6th July 2023

Lyme Disease

A tick-transmitted infection primarily caused by the spirochaete bacteria, Borrelia burgdorferi. Most cases have been reported in the USA and Europe. The most prevalent variant in Europe is B. garinii.

Infection is acquired in heavily wooded and leafy areas with peak cases occurring in summer. Ixodes ticks become infected by Borrelia from feeding on an infected animal (e.g. mouse, deer, sheep). Ticks then painlessly bite and feed on any part of the human body, usually a limb. Infection may be cleared by the host’s defences with no clinical manifestation, or the organism spreads via the skin, lymphatics and can disseminate in the blood to other organs.

There are 3 stages of Lyme disease, shown in table 4:

Table 4: Stages of Lyme disease

A clinical diagnosis can be made in patients with erythema migrans as it often develops before positive serology tests. In patients suspected of having Lyme disease without erythema migrans, an enzyme-linked immunosorbent assay (ELISA) test for Lyme disease IgM and IgG should be sent. If this is positive, an immunoblot test for Lyme disease should be sent. If negative, this test should be repeated 4-6 weeks later. Management is with doxycycline or amoxicillin for 21 days and is highly effective in the early Lyme disease stage.

Erythema migrans

Image Source: Wikimedia Commons (2019). Erythema migrans – erythematous rash in Lyme disease – PHIL 9875, Licensed under a creative commons licence. Available for free at: https://commons.wikimedia.org/wiki/File:Erythema_migrans_-_erythematous_rash_in_Lyme_disease_-_PHIL_9875.jpg  (Accessed on: 10 March 2022).