and flattening on one side. The flattened side gives the egg somewhat of a "D" shape as is shown below. The eggs are fully infectious within 4-6 hours after being laid, without the need for a soil incubation phase. Therefore, infection passes easily from person to person.

Pinworm eggs are typically deposited by the female on the perianal folds of the host; however, the worms and their eggs can occasionally get lodged in folds of intestinal mucosa, or other inopportune places in the intestine (eg. diverticula, appendix) and result in formation of an abscess (as seen here).

Case of the Week 148

2011-01-30T19:02:00.002-05:00

The following was found in a stool specimen and submitted to the Clinical Parasitology laboratory for identification. It measures approximately 1.3 cm in length. Identification?

Answer to Case 148

2011-01-30T17:34:00.000-05:00

Answer: Non-parasite.

This case was signed out as "Not a human parasite. Most closely food material."

Specifically, we thought this looked like a citrus fruit juice sac (the little pieces of a citrus fruit like an orange or grapefruit).

Go the the Visual Dictionary for a nice schematic of what I'm referring to.

In order to prove our hypothesis, one of our lab techs sacrificed her orange and we dissected it. I think the resemblance to our specimen is clear:

Case of the Week 147

2011-01-24T09:31:00.002-05:00

The following were seen on a peripheral blood smear from a patient who had traveled to an East African game park.

Answer to Case 147

2011-01-23T18:28:00.000-05:00

Answer: Trypanosoma brucei trypomastigotes

Given the history that this patient is from Eastern Africa, this organism is most likely to be T. brucei rhodesiense, which is limited in distribution to the Eastern side of the continent. However, as "Anonymous" mentioned in a comment to this case, the 2 T. brucei subspecies, T. brucei rhodesiense and T. b. gambiense, cannot be distinguished by morphology alone. Neuro_Nurse correctly points out that knowing the geographic exposure of the patient is very important for determining the most likely causative subspecies, since there is currently no geographic overlap between the two. Uganda is the only country in which both subspecies are found, and they currently occupy separate regions of the country. Clinically, infection with T. brucei rhodesience is typically more virulent and is treated with different anti-parasitic agents than infection with T. brucei gambiense.

Based on the blood smear morphology, a similar appearing trypanosome, T. cruzi, should also be considered in the differential. T. cruzi is found in South and Central America and causes American trypanosomiasis (a.k.a. Chagas disease). The most reliable method for differentiating the trypomastigotes (motile blood stage forms) of T. brucei and T. cruzi is by the size of the kinetoplast (see below, arrows). T. brucei has a relatively small kinetoplast, while T. cruzi has a larger kinetoplast. T. cruzi trypomastigotes also commonly form a "C" shape, although this is a less reliable feature. Finally, T. cruzi may also be found as a non-motile amastigote form in various tissues, while T. brucei is only found in the trypomastigote form in humans.

Case of the Week 146

2011-01-10T09:41:00.006-05:00

The following pieces of tissue (labeled "skin") were received in the laboratory from an 80 year old man. No further history was available. On closer examination, they appeared to be friable 'scabs' (CLICK ON IMAGES TO ENLARGE):

Examination with a dissecting scope (40x original magnification) revealed the following:

Some of them were moving!

Diagnosis?

Answer to Case 146

2011-01-09T09:16:00.000-05:00

Answer: Scabies caused by Sarcoptes scabiei (a.k.a. the "itch" mite)

This is a very remarkable case in that the mites are so numerous and that they were still alive when we received them. This degree of parasitism is consistent with Crusted or "Norwegian" scabies, occasionally seen in the elderly and individuals with a compromised or suppressed immune system. Patients with crusted scabies typically exhibit thick crusts of skin that contain thousands of mites. What is shown here is one of these crusts.

Some viewers commented that these organisms bore a resemblance to ticks; this is not surprising, since ticks and mites are both arachnids in the subclass Acari. They are differentiated by size (ticks are generally larger), and have a toothed hypostome and Haller's organ which ticks lack.

Thanks to everyone who wrote in on this case!

Case of the Week 145

2011-01-03T09:16:00.003-05:00

The following objects are Cyclops - one of the most common genera of microscopic fresh water Copepods (small crustaceans) that are involved in a number of parasite life cycles. So the question for this week: Which human parasites have Copepods in their life cycle? (CLICK ON IMAGES TO ENLARGE)

Answer to Case 145

2011-01-02T09:33:00.000-05:00

Answer: Copepods are involved in the following parasite life cycles:

1. Diphyllobothrium latum, the broad fish tapeworm
2. Dracunculus medinensis, the Guinea worm
3. Spirometra spp., the cause of sparganosis in humans
and
4. the agents of gnathostomiasis: Gnathostoma spinigerum and Gnathostoma hispidum

You all did a great job!

Case of the Week 144

2010-12-27T15:57:00.005-05:00

A 2 cm x 1 cm x 0.1 cm white smooth soft object was received in saline in the Parasitology lab. With manipulation (using a wooden applicator stick and wearing gloves), it was friable and fragmented easily. Some of the saline surrounding the object was pipetted onto a slide for examination, and the following objects were seen. They measure approximately 30 microns in diameter. Identification? (CLICK ON IMAGES TO ENLARGE)