A range of shirts, pants, socks and accessories sold in specialist camping and fishing retailers claim to protect against mosquito bites for various periods.
In regions experiencing a high risk of mosquito-borne disease, insecticide treated school uniforms have been used to help provide extra protection for students.
Some academics have even suggested fashion designers be encouraged to design attractive and innovative “mosquito-proof” clothing.
But while the technology has promise, commercially available mosquito-repellent clothing isn’t the answer to all our mozzie problems.
Some items of clothing might offer some protection from mosquito bites, but it’s unclear if they offer enough protection to reduce the risk of disease. And you’ll still need to use repellent on those uncovered body parts.
Bed nets have been used to create a barrier between people and biting mosquitoes for centuries. This was long before we discovered mosquitoes transmitted pathogens that cause fatal and debilitating diseases such as malaria. Preventing nuisance-biting and buzzing was reason alone to sleep under netting.
Bed nets have turned out to be a valuable tool in reducing malaria in many parts of the world. And they offer better protection if you add insecticides.
The insecticide of choice is usually permethrin. This and other closely related synthetic pyrethroids are commonly used for pest control and have been assessed as safe for use by the United States Environmental Protection Authority, the Australian Pesticides and Veterinary Medicines Authority and other regulatory bodies.
New technologies have also allowed for the development of long-lasting insecticidal bed nets, offering extended protection against mosquito bites, perhaps up to three years, even with repeated washing.
Innovations in clothing that prevent insect bites have primarily come from the United States military. Mosquito-borne disease is a major concern for military around the globe. Much research funding has been invested in strategies to provide the best protection for personnel.
Traditional insect repellents, such as DEET or picaridin, are applied to the skin to prevent mosquitoes from landing and biting.
While permethrin will repel some mosquitoes, treated clothing most effectively works by killing the mosquitoes landing and trying to bite through the fabric.
Clothing treated with permethrin has been shown to protect against mosquitoes and ticks, as well as other biting insects and mites. For these studies, clothing was generally soaked in solutions or sprayed with insecticides to ensure adequate protection.
Fabrics factory-treated with insecticides, as used by many military forces, are purported to provide more effective protection. But while some studies suggest clothing made from these fabrics provide protection even after multiple washes, others suggest the “factory-treated” fabrics don’t provide greater levels of protection than “do it yourself” versions.
Overall, the current evidence suggests insecticide-treated clothing may reduce the number of mosquito bites you get, but it doesn’t offer full protection.
More research is needed to determine if insecticide-treated clothing can prevent or reduce rates of mosquito-borne disease.
All products that claim to provide protection from insect bites must be registered with the Australian Pesticides and Veterinary Medicines Authority. This includes sprays, creams and roll-on formulations of repellents.
Anything labelled as “insect repelling”, including insecticide treated clothing, requires registration. Clothing marketed as simply “protective” (such as hats with netting) doesn’t. This approach reflects the requirements of the US EPA.
If you’re shopping for insect-repellent clothing, check the label to see if it states that it is registered by the APVMA. You should see a registration number and the insecticide used in the fabric clearly displayed on the clothing’s tag.
While some products will be registered, there are still some concerns about how the efficacy of mosquito bite protection is assessed.
There is likely to be growing demand for these types of products and experts are calling for internationally accepted guidelines to test these products. Similar guidelines exist for topical repellents.
Finally, keep in mind that while various forms of insecticide-treated clothing will help reduce the number of mosquito bites, they won’t provide a halo of bite-free protection around your whole body.
Remember to apply a topical insect repellent to exposed areas of skin, such as hands and face, to ensure you’re adequately protected from mosquito bites.
Let’s look at the research.
The most reputable source for shark incident data in Australia is the Australian Shark Attack file, which is collated at Sydney’s Taronga Zoo.
The map below, created by The Conversation using data from the Australian Shark Attack File, shows incidents between sharks and humans in Australia between 1997 and 2017.
You can use the filter buttons in the map to explore the data by year, season, the type of injury, the type of shark involved, the type of incident – or a combination of all the filters. Press the ‘show all’ button to reset the search.
The number of recorded encounters between sharks and humans in Australia increased modestly between 1997 and 2017, but the reason for this is unclear. Over those two decades, the Australian population increased by 33%, but that alone doesn’t explain the increase in recorded shark encounters.
Correcting for the growth in human population in Australia, the data show that between 1997 and 2017:
Encounters between humans and sharks are extremely variable over time, and difficult to predict. The increases in recorded incidents between 1997 and 2017 are relatively small, and may be explained by factors not related to shark populations – such as increases in the reporting of shark encounters, or increasing beach use.
White Sharks (formerly Great White Sharks) are recorded as being responsible for 28 of the 36 fatal shark encounters in Australian waters between 1997 and 2017, and are the primary target of shark mitigation strategies of the Western Australian, New South Wales and Queensland governments.
So, has there been an increase in the number of White Sharks in Australian waters?
Estimating population numbers in the marine environment is difficult, especially for long-lived migratory species like White Sharks.
However, there is no evidence that White Sharks numbers are on the rise, either in Western Australia or along the Eastern coast. Despite targeted conservation efforts, the available research show stable or slightly declining numbers in these populations.
There are two distinct populations of White Sharks off Australian coasts – one to the west, and another to the east of Bass Strait, which separates Tasmania from mainland Australia. The eastern population includes New Zealand White Sharks.
Recent work by the CSIRO through the National Environmental Science Program’s Marine Biodiversity Hub using innovative DNA analysis has provided us with the most detailed and reliable estimates of population size we have for this species.
The CSIRO study shows there has been a slight decline in adult White Shark populations since the year 2000.
Current adult abundance for the eastern Australasian population is estimated at 750, with an uncertainty range of 470 to 1,030. The southern-western adult population is roughly double the size, estimated at 1,460, with an uncertainty range of 760 to 2,250.
Including the available information about juvenile White Sharks, estimates of total size for the eastern population in 2017 was 5,460, with an uncertainty range of 2,909 to 12,802.
It’s difficult to detect population trends with White Sharks because of the length of time it takes juveniles to reach maturity – around 15 years. As protection of White Sharks began in the late 1990s, any changes in abundance would only be starting to appear in current populations.
The traditional way of measuring shark and fish populations is by examining catches in commercial fisheries over long time periods. By correcting for the level of fishing effort – which is done by looking at things like the number of nets, hooks and tows deployed by fishermen – scientists can assume that changes in the “catchability” of sharks is related to their abundance.
But due to the relative rarity of catches of White Sharks by fishing vessels, this approach is less reliable for this species than the more recent genetic studies conducted by the CSIRO and outlined above.
Western Australia has a detailed measure of White Shark numbers assessed by catch data. A report published by the Western Australian Department of Fisheries in 2016 attempted to model changes in the southern-western Australian White Shark population since the late 1930s. The authors outlined four different plausible scenarios, none of which suggested a continuous increase in the number of White Sharks.
In New South Wales, there has been a cluster of shark bites in recent years. Data from the NSW Shark Meshing (Bather Protection) Program, managed by the NSW Department of Primary Industries, show a recent increase in White Sharks caught in nets placed near ocean beaches.
But when it comes to thinking about shark populations, we should not assume that these two facts are related. It’s important to remember that just because two things may correlate, it doesn’t mean that one caused the other.
These patterns could mean that the animals are coming closer to shore, rather than a population increase (or decrease).
A 2016 paper examined six global shark bite “hotspots” – the United States, South Africa, Australia, Brazil, Reunion Island and the Bahamas – and concluded that when it comes to encounters between sharks and humans, there are a range of causes at play.
The authors also noted that shark encounters appear to happen in clusters. For example, 2009 saw a spike in shark encounters off the New South Wales coast. This coincided with an increase in beach attendance and beach rescues during what was an unusually warm summer for south-east Australia.
A 2011 paper highlighted the popularity of water sports as a factor contributing to increased human-shark encounters. More people are taking part in water sports, and improvements in wetsuit technology mean that people are in the water for longer throughout the year.
However, there is limited information on the number of people who use Australian beaches, so this explanation needs to be further studied.
It’s vital that any strategies put in place to reduce the number of unprovoked encounters between humans and sharks in Australian waters are carefully considered, and based on the best available research.
The first thing to say about shark attack deaths is that they are very rare, with only about two per year in Australia. But still, every year without fail, people die from shark bites, both here and around the world.
According to official statistics, the United States records by far the most unprovoked shark bites – an average of 45 per year over the past decade. However, only 1.3% of these incidents were fatal – 0.6 deaths per year.
Australia records fewer bites than the US (an average of 14 per year), but a much greater proportion of them are deadly: (1.5 per year, or close to 11%). So what is it that (relatively speaking) makes Australia more prone to deadly shark attacks?
My new book Shark Attacks: Myths, Misunderstandings and Human Fear addresses this and other questions about sharks, with the aim of dispelling common myths and providing the knowledge needed for decisions made on science rather than fear and emotion.
In a way, Australia has a “perfect storm” of conditions for serious shark attacks. The first reason is that Australians (and visitors to Australia) love the ocean. Some 85% of Australians live within 50km of the coast, and Australian coastal areas account for the most prominent growth outside of capital cities. Beaches are also favoured recreational destinations in Australia and coastal locations are heavily targeted in tourism, attracting nearly 60% of international tourists.
Next, the sharks themselves. Australia has the world’s highest diversity of sharks and rays, including roughly 180 of the 509 known shark species.
But neither of these factors, even taken together, is enough to explain why deaths are more prevalent in Australia. What we really need to look at is dangerous sharks.
Only 26 shark species have been definitively identified as biting humans without provocation, although the true number is likely to be somewhat higher. Of these 26 species, 22 (85%) are found in Australian waters.
All 11 of the species known to have caused fatal unprovoked bites on humans can be found in Australian waters. And crucially, Australia’s coastal waters are home to all of the “big three” deadly species: white sharks, tiger sharks, and bull sharks.
These species account for all but three of the 27 fatal shark attacks worldwide from 1982-2011. All of the big three species are inquisitive, regularly frequent coastal environments, and are formidably big and strong.
They also have complex, unpredictable behaviour. But despite this difficulty, we can identify factors that make them more likely to swim in areas routinely used by humans.
Most fish are ectothermic, or cold-blooded, with body temperatures very close to that of the surrounding water. This restricts their range to places where the water temperature is optimal.
In contrast, white sharks and a few other related species can retain the heat generated by their muscles predominantly during swimming, enabling them to be swift and agile predators even in cold water. They do this with the help of bunches of parallel arteries and veins in their brains, eyes, muscles and stomachs that function as “heat exchangers” between incoming and outgoing blood, allowing them to keep these crucial organs warm.
White sharks are so good at retaining heat that their core body temperature can be up to 14.3℃ above the surrounding water temperature. This allows them to move seasonally up and down Australia’s east and west coasts, presumably following migrating prey species.
Bull sharks, meanwhile, are the only sharks known to withstand wide variations in water salinity. This means they can easily move from salty oceans to brackish estuaries and even travel thousands of kilometres up river systems. As a result they can overlap with human use areas such as canals, estuaries, rivers and even some lakes. One female bull shark was observed making a 4,000km round-trip to give birth in a secluded Madagascan estuary rather than the open ocean.
As a result, most bull sharks found in river systems are juveniles, but these areas may also be home to large, pregnant females who need to eat more prey to sustain themselves. As rivers are often clouded by sediment, there is an increased risk that a human may be mistaken for prey in this low-visibility environment.
Tiger sharks mainly stay in coastal waters, although they also venture into the open ocean. Their movements are unpredictable, they eat a wide range of prey, are naturally curious and opportunistic, and can be aggressive to humans.
Tiger sharks are clever too – they are thought to use “cognitive maps” to navigate between distant foraging areas, and have hunting ranges that span hundreds of thousands of square kilometres so as to maintain the element of surprise. As a result, tiger sharks’ distribution in Australian waters covers all but the country’s southern coast.
Taken together, it’s clear that Australia’s waters are home to three predators that can pose a real danger, even if only an accidental one, to humans.
But remember that shark attacks are incredibly rare events, and fatal ones even rarer still. There are also lots of tips we can use to minimise the risk of having a negative encounter with a shark.
Don’t swim in murky, turbid or dimly lit water, as sharks may not be able to see you properly (and you may not be able to see them). Avoid swimming in canals, or far from the shore, or along dropoffs. Swim in designated areas and with others, and avoid swimming where baitfish (or bait) may be present. And of course, always trust your instincts.
This is an article from Curious Kids, a series for children. The Conversation is asking kids to send in questions they’d like an expert to answer. All questions are welcome – serious, weird or wacky!
If a lethally poisonous snake bites another lethally poisonous snake of the same species does the bitten snake suffer healthwise or die? – Ella, age 10, Wagga Wagga.
That’s a great question.
If a venomous snake is bitten by another venomous snake of the same species, (for example during a fight or mating), then it will not be affected.
However, if a snake is bitten by a venomous snake of another species, it probably will be affected.
This is probably because snakes have evolved to be immune to venom from their own species, because bites from mates or rivals of the same species probably happen fairly often.
But a snake being regularly bitten by another snake from a different species? It’s unlikely that would happen very often, so snakes haven’t really had a chance to develop immunity to venom from other species.
Many people believe that snakes are immune to their own venom so that they don’t get harmed when eating an animal it has just injected full of venom.
But in fact, they don’t need to be immune. Scientists have found that special digestive chemicals in the stomachs of most vertebrates (animals with backbones) break down snake venom very quickly. So the snake’s stomach can quickly deal with the venom in the animal it just ate before it has a chance to harm the snake.
People that have snakes as pets often see this. If one venomous snake bites a mouse and injects venom into it, for example, you can then feed that same dead mouse to another snake. The second snake won’t die.
By the way, scientists usually use the word “venomous” rather than “poisonous” when they’re talking about snakes. Many people often mix those words up. Poisons need to be ingested or swallowed to be dangerous, while venoms need to be injected via a bite or a sting.
Some snakes can inject their toxins into their prey, which makes them venomous. However, there seem to be a couple of snake species that eat frogs and can store the toxins from the frogs in their body. This makes them poisonous if the snake’s body is eaten. Over time, many other animals will have learned that it is not safe to eat those snakes, so this trick helps keep them safe.
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Despite the common belief that Australia has some of the most venomous snakes in the world, our new research shows being bitten by a snake is uncommon in Australia and dying from a snakebite is very rare.
And of the few unlucky people to collapse after venom enters their bloodstream, a bystander performing cardiopulmonary resuscitation (CPR) is the most likely thing to save them.
These are just some of the findings from 10 years of data from the Australian Snakebite Project published today in the Medical Journal of Australia.
Although many people go to hospital with a suspected snakebite, many do not turn out to have envenomation (when venom enters the bloodstream) after all.
In more than 90% of cases people are bitten by a non-venomous snake, venom is not injected when the snake bites (known as a “dry bite”) or are not even bitten by a snake (known as a “stick” bite).
Our analysis of about 1,548 cases of suspected snakebites from all around Australia, showed there were on average just under 100 snake envenomations a year, and about two deaths a year.
The most common snakebites were from brown snakes, then tiger snakes and red-bellied black snakes. Brown snakes were responsible for 40% of envenomations. Collapsing, then having a heart attack out of hospital was the most common cause of death (ten out of 23), and most deaths were from brown snakes.
Venom from a snakebite travels via the lymphatic system to the bloodstream. There, it circulates to nerves and muscles where it can cause paralysis and muscle damage. In the blood itself, the venom destroys clotting factors, which makes the blood unable to clot, increasing the risk of bleeding.
In the most severe cases, most commonly in brown snake bites, someone can collapse because they have low blood pressure (we don’t know for certain what causes the low blood pressure). In this situation, insufficient blood is pumped around the body for the brain and other vital organs.
Clearly the accurate diagnosis of snake envenomation and the timely administration of antivenom are essential to treating snakebites in hospital.
But when people collapse, CPR will keep the blood circulating to the vital organs – and is life-saving – however inexpertly a bystander performs it.
In other words, we found basic first aid before people reached hospital, of which bystander CPR is one, may be more important than any changes in how people are treated in hospital to improve people’s chance of survival. People who survived after collapsing received CPR on average within one minute of being bitten compared with 15 minutes for those who died.
Our study also showed that in most cases, people used other first-aid measures (pressure bandages and immobilising both the limb and the patient). These aim to prevent the venom travelling from the bite site, via the lymphatic system, to the bloodstream.
Our study confirmed the role of antivenom in treating snakebites and the need for it to be administered before irreversible damage is done to the nervous system and paralysis occurs.
However, we found one in four patients given antivenom had an allergic reaction to it and about one in 20 have severe anaphylaxis requiring urgent treatment.
So it is essential only patients with snake envenomation, and not just a suspected snakebite, are treated with antivenom. We found 49 patients (around 6%) were given antivenom unnecessarily, out of the total 755 patients who received it.
So we need to find ways to make sure patients get antivenom as early as possible. This requires laboratory tests that can identify patients with snake envenomation in the first couple of hours after the bite.
It is also essential anyone bitten by a snake or suspected to be bitten by a snake seeks immediate medical attention and goes to hospital by ambulance.
But the best thing is to avoid being bitten in the first place:
Recent news reports that a man had both his legs amputated after being bitten by a white-tailed spider have again cast this relatively harmless spider in a negative light. Experts have since said amputations may have been wrongly blamed on a spider bite, and authorities now consider a bacterial infection to be responsible for the man’s injuries. Despite this, the damage to the largely harmless white-tail may have been done.
The venom from the white-tailed spider is listed as non-lethal.
It has not been shown to cause necrotic ulcers, which could result in the need for amputation. And there has never been any clear evidence necrotising arachnidism – the name give to a syndrome where the skin blisters and ulcerates following spider bites – has been seen in Australia.
There is currently no clinical test to determine if you have been bitten by a spider. And there is no blood or swab test that can be performed to positively identify what spider it is if a bite is suspected. Whether it is a bite from a spider or another insect, the management is the same – most will get better without any medical treatment.
The majority of spiders in Australia are voracious predators of insects. For the most part, they play a useful role in lowering insect numbers.
The venom transmitted through bites of some Australian spiders can cause harm to humans and even be life-threatening. The better known of these are the redback spider (Latrodectus hasselti), and the funnel-web spiders (genera Atrax and Hadronyche). Antivenom is available for both spiders.
Redback spider venom can cause a lot of pain. Advice would be to go to hospital if pain lasts for longer than a few hours and simple pain relief is not helping. Funnel-web spider venom can cause local swelling in addition to increasing heartbeat, salivation, muscle spasms and respiratory distress (trouble breathing).
Without appropriate first aid, quick access to hospital and antivenom, these bites can be lethal. For the “big black hairy” funnel-webs, appropriate first aid needs to be applied and it is advisable to call 000.
Other spiders that have concerning bites include the trapdoor, whistling, sac, ground, orb and huntsman spiders. These may cause milder symptoms such as headache, swelling and pain, which does not last for a long time.
White-tailed spiders (Lampona sp.) can be recognised by their cylindrical body shape and a white or grey spot on the end of their abdomen. They are found in eastern and most southern areas of Australia and New Zealand.
These spiders are active hunters, preying on other types of spiders and insects. They may transiently roam inside houses, especially in warmer weather, where they may be found in bedding or clothing that has been left on the floor.
One study of over 70 spider bite cases in which white-tailed spiders were identified showed patients experienced only a mild localised reaction, such as swelling, local pain or headache. To date clinical research has not been able to associate tissue loss with the venom of these spider bites.
The man at the centre of the recent story linking amputations to a white-tail spider bite was said to have a “flesh eating” infection. But there is a very low probability of an association between spiders and necrotisisng fasciitis (commonly known as flesh-eating disease).
Of course, any injury that causes a break in our skin leaves the capacity for bacteria to enter our body. Therefore be sure to keep an injury area clean. Questions have been raised as to the possibility of a spider introducing infections, but again, despite it being theoretically possible, it is unlikely.
Contributing factors to infection are if people have conditions such as diabetes or take medications, such as steroids like prednisolone, that lessen the body’s ability to fight infection.
For first aid after a spider bite, please see the Australian guidelines. Many bites don’t result in envenoming and death is very rare, so it is important to remain calm. But seek medical attention if there are concerning symptoms such as those described above: difficulty breathing, increased heartbeat and pain lasting longer than an hour.