How is Lyme disease spread? The bacteria that causes Lyme disease are part of a natural cycle of infected ticks feeding on animals such as mice, opossums, dogs or deer. Cases of Lyme disease have also been reported in dogs and horses. Ticks can feed on a human, and, if the tick is infected with the bacteria, can cause an infection. Person-to- person spread of Lyme disease does not occur. What are the symptoms of Lyme disease? The illness usually occurs during the summer months and generally starts as a large circular reddish expanding rash around or near the site of the tick bite. Multiple rash sites may occur. During the rash stage, or occasionally prior to the rash, other symptoms such as fever, headache, fatigue, stiff neck, muscle and/or joint pain may be present