Cause and Transmission
Lymes disease is caused by Gram-negative, spirochetal bacteria from the genus Borrelia. At least 11 Borrelia species have been discovered, three of which are known to be Lyme-related. The Borrelia species that cause Lyme disease are collectively known as Borrelia burgdorferisensu lato, and show a great deal of genetic diversity. When making a diagnosis of Lyme disease, health care providers should consider other diseases that may cause similar illness. Most, but not all, patients with Lyme disease will develop the characteristic bullseye rash, but many may not recall a tick bite.
Lymes disease is classified as a zoonosis, as it is transmitted to humans from a natural reservoiramong rodents by ticks that feed on both sets of hosts. Hard-bodied ticks of the genus Ixodesare the main vectors of Lyme disease. Most infections are caused by ticks in the nymphal stage, as they are very small and may feed for long periods of time undetected. Larval ticks are very rarely infected. Tick bites often go unnoticed because of the small size of the tick in its nymphal stage, as well as tick secretions that prevent the host from feeling any itch or pain from the bite. However, transmission is quite rare, with only about 1% of recognized tick bites resulting in Lyme disease; this may be because an infected tick must be attached for at least a day for transmission to occur.
Lymes disease is classified as a zoonosis, as it is transmitted to humans from a natural reservoiramong rodents by ticks that feed on both sets of hosts. Hard-bodied ticks of the genus Ixodesare the main vectors of Lyme disease. Most infections are caused by ticks in the nymphal stage, as they are very small and may feed for long periods of time undetected. Larval ticks are very rarely infected. Tick bites often go unnoticed because of the small size of the tick in its nymphal stage, as well as tick secretions that prevent the host from feeling any itch or pain from the bite. However, transmission is quite rare, with only about 1% of recognized tick bites resulting in Lyme disease; this may be because an infected tick must be attached for at least a day for transmission to occur.
