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Lyme disease, also known as Lyme borreliosis, is a tick-borne disease caused by species of Borrelia bacteria, transmitted by blood-feeding ticks in the genus Ixodes. It is the most common disease spread by ticks in the Northern Hemisphere. The rash is typically neither itchy nor painful. If an infection develops, several antibiotics are effective, including doxycycline, amoxicillin and cefuroxime.

Prevention includes efforts to prevent tick bites by wearing clothing to cover the arms and legs and using DEET or picaridin-based insect repellents. , clinical trials of proposed human vaccines for Lyme disease were being carried out, but no vaccine was available. A vaccine, LYMERix, was produced but discontinued in 2002 due to insufficient demand.

|File:Solid_erythema_migrans_rash_on_the_neck_of_a_woman_with_Lyme_disease.jpg|Erythema migrans ("migrating redness") on a woman's neck. Rashes from non-Lyme causes may look similar.

The incubation period is usually one to two weeks, but can be much shorter (days) or much longer (months to years).

The rash is usually circular or oval, red or bluish, and may have an elevated or darker center. This can make obtaining a diagnosis particularly challenging, especially with the rise of co-infection.

Asymptomatic infection exists, but some studies suggest that this occurs in less than 7% of infected individuals in the United States as opposed to about 50–70% of cases in Europe. Lymphocytic meningitis causes characteristic changes in the cerebrospinal fluid (CSF) and may be accompanied for several weeks by variable headache and, less commonly, usually mild meningitis signs such as inability to flex the neck fully and intolerance to bright lights but typically no or only very low fever. After several months neuroborreliosis can also present otolaryngological symptoms. Up to 76.5% of them present as tinnitus, the most common symptom. Vertigo and dizziness (53.7%) and hearing loss (16.7%) were the next most common symptoms. In children, partial loss of vision may also occur. Mononeuritis multiplex is an inflammation causing similar symptoms in one or more unrelated peripheral nerves. In European adults, the most common presentation is a combination of lymphocytic meningitis and radiculopathy known as Bannwarth syndrome, accompanied in 36-89% of cases by facial palsy. Symptoms may include heart palpitations (in 69% of people), dizziness, fainting, shortness of breath, and chest pain.]]

Lyme arthritis occurs in up to 60% of untreated people, typically starting about six months after infection.

A neurologic syndrome called Lyme encephalopathy is associated with subtle memory and cognitive difficulties, insomnia, a general sense of feeling unwell, and changes in personality. Lyme encephalopathy is controversial in the US and has not been reported in Europe. The Lyme-related Borrelia species are collectively known as Borrelia burgdorferi sensu lato, and show a great deal of genetic diversity.

B. burgdorferi sensu lato is a species complex made up of 20 accepted and three proposed genospecies. Eight species are known to cause Lyme disease: B. mayonii (found in North America), B. burgdorferi sensu stricto (found in North America and Europe), B. afzelii, B. garinii, B. spielmanii, and B. lusitaniae (all found in Eurasia). Death of horses as a result of Borrelia burgdorferi infection remains unknown.

Currently, there is no approved Lyme disease vaccine for horses. However, a study demonstrated that ponies could be protected using an aluminum adjuvanted recombinant outer-surface protein A (rOspA) vaccine. While horses have been administered a Lyme disease vaccine designed for dogs, it elicits only a short-lasting antibody response.

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Further reading

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  • CDC – Lyme Disease
  • Association for Public Health Laboratories guide – Suggested Reporting Language, Interpretation and Guidance Regarding Lyme Disease Serologic Test Results
  • NIH – Lyme Disease
  • NICE Guidelines – Lyme Disease
  • UK's One Health Vector-Borne Diseases Hub