8 deadliest spiders on Earth

 

Story by Christina Hughes

Spiders are some of the most successful arthropods on the planet, having colonized every continent except Antarctica. 

Not all of these eight-legged arachnids are venomous, but some can be deadly to humans. 

From the notorious black widow to the ultra-deadly funnel web spider, here are some of the deadliest spiders on Earth.

Brown widow spider©Vinícius Souza via Alamy Stock Photo

Latrodectus geometricus is the scientific name for the brown widow spider. It looks similar to its infamous "cousin" the black widow, right down to the hourglass-shaped marking on its abdomen, but there are some key differences. The brown widow’s marking is orange and yellow rather than red, and as their name suggests, they predominantly have tan and brown mottling and a spiky, rather than smooth, appearance. Believed to originate in South America, the brown widow spider is found all around the world.

The brown widow's venom is less toxic than that of its black cousin. However, it can still be deadly. Although they don't deliver as much venom as a black widow, the brown widow's bite can still cause latrodectism due to its neurotoxic venom. Symptoms of lactrodectism include pain, perspiration, muscle rigidity and vomiting.

Red widow spider©Premaphotos via Alamy Stock Photo

Living mostly in sand dunes in Central and Southern Florida, the red widow spider (Latrodectus bishop) is another member of the notorious "widow" family. Their venom is just as lethal as brown and black widows, but as they live so far from human contact there has been no recorded bite in medical literature. The female red widow spider's venom is a neurotoxin which is thought to cause prolonged muscle spasms.

The red widow spider has a red-orange head and legs and a black abdomen with yellow rings around red dots. Rather than an hourglass marking like its "cousins," the red widow usually has one or two red marks.

Redback spider©By Toby Hudson - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=18357323

Due to its strikingly similar appearance, the redback spider (Latrodectus hasselti) was once thought to be a sub species of the black widow spider, but it is a distinct species. Also known as the Australian black widow, you can find this creepy crawly throughout Australia, Southeast Asia and New Zealand. The redback spider has even been found in Japan, the United Arab Emirates and Belgium due to inadvertent introductions.

Highly venomous, the bite from the female redback spider can be life-threatening. Using its fangs, it injects a complex venom that causes intense pain at the bite area, in addition to sweating and goosebumps. As time goes on, these symptoms worsen and there may also be redness and swelling, as well as nausea, muscle twitching, headache and fever. Respiratory failure may occur in severe cases. Thankfully, in 1956 scientists released a redback spider antivenom which is very effective, even when used several weeks after the initial bite. No deaths have been reported since.

Funnel-web spiders©Australian Reptile Park

Normally in the world of spiders it is the female that is more deadly, but for funnel-web spiders (Atrax) the male has the more toxic bite. Any attack must be treated quickly with antivenom, especially if a child has been bitten. There have been several recorded fatalities due to the venomous bites of the funnel-web spider, with death occurring within the hour after being bitten. However, since the development of the antivenom in 1981, there haven’t been any more recorded deaths. Predominantly located in southeast Australia (Sydney), funnel-web spiders are also found in New Zealand, Chile and Europe.

Interestingly, animals such as cats and dogs can actually survive a funnel web bite – it takes about 30 minutes for their body to neutralize the toxin – it's just humans who have such a severe reaction. This venom effects the nervous system and causes symptoms such as an elevated heart rate, numbness/tingling of the mouth and difficulty breathing.

Six-eyed sand spider©Papilio via Alamy Stock Photo

Found in deserts in southern Africa, the six-eyed sand spider (Hexophthalma hahni) buries itself in the sand to ambush unsuspecting prey. The small, stiff hairs that cover the spider helps to hold sand particles in place, adding to its camouflage. It's otherwise known as the six-eyed crab spider due to its crab-like legs.

Another arachnid that produces venom with necrotic effects, the six-eyed sand spider is the most venomous of any of its arachnid relatives, toxicology studies reveal. Scientists have found that there are proteins within their venom that can cause tissue destruction, blood vessel leakage, and thinning of the blood. No antivenom currently exists.

Mouse spider©Peripitus, CC BY-SA 3.0 , via Wikimedia Commons

Black in color with stocky, thick legs and a distinctively bulbous head and jaw regions, the mouse spider (Missulena) looks a lot more frightening than its name sounds. One species is located in Chile, another in South America and the rest distributed throughout Australia. They live in soil-covered burrows, popping out the hinged trapdoor top to attack prey.

Their hard, large fangs can cause a deep and very painful bite. However, while scientists believe that the venom of the mouse spider is very toxic, it is rarely injected. As so few cases have been reported, it is thought that mouse spiders don't use a lot of venom or may even "dry bite." Fortunately, funnel-web spider antivenom has proven effective in cases of mouse spider bite.

Black widow spider©Kimberly Hosey/Getty Images

In the genus Latrodectus, the black widow is one of the most venomous spiders and is found on every continent except Antarctica. In North America, they're commonly found in southern Canada and in the northeastern United States. You can identify the female black widow spider by its shiny black body and distinct red hourglass-shape on the underside of the abdomen. The male black widow is smaller in size, brown or gray in color with small red sports and does not have the hourglass marking.

While both male and female black widows are venomous, only the female is dangerous to humans. The venom of a black widow is reported to be 15 times stronger than that of a rattlesnake, although they don’t deliver as much venom in their bite, so fatalities are rare. That’s not to say a black widow bite isn’t painful! Those unlucky enough to be bitten by a black widow will experience nausea, fever, sweating, restlessness, muscle cramps and labored breathing, and these symptoms may last for several days.

Brown recluse spider©Rick Vetter

As their name suggests, brown recluse spiders (Loxosceles reclusa) have a shy nature and tend to hide away in dark, sheltered places. However, the brown recluse spider will bite if they feel threatened, and their bites can be deadly. They are usually found in the south and central United States, spanning southeastern Nebraska to southwestern Ohio, south to northwestern Georgia and into Texas.

The brown recluse spider can be dangerous to people because their venom contains a toxin that can cause skin necrosis (rotting). For the most part, symptoms, such as burning and itching at the bite site, as well as fever and nausea, develop a few hours after a bite. In extreme cases, the venom can lead to serious reactions or even death, especially to more vulnerable groups such as young children and the elderly.

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The science is clear: Vaccines are safe, effective, and do not cause autism

Johns Hopkins public health expert Daniel Salmon discusses vaccine safety and the potential hazards posed by fewer children being vaccinated

Scientists and medical experts were alarmed Tuesday by news reports of a Trump Tower meeting between President-elect Donald Trump and Robert F. Kennedy Jr., two men who have promoted widely debunked anti-vaccination theories suggesting a link between vaccines and autism.

Kennedy said Trump asked him to chair a new commission on vaccine safety, though a Trump spokeswoman later said no final decision had been made.

From The Washington Post:

If Trump follows through, the stunning move would push up against established science, medicine and the government's position on the issue. It comes after Trump—who has long been critical of vaccines—met at Trump Tower with Kennedy, who has spearheaded efforts to roll back child vaccination laws.

For more information on vaccine safety and insight on the potential public health dangers of promoting anti-vaccine conspiracy theories, the Hub reached out to Daniel Salmon, an associate professor at the Johns Hopkins Bloomberg School of Public Health. Salmon is deputy director of JHU's Institute for Vaccine Safety, and his research and practice focuses on optimizing the prevention of childhood infectious diseases through the use of vaccines.

Are vaccines safe and effective?

Vaccines are very safe and very effective. Vaccines routinely recommended in the U.S. today provide high levels of protection against targeted diseases.

The benefits of vaccines greatly outweigh their risks. The safest decision for parents is to vaccinate their children according to the recommended schedule.

The most variability in vaccine effectiveness is with flu or influenza vaccines, where effectiveness varies by year and how well the vaccine that year matches the circulating influenza viruses. During seasons when the flu vaccine matches most circulating flu viruses, flu vaccines reduce the risk of flu illness by 50-60% in the overall population. Vaccine effectiveness can be higher or lower for subpopulations depending on their ability to fully respond to the vaccine.

The effectiveness of other vaccines routinely used in the U.S. varies, but for most vaccines, 80-99% of vaccinated people are protected. Two doses of MMR, or Measles-Mumps-Rubella, vaccine, for example, provides about 99% protection against measles.

Adverse reactions to vaccines are either minor or very rare. Common adverse reactions include fever, tiredness, and a sore arm. Serious adverse events are very, very rare. For example, some vaccines cause fever in children and very rarely, febrile seizures. Febrile seizures can be scary for parents but have not been shown to cause long-term disabilities or problems.

Influenza vaccination in recent years has been associated with a very small increased risk of Guillain-Barré Syndrome, or GBS, in adults, leading to about 1-3 excess cases of GBS per million persons vaccinated. This is much less than the estimated risk after wild-type influenza infection, providing further evidence that the benefits of influenza vaccination greatly outweigh the risks.

Is there any scientific evidence of a connection between vaccines and autism?

No. Vaccines in routine use in the United States do not cause autism. There have been 13 methodologically sound, controlled epidemiological studies reporting no association between autism spectrum disorders (ASD) and receipt of MMR vaccine, thimerosal in vaccine, and simultaneous vaccination with multiple vaccines, in addition to the relevant systematic reviews and one meta-analysis.

The evidence from all studies, including methodologically flawed studies, have been reviewed by the Institute of Medicine, the Centers for Disease Control and Prevention, the Vaccine Injury Compensation Program, and the American Academy of Pediatrics. All have concluded that vaccines do not cause autism or ASD.

Are there any compelling medical reasons that parents would not have their children vaccinated, even in limited cases?

There are people for whom some vaccines are contraindicated, or who are vaccinated with precautions. The manufacturers of vaccines with approval from the FDA include contraindications in the package labels. The CDC and the American Academy of Pediatrics provide more detailed information and recommendations for individuals and populations that should or should not receive individual vaccines. For example, persons with severe immunocompromising conditions—such as leukemia or untreated AIDS, or those who have had a bone marrow transplant—should not receive live vaccines.

What are the public health ramifications of fewer children being vaccinated?

Unvaccinated children are at increased risk of acquiring disease and transmitting these diseases to other children. Drops in vaccine coverage have resulted in outbreaks and resurgence of diseases. Vaccine refusal has been associated with outbreaks of invasive Haemophilus influenzae type b disease, varicella, pneumococcal disease, measles, and pertussis in the United States and other countries. For example, parts of Europe have seen large outbreaks of measles as some parents are refusing measles vaccines for their children amid safety concerns. In the 1970s and 1980s, many countries—Japan, the U.K., Sweden—saw a major resurgence of pertussis, also known as whooping cough, as safety concerns led to substantial drops in pertussis vaccine coverage.

Experts Say Vegetable Oil May Not Be As Healthful As We Thought

JOHN TURNER VIA GETTY IMAGES

Data from an unpublished trial reveals replacing saturated fats with corn oil doesn’t help reduce cardiovascular disease or death. 

Never-published data on vegetable oil and heart health reveals some disturbing trends.

Anna Almendrala

The American Heart Association, U.S. Dietary Guidelines and most doctors and nutritionists say that if you eat more “healthy fats” from vegetable and seed oils and less “bad fats” from red meat and dairy products, you’re on your way to better cardiovascular health. 

It turns out that may not be supported by the highest standards of scientific evidence. A new analysis of never-before-published trial data from the 1960s and ‘70s pokes holes at the notion that we can stave off heart attack and stroke by eating more polyunsaturated fat (the “healthy” kind). Instead, it suggests that some people who eat more of this fat from vegetable and and seed oils — specifically, those that are high in omega-6 fatty acids — actually have a higher risk of death than those who have a diet high in saturated fat. 

The study’s findings were never published in full, perhaps because they went against the emerging and increasingly popular hypothesis that saturated fat in foods like red meat and dairy causes cholesterol levels in blood to rise, increasing the risk of cardiovascular disease and death. This hypothesis, called the Lipid Hypothesis, is currently a generally accepted piece of conventional wisdom in the nutrition science community. With help from the son of one of the original investigators, two researchers recently unearthed and re-analyzed the previously unpublished data. What they found contradicts the Lipid Hypothesis, and could change the way we view “healthy” polyunsaturated fats.  

The analysis, published Tuesday in the British medical journal BMJ, is a sequel of sorts for lead researchers Daisy Zamora of the University of North Carolina, Chapel Hill and Christopher Ramsden of the National Institutes of Health. Back in 2013, they performed a similar analysis on another set of previously unpublished data, known as the Sydney Diet Heart Study, and came to similar conclusions: Substituting saturated fat with oils high in omega-6 acids, also known as linoleic acids, actually increases the risk of death from all causes, coronary heart disease and cardiovascular disease.

“Our research highlights the paucity of evidence supporting the dietary replacement of saturated fat with vegetable oils rich in linoleic acid for heart health,” Zamora told The Huffington Post.

Experts say that, combined, these two trials could upend the way we view healthy eating — especially when it comes to our relationship with so-called “healthy” oils. 

This new finding is based on data from 1968 

Back in 1968, the U.S. Public Health Service and National Heart Institute funded a five-year study called the Minnesota Coronary Experiment to see whether replacing saturated fat with vegetable oil would prevent heart attacks, stroke and death. To have complete control over what study participants ate and didn’t eat, researchers Ivan Frantz and Ancel Keys — who famously made the connection between a Mediterranean diet and better heart health — divided over 9,000 adults in nursing homes and mental hospitals into two groups in a double blind, randomized trial.

The intervention group reduced their saturated fat intake about 50 percent compared to their normal diet, and upped their vegetable oil intake more than 280 percent in the form of corn oil. The control group was put on a diet much lower in polyunsaturated fats and higher in saturated fat — in other words, more typical of the average American diet. 

These experimental diets lasted between 41 to 56 months, depending on the institution. Then Frantz and Keys followed up with roughly 2,403 participants who stayed on their new diets for a year or more, and measured their cholesterol levels several times over an average of three years. They also conducted autopsies participants who died during the experiment to see whether there were any differences in their arterial or heart health at death.

The unexpected (and perhaps unwanted) results

Frantz and Keys found that the intervention group participants, who swapped more corn oil for saturated fat, did indeed lower the levels of cholesterol in their blood compared to the control group and baseline levels. The intervention worked as they predicted.

However, later analyses reported in a 1981 master’s thesis paper by now-retired biostatistician Steven K. Broste found that the though the intervention group lowered their cholesterol levels, they didn’t lower their risk of death. In fact, participants who were over 65 when they started the experiment actually had a higher risk of death if they had been part of the group eating more vegetable oils.

The autopsies Frantz and Keys conducted were even more disquieting. Among the 149 autopsies for which there was complete information, 41 percent of the intervention group showed signs of at least one heart attack, while only 22 percent of the participants in the control group — the high saturated fat group — showed the same. Deceased people from the intervention group also had similar levels of fatty plaque buildup in the arteries and hardened arteries compared to the control group.

After collecting all the data from the Minnesota trial, Zamora and Ramsden combined it with four published randomized, controlled trials that also substituted saturated fat with vegetable oils high in linoleic acid. Like the Minnesota trial, this additional meta-analysis found there was no benefit to switching to these oils when it came to death by coronary heart disease or death by any cause.

“It’s truly a shame that Americans are being recommended to consume these industrial seed oils, as it’s in direct contradiction to the highest level of evidence in the literature,” observed James DiNicolantonio, a cardiovascular research scientists at St. Luke’s Mid America Heart Institute who wasn’t involved in these studies. 

For unknown reasons, Frantz and Keys never published the full results of this experiment. Their study has the distinction of being one of the very few randomized, controlled trials — considered the highest standard of medical evidence — to evaluate the effects of lowering saturated fat on heart health.

In their 2016 re-analysis, Zamora and Ramsden speculate that perhaps the researchers didn’t publish the findings in full because they were so “contrary” to the popular scientific beliefs of the time.

“There would have been little or no scientific or clinical trial literature at the time to support findings that were so contrary to prevailing beliefs and public policy,” they wrote. “And, finally, it is possible that medical journal reviewers would not have accepted study results for the reasons cited above.”

Some vegetable oils are better for you than others

It’s important to note that Frantz and Keys’ trial was conducted when Americans were eating more corn oil and margarine made from corn oil, and that corn oil was the only polyunsaturated fat that was used in the experiment. Corn oil is high in omega-6 fatty acids, and while our bodies need some amount of omega-6 fatty acids to function properly, Zamora and Ramsden note that too much of it could have a “wide range of biochemical consequences” that could perhaps be negative. This nuance isn’t reflected in the most up-to-date nutritional advice in the federal dietary guidelines, which state simply we should eat less saturated fat and more polyunsaturated fat without mention of omega-6 acids.

Rebecca Blake, a registered dietitian and administrative director for medicine at Mt. Sinai-Beth Israel, put it this way: “We don’t usually consider corn oil the gold standard of healthy oils.

“It’s fine — it’s a vegetable oil,” she continued. “But it’s not olive oil, and it’s not like having a diet that’s high in healthy fats like fatty fish.”

 

Some other sources of polyunsaturated fats, like fatty fish, contain both omega-6 and omega-3 fatty acids. It’s this combination that could be the key to protecting people’s hearts, rather than just consuming polyunsaturated fats as a class, notes Tom Brenna, a professor of human nutrition at Cornell University.

“This gives us strong reason to think carefully about the composition of polyunsaturated fatty acids,” said Brenna. “The analysis does not say that polyunsaturated fatty acids in general are a bad substitute, but that they’re seeing negative things exclusively with omega-6 fatty acids.”

He also expressed regret that nutrition experts have not been able to effectively communicate this to the general public. Brenna, who served on the committee of scientists who helped create the 2015-2020 U.S. Dietary Guidelines, says it isn’t as simple as rattling off the names of certain plant oils. Different types of oils have different fatty acid profiles, which all act on your body in different ways. 

“You can no longer just say eat one kind of oil or another kind of oil,” he said. “You have to specify which one it is, and we have not, as a society, figured out how to talk about that yet.” 

For the record, the only oils that Brenna can wholeheartedly recommend are olive oil, avocado oil and high-oleic sunflower oil. 

“It gets so confusing for people, but it shouldn’t be,” Brenna concluded. “We should figure out a way to deal with this behind the scenes, so that people don’t have to become chemists in order to eat.”

CORRECTION: A previous version of this story incorrectly stated that the researchers added data from an additional five randomized controlled trials. In fact, they added data from four trials. Also, a portion of a quote from an outside researcher that appeared to misinterpret Zamora and Ramsden’s analysis has been removed.