Letter to the Editor: Stinging Catfish Poisoning

To the Editor:

H. fossilis (Bloch, 1794), commonly known as the stinging catfish, is the only species belonging to the family Heteropneustidae found in Asia. Stinging catfish have an elongated, subcylindrial body; just beyond the ventral fin bases, the body tapers off to the tail (Fig. 1). The head is depressed and bony plates cover the top and sides. The snout is depressed, and the nostrils are far apart, the slit-like anterior nostrils are positioned behind the nasal barbules. There are four pairs of rather long barbells, the maxillary pair extending as far as the ventral fins, and the two pairs of mandibular barbells and the nasal barbules reaching the end of the pectoral fins. The mouth is small and terminal. The eyes are relatively small, lateral in position, and with a free orbital rim [1]. H. fossilis are facultative air-breathers that inhabit the swamps of southeast Asia and are quite common. It is dangerous due to the connection between the spines in the pectoral fin and the venom glands. In its natural environment, the fish can reach up to 70 cm in length; however, when bred in the aquarium it is significantly smaller. The males of this species have venom glands located near the spine of the pectoral and dorsal fins. Fishermen are afraid of this fish and if they catch it in their nets, they remove it with a piece of cut-off net, with great care.

Figure 1. Stinging catfish Heteropneustes fossilis.

A 17-year-old man presented to the Department of General Surgery of the District Hospital in Limanowa with a slight injury to the fifth finger of his right hand. He was an aquarium fish breeder. While cleaning his fish tank, he was stung by a ray of the pectoral fin of the stinging catfish (length about 15 cm). The patient was admitted, due to his having fainted. He complained of numbness, dizziness, and quite intense pain at the site of the injury progressively extending into the surrounding areas. At the base of the finger there was a puncture wound about 1 mm in diameter with small edema and erythema. On admission, his temperature was 37.2°C, with a heart rate of 96 and blood pressure of 110/60. Tests were made for the following: ESR, complete blood count, electrolytes, enzymes, and coagulation profile. All of them were normal. Incomplete right bundle branch block was noted on the ECG, but was not considered due to stinging catfish poisoning. The Poison Information Centre of the Clinic of Toxicology, the Jagiellonian University Medical College, Kraków, was consulted. The area of wound was infiltrated with 1% lidocaine and examined carefully. Pieces of foreign material were removed. The wound was thoroughly irrigated and cleansed with antiseptic solution and left open. A plain radiographic study of the injured area excluded retained barbs or other foreign material. The affected hand was immersed in hot water (45°C) for approximately 45 minutes for inactivated venom in the wound. The patient received a prophylactic short course of oral antibiotic therapy with Trimethoprim-sulfamethoxazole. After 24 hours of observation, the patient was discharged from the hospital at his own request under the care of his father. As injuries inflicted by fish may result in delayed presentation of infection it was suggested that the patient be admitted for observation. Over the next month, the wound healed slowly by second intention. At 2 months the wound appeared to be completely healed without any complication. The hand had healed completely without any deficits in motor and sensory function.

In the Clinic of Toxicology of the Jagiellonian University Medical College, various patients are evaluated and hospitalized due to bites inflicted by animals occurring naturally in Poland, as well as those bred in home terrariums [2]. The management, in the case of the poisoning with the stinging catfish venom, is predominantly symptomatic [3&4]. The treatment is predominantly symptomatic. In some fish, there are masses of one-cell glands, mainly serous, in the proximity of the spines. In others, those one-cell glands may be grouped in larger aggregates of cells called venom glands, that may form organs resembling multicellular glands of terrestrial animals. They are usually located around the spines or hard rays of the fins. Even if covered with a connective tissue sheath, the aggregates of the venom cells do not have any common outlet; they are not, therefore, proper multicellular glands. The venom glands of the catfish are covered with a thin sheath and they release their contents when the fin ray is pressed. Spines are derived from fin rays [3]. When the spine penetrates the body of its prey, it presses its base against the cells, squashes them, and squeezes the venomous contents into the wound. The venom appears to contain several components, some lethal to mice and two dermonecrotic fractions [4]. The severity of the poisoning depends on the fish species, the number of stings, and the amount of venom released. The potency of the venom is varied. Venom causes various inflammatory conditions with erythema, edema, local hemorrhage, and tissue necrosis. Other possible signs and symptoms are tachycardia, weakness, hypotension, nausea and vomiting, paraesthesias, dizziness, and respiratory distress [3&4].

The stinging catfish has become a popular aquarium fish in Poland and is available in almost every pet shop. It is also bred on a large scale [5]. Examples of this fish injury are therefore likely to become more common, and with freer movement of goods within the EEC more widespread.