Abstract

Mechanical removal was examined as a method for eliminating philometrid nematodes from the periocular space of infected fish. The technique was tested on 17 wild caught pond fish [4 redear sunfish (Lepomis microlophus) and 5 bluegill (Lepomis macrochirus)] that developed clinical exophthalmia during routine quarantine. Bilateral periocular nematode infestation with adult philometridswas confirmed in the necropsy of an affected bluegill that was humanely euthanized with MS-222 for necropsy diagnosis. Each of the remaining 17 affected fish were anesthetized and maintained with buffered MS-222. A 24 gauge 3/4" catheter needle was used to make small incisions in the dorsal and ventral conjunctiva of each eye. The periocular space was then flushed with sufficient volume of 0.9% sterile NaCl solution to force the worms to extrude through the incisions using the catheter and a 60 ml syringe. Thumb forceps were used to grasp and remove the partially exposed live nematodes. Each incision site was treated with ophthalmic 0.03% flurbiprofen sodium drops and 10% povidone iodine ointment. The fish were then recovered from anesthesia and maintained in water with 3 to 5 ppt sodium chloride. In hopes of eliminating any parasites that might have encysted in internal tissue, the fish were treated with 2 mg/L fenbendazole in tank water.

A total of 21 nematodes were removed using the technique. The maximum number of parasites removed from a single fish was four, and no parasites were removed from 24 of the 34 eyes operated. One juvenile redear sunfish and one juvenile bluegill died two days following the procedure but the other 15 fish recovered uneventfully and remain well 50 days after the completion of the mechanical worm removal procedure. No signs of Philometra in the periocular spaces have been observed since the procedures. The exophthalmia resolved in all fish regardless of whether or not worms were found in and removed from their periorbital spaces. Though the role of the removal of the worms in the resolution of the exophthalmia is unclear, the procedure appears to have been an effective method for removal of adult Philometra sp. from the periocular spaces of fish.