Sunday, August 24, 2014

Case of the Week 316

The following were found on a 10-year old boy from the northeastern United States.  Identification?

Saturday, August 23, 2014

Answer to Case 316

Answer:  Larval ticks, Ixodes species

These little guys were a bit hard to make out due to their small size, but you can nicely see several characteristic features, including 6 legs (versus the 8 legs of nymphs and adults), and - if you squint - a U-shaped anal groove, consistent with Ixodes species.
As mentioned by FP in Burlington, VT, Borrelia burgdorferi, the agent of Lyme disease, is not transmitted tranovarially from mother to larva. Therefore, larvae are not infected and cannot transmit this bacterium to humans.  Larvae can become infected when they take their first blood meal, after which they molt into nymphs. Therefore, unlike larvae, nymphs ARE capable of transmitting B. burgdorferi to humans, and present a particular hazard due to their small size which makes them easy to overlook.

Monday, August 18, 2014

Case of the Week 315

The following structure was seen in the diaper of a 2 year old girl and sent to the lab for identification.  It is approximately 12 cm in length.

In the lab, the following eggs were expressed from the structure. They measure approximately 100 micrometers in length. Identification?

Sunday, August 17, 2014

Answer to Case 315

Answer:  Moniliformis moniliformis, one of the principle agents of acanthocephaliasis.

The adult worm has a very characteristic morphologic appearance, which Heather A. aptly describes as resembling a "bendy straw" (see Here for information about bendy straws). Not shown here (since it was retracted into the worm) is the hooked proboscis from which the acanthocephalans get their name (Acanth is Greek for spiny or thorny).

The eggs are also characteristic, with a relatively large size (90-120 micrometers long) and internal larva with rostellar hooks.

Humans are accidental hosts, usually acquiring infection via ingestion of an infected insect such as a cockroach or beetle.  Moniliformis moniliformis does not always mature in humans, and when it does, it seldom produces eggs.  Therefore, this case is interesting in that a mature and gravid female was identified.

Monday, August 11, 2014

Case of the Week 314

The following images are from a filtered urine specimen in a patient with dysuria.  No further history is available.  Identification?

Sunday, August 10, 2014

Answer to Case 314

Answer:  Not a parasite:  uric acid crystals

Crystals are commonly seen in urine specimens and can be a very good mimic for parasite eggs.  This is particularly true for the 'lemon-shaped' uric acid crystals which mimic Schistosoma haematobium eggs.  You can differentiate uric acid crystals from S. haematobium eggs by the following features:

1. Uric acid crystals vary in size and shape and are often much smaller than S. haematobium eggs. In contrast, S. haematobium eggs are regular in size and shape, and quite large (approximately 150 micrometers in length).
2. Uric acid crystals commonly have points on both ends instead of the single 'pinched-off' spine of S. haematobium eggs. They can also have lateral points or take on other shapes.
3. There are no internal parasite structures in crystals
4. Finally, crystals often fracture and break, although this is not shown in this case.

Here is a picture from this case that demonstrates many of these features, including points at both ends, variability in size and shape and lack of internal parasite structures.

Thank you all for writing in on this case!  Crystals can be challenging, so I like to show them whenever they come up in my lab.

Monday, August 4, 2014

Case of the Week 313

The following case was generously donated by Florida Fan.  These images were all obtained from specimens submitted from a 5-year old girl who was possibly the daughter of a migrant farmer.  Identification?  Bonus:  name the forms!

This one is my favorite:

Sunday, August 3, 2014

Answer to Case 313

Answer:  Pediculus humanus capitis

All that wrote in got this correct:  This case donated by Florida Fan nicely demonstrates 4 different stages/sexes; in order of presentation:

Adult male
Adult female
Eggs (nit) cemented onto a hair shaft
and last but not least, a nymph hatching from an egg!