The bacterial infection had a low survival rate without treatment, and had spread to virtually all of the colonies and nests on mainland New Zealand.
This meant the wildlife hospital would this year care for almost all the hoiho chicks from the Catlins to North Otago.
Senior veterinary nurse and practice manager Angelina Martelli said it was the busiest time of year for the hospital.
"It's a constant putting the washing on, cleaning syringes, drawing up new food, writing up their daily record sheets, checking all the checks."
They would often start about 6.45am, and the day did not end until after 8.30pm.
About 20 specialist volunteers from across the country had pitched in.
"They've all come at different times ... they come from other institutions."
This included people from Wellington Zoo, Auckland Zoo and Kelly Tarlton's Aquarium.