Lyme borreliosis, or Lyme disease (LD), is a tick-borne zoonotic infection of biomedical significance, caused by Borrelia burgdorferi sensu lato (s.l.) spirochetes and transmitted by Ixodes species ticks. It usually circulates among wildlife vertebrate reservoirs and vector ticks but may infect humans, causing multisystem problems. In far western and northern North America, the host reservoirs, tick vectors, and genospecies of Borrelia are well known but not so in the southern U.S., where there is controversy as to the presence of ''true'' LD. Here we report the presence of the LD spirochete B. burgdorferi sensu stricto (s.s.) and Borrelia bissettii, three main reservoir hosts, and two enzootic tick vectors in the southeastern U.S. The two enzootic tick vectors, Ixodes affinis and Ixodes minor, rarely bite humans but are more important than the human biting ''bridge'' vector, Ixodes scapularis, in maintaining the enzootic spirochete cycle in nature. We also report extraordinary longevities and infections in the reservoir rodents Peromyscus gossypinus, Sigmodon hispidus, and Neotoma floridana.L yme borreliosis (LB) is an infection of public health importance with endemic foci in North America and Eurasia. It is the most common vector-borne infectious disease in the U.S. (1) and Europe (2). The disease may affect the skin, joints, and cardiovascular and nervous systems. It may range from severe to mild or even asymptomatic and may become chronic if not treated promptly. The causative agent of Lyme disease (LD) is a spirochete, Borrelia burgdorferi sensu lato (s.l.), which is transmitted primarily by Ixodes spp. ticks (3). LB is a zoonosis in which humans and domestic animals are incidental to its usual wildlife reservoir hosts (4). The primary reservoir hosts in hyperendemic foci of the spirochete in the northeastern and north central U.S. are species of Peromyscus mice (5), although several other mammalian and avian species are reservoir-competent to various degrees and can be important locally throughout the U.S. (6) and globally (7). It is important to identify the main reservoir host species in each particular geographic area, because the vertebrate species composition may affect local B. burgdorferi abundance in nature. It is also important to identify the main local vector tick species responsible for transmission of the spirochete to humans and the tick enzootic vectors, as well as the local genospecies of B. burgdorferi s.l.At least 11 genospecies comprise the B. burgdorferi s.l. complex worldwide, and three of these occur in the southeastern U.S.: Borrelia andersonii, Borrelia bissettii, and B. burgdorferi sensu stricto (s.s.) (8, 9). Of the 11 genospecies described globally, only three have been confirmed to have been cultured from humans: B. burgdorferi s.s. (North America and western Europe), Borrelia garinii, and Borrelia afzelii (Europe and Asia). Additionally, B. bissettii was reportedly cultured from several patients in Slovenia (10), but this has yet to be confirmed.In North America, two tick spec...
