This week's case is very appropriate for Halloween! The following object was found attached to the wall of the terminal ileum during screening colonoscopy. It was removed and sent to the parasitology laboratory for identification where it was cleared and mounted on a glass slide. It is approximately 1-cm long. Images by Heather Morris.
What is your diagnosis? The answer will be posted on Halloween, courtesy of Dr. Jacob Rattin.
Answer to the Parasite Case of the Week 759: Female Ancylostoma duodenale
The following explanation is by the outstanding PGY-2
pathology resident, Dr. Jacob Rattin:
In humans, intestinal hookworm infection is predominantly caused
by Ancylostoma duodenale, Necator americanus, and A.
ceylanicum. Adult hookworms live in the small intestine (typically the
distal jejunum) and use specially-adapted mouthparts to attach to the intestinal mucosa
and feast upon the host’s blood (creepy!). Females release unembryonated eggs
into the feces where they mature in the soil and then release larvae. These
infectious larvae can pierce human skin and travel in the blood to the lungs
where they can penetrate alveoli and make the ascent up the bronchial tree and
into the pharynx. After being swallowed, they make their way to the small
intestines where they attach. Chronic infection results in iron-deficiency
anemia and malnutrition (dreadful!). Rarely, heavy infection can result in
death, especially in infants.
The sizes and morphology of rhabditiform larvae, filariform
larvae, and adults differ. For ease of comparison and reference, a table has
been made for Ancylostoma duodenale.
|
Stage |
Size |
Morphology |
|
Rhabditiform
(L1) larvae |
250-300 µm
long |
- Long buccal
canal - Inconspicuous
genital primordium - Can occasionally
be seen in stool when there is a delay in processing (see
COTW 757), and need to be distinguished from L1 Strongyloides
stercoralis larvae. |
|
Filariform
(L3) larvae |
500-700 µm long |
- Ensheathed,
pointed tail |
|
Adults |
Females: 10-15
mm long Males: 8-12
mm long |
- Sharp teeth - the male
tail has a large fan-like copulatory bursa, while the female has a pointed
tail. |
The buccal capsule shows the characteristic cutting teeth in
this image of Ancylostoma duodenale, which differentiates it from
Necator, which has cutting plates. The teeth of A. ceylanicum have
a similar appearance to that of A. duodenale but have larger from teeth.
This scary appearance really shows how A. duodenale is
like a real vampire!
For extra tricks and treats, check out my past parasite-themed Halloween images:
https://www.parasitewonders.com/parasites/fun-parasite-images
This week's case was generously donated by Professor Philippe Poirier, Dr. Céline Nourrisson, and Dr. Maxime Moniot, Parasitology-Mycology Department, National Reference Centre for Cryptosporidiosis, Microsporidia and Other Digestive Protozoa, Clermont-Ferrand Teaching Hospital, France.
The following objects were seen in a stool specimen from a patient with diarrhea.
Concentrated wet prep:
Answer to the Parasite Case of the Week 758: Balantioides coli
This protozoan is the largest to infect humans, and is the only human ciliated parasite. It has circumferential cilia and a large macronucleus (not well appreciated in the slides here) which give it a striking appearance. Note the characteristic 'boring' (rotary) motility - nothing boring about this parasite!
Thanks again to our contributors, Professor Philippe Poirier, Dr. Céline Nourrisson, and Dr. Maxime Moniot, Parasitology-Mycology Department, National Reference Centre for Cryptosporidiosis, Microsporidia and Other Digestive Protozoa, Clermont-Ferrand Teaching Hospital, France.
The following objects were seen in a fresh stool specimen collected at a field station in Uganda. The objects are approximately 280 µm long and no longer motile upon examination. What is your identification?
Answer to Parasite Case of the Week 757: Hookworm rhabditiform (L1) larvae
Many of you questioned if these were Strongyloides stercoralis larvae, since this parasite most often presents with L1 larvae in stool. In comparison, hookworm larvae are rarely seen in stool, and only when there is a prolonged period between specimen collection and placement in fixative (as occurred in this case). Fortunately, hookworm L1 larvae can be differentiated from those of S. stercoralis L1 larvae by several morphologic features:
Note the long buccal cavity in this case:
Here is a nice image from Case of the Week 459 showing the two L1 larvae side-by-side:
While I tried to provide you some clues to the diagnosis (received fresh, not in preservative, and larvae were no longer motile upon examination), this was definitely a challenging case!
Thanks to everyone who wrote in with their thoughts.
