June 2021

What's on the hook?

Several crappie fish were submitted from the Atoka Lake (Oklahoma) for necropsy due to lacerations observed by anglers. Samples were collected for parasitology testing, including fecal samples and the stomach of the fish. Examination of the stomach content revealed the following parasites in one of the fish (Image 1), and fecal centrifugation with Sheather’s sugar solution revealed the presence of larvated eggs (Image 2).  

Image 1: Anterior end of parasite found in stomach (~7mm in length).

Image 2: Egg found in fecal flotation measuring 37.5 x 25µM. 

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What's your diagnosis?

​Spinitectus spp. are parasites of the stomach and intestines of fish and frogs. Larvae of this parasite genus develop in mayfly larvae. Adults have a cuticle with series of transverse rings with backwardly directed spines (Image 3) diminishing in size and number. The buccal cavity has a cylindrical or funnel-shaped esophagus.  Males have a spirally coiled tail with unequal spicules. Females are oviparous, with thick-shelled, ellipsoidal eggs.  Generally Spinitectus spp. are not pathogenic but in occasions they can cause granulocytic gastritis or enteritis.  In this case it was only an incidental finding.

Image 3.