Humans get lyme disease from infected ticks. ticks get infected by feeding on animals with lyme disease, but the ease of transmission from host animal to tick varies. with most species of host animal, transmission of lyme disease to ticks is extremely rare, but white-footed mice are an exception, readily passing lyme disease to ticks. and white-footed mouse populations greatly expand, becoming the main food source for ticks, in areas where biodiversity is in decline.