December 2015

Wellness fecals from a 15-head herd in Muskogee, OK

Fifteen fecal samples from cows in Muskogee, OK were submitted to the Oklahoma Animal Disease Diagnostic Laboratory in Stillwater, OK as part of a routine wellness screen. The veterinarian that submitted the samples was specifically curious about Fasciola hepaticainfections. Fecal sedimentations were prepared, and the following egg was detected from one of the cows.

​100X total magnification:

​400X total magnification, stained with methylene blue:

What's your diagnosis?

Answer

This is not an egg of Fasciola hepatica, but rather an egg of Paramphistomum cervi, commonly known as the rumen fluke. Although F. hepatica and P. cervi have similar life cycles, requiring an aquatic snail as an intermediate host and encysting as infective metacercariae on aquatic vegetation, they inhabit different locations within ruminant hosts as adults; Fasciola hepatica resides in liver bile ducts, while P. cervi parasitizes the rumen, as its common name implies. Eggs of these two flukes also appear similar. Both are large (~120 µm length) and ovoid with an operculum. Eggs of F. hepatica, however, are yellow-brownish while P. cervieggs are relatively clear. Staining with methylene blue may help to distinguish the coloration better, as stained F. hepatica eggs will appear amber in color while P. cervi eggs will still appear relatively clear.