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Echinoderm Envenomation

Author: Scott A Gallagher, MD, FACEP, Chairman, Department of Emergency Medicine, Aspen Valley Hospital; Senior Clinical Instructor, Department of Surgery, School of Medicine, University of Colorado Health Sciences Center
Contributor Information and Disclosures

Updated: Mar 10, 2008

Introduction

Background

The phylum Echinodermata includes a diverse group of marine animals that are slow moving and nonaggressive, including brittle stars (class Ophiuroidea), starfish (class Asteroidea), sea urchins (class Echinoidea), and sea cucumbers (class Holothuroidea). These animals have pentamerous (5-part) radial symmetry and calcareous skeletons that form thick outer plates and protective spines in some; hence, they are named Echinodermata, which means spiny skin. Injury and envenomation occur almost exclusively from accidental contact or careless handling; bathers, divers, and fishermen are at greatest risk. Poisonous echinoderm ingestions or intoxications are not covered in this article.

Pathophysiology

While most echinoderms are poisonous, and many have sharp spines or spicules capable of causing injury, only a few members of the Asteroidea, Echinoidea, and Holothuroidea classes are capable of causing venomous injuries in humans. In this article, envenomation refers to the parenteral or topical application of toxins produced in specialized glands and tissues with modified application structures (spines, pedicellaria, tentacles). This definition is in contrast to poisoning or intoxication, which refers to the oral ingestion of toxins produced or accumulated in nonspecialized glands or tissues.

Brittle stars (class Ophiuroidea; see Media file 6) are not generally considered capable of causing venomous injuries in humans. However, some brittle stars (Ophiomastix annulosa) do possess toxins and are capable of causing paralysis and death in small animals. These animals should be handled with care.

Sea urchins (Echinoidea) capable of causing venomous injuries in humans use specialized spines (long or short) and pedicellaria (delicate seizing organs equipped with pincerlike jaws) to deliver their venom. Although both structures are present, generally only one is venomous in a given species. Thus, grouping the venomous urchins into 1 of the following 3 categories is convenient:

• Long-spined species may inject venom during a puncture with rupture of the overlying integument (Diadema species; see Media file 5) or with fracture and release of venom from hollow-lumen spines (Echinothrix species).

• Short-spined species similarly may envenom during puncture when downward pressure ruptures the surrounding integument (Phormosoma species), or they may deliver a severe sting without puncture via venom glands located at the spine tips (Asthenosoma species, Araeosoma species).
• Species with pedicellaria include those reputed to be the most venomous of all sea urchins, the flower urchin (Toxopneustes pileolus), and others that are less venomous (Tripneustes species). Pedicellaria are small, delicate, tripled-jawed seizing organs that are supported by a long stalk and interspersed among numerous nonvenomous spines. Fanglike appendages are associated with venom glands at the tips of each jaw. The fangs are capable of penetrating skin and may be difficult to dislodge because the valve muscles tightly close each jaw. Pedicellaria continue envenoming even when detached from the urchin body and, thus, should be removed promptly.

Sea cucumbers (Holothuroidea) are generally regarded as nonvenomous, although many are poisonous to eat without proper preparation. The Cuvierian tubules of some sea cucumbers are toxic and may be extruded from the anus as a defensive mechanism when the animal is disturbed or irritated (Bohadschia argus; see Media file 4).

Frequency

United States

Echinoderm envenomations do not represent a significant public health problem, although little epidemiologic data are available. Venomous echinoderms are encountered principally in tropical seas. Nonvenomous traumatic injuries from echinoderms are not uncommon in the United States, especially in coastal communities where sea urchins live.

International

Echinoderm envenomations are quite common, although little epidemiologic data are available.

The most common starfish envenomization results from contact with the crown-of-thorns starfish (Acanthaster planci), which populates reefs of the Indo-Pacific from east Africa to Central America. Similarly, sea urchins capable of envenomation tend to be concentrated in tropical and subtropical marine regions. The Indo-Pacific is the home of all categories of venomous urchins, including Diadema, Echinothrix, and Toxopneustes species and the venomous genera of sea cucumbers (Holothuria). For some Chinese, Malay, and Pacific Island gourmets, properly prepared sea cucumbers are prized as a delicacy (eg, beche-de-mer, trepang).

Mortality/Morbidity

Significant local and systemic effects are possible following echinoderm envenomation from any of the 3 venomous classes, starfish (Asteroidea), sea urchins (Echinoidea), and sea cucumbers (Holothuroidea). However, a clear link between echinoderm envenomation and death (other than subsequent drowning) cannot be found in the literature, despite several anecdotal reports of fatalities.^4,2,5,6 Detailed documentation is sparse, and death must be very rare. This is in contrast to poisoning or intoxication following ingestion of certain echinoderms, which has been well documented to result in severe illness and fatality.

Clinical

History

Immediate and often incapacitating pain is described following puncture wounds from the crown-of-thorns starfish (Acanthaster planci), long-spined urchins (Diadema species, Echinothrix species), and some short-spined urchins (Phormosoma species). Similarly, pedicellaria-containing urchins (Toxopneustes species, Tripneustes species) and other short-spined urchins (Asthenosoma species, Araeosoma species) may deliver a severe sting at the slightest touch without inflicting any puncture at all. Significant ocular inflammation, dermatitis, and pain may follow topical exposure to the holothurin toxins of venomous sea cucumbers.

• Crown-of-thorns starfish (Acanthaster planci)
  • Envenomation begins with penetration of the skin with the long remarkably sharp dorsal spines. Usually, but not invariably, immediate excruciating burning pain is experienced at the puncture site. Divers are reportedly at risk of unsafe ascent, disorientation, and loss of control because of the intense pain. A single puncture may result in several hours of pain, while multiple or intraarticular punctures may lead to pain, discomfort, and limitation of joint movement for several weeks.
  • Bleeding at the puncture site may be prolonged in some patients and is followed by surrounding ecchymosis and soft tissue swelling. Systemic symptoms of protracted nausea and vomiting, headache, arthralgias, paresthesias, and muscular paralysis are less substantiated than the other symptoms described but, nevertheless, are reported in several texts. Case reports of edema and pruritus suggest the possibility of allergic reaction, although no reports of anaphylaxis or fatality are mentioned.
  • Common complications result from retained foreign material and include secondary infection and granuloma formation.
• Sea urchins: The mechanism of envenomation varies among the 3 groups.
  • Long-spined urchins (Diadema species, Echinothrix species) are capable of causing deeply penetrating injuries. Envenomation initially results in severe burning pain, which is localized to the puncture site and may last several hours, reappearing with any pressure on the wound site. Localized edema, erythema, warmth, and bleeding may follow. The systemic symptoms of nausea, vomiting, paresthesias, muscular paralysis, and respiratory distress occur in the most severe cases. Delayed sequelae include wound tattooing as pigment is leeched from dark-colored spines into the surrounding tissue, synovitis if a joint space is violated, and secondary wound infection or granuloma formation if foreign material is retained.
  • Some short-spined urchins have spines tipped with balloonlike venom sacs that are capable of delivering a severe sting without inflicting a penetrating wound (Asthenosoma species, Araeosoma species), while others envenom in a fashion similar to long-spined urchins, releasing venom into the wound when the spine penetrates the skin (Phormosoma species).
  • Urchins with pedicellaria may envenom following simple handling if sufficient contact occurs. The flower sea urchin (Toxopneustes pileolus) is reputedly the most venomous of urchins. Intense radiating pain, paresthesias, hypotension, respiratory distress, and muscular paralysis are potential sequelae of contact with this species and may last up to 6 hours. Reportedly, a female pearl diver became unconscious after accidental contact with the flower sea urchin and subsequently drowned.
• Sea cucumbers
  • Envenomation follows contact with the toxin-containing body wall or the organs of Cuvier, a mass of white, pink, or red tubules just inside the anus. In some species, long sticky threadlike organs may be extruded from the anus when the animal is disturbed. Direct contact with these organs, or even fragments released in close proximity to a diver, may induce a papular contact dermatitis, severe ocular inflammation, and, purportedly, blindness.
  • Similarly, toxic mucous secretions on sea cucumber skin can be a skin and eye irritant. These toxins, known as holothurins, also are elaborated in the body wall and, thus, are capable of causing severe illness or death upon ingestion.

Physical

The severity of envenomation depends on multiple factors, including the offending species; site and number of stings; the size, maturity, and age of the animal; and the underlying health and individual sensitivity of the individual exposed.

• Puncture wound
  • In addition to immediate pain, deep puncture wounds that accompany envenomation by crown-of-thorns starfish (Acanthaster species), long-spined urchins (Diadema species, Echinothrix species), and some short-spined urchins (Phormosoma species) often are associated with retained spine fragments and persistent discomfort. Violet or black discoloration of the wound may occur as pigment from dark-spined species (Diadema, Strongylocentrotus) leeches into the wound; this discoloration usually is not permanent. Bleeding, ecchymosis, surrounding erythema, edema, and even pruritus may follow spine puncture by Acanthaster species.
  • Complications arise when punctures occur in proximity to a joint space (eg, synovitis), nerves (eg, neuropathy), vessels (eg, hemorrhage), or when wounds become indolent, often because of retained spine fragments (eg, chronic pain, granuloma, secondary infection).
  • Nonpenetrating wounds result from envenomation by some short-spined urchins (Asthenosoma species, Araeosoma species) and pedicellaria-containing urchins (Toxopneustes species, Tripneustes species). Although the local complications that follow puncture wounds do not occur, significant pain and systemic effects result.
  • Sea cucumber envenomations similarly are not associated with puncture wounds. Contact with the venomous tentacular organs of Cuvier or dispersed fragments may result in severe dermatitis, conjunctivitis, keratitis, and, possibly, blindness.
• Systemic effects
  • A panoply of systemic effects has been described following echinoderm envenomations; they commonly include nausea, vomiting, paresthesias, generalized weakness, respiratory distress, and delirium. Claims of cardiac dysrhythmias, paralysis, and fatality are difficult to substantiate. The most severe echinoderm envenomations result from stings by the flower sea urchin (Toxopneustes pileolus) and have caused at least 1 death following loss of consciousness and subsequent drowning in a Japanese pearl diver.
  • No deaths are known to have resulted from the crown-of-thorns starfish (Acanthaster planci), although injury eventually resulting in leg amputation has been reported. Long-spined black sea urchins (thought to be Diadema species) have been implicated twice in severe neurologic sequelae, one case of meningoencephalitis and another of Guillain-Barré syndrome. The theoretic possibility of anaphylactic reaction to echinoderm venoms is entertained by some, although no cases have been documented to date.
• Delayed sequelae
  • Delayed sequelae include chronic pain, granuloma formation, wound tattooing, and secondary infection.
  • Tetanus may result following echinoderm envenomations accompanied by puncture wounds.

Causes

Echinoderms are slow moving and nonaggressive; injury and envenomation occur as the result of accidental exposure or careless handling.

• Bathers, waders, and divers are at risk of stepping on or being forced against the sharp spines of venomous sea urchins and starfish, especially in waters with strong surges, currents, or poor visibility.
• Fishermen and overly curious individuals often become envenomed through careless handling.
• The sharp spines of venomous long-spined urchins, certain short-spined urchins, and starfish can easily penetrate wet suits and gloves. The stinging tips of other short-spined urchins and those with pedicellaria easily envenomate through exposed skin.
• Sea cucumbers may induce severe contact dermatitis or ocular injury in divers following unprotected handling or mask clearing in close proximity to the animal.

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