A flesh-eating fly is spreading. It can infest humans and their pets

A flesh-eating parasitic fly is invading North and Central America. The consequences could be severe for the cattle industry, but this parasite is not picky – it will infest a wide range of hosts, including humans and their pets.
The 'New World screwworm' (Cochliomyia hominivorax) was previously eradicated from these regions. Why is it returning and what can be done about it?
Flies fulfil important ecological functions, like pollination and the decomposition of non-living organic matter. Some, however, have evolved to feed on the living.
The female New World screwworm fly is attracted to the odour of any wound to lay her eggs. The larvae (maggots) then feed aggressively on living tissue causing immeasurable suffering to their unlucky host, including death if left untreated.
Cattle farmers in Texas estimated in the 1960s that they were treating around 1 million cases per year.
Between the 1960s and 1990s, scientists and governments worked together to use the fly's biology against it, eradicating the New World screwworm from the US and Mexico using the sterile insect technique (SIT).
A female screwworm mates only once before laying her eggs, whereas the males are promiscuous. During the eradication process, billions of sterile males were released from planes, preventing any female that mated with them from producing viable eggs.
In combination with chemical treatment of cattle and cool weather, populations of the screwworm were extinct in the US by 1982. The eradication campaign reportedly came at cost of US$750 million (£555 million), allowing cattle production to increase significantly.
For decades, a facility in Panama has regularly released millions of sterile flies to act as a barrier to the New World screwworm spreading north from further south.
However, since 2022 – and after decades of eradication – the New World screwworm has once again spread northwards through several countries in Central America. Cases exploded in Panama in 2023 and the fly had reached Mexico by November 2024.
Scientists have suggested several hypotheses for this spread, including flies hitchhiking with cattle movements, higher temperatures enhancing fly development and survival, and the possibility that females are adapting their sexual behaviour to avoid sterile males.
Around 17 million cattle are now at risk in Central America, but worse may be to come. Mexico has twice as many cattle, and the spread towards the US continues, where around 14 million cattle would be at risk in Texas and Florida alone.
Humans are not spared, with at least eight cases of the flies infesting people in Mexico since April.
Live animal ban
The US has responded by temporarily restricting live animal imports from Mexico. The governments of the US, Central American countries and Mexico are also working together to heighten surveillance and work towards the eradication of the New World screwworm by stepping up sterile insect releases.
Sterile male screwworm pupae (juveniles) are currently produced and safely sterilised by irradiation at a rate of over 100 million per week at a facility in Panama. This is jointly funded by the US Department of Agriculture (USDA) and Panama's Ministry of Agriculture Development. However, a successful eradication campaign may need several times this number of sterile flies.
For example, sterile fly production for releases in Mexico in the 1980s were reportedly in excess of 500 million flies per week. To combat this shortfall, the USDA is focusing releases in critical areas of Mexico and is already investing US$21 million to equip a fruit fly production facility in Metapa, Mexico, to also produce 60 million to 100 million sterile screwworm per week.
Fly production, sterilisation and release is a long process, and a reduction in wild screwworm populations would not be immediate. History has shown us that integrated control with anti-parasitic veterinary medicines are essential to repel flies and treat infestations as they arise.
Surveillance with trained personnel is also essential but is a great challenge due to an entire generation of veterinarians, technicians and farmers who have no living memory of screwworm infestations.
Finally, climate warming means that we may not be blessed with the cool weather that facilitated previous eradication, and further work is needed to determine how this will impact current eradication plans.

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Daily Mail​

12 hours ago

• Daily Mail​

Scientists blame climate change for the UK heatwave: 32°C temperatures were made 100 TIMES more likely by global warming.

As the UK braces for the first heatwave of 2025, scientists warn that climate change is responsible. This weekend's 32°C (90°F) forecast was made 100 times more likely by global warming, according to the research group World Weather Attribution. Before humans began to alter the climate with fossil fuels, the UK would only see these temperatures in June once every 2,500 years. Today, Britons should expect to be hit by similar life-threatening extremes once every 25 years. Due to human activity, the planet's climate is now 1.3°C (2.34°F) warmer than it was before the Industrial Revolution. This has made heatwaves like the one the UK is currently facing both more severe and more frequent. Historically, a June heatwave with three or more days above 28°C (82.4°F) would only happen about once every 50 years in the UK. Now, every June has a 20 per cent chance of experiencing a heatwave - 10 times more likely than in the pre-industrial period. Scientists found that three-day heatwaves in southeast England are now 3°C (5.4°F) hotter due to human-caused climate change heating the planet This week, the UK has experienced prolonged and intense heat building to a peak over the weekend. The current forecast predicts maximum temperatures to reach 32°C (90°F) in some locations, with heatwave thresholds likely to be exceeded across the country. The hottest area, Humberside, is predicted to reach 33°C (91.4°F) on Saturday, while London exceeds 30°C (86°F) until Monday. On Thursday, the UK Health Security Agency (UKHSA) issued an amber heat alert for the whole of the UK, warning that there could be a 'rise in deaths'. In a new report, World Weather Attribution finds that these temperatures were made hotter and more likely by human-caused climate change. Dr Friederike Otto, a climate scientist at Imperial College London and co-lead of World Weather Attribution, says: 'We know exactly what has intensified this heatwave - burning oil, gas and coal, which has loaded the atmosphere with planet-heating greenhouse gases.' Overall, June heatwaves are now about 2-4°C (3.6-7.2°F) more intense due to climate change. In the report, the researchers warn that this is enough of a difference to turn June's forecast from 'warm sunny weather into dangerous heat'. While many people might be looking forward to enjoying the hot weather over the weekend, heatwaves are the deadliest extreme event in the world and kill hundreds of thousands each year. Professor Mike Tipton, a human physiologist from the University of Portsmouth who was not involved with the study, says: 'The human body is not designed to tolerate prolonged exposure to this sort of extreme heat. 'We know that when temperatures rise above 30 degrees there is a spike in excess deaths, particularly in vulnerable groups, and unfortunately we are likely to see that again in the coming days and weeks as the mercury once again rises to these dangerous levels.' Heatwaves are especially dangerous in June when people have not yet had a chance to acclimate to the heat. This is especially problematic for the elderly and infirm who might not be able to get outside to cool off or monitor their own temperature. During 2022, the UK experienced its most deadly heatwave on record when a record temperature of 40.3°C (104.5°F) was recorded at Coningsby, Lincolnshire. More than 1,000 excess deaths among older people were recorded around the four-day peak of the heatwave, with more than 3,000 heat-related deaths in England over summer 2022. Professor Tipton says: 'With the evidence that 32-degree days in June are now 100 times more likely, it is undeniable that climate change is now costing British lives.' This comes after a study conducted by the Met Office predicted that summers rivalling the famous 1976 heatwave could become the norm as the climate continues to warm. During that summer, the UK spent a sweltering fortnight above the heatwave threshold of 28°C (82°F). Looking ahead, the Met Office warns that the UK might spend two-thirds of the summer at those temperatures, with continuous heatwaves lasting up to a month. The study warned there is now a 50/50 chance of the UK hitting 40°C again in the next 12 years, with a maximum of 46.6°C (115.9°F) now 'plausible' in today's climate. World Weather Attribution also warns that climate change is increasing the risk of wildfires in the UK. Theodore Keeping, wildfire researcher at Imperial College, says: 'Hotter temperatures mean an exponential increase in the evaporation of moisture from vegetation. 'This leads to much drier conditions, and results in a higher chance of wildfires starting and spreading as leaf litter and grasses become tinder dry.' The UK is already in the midst of a record year for wildfires, smashing the all-time record in the first four months of the year. Tom Lancaster, land, food and farming analyst at the Energy and Climate Intelligence Unit, says: 'We're in the midst of a record-breaking year for wildfires, with exceptionally severe fire risk forecast for this weekend, bringing home the reality of continuing to pump carbon emissions into the atmosphere.' Ahead of this weekend's heatwave, emergency services around the country have issued warnings about the increased risk of fires. According to the Met Office, the fire severity risk is currently 'very high' in many places and 'high' in others. Mr Keeping adds: 'People going outside to enjoy the warm weather should not be using fire or disposable barbecues, dispose of cigarette butts carefully and should immediately notify emergency services if they do notice a fire.

BBC News

18 hours ago

• BBC News

Why your fingers wrinkle in water (and what it can reveal about your health)

The skin on our fingertips and toes shrivels like prunes when soaked for a few minutes in water. But is this an adaptation that occurred to help us in our evolutionary past? And what can it reveal about your health today? Spend more than a few minutes soaking in a bath or paddling around a swimming pool and your fingers will undergo a dramatic transformation. Where there were once delicate whorls of lightly ridged epidermis, engorged folds of ugly pruned skin will now be found. And according to a recently published study, this striking change is worth a closer inspection – each time your fingertips pucker in this way, the wrinkles create the same pattern. It is the latest discovery about a phenomenon that has occupied the thoughts and work of scientists for decades. Bafflingly, only the skin on our fingers and toes wrinkles when immersed in water. Other body parts such as our forearms, torso, legs and face remain no more crinkled than they were before being submerged. Most researchers in the field have puzzled over what causes this puckering in the first place, but more recently the question of why and what purpose it may serve, has attracted their attention. Perhaps more intriguing still, however, is what our shrivelled fingers can reveal about our own health. Scientists have discovered changes in how our fingers wrinkle can point to diseases including type 2 diabetes, cystic fibrosis, nerve injuries and even cardiovascular problems. What causes our fingers to wrinkle It takes around 3.5 minutes in warm water – 40C (104F) is considered the optimal temperature – for your fingertips to begin wrinkling, while in cooler temperatures of about 20C (68F) it can take up to 10 minutes. Most studies have found it takes around 30 minutes of soaking time to reach maximum wrinklage, however. (Interestingly, recent research has shown that soaking your hands in warm vinegar can make your skin wrinkle far faster – in around just four minutes.) Fingertip wrinkling was commonly thought to be a passive response where the upper layers of the skin swelled as water flooded into the cells via a process known as osmosis – where water molecules move across a membrane to equalise the concentration of the solutions on either side. But as long ago as 1935, scientists have suspected there is more to the process than this. Doctors studying patients with injuries that had severed the median nerve – one of the main nerves that run down the arm to the hand – found that their fingers did not wrinkle. Among its many roles, the median nerve helps to control so-called sympathetic activities such as sweating and the constriction of blood vessels. Their discovery suggested that the water-induced wrinkling of fingertips was in fact controlled by the nervous system. Later studies by doctors in the 1970s provided further evidence of this, and they proposed using the immersion of the hands in water as a simple bedside test to assess nerve damage that might affect the regulation of unconscious processes such as blood flow. Then in 2003, neurologists Einar Wilder-Smith and Adeline Chow, who were working at the National University Hospital in Singapore at the time, took measurements of blood circulation in the hands of volunteers as they soaked them in water. They found that as the skin on the volunteers' fingertips began to wrinkle, there was a significant drop in blood flow in the fingers. When they applied a local anesthetic cream that caused the blood vessels in the fingers of healthy volunteers to temporarily constrict, they found it produced similar levels of wrinkling as water immersion. "It makes sense when you look at your fingers when they go wrinkly," says Nick Davis, a neuroscientist and psychologist at Manchester Metropolitan University, who has studied fingertip wrinkling. "The finger pads go pale and that is because the blood supply is being constricted away from the surface." Wilder-Smith and his colleagues proposed that when our hands are immersed in water, the sweat ducts in our fingers open up to allow water in, which leads to an imbalance in the salts in our skin. This change in the salt balance triggers the firing of nerve fibres in the fingers, leading to the blood vessels around the sweat ducts to constrict. This in turn causes a loss of volume in the fleshy area of the fingertip, which pulls the overlying skin downwards so that it distorts into wrinkles. The pattern of the wrinkles depends on the way the outermost layer of skin – the epidermis – is anchored to the layers beneath it. More like this: There have also been suggestions that the outer layers of skin may also swell a little to enhance the wrinkling. By osmosis alone, however, our skin would need to swell by 20% to achieve the wrinkles we see in our fingers, which would leave them hideously enlarged. But when the upper layers of skin swell slightly and the lower levels shrink at the same time, the wrinkling becomes pronounced far sooner, says Pablo Saez Viñas, a biomechanical engineer at the Technical University of Catalonia, who has used computer modelling to examine the mechanism. "You need both to have normal levels of wrinkles," he says. "If you don't have that neurological response, which happens in some individuals, wrinkles are inhibited." But if wrinkling is controlled by our nerves, it means our bodies are actively reacting to being in water. "That means it is happening for a reason," says Davis. "And that means it could be giving us an advantage." Why did our fingers evolve to wrinkle in water? It was a question from one of his children during a bath about why their fingers had gone wrinkly that recently led Davis to dig into what this advantage could be. With the help of 500 volunteers who visited the Science Museum in London during 2020, Davis measured how much force they needed to use to grip a plastic object. Perhaps unsurprisingly, those with dry, unwrinkled hands needed to use less force than people whose hands were wet – so their grip on the object was better. But when they submerged their hands in a water bath for a few minutes to turn their hands wrinkly, the grip force fell between the two even though their hands were still wet. "The results were amazingly clear," says Davis. "The wrinkling increased the amount of friction between the fingers and the object. What is particularly interesting is that our fingers are sensitive to this change in the surface friction and we use this information to apply less force to grip an object securely." The object that Davis' volunteers were gripping weighed less than a couple of coins, so the amount of grip required was small. But when performing more arduous tasks in a wet environment, this difference in friction could become more important. "If you don't have to squeeze as hard to grip something, the muscles in your hands get less tired and so you can do it for longer," he says. His findings match those by other researchers who have found that the wrinkling of our fingertips makes it easier for us to handle wet objects. In 2013, a team of neuroscientists at Newcastle University in the UK asked volunteers to transfer glass marbles of varying sizes and fishing weights from one container to another. In one case the objects were dry, and in the other they were at the bottom of a container filled with water. It took 17% longer for the participants to transfer the submerged objects with unwrinkled fingers than when they were dry. But when their fingers were wrinkled, they could transfer the submerged marbles and weights 12% quicker than when their fingers were wet and unwrinkled. Interestingly, there was no difference in transferring the dry objects with wrinkled or unwrinkled fingers. There are other baffling mysteries – women take longer to develop wrinkles than men do Some scientists have suggested that the wrinkles on our fingertips and toes may act like rain treads on tyres or the soles of shoes. The channels produced by the wrinkles help to squeeze water away from the point of contact between the fingers and an object. This suggests that humans may have evolved fingertip and toe wrinkling at some point in our past to help us grip wet objects and surfaces. "Since it seems to give better grip under water, I would assume that it has to do with either locomotion in very wet conditions or potentially with manipulating objects under water," says Tom Smulders, an evolutionary neuroscientist at Newcastle University who led the 2013 study. It could have given our ancestors a key advantage when it came to walking over wet rocks or gripping branches, for example. Alternatively, it could have helped us when catching or foraging for food such as shellfish. "The latter would imply it is unique to humans, whereas if it's the former, we would expect it to happen in other primates as well," says Smulders. Finger wrinkling has yet to be observed in our closest relatives in the primate world such as chimpanzees, but the fingers of Japanese macaque monkeys, which are known to bath for long periods in hot water, have been seen to also wrinkle after they have been submerged in water. But the lack of evidence in other primates does not mean it doesn't happen, it may simply be because no-one has looked closely enough yet, says Smulders. "We don't know the answer to this question yet." There are some other interesting clues about when this adaptation may have appeared in our species. Fingertip wrinkling is less pronounced in saltwater and takes longer than it does in freshwater. This is probably because the salt gradient between the skin and surrounding environment is lower in saltwater, and so the salt imbalance that triggers the nerve fibres is less dramatic. So, it could be an adaptation that helped our ancestors live in freshwater environments rather than along coastlines. But there are no firm answers, and some believe it could just be a coincidental physiological response with no adaptive function. What can we learn from the wrinkles? Strangely there are other baffling mysteries – women take longer to develop wrinkles than men do, for example. And why exactly does our skin return to its normal state – normally after 10-20 minutes – if there is no clear disadvantage to our grip on dry objects of having wrinkly fingertips? Surely if having wrinkly fingers can improve our grip in the wet, but not harm it when dry, why would our fingertips not be permanently wrinkly? One reason for that could be the change in sensation the wrinkling also causes. Our fingertips are packed with nerves, and the pruning of our skin changes the way we feel things we touch (although one study has shown it does not affect our ability to discriminate between objects based on touch). "Some people have a real aversion to it because picking something up with wrinkly fingers feels weird," says Davis. "It could be because the balance of skin receptors have changed position, but there could be a psychological dimension too. It would be fun to investigate why. There could be other things we can do less well with wrinkly fingers." But the wrinkling of our fingers and toes in water can reveal key information about our health in surprising ways too. Wrinkles take longer to form in people with skin conditions like psoriasis and vitiligo, for example. Patients with cystic fibrosis experience excessive wrinkling of their palms as well as their fingers, and this has even been noticed in people who are genetic carriers of the disease. Patients suffering from type 2 diabetes also sometimes show markedly decreased levels of skin wrinkling when their hands are placed in water. Similarly reduced wrinkling has been seen in people who have suffered heart failure, perhaps due to some disruption in the control of their cardiovascular system. Unsymmetrical wrinkling of the fingers – where one hand wrinkles less than the other despite the same immersion time – has even been suggested as an early sign of Parkinson's disease as it indicates the sympathetic nervous system is not functioning correctly on one side of the body. So, while the question of why our fingers and toes began wrinkling in water in the first place remains open, our pruney digits are proving useful to doctors in other surprising ways. * This article was originally published on 21 June 2022. It was updated on 19 June 2025 to include details of a new study on the repeatability of wrinkle patterns on wet fingers. -- If you liked this story, sign up for The Essential List newsletter – a handpicked selection of features, videos and can't-miss news, delivered to your inbox twice a week. For more science, technology, environment and health stories from the BBC, follow us on Facebook, X and Instagram.

The Independent

a day ago

• The Independent

Psychopaths are most likely to live in these US states

A new study indicates a correlation between adverse social conditions and higher levels of psychopathy, narcissism, and sadism. The research analyzed data from 1.8 million people across 183 countries, including 144,000 in the U.S., linking personality traits to societal factors like poverty, inequality, and violence. Researchers found that in societies where rules are broken and conditions are poor, individuals tend to prioritize self-interest, leading to higher 'Dark Factor' levels. U.S. states such as Louisiana, Mississippi, Texas, Nevada and New York were identified with higher 'Dark Factor' levels, while Utah, Vermont, and Alaska showed lower levels. The study suggests that personality is shaped by societal conditions, implying that reforms to reduce corruption and inequality could help prevent the development of negative personality traits.