The South American astroblepins have flattened suctorial lips that allow them to scale cliffs. Tiny
South American (Amazonian) catfish of the genus Vandellia are known as "urethra fish" in English, "candirú"
by Brazilians, and "canero" by Spanish speakers. Approximately an inch long, they carry short spines on their
gill covers . The fish is putatively attracted to urine (water motion, warmth) and can swim up the human
urethra or other urogenital apertures, where it extends the gill covers and thus becomes embedded, preventing
removal by pulling on the fish's tail. Within the urethra, it causes extreme pain and inflammation. Since the
animal normally seeks the outflow stream from a larger fish's gills, perhaps it is not urinophilic, but merely
swimming upstream. Natives wear pudendal shields when urinating in natural bodies of water. A tight-fitting
bathing suit is certainly prudent.
At best, extraction is painful. Amputation of the penis by natives has been described in the older
literature. Ingestion of the green fruit of the jagua tree or buitach apple (Genipa americana L.) as a concoction
(tea) apparently works to dispel the urethra-lodged candirú by the action of a large quantity of citric acid
(mega-dose vitamin C), which softens calcium spines.
The venom apparatus of the common catfishes consists of the single dorsal and two pectoral fin spines
("stings") and the axillary venom glands. Both the dorsal and pectoral spines are exquisitely sharp and can be
locked into an extended position by the fish when it is handled or becomes excited. The spines are enveloped
by glandular tissue within an integumentary sheath; some spines have sharp retrorse teeth. Scattered reports
note envenomation in persons who handled only the tail of the fish, such as the Arabian Gulf catfish (Arius
thalassinus), which suggests the presence of a toxic skin secretion (crinotoxin). Other observers note that
toxin released from epidermal skin cells can cause throbbing pain, tissue necrosis, and perhaps muscle
fasciculations. Oriental catfish toxin, which is poorly antigenic, contains vasoconstrictive, hemolytic, edema-
forming, dermatonecrotic, and other biogenic fractions. It behaves in vivo much like a milder version of
stingray venom. In contrast, the crinotoxin of the Arabian Gulf catfish contracts smooth muscle and stimulates
the release of prostaglandins; pretreatment with atropine and indomethacin attenuates the response.
Furthermore, wound healing responses are accelerated by repeated local application of preparations from the
epidermal secretions of another Arabian gulf catfish (Arius bilineatus Valenciennes).
Most stings are incurred when a fish is handled, which creates an injury out of proportion to the
mechanical laceration. When the spine penetrates the skin, the integumentary sheath is damaged and the
venom gland exposed. Catfish stings are described as instantaneously stinging, throbbing, or scalding, with
central radiation up the affected limb. Normally the pain subsides within 30 to 60 minutes, but in severe cases
it can last for up to 48 hours. The area around the wound quickly appears ischemic, with central pallor that
gradually becomes cyanotic before the onset of erythema and edema. Swelling can be severe and secondary
infections are frequent; gangrenous complications have been reported. Common side effects include local
muscle spasm, diaphoresis, and fasciculations. Bleeding from the puncture wounds may be more severe than
expected. Less common sequelae are peripheral neuropathy, lymphedema, adenopathy, lymphangitis,
weakness, syncope, hypotension, and respiratory distress. Death is extremely rare. The sting of the marine
catfish is usually more severe than that of its freshwater counterparts and may have a propensity to more local
hemorrhage.
36
Infection risk is similar to that for any aquatic-acquired wound, in that Vibrio and Aeromonas
species may be pathogens and the infection may be polymicrobial. Other organisms that have been reported to
be associated with marine or freshwater catfish-related injuries include Edwardsiella tarda, Citrobacter
freundii, Fusobacterium mortiferum, Morganella morganii, Providencia rettgeri, Enterococcus faecalis,
Pseudomonas aeruginosa, Mycobacterium terrae, and Enterobacter cloacae. E. tarda is a gram-negative
bacillus of the family Enterobacteriaceae that is mainly associated with aquatic environments and the animals
that inhabit them, particularly catfish and other cold-blooded animals. It may be a pathogen for eels and
catfish. If E. tarda infection is determined, it is sensitive in vitro to ampicillin, aminoglycosides,
-lactamase
stable cephalosporins, quinolones, tetracycline, and trimethoprim-sulfamethoxazole.
There are no specific antidotes. As with stingray and scorpionfish envenomations, the success of
therapy is related to the rapidity with which it is undertaken. With catfish envenomations, in contrast to those
of stingrays, constriction bandages have not been shown to be of value. The wound should be immediately
immersed in nonscalding hot water to tolerance (upper limit 113
o
F or 45
o
C) for 30 to 90 minutes or until
there is significant pain relief. This may inactivate heat-labile components of the venom and perhaps helps to
reverse local toxin-induced vasospasm. There is no evidence that adding mineral salts, solvents, antiseptics, or
