§ 207-kkk. Disabilities of firefighters in certain cities caused by Parkinson's Disease. Notwithstanding any other provisions of this chapter to the contrary, any condition of impairment of health caused by Parkinson's Disease resulting in total or partial disability or death to a paid member of a fire department in a city with a population of one million or more, or any retired member of such department who has been retired for two or less years, who successfully passed a physical examination on entry into the service of such department, which examination failed to reveal any evidence of such condition, shall be presumptive evidence that it was incurred in the performance and discharge of duty unless the contrary be proved by competent evidence.