CATFISH SPINE ENVENOMATION (Excerpt from the formal publication by
ANDRA L. BLOMKALNS, MD, EDWARD J. OTTEN, MD
From the Department of Emergency Medicine. University of Cincinnati College of Medicine. Cincinnati. OH.)
Catfish stings are not an uncommon hazard of both recreational and commercial fishing. Of the some 1000 species of catfish in the world, most can inflict venomous stings through their dorsal and pectoral spines. These stings, in addition to being inoculating puncture wounds, are true envenomations and most often occur in the hands during attempts to unhook catfish or in the feet while wading. These wounds require judicious care and symptomatic relief, prophylactic antibiotic administration, and reliable follow-up from the emergency department.
The dorsal and pectoral fins are associated with most of the morbidity resulting from catfish encounters. These fins have cartilaginous, serrated spines that are held erect when the catfish is disturbed. Venom glands are enclosed in a delicate integumentary sheath, and they release their contents when traumatized. The venom causes a severe local inflammatory reaction, with erythema, edema, local hemorrhage, and tissue necrosis in excess of that caused by the wound alone. Other systemic symptoms may be present as well, including tachycardia, weakness, hypotension, nausea and vomiting, paresthesias, dizziness, loss of consciousness, and respiratory distress. The venom is a complex composition of hemolytic, dermonecrotic, edema-producing, and vasospastic factors whose potency is largely inversely proportional to fish size and is a defensive mechanism. Exact venom constituents vary from species to species. Saltwater and tropical species generally produce the worst symptoms and, often, the worst infections.
A second toxic mechanism, crinotoxicity, has been identified in some catfish species, namely Arius thalassinus and Platatus lineatus. Crinotoxins are proteinacous substances found in the epidermal secretions coating the entire surface, not just the spines, and are released when the catfish is excited or threatened. If exposed to open skin, these toxins can cause similar symptoms of throbbing pain, tissue necrosis, and, possibly, muscle fasciculation.
The most serious long-term complications of catfish spine envenomations involve infections. Since catfish-inflicted wounds are most often puncture wounds rather than lacerations, these injuries are essentially bacterial inoculums set up for infection. One series of case reports reported serious infections requiring ray amputations in two patients; another reported wound progression to dry gangrene, necessitating digit amputation.
Organisms in many reports included Klebsiella,Erysipelothrix, Nocardia, Chromobacterium, Sporothrix, Actinomyces, Edwardsiella, Mycobacterium, Aeromonas, and Vibrio. It was noted that patients with predisposing illnesses and in immunocompromised states are especially susceptible to infections from Vibrio, The microbiologies of freshwater and saltwater infections differ greatly, but the most worrisome organisms are the Vibrio species for saltwater infections and Aeromonas for freshwater infections. Aeromonas infections can look very much like typical streptococcal or staphylococcal cellulitis, but are resistant to penicillins and cephalosporins. Empiric therapy against gram-negative rods is suggested, with ciprofloxacin being the single most popular and effective agent against freshwater and saltwater bacterial isolates, Aminoglycosides have been advocated by others. However, in the absence of serious bacterial infection, oral cephalosporins are advocated by some authors.
Treatment should begin with careful cleansing of the surrounding skin surface, Symptomatic measures should include local infiltration of a long-acting local anesthetic without epinephrine and regional blocks when feasible after a careful neurologic exam. As the venoms are all heat-labile to some degree, immersion of the affected extremity in warm water may be the most beneficial and expeditious symptomatic treatment measure, Water temperatures from at least 45°C (l13°F) to as hot as can be tolerated without scalding have been advocated, Effectiveness, patient tolerance, and the necessity to manipulate the hand for treatment should dictate total immersion time. Although not all catfish spines are reliably radio-opaque, radiographs to inspect for foreign bodies should be included in all cases. These films require careful and meticulous examination to visualize free tiny serrations. Tetanus prophylaxis should be given when indicated, After reasonable pain management, attempts should be made to irrigate, explore, and debride the wound if evidence of a foreign body is present on a plain radiograph, keeping in mind that smaller spine components and epidermal fragments may not be present on the radiograph at all. Due to the structural nature of the spine, spine extraction and debridement can be difficult, as was the case with the presenting patient. The angled serrated edges prevent easy retrograde extraction and often remain behind if the spine is extracted using excessive force. If gentle traction fails to produce an intact spine, circumferential excision in the operating room may be necessary.