Upon any outbreak of rabies or when rabies has been diagnosed within the County, and when in the judgment of the Health Officer there is imminent danger of the spread of the disease, the Health Officer shall publish a notice to that effect in the official newspaper of the County for three successive days. For a period of six weeks following the final publication of the notice, the owner or custodian of a dog shall keep the dog securely confined at all times by leash or in a tight enclosure from which the dog cannot escape. During said period any dog found running at large in the County shall be impounded and unless claimed and redeemed by its owner within two days following such impounding, may be destroyed by the proper authorities. Any person charged with the enforcement of this Chapter may destroy any dog found running at large within the County when, after reasonable effort, he is unable to impound the dog or after reasonable investigation, is unable to locate the owner or custodian thereof. The Health Officer shall have authority to extend the six-week time period for additional six-week periods by notice given in the manner provided above until, in his judgment, the imminent danger of the spread of the disease is no longer present.