Can Genetic Testing Help Shed Light on the Autism Epidemic?
Autism cases are still on the rise, and scientists don't know why. In April, the Centers for Disease Control (CDC) reported that rates of autism had increased once again, now at an estimated 1 in 59 children up from 1 in 68 just two years ago. Rates have been climbing steadily since 2007 when the CDC initially estimated that 1 in 150 children were on the autism spectrum.
Some clinicians are concerned that the creeping expansion of autism is causing the diagnosis to lose its meaning.
The standard explanation for this increase has been the expansion of the definition of autism to include milder forms like Asperger's, as well as a heightened awareness of the condition that has improved screening efforts. For example, the most recent jump is attributed to children in minority communities being diagnosed who might have previously gone under the radar. In addition, more federally funded resources are available to children with autism than other types of developmental disorders, which may prompt families or physicians to push harder for a diagnosis.
Some clinicians are concerned that the creeping expansion of autism is causing the diagnosis to lose its meaning. William Graf, a pediatric neurologist at Connecticut Children's Medical Center, says that when a nurse tells him that a new patient has a history of autism, the term is no longer a useful description. "Even though I know this topic extremely well, I cannot picture the child anymore," he says. "Use the words mild, moderate, or severe. Just give me a couple more clues, because when you say autism today, I have no idea what people are talking about anymore."
Genetic testing has emerged as one potential way to remedy the overly broad label by narrowing down a heterogeneous diagnosis to a specific genetic disorder. According to Suma Shankar, a medical geneticist at the University of California, Davis, up to 60 percent of autism cases could be attributed to underlying genetic causes. Common examples include Fragile X Syndrome or Rett Syndrome—neurodevelopmental disorders that are caused by mutations in individual genes and are behaviorally classified as autism.
With more than 500 different mutations associated with autism, very few additional diagnoses provide meaningful information.
Having a genetic diagnosis in addition to an autism diagnosis can help families in several ways, says Shankar. Knowing the genetic origin can alert families to other potential health problems that are linked to the mutation, such as heart defects or problems with the immune system. It may also help clinicians provide more targeted behavioral therapies and could one day lead to the development of drug treatments for underlying neurochemical abnormalities. "It will pave the way to begin to tease out treatments," Shankar says.
When a doctor diagnoses a child as having a specific genetic condition, the label of autism is still kept because it is more well-known and gives the child access to more state-funded resources. Children can thus be diagnosed with multiple conditions: autism spectrum disorder and their specific gene mutation. However, with more than 500 different mutations associated with autism, very few additional diagnoses provide meaningful information. What's more, the presence or absence of a mutation doesn't necessarily indicate whether the child is on the mild or severe end of the autism spectrum.
Because of this, Graf doubts that genetic classifications are really that useful. He tells the story of a boy with epilepsy and severe intellectual disabilities who was diagnosed with autism as a young child. Years later, Graf ordered genetic testing for the boy and discovered that he had a mutation in the gene SYNGAP1. However, this knowledge didn't change the boy's autism status. "That diagnosis [SYNGAP1] turns out to be very specific for him, but it will never be a household name. Biologically it's good to know, and now it's all over his chart. But on a societal level he still needs this catch-all label [of autism]," Graf says.
"It gives some information, but to what degree does that change treatment or prognosis?"
Jennifer Singh, a sociologist at Georgia Tech who wrote the book Multiple Autisms: Spectrums of Advocacy and Genomic Science, agrees. "I don't know that the knowledge gained from just having a gene that's linked to autism," is that beneficial, she says. "It gives some information, but to what degree does that change treatment or prognosis? Because at the end of the day you have to address the issues that are at hand, whatever they might be."
As more children are diagnosed with autism, knowledge of the underlying genetic mutation causing the condition could help families better understand the diagnosis and anticipate their child's developmental trajectory. However, for the vast majority, an additional label provides little clarity or consolation.
Instead of spending money on genetic screens, Singh thinks the resources would be better used on additional services for people who don't have access to behavioral, speech, or occupational therapy. "Things that are really going to matter for this child in their future," she says.
These technologies may help more animals and plants survive climate change
This article originally appeared in One Health/One Planet, a single-issue magazine that explores how climate change and other environmental shifts are making us more vulnerable to infectious diseases by land and by sea - and how scientists are working on solutions.
Along the west coast of South Florida and the Keys, Florida Bay is a nursery for young Caribbean spiny lobsters, a favorite local delicacy. Growing up in small shallow basins, they are especially vulnerable to warmer, more saline water. Climate change has brought tidal floods, bleached coral reefs and toxic algal blooms to the state, and since the 1990s, the population of the Caribbean spiny lobster has dropped some 20 percent, diminishing an important food for snapper, grouper, and herons, as well as people. In 1999, marine ecologist Donald Behringer discovered the first known virus among lobsters, Panulirus argus virus—about a quarter of juveniles die from it before they mature.
“When the water is warm PaV1 progresses much more quickly,” says Behringer, who is based at the Emerging Pathogens Institute at the University of Florida in Gainesville.
Caribbean spiny lobsters are only one example of many species that are struggling in the era of climate change, both at sea and on land. As the oceans heat up, absorbing greenhouse gases and growing more acidic, marine diseases are emerging at an accelerated rate. Marine creatures are migrating to new places, and carrying pathogens with them. The latest grim report in the journal Science, states that if global warming continues at the current rate, the extinction of marine species will rival the Permian–Triassic extinction, sometimes called the “Great Dying,” when volcanoes poisoned the air and wiped out as much as 90 percent of all marine life 252 million years ago.
Similarly, on land, climate change has exposed wildlife, trees and crops to new or more virulent pathogens. Warming environments allow fungi, bacteria, viruses and infectious worms to proliferate in new species and locations or become more virulent. One paper modeling records of nearly 1,400 wildlife species projects that parasites will double by 2070 in the far north and in high-altitude places. Right now, we are seeing the effects most clearly on the fringes—along the coasts, up north and high in the mountains—but as the climate continues changing, the ripples will reach everywhere.
Few species are spared
On the Hawaiian Islands, mosquitoes are killing more songbirds. The dusky gray akikiki of Kauai and the chartreuse-yellow kiwikiu of Maui could vanish in two years, under assault from mosquitoes bearing avian malaria, according to a University of Hawaiʻi 2022 report. Previously, the birds could escape infection by roosting high in the cold mountains, where the pests couldn’t thrive, but climate change expanded the range of the mosquito and narrowed theirs.
Likewise, as more midge larvae survive over warm winters and breed better during drier summers, they bite more white-tailed deer, spreading often-fatal epizootic hemorrhagic disease. Especially in northern regions of the globe, climate change brings the threat of midges carrying blue tongue disease, a virus, to sheep and other animals. Tick-borne diseases like encephalitis and Lyme disease may become a greater threat to animals and perhaps humans.
"If you put all your eggs in one basket and then a pest comes a long, then you are more vulnerable to those risks," says Mehroad Ehsani, managing director of the food initiative in Africa for the Rockefeller Foundation. "Research is needed on resilient, climate smart, regenerative agriculture."
In the “thermal mismatch” theory of wildlife disease, cold-adapted species are at greater risk when their habitats warm, and warm-adapted species suffer when their habitats cool. Mammals can adjust their body temperature to adapt to some extent. Amphibians, fish and insects that cannot regulate body temperatures may be at greater risk. Many scientists see amphibians, especially, as canaries in the coalmine, signaling toxicity.
Early melting ice can foster disease. Climate models predict that the spring thaw will come ever-earlier in the lakes of the French Pyrenees, for instance, which traditionally stayed frozen for up to half the year. The tadpoles of the midwife toad live under the ice, where they are often infected with amphibian chytrid fungus. When a seven-year study tracked the virus in three species of amphibians in Pyrenees’s Lac Arlet, the research team found that, the earlier the spring thaw arrived, the more infection rates rose in common toads— , while remaining high among the midwife toads. But the team made another sad discovery: with early thaws, the common frog, which was thought to be free of the disease in Europe, also became infected with the fungus and died in large numbers.
Changing habitats affect animal behavior. Normally, spiny lobsters rely on chemical cues to avoid predators and sick lobsters. New conditions may be hampering their ability to “social distance”—which may help PaV1 spread, Behringer’s research suggests. Migration brings other risks. In April 2022, an international team led by scientists at Georgetown University announced the first comprehensive overview, published in the journal Nature, of how wild mammals under pressure from a changing climate may mingle with new populations and species—giving viruses a deadly opportunity to jump between hosts. Droughts, for example, will push animals to congregate at the few places where water remains.
Plants face threats also. At the timberline of the cold, windy, snowy mountains of the U.S. west, whitebark pine forests are facing a double threat, from white pine blister rust, a fungal disease, and multiplying pine beetles. “If we do nothing, we will lose the species,” says Robert Keane, a research ecologist for the U.S. Forest Service, based in Missoula, Montana. That would be a huge shift, he explains: “It’s a keystone species. There are over 110 animals that depend on it, many insects, and hundreds of plants.” In the past, beetle larvae would take two years to complete their lifecycle, and many died in frost. “With climate change, we're seeing more and more beetles survive, and sometimes the beetle can complete its lifecycle in one year,” he says.
Quintessential crops are under threat too
As some pathogens move north and new ones develop, they pose novel threats to the crops humans depend upon. This is already happening to wheat, coffee, bananas and maize.
Breeding against wheat stem rust, a fungus long linked to famine, was a key success in the mid-20th century Green Revolution, which brought higher yields around the world. In 2013, wheat stem rust reemerged in Germany after decades of absence. It ravaged both bread and durum wheat in Sicily in 2016 and has spread as far as England and Ireland. Wheat blast disease, caused by a different fungus, appeared in Bangladesh in 2016, and spread to India, the world’s second largest producer of wheat.
Insects, moths, worms, and coffee leaf rust—a fungus now found in all coffee-growing countries—threaten the livelihoods of millions of people who grow coffee, as well as everybody’s cup of joe. More heat, more intense rain, and higher humidity have allowed coffee leaf rust to cycle more rapidly. It has grown exponentially, overcoming the agricultural chemicals that once kept it under control.
To identify new diseases and fine-tune crops for resistance, scientists are increasingly relying on genomic tools.
Tar spot, a fungus native to Latin America that can cut corn production in half, has emerged in highland areas of Central Mexico and parts of the U.S.. Meanwhile, maize lethal necrosis disease has spread to multiple countries in Africa, notes Mehrdad Ehsani, Managing Director for the Food Initiative in Africa of the Rockefeller Foundation. The Cavendish banana, which most people eat today, was bred to be resistant to the fungus Panama 1. Now a new fungus, Panama 4, has emerged on every continent–including areas of Latin America that rely on the Cavendish for their income, reported a recent story in the Guardian. New threats are poised to emerge. Potato growers in the Andes Mountains have been shielded from disease because of colder weather at high altitude, but temperature fluxes and warming weather are expected to make this crop vulnerable to potato blight, found plant pathologist Erica Goss, at the Emerging Pathogens Institute.
Science seeks solutions
To protect food supplies in the era of climate change, scientists are calling for integrated global surveillance systems for crop disease outbreaks. “You can imagine that a new crop variety that is drought-tolerant could be susceptible to a pathogen that previous varieties had some resistance against,” Goss says. “Or a country suffers from a calamitous weather event, has to import seed from another country, and that seed is contaminated with a new pathogen or more virulent strain of an existing pathogen.” Researchers at the John Innes Center in Norwich and Aarhus University in Denmark have established ways to monitor wheat rust, for example.
Better data is essential, for both plants and animals. Historically, models of climate change predicted effects on plant pathogens based on mean temperatures, and scientists tracked plant responses to constant temperatures, explains Goss. “There is a need for more realistic tests of the effects of changing temperatures, particularly changes in daily high and low temperatures on pathogens,” she says.
To identify new diseases and fine-tune crops for resistance, scientists are increasingly relying on genomic tools. Goss suggests factoring the impact of climate change into those tools. Genomic efforts to select soft red winter wheat that is resistant to Fusarium head blight (FHB), a fungus that plagues farmers in the Southeastern U.S., have had early success. But temperature changes introduce a new factor.
A fundamental solution would be to bring back diversification in farming, says Ehsani. Thousands of plant species are edible, yet we rely on a handful. Wild relatives of domesticated crops are a store of possibly useful genes that may confer resistance to disease. The same is true for livestock. “If you put all your eggs in one basket and then a pest comes along, then you are more vulnerable to those risks. Research is needed on resilient, climate smart, regenerative agriculture,” Ehsani says.
Jonathan Sleeman, director of the U.S. Geological Survey National Wildlife Health Center, has called for data on wildlife health to be systematically collected and integrated with climate and other variables because more comprehensive data will result in better preventive action. “We have focused on detecting diseases,” he says, but a more holistic strategy would apply human public health concepts to assuring animal wellbeing. (For example, one study asked experts to draw a diagram of relationships of all the factors affecting the health of a particular group of caribou.) We must not take the health of plants and animals for granted, because their vulnerability inevitably affects us too, Sleeman says. “We need to improve the resilience of wildlife populations so they can withstand the impact of climate change.”
The Friday Five: Artificial DNA Could Give Cancer the Hook
The Friday Five covers five stories in research that you may have missed this week. There are plenty of controversies and troubling ethical issues in science – and we get into many of them in our online magazine – but this news roundup focuses on scientific creativity and progress to give you a therapeutic dose of inspiration headed into the weekend.
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Here are the promising studies covered in this week's Friday Five:
- Artificial DNA gives cancer the hook
- This daily practice could improve relationships
- Can social media handle the truth?
- Injecting a gel could speed up recovery
- A blood pressure medicine for a long healthy life