Sunday, November 10, 2013

Answer to Case 281

Answer:  Trichinella species larvae.

This is the classic appearance of Trichinella larvae coiled within muscle.  To answer Yenni's question, this biopsy was taken from the patient's thigh, which was quite swollen and inflamed.  In autopsy specimens, good locations to look for Trichinella spp. larvae are the diaphragm and tongue.

As correctly pointed out by Anonymous, we cannot tell the species simply by looking at the larvae in biopsy, although it is possible to place the nematode in either the encapsulated group (e.g. with Trichinella spiralis) or the unencapsulated group (Trichinella pseudospiralis).  A number of species have been detected from human cases in the U.S. including T. nativa, T. spiralis, and Trichinella T6.  

bks asked about the risk of acquiring trichinosis from undercooked store-bought pork in the U.S.  The good news is that the risk is extremely low, due to federal regulations (e.g. pigs cannot be fed uncooked meat or raw garbage) and meat inspections by the USDA.  Instead, the greatest risk is from eating the meat of wild carnivores such as bear, wild pig, boar, fox and cougar.  This is in marked contrast to the risk worldwide which is still due to eating pork.

To prevent trichinosis, it is best to thoroughly cook your meat (internal temperature of 160°F (71°C)). Of interest, curing and salting or freezing will kill most, but not all larvae, and some larvae are freeze-resistant. Yikes!  Best to cook thoroughly, not using a microwave due to the uneven heating that may result.

And now a poem from Blaine Mathison, sampling RUN DMC!

This meal may send us to the hospital
With problems musculoskeletal
It’s Trichinella all-right
Coiled in a cyst nice and tight

Lesson learned, my rhymes are not just anecdotal

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