CASE REPORT

Stonefish “Okoze” Envenomation during Food Preparation
Ryo Yamamoto, Masaru Suzuki, Shingo Hori and Naoki Aikawa

Department of Emergency & Critical Care Medicine, School of Medicine,
Keio University, Tokyo, Japan(Received for publication on April 15, 2009)(Revised for publication on August 10, 2009)(Accepted for publication on September 17, 2009)

Stonefish is a dangerous and venomous fish commonly found in the shallow waters of the Pacific region. Its envenomation is reported worldwide with increasing frequency. Although envenomation usually occurs in those engaged in marine sports, chefs may suffer envenomation
during cutting stonefish, which is eaten either sliced raw, boiled, or deep-fried by Japanese.
Since many people cook and eat Japanese food, it is important to know that cutting a stonefish
for cooking carries the risk of envenomation. However, most primary and emergency physicians have not encountered cases of envenomation during food preparation. Here we describea case of envenomation occurring while cooking. The patient was a healthy 33-year-old man
working as a chef in a Japanese restaurant. He was presented to an academic emergency department after suddenly developing severe pain in his right fourth finger while cutting a stonefish. The finger was reddish, swollen, and tender. The pain reduced after immersing his hand in
hot water, and disappeared within 18 h without any complication. In this report, we describe
the history of stonefish envenomation and provide a brief review of the literature related tothis form of envenomation. (Keio J Med 59 (1) : 19－22, March 2010)

Keywords: stonefish, envenomation
Introduction

countered cases of envenomation occurring while cooking. Here we present a case of envenomation that occurred while cutting the stonefish okoze.

The stonefish “okoze” is considered the most venomousof fish. It lives in the shallow waters of the Pacific region. Each stonefish has 13 dorsal spines, and each spine
is connected to a pair of venom glands capable of producing a very potent but heat-labile venom.1, 2 The venom contains a proteinaceous toxin, which initially causes
severe pain around the site punctured by the fins. It has
also been reported to be myotoxic, neurotoxic, vasopermeable, and cardiotoxic.3, 4 The craggy and warty surfaceof the fish provides excellent camouflage against the surrounding mud. Swimmers or divers are usually injuredby accidentally treading on the fish. Therefore, patientswith stonefish envenomation often present to hospitals inlocations where beach activities are a common pastime.
In some parts of Asia, such as Japan, stonefish is considered a great delicacy. Cutting this fish is a well-known
occupational hazard for seafood handlers. However,most primary and emergency physicians have not en-Case Report
A healthy 33-year-old man working as a chef in a Japanese restaurant was presented to an academic emergency
department (ED) by ambulance because of sudden severe pain in the fourth finger of his right hand. The pain
started while he was cutting an okoze (Fig. 1A). His finger was punctured by the spine of the stonefish (Fig. 1B).
He described the pain as intense, constant, throbbing,and extending with numbness to the right palm, although
he had no cardiopulmonary symptoms such as dyspnea,wheezing, palpitation, faintness, or lightheadedness. His
vital signs were stable and normal. Physical examination
revealed redness and swelling of the finger with bruisingon the fingertip (Figs. 2 and 3) and tenderness of the entire finger. There were no other skin or mucosal lesions.

Reprint requests to: Ryo Yamamoto, MD, Department of Emergency & Critical Care Medicine, School of Medicine, Keio University, 35 Shinanomachi, Shinjuku, Tokyo 160-8582, Japan, Tel: +81-3-3225-1323, Fax: +81-3-3353-2232, E-mail: redskybluesea@hotmail.com
19

Yamamoto R, et al: Stonefish “Okoze” Envenomation

20AB

Fig. 1 (A) Stonefish “Okoze” (Reprinted photo from Kanagawa Prefectural Museum of Natural History). 13 dorsal spines are armed
with toxic fish venom. (B) Scheme of stonefish “Okoze.” Spines inside dotted frame have toxic venom.

Other physical and neurological findings showed no abnormalities. He had no history of allergies, and laboratory and imaging tests were not needed.
Based on the symptoms of the present illness andphysical examination findings, the patient was diagnosed
with stonefish envenomation. However, pricks or residual fins were not detected in the finger. After irrigationand sterilization with alcohol, his right hand was immediately placed in a basin of hot water to relieve the pain.
The pain and numbness disappeared within 30 min of
hot water immersion. No other symptoms developed
during his stay in the ED. Four days later, he reported
that the pain and tenderness lasted for only 18 h and disappeared by the next morning, without the need to take apainkiller or an antimicrobial agent.
Written informed consent for publishing the report ofthis case was obtained from the patient.
Discussion
In this report, we describe a case of stonefish envenomation that occurred while cutting the stonefish okoze,
which is considered an occupational hazard for seafood
handlers. Although stonefish envenomations have beenreported worldwide with increasing frequency, most reports describe envenomation occurring among individuals engaged in marine sports.1, 5, 6 To our knowledge, thecase described here is the first report of envenomation
occurring while cooking; it is not related to marine activities. Since diagnosis is made based on the history, it isimportant to know that cutting a stonefish while cooking
Japanese food carries a risk of envenomation.
Stonefish belong to the Synanceiidae family, whose
members are equipped with a sophisticated defense
mechanism. Dorsal spines armed with toxic fish venom
prevent attack from their natural foes. They live in tropical and warmer temperature oceans worldwide and canlie perfectly camouflaged under the sand in shallow wa-ters, and hence, envenomation by these fish usually occurs among individuals who step on their ventral finsduring marine activities and water sports.1 Interestingly,Japanese chefs also suffer stonefish envenomation while
cutting okoze, a kind of stonefish. Okoze is considered adelicacy or savory dish in some parts of Asia, including
Japan, although it is rarely eaten in other countries.7 Thisdifference in the cuisine culture relates to the types ofstonefish living in the local area. Envenomations during
marine sports are mainly caused by Synanceia verrucosa, which is inedible, as well as S. nana and S. hornium.
Inimicus japonicus, also known as okoze in Japan, lives
mainly in Asia, and the Japanese eat it sliced raw, boiled,or deep-fried.
Expert chefs do not usually suffer envenomation because they avoid the ventral fins when handling the fish;
however, some chefs in training and those unfamiliar
with Japanese food may be injured through contact withokoze. Since many people eat Japanese food and cook
many kinds of fish, including venomous fish such asstonefish, scorpionfish, and stingray, cases of envenomations occurring while cooking may increase. To preventstonefish envenomation, chefs cooking Japanese foodneed to know which types of stonefish contain venom
and where such venom is stored; the chefs must also develop expertise in handling these fish. The standard technique is to insert the second finger into the mouth of thefish to hold it while cutting off the ventral fins. Furthermore, health professionals must know that food handlers
are at risk of stonefish envenomation while cutting okoze
and must teach proper techniques to chefs unfamiliar
with these fish.
Many case reports and series have shown that stonefish envenomation is usually self-limiting with no significant consequences. Primary care providers must therefore be educated about pain relief, including hot water
immersion, administration of oral or parenteral opioid
analgesics, and local infusion of lidocaine, which are all

Keio J Med 2010; 59 (1): 19－22

21Fig. 3 The fourth finger of the right hand. Bruising was revealedon the fingertip, 30 minutes after injury.

Fig. 2 The right hand of the patient on arrival. The fourth fingerof the right hand had redness and swelling, 30 minutes afterinjury.

essential for treatment.6 A study has reported that thefoot is the most common site of injury, accounting for
83% of cases. In this study, it has been reported that only
17% of injuries are on the fingers.8 However, as an occupational hazard for workers in the food industry, themost commonly injured site may be the hand, including
the index finger. The stonefish venom verrucotoxin is an
unstable protein with a pH of 6.0 and molecular weightof 150,000. Laboratory studies have shown that the venom contains a proteinaceous toxin, which is myotoxic,neurotoxic, vasopermeable, and cardiotoxic. 3, 9 One
study found that the toxin inhibits KATP current throughthe muscarinic M 3 receptor-PKC pathway. 9 Anotherstudy reported that the toxin modulates Ca2+ channel activity through the beta-adrenoreceptor-cAMP-PKA pathway.3 Although the toxicities are not yet fully understood, it is well known that the toxin is denatured byheat, which may result in a loss of toxicity. Thus, it has
been recommended that the affected site be immersed in
nonscalding hot water (45°C) for 30 to 90 min or until
the pain subsides. Studies have concluded that hot water
soaks are effective in controlling the pain in 74% of cases.2, 4 In the present case, hot water immersion was performed for 30 min, and the patient’s pain subsequently
disappeared after 18 h.
In most patients, the pain disappears completely andsensation returns; however, there have been rare reported
cases of respiratory weakness, heart failure, convulsions,

necrotizing fasciitis, and severe tissue necrosis.1, 6, 7, 10Some of them have also recommended prophylactic useof antimicrobial agents. Activity and proliferation ofsome microbes, such as Vibrio vulnificus, are positivelycorrelated with surrounding temperature. Thus, a hot water bath used in the absence of concomitant prophylactic
antimicrobial agents may raise the subcutaneous temperature of the affected area and consequently facilitate theactivity and proliferation of those microbes.2, 7 Therefore,
administration of antimicrobial chemotherapy before orduring hot water immersion should be considered, although prophylactic antimicrobial chemotherapy hasbeen controversial. In the present case, despite the absence of antimicrobial chemotherapy, there was no bacterial infection on the finger. In all cases, the patient’scondition should be carefully and closely monitored, regardless of whether prophylactic antimicrobial chemotherapy is included in the treatment.
In conclusion, stonefish envenomation can occur
among chefs in Japanese restaurants as well as individuals engaged in water sports. Since many people cook andeat Japanese food, health professionals should be awarethat cutting okoze is a risk factor for stonefish envenomation and should know how to apply pain relief, including hot water immersion therapy.
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