Monday, July 16, 2018

Case of the Week 502

This week's case is of a patient with recurrent fevers. No further history is available, but the following were noted on Giemsa-stained thin blood films:

Identification? What additional test would be helpful for confirming your diagnosis?

Tuesday, July 10, 2018

Case of the Week 501

This week's case features a zoonotic infection that can potentially involve humans. The patient is a sheep named Mr. Grumpy. Although grumpiness is his usual state of being, he was particularly grumpy when I saw him because he had a wound infested with maggots. Wounds in sheep can be difficult to detect early on because they are often hidden under dense wool. Poor Mr. Grumpy had likely acquired his wound while in a new pasture, and it had taken several days before behavior changes alerted the owners to his condition.

Here is the original photo of his wound (warning - not for the squeamish), followed by one after he has been shorn and cleaned up a bit:

Many thanks to Terri who allowed me to participate in removing the maggots from Mr. Grumpy and make him (hopefully) less grumpy. Harry (my student from London) and I plucked them one at a time from the wound and placed them in 70% ethanol for transport to the lab:

Here is a close up of the wool above the wound where a lot of the maggots were hiding:

Here they are some that were removed from the deep wound:

Once we were back in the lab, this is what we saw:

What is the identification of these maggots?

Here he is today - doing much better!

Sunday, July 8, 2018

Answer to Case 501

Answer: blow fly larvae; either Phormyia regina (black blow fly) or Cochliomyia macellaria (secondary screwworm)

This was a tricky one given the somewhat overlapping features of these two species' third instar larvae. If you follow the CDC's pictorial key, you get to the following branch point where you have to decide if:
1. There is a clearly visible button
2. The walls of the slits have lateral swellings

Having examined the maggots myself, I can say that the button is present, but not very distinct, and I believe I see faint lateral swellings on the slides. Therefore, my interpretation is that this is Cochliomyia macellaria. Here is my best attempt to capture these diagnostic features:
There is little clinical difference between P. regina and C. macellaria. Both can colonize the wounds of livestock and humans and feed on dead tissue. Fortunately neither feed on living tissue and therefore don't pose the same risk to livestock as the primary screwworm, Cochliomyia hominivorax, which has been eliminated from the United States using a sterile fly release program. Of note, C. hominivorax recently made a comeback in the Florida keys, necessitating a renewed sterile fly release program to eliminate the population. The University of Florida Entomology and Nematodology Department has a nice educational piece on the primary screwworm that you can read HERE.

Thanks to all of my entomology-minded colleagues who took the time to write in on this post!

Monday, July 2, 2018

Case of the Week 500!!!

Welcome to my 500th Parasite Case of the Week - a special celebration of our parasitology community.

I feel so fortunate to have such wonderful readers. You keep me on my toes, send me amazing cases, and teach me a lot. I had asked for submissions of your parasite-related artwork and received some amazing entries. I put the names of all contributors into a hat and randomly selected the following 3 names:
Sheldon Campbell
Piotr Kochan
Melanie Riblett

Congratulations! I will reach out to you later to give you your prizes :)

So now without further ado, here are all of the fabulous parasite creations of our talented group:

Kate Grannis - chalk art
Marc Courturier - baked goods

Blaine Mathison - Halloween cupcakes! AND pinworm eggs - a giant scotch tape prep:

 Andrea Dahl - multimedia ticks!

Melissa Blessing - Giant Microbe® ghostie and bandit

Heather Rose and family - Ixodes scapularis adults and larva

Mark Fox - ink drawing of Haemonchus contortus

Alexandra Bryson - Loa loa costume

Kelly Hedlund (submitted by Ryal Relich) - Trypanosoma cruzi crochet art

The Winters - Clonorchis and snail host costumes
Mark Fox and Kristine - our lovely hookworm couple

Piotr Kochan - photography, Ascaris and Giardia

Idzi Potters - photography
'nebula' stool crystal
 Toxocara cati adult worm
 Tunga penetrans
Tunga party!
Melanie Riblett - Easter eggs!
Frances Dodge - photography

And finally, from Sheldon Campbell, the fabulous singing microbiologist:
Click HERE to hear Sheldon live!

Home in the Gut

Copyright © 2001 by Sheldon Campbell

Oh give me a home where the parasites roam

Where the worms play in cheerful delight

Where the ova are shed, and the larvae are bred

And the pinworms crawl out in the night


Home, home in the gut

Where the worms play in cheerful delight

Where the ova are shed, and the larvae are bred

And the pinworms crawl out in the night

Oh hookworm am I, my ova go by
In your stool and then hatch in the mud
They punch through your skin, and migrate again
To the gut, where they suck out your blood


I live in the stream of the bile that's green
I'm Clonorchis, so please get it right
And my life's greatest wish is to enter a fish
And then you with your sushi tonight


I cling to the wall, a tapeworm so tall
Borne by pork I came to this new home
Now while I procreate, you've got a sure date
'Cause with me you are never alone


Please come swim with me, so that we can be free
To burrow into your bare legs
We just copulate, so we can populate
Your liver with our extra eggs


The rectum’s my home, but I would love to roam
And lay my eggs out on your butt
I know it’s a bitch, but when you scratch that itch
My kids get into your kid’s gut. 

Monday, June 25, 2018

Case of the Week 499

Reminder - I am still taking parasite art submissions for Case of the Week 500! I will feature all artwork on my blog, along with the results of the drawing for 3 prizes :)

Now for this week's case, we have a very interesting submission from Dr. David Peaper. The patient is an elderly woman presenting with hematemesis. She underwent upper endoscopy and biopsies were taken from areas of erosion/inflammation. The biopsies were submitted for comprehensive vial culture, and the following were observed in the MRC-5 shell vials and traditional tube cultures.


Sunday, June 24, 2018

Answer to Case 499

Answer: Strongyloides stercoralis adult female worm and larvae.

The video shows both an adult and the larvae:
Capillaria philippinensis can have a similar presentation to S. stercoralis, with both adults and larvae present in the intestine; however, Capillaria is an obligate parasite and would not likely survive in the viral culture media for very long. If in doubt, you could differentiate C. philippinensis adults and larvae by examining good wet preparations of this specimen. Capillaria adults have a prominent stichosome whereas Strongyloides adults do not. Also, Capillaria rhabditiform larvae do not have a prominent genital primordium and clavate eosphagus like Strongyloides does. Unfortunately the buccal cavity is not clearly seen, but it appears to be relatively short.

Monday, June 18, 2018

Case of the Week 498

Dear readers, I will soon be posting my 500th Case. Hooray!! To celebrate, I would like to recognize the creativity of my readers by displaying a photograph of your parasite-related artwork on my blog. I will then put the names of all of the individuals who submitted a photo of their art in a hat and pick 3 names to receive a special parasite prize ☺ If you would like to send me a photo that I can post on my blog on July 2nd, please send it to

Now for this week's case - some beautiful eggs from my lab (images and video by Heather Rose):


Sunday, June 17, 2018

Answer to Case 498

Answer: Taenia sp. eggs. I forgot to mention that the stool specimen came from a human patient. Therefore, the main considerations are Taenia solium and Taenia saginata. If the patient acquired infection in Asia, then Taenia asiatica should also be considered. You cannot differentiate the 3 species based on the egg alone, instead, morphologic features of the adult worm (T. saginata/T. asiatica vs. T. solium) and molecular testing (T. saginata vs. T. asiatica) are needed. The photographs and video beautifully highlight the key diagnostic features:

As a side note, the eggs of Echinococcus species have a very similar appearance but would be found in the stool of infected dogs and other canids, and NOT in human stool.

Thanks again to Heather in my lab for the beautiful photos and video!

Monday, June 11, 2018

Case of the Week 497

This week's case was generously donated by Florida Fan. The following bug were submitted by the physician of a 69-year-old woman. No further history is available. As Florida Fan says, "Here comes the summer, and with it comes the bugs."


Sunday, June 10, 2018

Answer to Case 497

Answer: Cimex species; bed bug
As Blaine mentioned: "B&B Bugs is back! Beautiful brown biting, blood-sucking bed bug! Boo-yeah!" William mentioned that the pronotal hairs are not long enough to be a bat bug - an important consideration since bat bugs can be found near human dwellings and may bite humans when their preferred (bat) host is not available.

See Case of the Week 395 for more information and photos.

B&B Bugs = Bobbi and Blaine!