Diseases spread by ticks are no recent phenomena to the new world.
Most new cases were observed in the summer and early fall of each year, and the incidence was soon linked to recent tick bites in a high percentage of patients. The organism that causes Lyme disease is a bacterium, Borrelia burgdorferi , which was cultured from the midgut of Ixodes ticks in the mid 1980s. We now have the full sequence of the B. burgdorferi genome. It has a total of 853 genes on one linear chromosome and a further 430 genes on 11 plasmids. The chromosomal genes are required for cell growth, although there are no genes present that are involved in the synthesis of amino acids, fatty acids, enzyme cofactors, or nucleotides.