Answer to Case 759

 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

Answer to Case 700

 Answer: Shown here is the head and front legs of Pediculus humanus, the human body/head louse. It's very hard to tell the gender from just the portion that I showed you, so here is an image of the complete body. As you can tell from the pointed posterior, this is a male rather than a female. Thanks to all who hazarded a guess!

Thank you all for the kind words of support for reaching this milestone as well. I couldn't do it without you. Your comments, contributed cases and support over the year continue to inspire me, and I always learn something from each case.

Answer to Case 698

 Answer to Parasite Case of the Week 698: Cutaneous/furuncular myiasis due to Cordylobia anthropophaga (a.k.a. the tumbu or mango fly). As nicely described by Florida Fan, the spiny body, sinuous posterior slits without distinguishable peritreme, and the geographic location all are consistent with C. anthropophaga. Idzi P. added that "the evenly distributed and pigmented cuticular spines are also supportive of this identification." The presence of 3 slits indicates that this is a third stage larva, which allows for identification using commonly-available identification keys. 

Here is a closer view of the posterior spiracles, showing the characteristic posterior slits:

Cordylobia anthropophaga has a fascinating life cycle. The adult female fly lays 500-700 eggs at a time in dry soil contaminated with urine and feces. They have also been known to lay their eggs on clothing that are hung out to dry. Larvae hatch from the eggs and can remain alive in the environment for up to 2 weeks, residing just below the surface of the soil . When the soil is disturbed by a potential host, the larvae quickly emerge, and each can penetrate the skin of the host and create a cavity in which to live, feed, and mature. The posterior end of the larva faces outward within the resultant furuncle to allow for respiration through the posterior spiracles. Larvae go through 3 stages (referred to as L1, L2, L3) over a period of 8 or more days, and will then drop from the host and pupate in the environment. In warm climates, the adult fly hatches after 10-11 days.

I will always remember the story from a family member who went on a lavish African safari several decades ago and was somewhat embarrassed when the housekeeper insisted on ironing her undergarments after they had been hanging on the line to dry. When she told the housekeeper not to bother, she was very quickly informed why this was necessary - in very graphic detail! (You can see a rather disturbing case of furuncular myiasis of the breast HERE).

Thanks again to Dr. Richard Bradbury for donating this fascinating case.

Case of the Week 700

 Dear Readers, I can't believe that I am celebrating my 700th post! In honor of this day, I am featuring the image that started it all - my 'mascot' of sorts. Can anyone tell me what this is? 

Answer to Case 701

Answer to the Parasite Case of the Week 701: Female Pthirus pubis, a.k.a, the 'crab' or 'pubic' louse. She is gravid - with 2 eggs! I've seen many female crab lice with eggs, but never one with two eggs at once, so when I came across this specimen, I immediately wanted to share it with you. An anonymous reader commented that "She's very likely to die prematurely from being egg bound, and will suffer from that full feeling."  I thought that was a very interesting (and rather witty) statement. Does anyone know if a female P. pubis with 2 eggs is less likely to survive?

Note that the pubic louse is shaped somewhat like a pelvis - a helpful feature for differentiating it from the head/body louse, which has a much longer body. The pelvis reference is useful since P. pubis is sexually-transmitted. It's also important to note that both the pubic and head/body louse have large raptorial (grasping) claws, but the pubic louse has larger claws on the second and third legs which, in combination with its body shape, make it look particularly crab-like.

As mentioned by Sam, we can tell that this is a female due to the morphology of the posterior end, whereas the male posterior end is more rounded. He also commented that "This louse causes genital crabs. The claws are designed to latch onto the course pubic hairs of the genital area, allowing sexual transmission of this ectoparasite."  Here is a side-by-side comparison of the 2 human lice (Pediculus humanus and Pthirus pubis) for comparison. Also check out Case of the Week 700 for a nice example (and my mascot!) of P. humanus.

Head/body louse (left) and pubic louse (right)

Thank you all for the excellent comments on this case!