If a croc bite doesn’t get you, infection will



Image 20170419 32700 mceytd
Open wide … the mouths of crocodiles like this contain bacteria that cause potentially lethal infections in people they bite.
from www.shutterstock.com

Simon Smith, James Cook University

Most people assume if you’re unlucky enough to be bitten by a crocodile, then a severed limb or other severe trauma is all you have to worry about. But new research is emerging about serious infections you can catch from a bite that might kill you instead. The Conversation

Our study, published earlier this week, showed the range of bacteria crocodiles can transfer to their human victims. The good news is they can be cured with a much simpler antibiotic treatment than we realised.

Since crocodiles were granted protected species status in the 1970s in Australia, they have attacked more than 100 humans.

For those lucky to survive, their injuries often become infected. Bacteria can enter the body via the deep cuts from a crocodile’s teeth or from wounds occurring when people try to escape.

Bacteria living in crocodiles’ mouths can come from the intestines of other animals they eat or from the water in which they live.

When people are trying to escape a crocodile attack, bacteria living in the soil and mud also pose a risk. And bacteria commonly living on our skin without causing problems can cause infection when the skin’s protective barrier is lost.

If untreated, bacteria can cause severe wound infections. Without treating these infections properly, the victim’s tissues die and their arms and legs may need to be amputated. Infection can also enter the bloodstream and spread to the rest of the body causing multiple organ failure and death.

How do we treat croc bite infections?

Australian guidelines recommend how to treat infections after bites from animals in general. But until recently we didn’t know much about which antibiotic is best for people who have been attacked by a crocodile.

Crocodiles make the front page across Australia’s Top End.
NT News

Some 25 years ago, a study in the Northern Territory found over half of people who had been attacked by a crocodile had infected wounds.

Researchers found a wide variety of bacteria you would expect to find in the water, the soil, the intestines of animals and on the skin of humans. To kill all of these potential infection causing bacteria, they recommended a complex treatment of four different antibiotics which would mean up to 14 injections a day. With so many antibiotics, this increases the risk of potential side effects and the cost of patient care.

So, we reviewed all cases of people who had been treated for a crocodile attack in Far North Queensland and attended the Cairns Hospital over a 25-year period.

A total of 15 people needed medical attention after a crocodile attack over this time, including several crocodile handlers. Four people were clearly infected by the time they reached hospital. A further two had bacteria in their wounds and almost all needed surgery.

Surgery is essential to prevent new or worsening infection after any bite as surgeons can remove already-infected tissue and help flush out any bacteria hiding in the wounds.

Despite finding lots of different bacteria, we discovered antibiotics given orally (amoxycillin-clavulanate) in mild infections or intravenously (piperacillin-tazobactam) for severe infections would be suitable to kill almost all of the bacteria found after a crocodile attack.

Although all of these patients were treated at Cairns Hospital, the results of the study will likely influence national guidelines for the management of crocodile attacks. The results may even help doctors in other countries.

Prevention is your best bet

Although we did not find it in our study, another important thing to remember is tetanus – an infection that can be contracted through dirty wounds – may also develop after a crocodile attack and this can be prevented by vaccination.

When it comes to crocodile attacks, like most things in health, prevention is better than cure. People should take care when visiting areas where crocodiles live. If people are attacked and lucky enough to survive, they are likely to require surgery and have a high chance of developing an infection.

A crocodile is a beautiful creature to observe from a distance, but in the words of American composer Frank Churchill:

Don’t be taken in by his welcome grin.

Simon Smith, Adjunct Lecturer (Clinical), Medicine, James Cook University

This article was originally published on The Conversation. Read the original article.

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Hissstory: how the science of snake bite treatments has changed


Peter Hobbins, University of Sydney

Summer is traditionally Australia’s snake bite season, when both snakes and people become more active. The human death toll is now admirably low, but it wasn’t always so.

Although colonial statistics are highly unreliable, in 1882-1892 about 11 people died from snake bites across Australia a year. Since then, the continent’s population has grown from 2.2 million to 24.3 million, yet on average just two people died from snake bites a year in 2001–2013. While improved transport, communications and ambulance services have all contributed, so have the first aid and medical measures used to counteract snake venom.

Complex colonial remedies

A typical case from 1868 suggests the complexity – and desperation – of colonial remedies. When Victorian railway workers killed a brown snake at Elsternwick Station, they threw its body to stationmaster John Brown. Either the serpent was still alive, or Brown brushed its fangs, when he struck it “with an angry gesture”. The usual signs of envenomation (venom injected into the skin) soon appeared: vomiting, physical weakness then creeping paralysis followed by “coma”. Death, seemingly, was inevitable.

The stationmaster was rushed to nearby Balaclava, where surgeon George Arnold tied a ligature (tourniquet) around Brown’s arm before slicing out the bite site, hoping to remove the venom. He then poured ammonia (a hazardous chemical used today in cleaning) onto the wound to neutralise any remaining venom before urging Brown to drink six ounces (175mL) of brandy to stimulate his circulation.

He waved pungent smelling salts under Brown’s nose then applied a paste-like poultice of mustard to his patient’s hands, feet and abdomen to alleviate internal congestion. Further stimulation followed via electric shocks before the staggering, semi-conscious stationmaster was marched up and down to keep him awake – and alive. Brown, nevertheless, kept deteriorating.

Arnold urgently summoned the colony’s only medical professor, George Halford at Melbourne University, who reluctantly agreed to apply his new snake bite remedy. He opened a vein in Brown’s arm and injected ammonia directly into the bloodstream. The stationmaster revived almost immediately, leading another doctor to assert “the injection of Ammonia saved the man’s life” (do not try this at home).

Name your poison

John Brown’s treatment followed a pattern familiar across Australia from 1800 into the 1960s. While many of the 1868 interventions now seem bizarre – or downright dangerous – they made sense in historical context. Until well into the 20th century, snake bite treatments alternated between three fundamental approaches.

In common with today’s understanding, most European settlers, and many Indigenous cultures, considered venom to be an external “poison” that moved through the body. Physical measures such as ligature or suction were thus common to expel venom or limit its circulation.

A second strand of remedies, from mustard poultices to injected ammonia, sought to counteract its ill effects in the body, often by stimulating heart function and blood flow.

The third approach was to directly neutralise venom itself, for instance, pouring ammonia onto the bite.

Until the 1850s, physical measures dominated, while the next 50 years were the heyday of opposing-action treatments. When Halford’s intravenous ammonia fell from favour (as it didn’t seem to work), it was replaced in the 1890s by injections of another notorious poison: strychnine. At first even more popular than ammonia, this highly toxic plant-based poison was blamed for killing more patients than it saved. Yet by far the most popular colonial remedy, both with practitioners and patients, was drinking copious quantities of alcohol, especially brandy.

The slow premiere of antivenoms

The third approach, directly neutralising venom, underlay both Australia’s hugely popular folk “cures” and the novel “antivenene” technology developed in the 1890s. Now they are known as antivenoms and are created by injecting venom into (generally) horses, prompting an immune response, then purifying antibodies from their blood to inject into snake-bitten patients.

But antivenenes suffered a slow gestation in Australia. The first, targeting black snake venom, was developed in 1897; experimental tiger snake antivenene followed in 1902. But antivenenes are tricky to produce, distribute and store. They also proved difficult to administer, sometimes provoking life-threatening anaphylactic reactions (a severe allergic response).

It wasn’t until 1930 that commercial tiger snake antivenene came onto the Australian market.

Other injections targeting a wider range of serpents. “Polyvalent” antivenene, which is effective against multiple venoms, only emerged from the mid-1950s. Meanwhile, patients continued to undergo various first-aid measures, particularly ligatures and Condy’s crystals (potassium permanganate, used to clean wounds) applied to the bite in the hope of inactivating venom.

Two eternal questions

Current snake bite management only stabilised in the 1980s. Two developments were key: rapid tests to identify the injected venom and a new first-aid strategy.

Scientist Struan Sutherland pioneered the “pressure immobilisation technique”. This recommends tightly wrapping a bandage around the bitten region, adding a splint and minimising movement to slow venom spread.

Not washing or cutting the bite site leaves a venom sample to aid identification and so choose the most appropriate antivenom.

But today’s management is still being evaluated because both venoms and treatments still pose clinical challenges, including severe reactions and long-term damage.

And just as in 1868, two eternal questions remain critical: was it truly a deadly serpent, and did it inject enough venom to kill?

The Conversation

Peter Hobbins, ARC DECRA Fellow, University of Sydney

This article was originally published on The Conversation. Read the original article.