However, as more time passed, Maggie continued to believe there was something wrong with her son's development and brought him to Professor Michael Fitzgerald at Trinity College, who diagnosed Merrick with Asperger Syndrome, Attention Deficit Hyperactivity Disorder (ADHD) and Oppositional Defiant Disorder (ODD).
The HSE later confirmed his diagnosis.
Merrick's conditions led to an extremely difficult home life.
"We were living in an estate in Portlaoise and Merrick was very violent with the other children," recalls Maggie.
"He would throw stones and attack the other children, who would naturally fight back. It escalated to the point where I nearly had a nervous breakdown and we needed to move, for Merrick's sake, for my sake and for the sake of my neighbours."
Finally, after months of campaigning the local council, the family were given alternative accommodation in nearby Stradbally. The quiet, leafy village location with woodlands all around caused an immediate change in Merrick's behaviour.
"Merrick relates to nature -- animals, wildness, trees, all those things," says Maggie.
But it was when Merrick started interacting with horses that his mother noticed the biggest change.
"I had an ex point-to-pointer that Merrick would sit up on after I rode and he loved it," she says. "However, I was aware of the safety issues so I decided to try to find him a horse that would be safer for him. I needed to find a horse that would understand Merrick."
Maggie researched various horse therapies and hand-picked horses that could be used as therapy horses.
Her own experience with horses was extensive, as she has been a British Horse Society instructor, managed mares and foals at Coolmore, ridden out for racing trainers and even worked as a horse wrangler in Alaska.
In order to help Merrick and other children like him, Maggie also trained in Equine Assisted Learning (EAL) and with Horse Boy founder Isaac Rupertson, who was featured in these pages this summer.
"Horses can promote self-awareness, encourage communication, encourage self-regulation and create appropriate focus," she says. "Equine Assisted Learning makes a direct connection between a child and a horse from the ground in a round pen."
EAL techniques are used to help both children and adults with co-ordination problems like dyspraxia, gross and fine motor skills, core muscle problem, as well as sensory problems, tantrums, high stress and anxiety disorders.
"Working with horses can help with ODD, ADHD, dyslexia and learning disabilities," says Maggie.
"Horse therapy can help with emotional and physical problems of any nature."
Last year, she was one of the founders of Laois Autism Resource Centre (ARC), which is now known as ARC Eireann.
However, while she trained as a horse therapist and worked with Merrick to overcome his problems, Maggie realised that there was simply no time to relax for parents of autistic children.
"These families never get holidays, never get any time to release," she says.
"So I decided to invent a residential horse camp where entire families could come for some release."
The idea was supported by lots of local people and businesses, including land-owner David Pennefeather, who offered his land beside Oughavale Woods in Stradbally for the camp.
Laois Sports Partnership also provided funding of €1,200 for the camp. Portarlington Scouts pitched their tents for families to stay in, Telfords provided gardening material, Laois Hire provided fencing and toilet facilities, Tesco provided free organic food, and Brownes Animal Feeds and Frontier gave horse supplies, while discounted organic meals were provided by local restaurant Stradbally Fayre.
Eight families signed up for the inaugural camp and there were eight therapists on hand to work with the autistic children and their families.
"We hacked in the woods each day on the therapy horses, while gardening, drama and art therapy were also a huge part of each day's schedule," says Maggie.
"Children with autism get a lot of sensory input from gardening and planting their own little plants and gardens.
"It's a very tactile therapy for them and their parents can join in and share in the therapy with their children," she says.
Twice a day, the families rode in the adjacent woods and each evening sat around a huge campfire to sing songs and play music before retiring to their tents.
The horses used were a mixture of Maggie's own horses and ponies and those of Limerick horse therapist Shelly Murtagh, who brought her own trick pony for the children to use. The pony is trained to perform tricks such as kneeling to one-word commands, which encourages the children to speak.
Another friend of Maggie's provided goats, rabbits, chickens and even a talking parrot to create sensory experiences for the children.
The camp cost €750 for a family of five, including therapy and food for all the family.
Although the camp was not cheap, its effect was enormous, with many of the children showing visible improvements.
Six-year-old Danny Castle is almost totally non-verbal, but sitting on a horse for the first time, he started pointing out colours of the other horses to his astounded mother Vicky, from Kinnegad, Co Westmeath.
"He struggles to talk," says Vicky. "Some days are better than others, one or two words. He started telling me the horses had shoes, the horses' colours and looking at the horses at the same time as he was speaking about them, and last night he sat by the fire and said "I'm cosy". He is making eye contact too. I will definitely be back."
Plans for the next residential horse camp are already under way for next spring, while there are also talks on holding one at Kill International Equestrian Centre.
In the meantime, Maggie is enlisting a host of celebrities to help raise funds and awareness of horse therapy.
She already has the backing of some very influential people in the horse world, including Tracy Piggott, trainer Jessica Harrington, Con Power and Billy Culbert.
The horse therapist is brimming with ideas for more autistic therapy in Ireland. Laois County Council has donated a two-acre site to Laois ARC in Stradbally, where Maggie plans to develop a community organic and sensory garden for people of all abilities this autumn.
For more information on autism and horse therapy for autism, go to www.arc- eireann.org or check out Laois ARC on Facebook.