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[Baylisascaris procyonis]

Baylisascaris procyonis eggs are 80-85 µm by 65-70 µm in size, thick-shelled, and usually slightly oval in shape.  They have a similar morphology to fertile eggs of Ascaris lumbricoides, although size is a distinguishing characteristic as A. lumbricoides eggs are smaller (55-75 µm by 35-50 µm).  B. procyonis eggs are not a diagnostic finding since they are not excreted in human feces.  The definitive host for B. procyonis is the raccoon.

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A: Egg of B. procyonis in formalin-fixed stool from a raccoon.  Animated image contributed by the Oregon State Public Health Laboratory.