Lyme disease, also known as Lyme borreliosis, is a vector-borne disease caused by the Borrelia bacterium, which is spread by ticks in the genus Ixodes. The most common sign of infection is an expanding red rash, known as erythema migrans, which appears at the site of the tick bite about a week afterwards. The rash is typically neither itchy nor painful. Approximately 70–80% of infected people develop a rash. Early diagnosis can be difficult. Other early symptoms may include fever, headaches and tiredness. If untreated, symptoms may include loss of the ability to move one or both sides of the face, joint pains, severe headaches with neck stiffness or heart palpitations. Months to years later repeated episodes of joint pain and swelling may occur. Occasionally shooting pains or tingling in the arms and legs may develop. Despite appropriate treatment about 10 to 20% of those affected develop joint pains, memory problems and tiredness for at least six months.Lyme disease is transmitted to humans by the bites of infected ticks of the genus Ixodes. In the United States ticks of concern are usually of the Ixodes scapularis type and must be attached for at least 36 hours before the bacteria can spread. In Europe Ixodes ricinus ticks may spread the bacteria more quickly. In North America the bacteria Borrelia burgdorferi and B. mayonii cause Lyme disease. In Europe and Asia Borrelia afzelii, Borrelia garinii, B. spielmanii and four other species also cause the disease.
Africa
In northern Africa, B. burgdorferi sensu lato has been identified in Morocco, Algeria, Egypt and Tunisia.Lyme disease in sub-Saharan Africa is presently unknown, but evidence indicates it may occur in humans in this region. The abundance of hosts and tick vectors would favor the establishment of Lyme infection in Africa. In East Africa, two cases of Lyme disease have been reported in Kenya. Asia
B. burgdorferi sensu lato-infested ticks are being found more frequently in Japan, as well as in northwest China, Nepal, Thailand and far eastern Russia. Borrelia has also been isolated in Mongolia. Europe
In Europe, Lyme disease is caused by infection with one or more pathogenic European genospecies of the spirochaete B. burgdorferi sensu lato, mainly transmitted by the tick Ixodes ricinus. Cases of B. burgdorferi sensu lato-infected ticks are found predominantly in central Europe, particularly in Slovenia and Austria, but have been isolated in almost every country on the continent. Number of cases in southern Europe, such as Italy and Portugal, is much lower. Diagnosed cases in some Western countries, such as Iceland, are rising. United Kingdom
In the United Kingdom the number of laboratory confirmed cases of Lyme disease has been rising steadily since voluntary reporting was introduced in 1986 when 68 cases were recorded in the UK and Ireland combined. In the UK there were 23 confirmed cases in 1988 and 19 in 1990, but 973 in 2009 and 953 in 2010.