Blue-ringed octopus (Hapalochlaena sp.) envenomation of a 4-year-old boy: A case report

Abstract

Introduction. The blue-ringed octopus (Hapalochlaena sp.) is a small animal, which can inject a toxin that produces a respiratory arrest within minutes. This envenomation is a rare occurrence with very few reported outcomes in children. Case report. A 4-year-old boy was bitten by a blue-ringed octopus (Hapalochlaena sp.) whilst playing at a popular beach in Queensland, Australia. Within ten minutes of the bite, he had vomited three times, lost the ability to stand and complained of blurred vision. An ambulance was called by the time he presented to the local emergency department (20 minutes after the bite) he had acute and progressive skeletal muscle weakness. He was intubated, ventilated, and transferred to a pediatric intensive care unit for specialized supportive care. He was ventilated for a total of 17 hours with spontaneous muscular activity returning at around 15 hours from envenomation. Discussion. If not treated appropriately the bite of this small and innocuous looking animal could have lead to death within minutes. Conclusion. This case report serves as a reminder of how appropriate treatment can ensure discharge from hospital with no long-term consequences. It also highlights the importance of education for beach goers and in particular parents to prevent exposure of tetrodotoxin to children.

Keywords:

• Emergency department
• Pediatric
• Toxins

Introduction

As more doctors travel to Australasia and work in emergency departments, the local knowledge of how to treat aquatic animal bites may be life-saving. The blue-ringed octopus (Hapalochlaena sp.) is a small animal, which can inject a toxin that produces a respiratory arrest within minutes. This envenomation is a rare occurrence with very few reported outcomes in children. Treatment is mainly supportive and rapid and appropriate actions allow patients to be discharged home within twenty-four hours for this potentially lethal envenomation.

Case report

In September 2006, a 4-year-old boy presented with an acute and progressive skeletal muscle weakness to the Emergency Department (ED) at Redcliffe Hospital in Queensland, Australia. Twenty minutes prior to presentation, he had been playing in the rock pools at a popular beach with his twin brother. His mother had seen him holding a grey/yellow octopus the size of a golf ball and her description of the animal indicated to a Hapalochlaena sp. Unfortunately, the specimen was not available for assessment by experts as it was placed back into the water prior to the development of symptoms. The boy complained that the octopus had bit him. Within ten minutes from initial exposure he had vomited three times, had lost the ability to stand, and complained of blurred vision. An ambulance was called and he was transferred to the ED with marked work of breathing. The medical team recognized the case as a Hapalochlaena sp. envenomation with two small bite wounds on the dorsal aspect of his left hand (Fig. 1). Although his cardio-vascular status remained stable urgent ventilatory support was required. Thirty minutes from the initial exposure he was intubated with a rapid sequence induction and was transferred to a paediatric intensive care unit for continued supportive management. He was ventilated for a total of 17 hours with spontaneous muscular activity returning at around 15 hours from envenomation. He was extubated with no complications and his cardiovascular parameters remained stable during his admission. He was discharged from the intensive care unit 28 hours after the initial bite with no long-term complications.

Fig. 1.  Two small bite wounds (circled with black pen) noted on the dorsal aspect of the left hand of a four year old boy.

Discussion

Hapalochlaena sp. is a small animal that lives in rock pools in seas around Australia, the Indian subcontinent, the Indo-pacific region and Japan (1,2). It is a small cephalopod that is normally grey/yellow in colour with a maximum weight of 100 grams and no greater than 20 cm in diameter from the tip of one arm to the tip of the other (2). It is normally a docile animal that will tend to flatten itself if disturbed. It will bite if it feels threatened such as when it is handled when the striking blue-rings become apparent, as described in this case. There have been three reported deaths in the world, two in Australia (1,3) and one in Singapore (4). The saliva of these animals contains a potent neuromuscular toxin called tetrodotoxin (TTX) (5) present in several marine and terrestrial animals such as puffer fish and toads (6). Specific to Hapalochlaena sp. the toxin is not only used as a defence mechanism but also used for the acquisition of prey. The distribution of the toxin has recently been reported to be present in all parts of the octopus body (5) confirming reports by Huang et al. in 1989 (7). The toxin is either injected using a beak that produces a painless bite (8), or is secreted directly into the water (5). Tetrodotoxin is a potent nerve and neuromuscular blocker that has minimal effects on cardiac muscle function. It is considered a potent poison, painless on exposure with the octopus being the only known animal to be able to survive exposure (2).

The toxin acts by blocking sodium channels, terminating nerve conduction, and muscular action potentials producing a progressive paralysis. Symptoms may develop within minutes of initial exposure and may start with vomiting, muscle weakness, and lead to paralysis of the respiratory muscles. Hypotension, bradycardia, and respiratory failure are recognized side effects and are treated as they develop (9). It is important to remember that fixed and dilated pupils may occur but these patients remain fully aware of there surrounding until hypoxia renders them unconscious (8).

Pathognomonic of a blue-ringed octopus bite is “collapse with paralysis, on or near a beach, shortly after a minor bite”. Although not all bites result in flaccid paralysis (some may have no symptoms or only regional symptoms), all patients with suspected envenomation should be observed closely for the first couple of hours, as respiratory arrest may occur with little warning. It is important to remember that these patients remain conscious even after the paralysis has occurred if no sedation is administered.

The outcome is good with no long-term consequences as long as specific attention is made to respiratory and cardiovascular support. Pre-hospital treatment includes first aid and pressure and immobilisation of the bitten limb. In-hospital treatment requires close observation and supportive measures; no anti-venom is currently available. If envenomation is suspected, close cardiovascular and respiratory observations should occur in a facility that can offer advanced life support. If no symptoms develop within six hours the patients can be discharge from hospital.

Conclusion

Blue ring octopus envenomation is a serious poisoning and individuals with suspected envenomation need to be observed closely and treated with supportive care. Education is the best from of treatment with particular attention needing to be placed with parents as curious children are at greatest risk of disturbing these otherwise non-aggressive animals.