Pets n Vets Queenstown manager Fiona Ross said cases of cat influenza and feline immunodeficiency virus (FIV) were up significantly and the cause was an increase in the number of abandoned cats.
Staff were inundated with inquiries about the number of wild cats in the resort and the apparent lack of measures to tackle the problem.
Owners not spaying or neutering their pets and abandoning them when they left town were reasons for the spike in stray cat sightings this season.
Virginia Pine, of Alexandra, the Central Otago inspector for Otago SPCA, said it was impossible to estimate how many "semi-wild" and feral cats were roaming in Wakatipu.
However, she had dealt with 15 cases in April, double the number in February and March.
Mrs Pine said semi-wild and feral cats were often not desexed, continued to mate and were attracted to hotel or restaurant kitchens to scavenge for food.
"Semi-wild cats . . . are only that way because nobody wants them. Their offspring are deemed to be a pest and fall into a legal grey area, where nobody wants to take responsibility for them."
Mrs Pine said there was no evidence to show humans could contract feline flu or FIV.
Public Health South medical officer of health Dr Marion Poore, of Dunedin, said feline flu or FIV was not known to be transmissible to humans.
"The main disease in cats that affect humans is toxoplasmosis. Cat scratches can cause local bacterial skin infection."
Lakes Environmental chief executive Hamish Dobbie said his organisation dealt with feral cats.
The general increase in felines in town was because of the cold weather in the hills and was not unexpected, but staff were called about stray cats only if they were causing a nuisance.
If the animals could be caught they would be put down.
Queenstown Lakes District Council parks manager Gordon Bailey said cats were not required to be registered and there was no law covering the control of felines.
"Council doesn't have a position on [abandoned cats] . . . and doesn't have the resources or budget to deal with it," he said.
