Marine Food-Borne Poisoning, Envenomation, and Traumatic Injuries

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142 Marine Food-Borne Poisoning, Envenomation, and Traumatic Injuries

Stephen Thornton, Richard F. Clark

image      Key Points

• Scombroid is thought to be caused by breakdown of histidine into histamine in dark-meat marine fish and can be managed with antihistamines.

• Ciguatera poisoning results from the consumption of large tropical predatory reef fish that have bioaccumulated ciguatoxin; it causes gastrointestinal distress and neurologic symptoms.

• Tetrodotoxin blocks sodium channels and can lead to ascending paralysis and respiratory failure.

• box jellyfish (Cubozoa). Portuguese man-of-war (Hydrozoa), and other stinging marine invertebrates envenomate humans via nematocysts that contain a stinging barb and venom.

• The box jellyfish (Chironex fleckeri) and related species cause the most morbidity and mortality of all marine envenomations.

• Acetic acid immersion is recommended for the treatment of box jellyfish envenomation but may worsen man-o-war envenomation.

• Hot water immersion appears to be an effective treatment of almost all marine envenomations.

• Sea snake venom is neurotoxic and myotoxic. Treatment with antivenom is effective.

• Evaluation for a retained foreign body should be considered with stingray and spiny fish envenomation.

• Wound infection is a common complication of spiny fish and stingray envenomation, and prophylactic antibiotics effective against common pathogens such as Vibrio species should be considered.

• Direct marine injuries are usually abrasions and contusions, but fatal attacks by sharks and large predatory fish do occur.

Perspective

As human contact with the ocean and the organisms that live in it continues to increase, the impact of poisonings, envenomations, and direct trauma by these marine organisms will also grow. Marine food-borne poisonings can cause large outbreaks, and direct envenomation by the innumerable stinging organisms in the ocean cause significant morbidity. Less common but more dramatic, attacks by sharks and other large marine organisms cause deaths every year. Thus, it is important for physicians to be aware of the hazards posed by marine organisms and be familiar with appropriate treatment options.

Epidemiology

Poisoning from the ingestion of marine animals such as shellfish and fish constitutes a small but consistent source of food poisoning outbreaks and illnesses.1 Although mortality is low, morbidity can be significant, with many patients needing to seek medical care.2 Tetrodotoxin poisoning is an exception, and significant mortality has been reported.3

Even though the vast majority of marine sea life is harmless to humans, a small but important percentage does cause human envenomation with resulting morbidity and mortality. It is difficult to quantify the annual number of marine envenomations because most victims will not seek medical care and reporting cases to health departments or poison centers is not mandatory. Some estimate the number of marine envenomations worldwide to be greater than 10 million per year, with the majority being caused by jellyfish.4 Deaths are reported every year from envenomation by certain species of jellyfish, most commonly the box jellyfish.5

The true number of traumatic injuries caused by marine life is difficult to estimate. Most will consist of only minor abrasions and contusions, but occasional fatal traumatic injuries do occur. Attacks by sharks and large predatory fish cause human fatalities every year.6 Stingray barbs can cause significant direct trauma and death.7

Marine Food-Borne Poisonings

Pathophysiology

The toxins responsible for the signs and symptoms of marine food-borne illnesses are primarily produced in microorganisms such as dinoflagellates, diatoms, and marine bacteria and are bioaccumulated by shellfish or fish, which are then ingested by humans and result in toxicity. Most of these toxins modulate neuronal and muscle sodium channels. Scombroid is not caused by a preformed toxin but rather by breakdown of histidine into histamine in inadequately stored dark-meat fish. Table 142.1 lists the common marine food-borne poisonings, causative toxins, and typical sources of such poisonings.8

Table 142.1 Common Marine Food-Borne Poisonings

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Presenting Signs and Symptoms

Table 142.1 lists the typical onset and common symptoms associated with marine food-borne poisonings. Typically, a history of seafood ingestion can be obtained. In most cases the symptoms are manifested within minutes to hours and include a mixture of gastroenteritis (nausea, vomiting, and diarrhea) and often dramatic neurologic findings.

Differential Diagnosis and Medical Decision Making

The differential diagnosis for marine food-borne poisoning includes disease processes that cause acute neurologic symptoms with or without gastrointestinal symptoms. Botulism, myasthenia gravis, poliomyelitis, and tick paralysis should be considered. In cases in which the neurologic symptoms are not as obvious, the more common bacterial causes of food-borne poisoning would also need to be considered. The diagnosis of marine food-borne poisoning must be made on a clinical basis because testing for the specific toxins is not readily available.

Treatment

Treatment of marine food-borne poisoning is entirely supportive (see Table 142.1

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