Under usual circumstances his carers would be at risk of a serious mauling from the 140kg beast.
But three-year-old Ariel is no ordinary animal - because just over a year ago he was struck down by a debilitating virus which paralysed all four of his legs.
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Caring: Ariel's owner Raquel Borges launched the Facebook campaign to raise money to care for her paralysed lion
An internet campaign has now been launched by his owner Raquel Borges and vet Livia Pereira to raise the $11,500 needed each month to pay for his treatment.
A staggering 35,000 people have already clicked the 'like' button on Ariel's Facebook page and sent in donations to help fund his daily caring routine.
Pereira said: 'When the Facebook campaign began in May, we had less than five followers, because it was designed to inform people of Ariel's case not to ask for help.
'But then we started asking for donations and the number of people following Ariel's case soared.'
Pereira, who cares for Ariel at her home, said that for unknown reasons his white blood cells were attacking his healthy cells due to a degenerative disease affecting his medulla.
This is a portion of the brainstem involved in motor functions.
Routine: Vet Livia Pereira has taken Ariel into her home so she can care for him full-time
Kindness: Vet Livia Pereira snuggles in to paralysed lion Ariel
She believed Ariel's symptoms were similar to those of multiple sclerosis, Parkinson's disease and Guillain-Barre syndrome - an autoimmune disorder that can cause paralysis.
A team of Israeli veterinary neurologists from the Hebrew University of Jerusalem, who tested Ariel to see what degenerative disease was involved, will publish their results later this month.
Their trip to Brazil was paid for by Graziela Barrette, a Brazilian model living in New York, who had been moved after hearing of Ariel's plight.
Ariel was born in the shelter that Borges and her husband run in the southern city of Maringa, where they care for sick or abandoned animals.
She said: 'He was a perfectly normal and docile lion that slept with me until he was 10-months-old.'
Passed out: Ariel lies on a mattress, propped up by packets of toilet rolls
Loving: Vet Livia Pereira kisses paralysed lion Ariel who has lost the use of his legs
But last year, after spending hours leaping and chasing balloons, Ariel started limping. 'I could tell he was in pain,' she added.
Days later he was unable to move his two hind legs and after surgery to remove a herniated disc he lost control of his front legs.
'He was submitted to a battery of tests and medical examinations that failed to show what was wrong with him, so three weeks ago we brought him to Sao Paulo where there are better-equipped veterinary clinics,' she added.
Pereira and Borges said they have received an offer from a Brazilian doctor to perform the blood-cleansing treatment called plasmapheresis on Ariel.
But because the equipment used to perform it must be modified for use on a large animal, it was not clear when that would take place.
Borges added: 'One thing we will never lose is our hope that Ariel will recover and start walking again.'
Video: Ariel on Brazilian TV show SBT after surgery to remove a herniated disc:
http://www.dailymail.co.uk/news/article-2014617/Save-lion-Desperate-plea-help-paralysed-Ariel-struck-mystery-disease.html
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