Stool transplants have dramatically reduced autism symptoms in children, according to new research.
The symptoms have almost halved in 18 children who received the treatment, known medically as microbiota transfer therapy.
The study is based on the theory that the neurological condition can be rooted in the intestine rather than in the brain.
Two years after the transplant, the children saw a decrease of about 45% in problems related to language, social interaction and behavior.
Children with autism have had far fewer behavioral and linguistic symptoms after a fecal transplant, according to a new study (file image)
Dr. Rosa Krajmalnik-Brown, a microbiologist at Arizona State University who jointly directed the study, said: "We are finding a very strong connection between the microbes that live in our intestines and signals that travel in the brain.
"Two years later, the children are doing even better, which is surprising."
In the beginning, 83% of the participants were assessed with a "severe" autism.
In the end, this had dropped to 17% – with 39% classified as "mild to moderate" and 44% below the cut-off even for mild ASD.
Recent research suggests that our intestinal bacteria, or "microbiomes", influence communication between brain cells and general neurological health.
Worldwide, interest is growing in the idea that abnormal amounts of some bugs could be responsible for triggering a variety of conditions.
"Many children with autism have gastrointestinal problems, and some studies, including ours, have found that these children also have worse symptoms related to autism," said Dr. Krajmalnik-Brown.
"In many cases, when you can treat these gastrointestinal problems, their behavior improves."
More than 700,000 people in the UK are autistic, which means that 2.8 million people have a relative on the spectrum. In the United States one child out of 59 is diagnosed with autism, one out of every 150 in 2000.
The apparent increase and lack of treatment has prompted researchers to enter the field and explore disability in innovative ways.
These include behavioral, vocal and social therapy, psychiatric drugs and dietary and nutritional approaches.
But no drug has been approved to treat the main symptoms such as social communication difficulties and repetitive behaviors.
One promising avenue is the collection of microbes that live in our intestines helping us digest food, train our immune systems and prevent excessive proliferation of harmful bacteria.
The study published in Scientific Reports found that most of the initial improvements in intestinal symptoms remained.
Furthermore, parents reported a slow steady decline in ASD symptoms both during treatment – and over the next two years.
Up to 50% of autistic patients have chronic gastrointestinal (GI) problems, mainly constipation and diarrhea that can last for many years.
Discomfort and pain can cause irritability, decreased attention and learning and adversely affect behavior.
A previous study with the antiobiotic vancomycin found significant temporary improvements in the symptoms of GI and autism.
But the benefits were lost a few weeks after stopping treatment despite the use of over-the-counter probiotics.
The dott. Krajmalnik-Brown and colleagues have shown that by transferring the healthy microbiota to individuals without certain intestinal bacteria, it is possible to "donate" a more diverse set of bacteria to the patient and increase health.
The therapy included the pre-treatment with vancomycin, a cleansing of the intestine, a suppressor of gastric acid and daily poop transplants for seven to eight weeks.
In the beginning it was discovered that the children had less diversity in their respective gut microbes and had become depleted of some useful bacteria strains, such as bifidobacteria and prevotella.
The dott. Krajmalnik-Brown said: "Children with autism have no important beneficial bacteria and have fewer options in the bacterial menu than important functions that bacteria supply in the intestine compared to typical developing children."
Treatment has substantially increased microbial diversity and the presence of useful bacteria, including Bifidobacteria and Prevotella.
After two years, the diversity was even higher and the presence of beneficial microbes remained.
The work does not only concern the treatment of patients, but also the learning from treatment in order to develop better formulations and optimize the dosage.
The dott. Krajmalnik-Brown said: "Understanding which microbes and chemicals produced by microbes are driving these behavioral changes is at the heart of our work."
Two years after stopping treatment, participants still had an average 58% reduction in gastrointestinal symptoms.
Furthermore, the parents of most of the 18 participants reported "a slow but steady improvement in ASD core symptoms".
Each family completed the study, and returned two years later for a follow-up assessment.
Treatment was generally well tolerated with minimal side effects.
Fecal transplants have been tested more than 30 years ago by Dr. Thomas Borody, an Australian gastroenterologist at the Sydney Center for Digestive Diseases.
He said: "I would call it the best improvement in a cohort that someone has achieved for autism symptoms."
Co-author Dr Greg Caporaso, one of the leading experts in microbiome data science at Northern Arizona University, says the team is "excited".
But more extensive clinical trials are needed involving hundreds of autistic children before they can be approved as a treatment by the US Food and Drug Administration.