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
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