Tuesday, November 25, 2008
Case of the Week 46
The following was submitted for identification to the parasitology laboratory. It was found on a patient's leg and the clinician queried myiasis, although there was no apparent wound in the patient's skin. What should you tell the concerned physician?
Monday, November 24, 2008
Answer to Case 46
Answer: You should tell the clinician that this is likely a free living insect larvae and that there is no need for further concern. In this instance, the clinical presentation does not suggest myiasis since the larvae was not found within human tissues. Furthermore, this larva clearly has legs, which is NOT a feature of myiasis-causing fly larvae.
Upon further questioning, the patient reported what appeared to be a moth's nest in the box springs of his bed. The nest contained larvae that were identical to what is shown.
Upon further questioning, the patient reported what appeared to be a moth's nest in the box springs of his bed. The nest contained larvae that were identical to what is shown.
Monday, November 10, 2008
Case of the Week 45
The following worms were removed from the small bowel during colonoscopy. At the time of the procedure, the endoscopist noted several punctate hemorrhages in the surrounding mucosa and rightly concluded that these represented previous attachment sites for the worms.
Light microscopy of the mouthparts revealed the following.
Identification?
Light microscopy of the mouthparts revealed the following.
Identification?
Sunday, November 9, 2008
Answer to Case 45
Answer: Hookworm. Necator americanus. You can distinguish N. americanus from the other hookworm Ancylostoma duodenale but the presence of cutting plates instead of teeth. See Case of the week 3 for an example of Ancylostoma mouth parts.
Monday, November 3, 2008
Case of the Week 44
The following is a routine hematoxylin and eosin stained histologic section of small bowel. The patient presented with watery diarrhea. Identification? What would a likely clinical scenario be for this infection. CLICK ON IMAGES TO ENLARGE.
Answer to Case 44
Answer: Giardiasis
Note that the organisms are cut in various planes so that you only rarely see a perfect pear shaped organism with 2 nuclei.
As part of this case, I asked the readers to propose a hypothetical scenario on how this infection was acquired. These are some of the answers I received:
1. Young, idealistic univerisity graduate takes the year before medical school to hike from Katahdin to Springer on the Appalachian Trial. Along about early October, somewhere in Blue Ridge of North Carlolina/Tennessee, after testing the limits of "minimalism" and ceasing to filter-sterilize his drinking water, he develops diarrhea so profuse that he's forced to hole up in a remote shelter for several days to regain strength. It is there that he first entertains a notion that the seemingly pristine "mountain streams" probably do serve as primary watershed for the many high-elevation pastures of nearby dairy and beef herds.
2. "Parasite Gal" and husband go hiking in the woods, get thirsty, and drink unfiltered water from a stream. Then, 24 hours later, they wish they were back in London.
I must admit that I am less fond of the second scenario, since it involves me personally!
Thank you for the creative responses.
Note that the organisms are cut in various planes so that you only rarely see a perfect pear shaped organism with 2 nuclei.
As part of this case, I asked the readers to propose a hypothetical scenario on how this infection was acquired. These are some of the answers I received:
1. Young, idealistic univerisity graduate takes the year before medical school to hike from Katahdin to Springer on the Appalachian Trial. Along about early October, somewhere in Blue Ridge of North Carlolina/Tennessee, after testing the limits of "minimalism" and ceasing to filter-sterilize his drinking water, he develops diarrhea so profuse that he's forced to hole up in a remote shelter for several days to regain strength. It is there that he first entertains a notion that the seemingly pristine "mountain streams" probably do serve as primary watershed for the many high-elevation pastures of nearby dairy and beef herds.
2. "Parasite Gal" and husband go hiking in the woods, get thirsty, and drink unfiltered water from a stream. Then, 24 hours later, they wish they were back in London.
I must admit that I am less fond of the second scenario, since it involves me personally!
Thank you for the creative responses.
Monday, October 27, 2008
Case of the Week 43
This weeks case may look familiar (hint: we've seen a similar case on Creepy Dreadful Wonderful Parasites before) but I thought that these pictures were so striking that I wanted to share them with you.
The following were submitted to the laboratory on a glass microscope slide. No history. Identification? (CLICK ON IMAGES TO ENLARGE)
The following were submitted to the laboratory on a glass microscope slide. No history. Identification? (CLICK ON IMAGES TO ENLARGE)
Answer to Case 43
Answer: Pthirus pubis, the crab louse.
Little known facts about the crab louse:
1. It's an obligate parasite, living and feeding only on humans.
2. It takes 4 to 5 blood meals a day.
3. The closely related body louse feeds even more frequently and can cause anemia in heavily infected individuals. Historically, children with louse-induced anemia looked pale and unwell - this is where the term "lousy" came from.
4. The crab louse most commonly inhabits the genital area but can also inhabit the hair under the arm pits, eye brows, and eye lashes. The latter may be seen in children and does not necessarily indicate sexual abuse; infection can be passed from one child to another through casual contact.
Little known facts about the crab louse:
1. It's an obligate parasite, living and feeding only on humans.
2. It takes 4 to 5 blood meals a day.
3. The closely related body louse feeds even more frequently and can cause anemia in heavily infected individuals. Historically, children with louse-induced anemia looked pale and unwell - this is where the term "lousy" came from.
4. The crab louse most commonly inhabits the genital area but can also inhabit the hair under the arm pits, eye brows, and eye lashes. The latter may be seen in children and does not necessarily indicate sexual abuse; infection can be passed from one child to another through casual contact.
Monday, October 20, 2008
Case of the Week 42
Cross-sections through an appendix removed for acute appendicitis revealed the following:
(H&E stained histologic images, Click to enlarge)
(H&E stained histologic images, Click to enlarge)
Answer to Case 42
Answer: Enterobius vermicularis (pinworm)
Shown are cross-sections of the adult worms within the lumen of the appendix. In some cross-sections you can see the characteristic eggs within the females (below is the egg in a stool iodine prep from a different patient).
What is also classic about this case is the location (appendix and cecum are traditional locations for the adult female pinworm) and the lateral alae on the worms. Alae, (plural of ala, Latin for 'wing') are longitudinal ridges seen in the larval forms of nematodes, (e.g. Ascaris lumbricoides), and the adult worm Enterobius vermicularis. In fact, Enterobius is the only ADULT worm with these ridges that parasitizes humans. Below is the cross-section from this case showing the lateral alae (arrows) as well as a longitudinal view of the adult worm in an iodine stool prep (arrow marks the ridge on one side of the worm). The ridges extend the length of the worm.
Tom was correct in mentioning Toxocara spp. since the larval form causes visceral larva migrans in humans. However, the larva are much smaller than the adult E. vermicularis and would be seen within the parenchyma of tissues (e.g. liver) in association with a marked inflammatory response.
Shown are cross-sections of the adult worms within the lumen of the appendix. In some cross-sections you can see the characteristic eggs within the females (below is the egg in a stool iodine prep from a different patient).
What is also classic about this case is the location (appendix and cecum are traditional locations for the adult female pinworm) and the lateral alae on the worms. Alae, (plural of ala, Latin for 'wing') are longitudinal ridges seen in the larval forms of nematodes, (e.g. Ascaris lumbricoides), and the adult worm Enterobius vermicularis. In fact, Enterobius is the only ADULT worm with these ridges that parasitizes humans. Below is the cross-section from this case showing the lateral alae (arrows) as well as a longitudinal view of the adult worm in an iodine stool prep (arrow marks the ridge on one side of the worm). The ridges extend the length of the worm.
Tom was correct in mentioning Toxocara spp. since the larval form causes visceral larva migrans in humans. However, the larva are much smaller than the adult E. vermicularis and would be seen within the parenchyma of tissues (e.g. liver) in association with a marked inflammatory response.
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