Marine injury, envenomation and poisoning

Stingray

Stingrays possess a barbed spine with an enveloping integumentary sheath and associated venom glands on the tail. Injury usually occurs when the animal is trodden on, resulting in a wound on the distal half of the lower limb. Often a combined penetrative–lacerative injury, these wounds can appear deceptively minor. Part of the barb and its integumentary sheath is frequently left in the wound and as such, all wounds require exploration, meticulous debridement and cleaning, and then consider delayed primary closure and prophylactic antibiotics.

Although the majority of injuries are minor, three deaths have been documented in Australia, the last occurring in 2006. All died from penetrating cardiac wounds. All wounds to the chest and abdomen need to be treated as a penetrating injury. The patient should be admitted and appropriately investigated and observed.

Disproportionate pain lasting hours presumably occurs from the accompanying venom, and immersion in hot water may be of benefit in addition to parenteral narcotics and regional anaesthesia. Local injury occurs from both direct trauma and envenoming. Systemic envenomation is rare and usually minor with nausea, headaches and light-headedness, though there are reports of seizures and cardiovascular collapse. Treatment is symptomatic and no antivenom is available.

Cnidaria

Only Chironex fleckeri (box jellyfish) and Carukia barnesi (‘classic’ Irukandji jellyfish) have been documented to cause deaths in Australian waters, with the Australian Resuscitation Council (ARC) attributing 80 deaths to C. fleckeri , and 2 to Irukandji syndrome. Children are particularly prone to a fatal outcome and account for the last 10 C. fleckeri deaths in the Northern Territory.

Victims of C. fleckeri envenomation are readily identifiable from the characteristic cutaneous features. In comparison, stings from C. barnesi and other Irukandji syndrome-inducing jellyfish may have minimal or absent cutaneous manifestations. Other cnidaria may cause serious envenomation, although no deaths have been recorded in Australian waters from these species. In recent years C. barnesi have been found near Fraser Island and this appears consistent with models predicting southerly migration from rising ocean temperatures.

Chironex fleckeri

C. fleckeri , commonly referred to as the box jellyfish, is found in tropical coastal and estuarine waters of northern Australia, predominantly between November and April. It, or similarly deadly cubomedusae, are likely to be found in other tropical environments including those of Papua New Guinea (PNG), the Indonesian archipelago and South East Asia, based on similar case reports from these areas. The bodies of mature animals may be 40 cm in size with as many as 60 tentacles trailing for up to 3 m. These tentacles have a typical banded appearance, that impart the characteristic frosted ladder cutaneous lesions. Lethal envenomation has only been reported where more than 2.5 m of tentacles have been involved. The venom is a complex mixture of proteins ranging in size from 54 to 150 kDa; however, most of these proteins are yet to be researched and only some are demonstrably antigenic to CSL box jellyfish antivenom.

In a prospective study of jellyfish stings presenting to the Royal Darwin Hospital over a 12-month period, of 23 patients with nematocyst proven C. fleckeri stings, only 1 required parenteral analgesia and 0 received antivenom. Most victims experienced minor dermatological injuries, which were successfully treated as though they were burns. However, shock and loss of consciousness from cardiorespiratory depression may occur and victims, especially children, have died within minutes of being stung.

Chironex stings can be prevented by avoiding swimming in their known habitat during the dangerous months of the year, which varies according to region but is generally November to April, or swimming within netted areas on beaches (mainly in Queensland). The wearing of ‘stinger’ suits or pantyhose confers effective protection of the covered areas and is further assisted by the swimmer entering the water slowly and affording the jellyfish time to take evasive action.

First aid

The ARC recommends the liberal dousing of vinegar to the affected site(s) for at least 30 seconds, as it is effective in preventing further triggering of undischarged nematocysts. However, published in vitro research casts some doubt on its utility, as it has been demonstrated that triggered nematocysts continue to contain residual venom, which is expelled after the application of vinegar, effectively increasing the volume of expressed venom by 60%.

Pressure immobilization bandages (PIB) are no longer recommended. Although previously advocated by the ARC, there is no evidence to support the application of ice packs to sting sites.