The "severely emaciated and malnourished" 1-year-old American bulldog-cross was discovered earlier this week by an animal control officer after receiving a Dunedin City Council report about a wandering dog.
SPCA inspector Sophia Tinirau said the officer was so concerned about Ludo's appalling condition, he was taken straight to Dunedin's SPCA.
"I was completely shocked when I saw Ludo.
"It's definitely one of the worst cases I've ever seen.
"It took my breath away for a moment when we took the jacket off and saw just how emaciated he was.
"My little hand could fit around his whole backside to hold his hipbones."
On top of the immense weight loss he has suffered, Ludo also requires specialist entropion eye surgery.
She said the "gentle giant" was pleased to have human attention when he was brought in.
"He headbutts you like a cat, because he is so excited to see you. He loves affection and cuddles."
She said he would remain at the SPCA for a few more weeks, at which time he would be ready to be rehomed.
"Ludo's transformation in just a few days has been incredible to witness.
"This is the most rewarding part of my job - seeing animals like Ludo go from nervous and emaciated, to happy and healthy individuals, really coming into their own personalities, where they are so happy, loved, and cared for again."
She said the people responsible for Ludo's condition were being investigated.
