[Last Modified: ]

August 2000
Answer to Case 41
This was a case of baylisascariasis, caused by Baylisascaris, an intestinal ascarid of raccoons (B. procyonis) and skunks (B. columnaris). The image shows key diagnostic features of a typical ascarid larva, including prominent lateral alae, excretory columns (canals), and gut. The key morphological features for B. procyonis were:

• the size of the worm (about 50 micrometers in diameter), which was large enough to rule out Toxocara (typically 16 to 18 micrometers in diameter). The large size also excludes other larval nematodes such as Strongyloides and Trichinella. The morphology of these worms is also very different from ascarid larvae.
• the presence of two large, prominent lateral alae (LA, Figure A).
• the presence of large excretory columns (EC, Figure A) and a granular appearance of the intestines (Int, Figure A). The lumen (Lu, Figure A) is patent.

The size (about 80 by 70 micrometers) and morphology of the eggs found in the raccoon feces are also consistent with eggs of B. procyonis.

A