A multisystem illness caused by the tick-borne spirochete Borrelia burgdorferi. The disease, also known as Lyme borreliosis, generally begins with a unique expanding skin lesion, erythema migrans, which is often accompanied by symptoms resembling those of influenza or meningitis. During the weeks or months following the tick bite, some individuals may develop cardiac and neurological abnormalities, particularly meningitis or inflammation of the cranial or peripheral nerves. If the disease is untreated, intermittent or chronic arthritis and progressive encephalomyelitis may develop months or years after primary infection.

The causative agent, B. burgdorferi, is a helically shaped bacterium with dimensions of 0.18–0.25 by 4–30 micrometers. Once thought to be limited to the European continent, Lyme borreliosis and related disorders are now known to occur also in North America, Russia, Japan, China, Australia, and Africa, where B. burgdorferi is maintained and transmitted by ticks of the genus Ixodes, namely I. dammini, I. pacificus, and possibly I. scapularis in the United States, I. ricinus in Europe, and I. persulcatus in Asia. Reports of Lyme disease in areas where neither I. dammini nor I. pacificus is present suggest that other species of ticks or possibly other bloodsucking arthropods such as biting flies or fleas may be involved in maintaining and transmitting the spirochetes.

All stages of Lyme borreliosis may respond to antibiotic therapy. Early treatment with oral tetracycline, doxycycline, penicillin, amoxicillin, or erythromycin can shorten the duration of symptoms and prevent later disease.

Prevention and control of Lyme borreliosis must be directed toward reduction of the tick population. This can be accomplished through reducing the population of animals that serve as hosts for the adult ticks, elimination of rodents that are not only the preferred hosts but also the source for infecting immature ticks with B. burgdorferi, and application of tick-killing agents to vegetation in infested areas. Personal use of effective tick repellents and toxins is also recommended. Infectious disease Insecticide

Lyme disease affects not only humans but also domestic animals such as dogs, horses, and cattle that serve as hosts for the tick vectors. Animals affected show migratory, intermittent arthritis in some joints similar to that observed in humans.