What Is Borrelia burgdorferi?

Borrelia burgdorferi is a spiral-shaped bacterium that causes Lyme disease. Lyme disease is an infectious illness transmitted to humans through the bites of black-legged ticks infected with B. burgdorferi. The infection is most commonly transmitted via Ixodes ticks, which are found in forests and shrubland across North America and Europe.¹

Symptoms of Lyme Disease Caused by Borrelia burgdorferi

Lyme disease progresses through three stages, each characterised by distinct symptoms.

Early Localised Stage

This stage occurs within days of a tick bite and may include:

• Erythema migrans: An expanding red rash with a characteristic 'bullseye' pattern
• Fever
• Fatigue
• Headache¹

Early Disseminated Stage

This stage occurs weeks after the bite and marks the spread of infection throughout the body:

• Multiple rashes
• Neurological symptoms: Including meningitis and facial nerve palsy
• Cardiovascular issues: Such as irregular heartbeats¹

Late Stage

This stage may develop months to years after the initial bite and includes:

• Chronic neurological issues: Such as memory loss and numbness
• Arthritis: Primarily affecting larger joints such as the knees
• Chronic skin conditions: Such as acrodermatitis chronica atrophicans, in rare cases¹

How Is Lyme Disease Transmitted in Nature?

Borrelia burgdorferi is maintained and transmitted between ticks and mammals, eventually reaching humans and initiating Lyme disease. The natural reservoirs for B. burgdorferi are small mammals such as the white-footed mouse in North America, and certain species of birds. These animals carry the bacterium naturally without developing signs of infection.¹

Lyme disease is transmitted to humans by the black-legged Ixodes tick (Ixodes ricinus in Europe). The tick typically takes two years to complete its lifecycle. During spring and summer, tick eggs hatch into larvae. Larvae feed on small mammals such as mice, and if those animals are infected, the larvae acquire B. burgdorferi. The larvae then develop into nymphs, which are the primary source of human infection, as they are small and feed on humans, pets, and wild animals. Infected nymphs can transmit B. burgdorferi during blood meals before developing into adult ticks.²

During autumn, adult ticks become active and feed on larger mammals such as deer, where reproduction occurs. After feeding, adult female ticks lay eggs in spring, restarting the cycle.²

How Do Humans Contract Lyme Disease?

Humans are accidental hosts of Borrelia burgdorferi and do not transmit the infection to other people or back to ticks. A tick attaches to the skin, feeds on blood, and in doing so transmits B. burgdorferi bacteria residing in its midgut into the host's body.²

What Is MALT Lymphoma?

Mucosa-Associated Lymphoid Tissue (MALT) lymphoma is a type of non-Hodgkin lymphoma that primarily affects the immune system. MALT is a component of the immune system located at mucosal surfaces throughout the body. Common sites of involvement include:

• Stomach: Most commonly linked to Helicobacter pylori infection
• Salivary glands: Associated with autoimmune conditions such as Sjogren's syndrome
• Thyroid: Linked to thyroid disorders such as Hashimoto's disease
• Skin: Known as cutaneous MALT lymphoma, presenting as red nodules or tumours on the skin³

The Link Between Borrelia burgdorferi and MALT Lymphoma

Borrelia burgdorferi infections can cause cutaneous MALT lymphoma through overactive immune stimulation, which drives B-cell proliferation that may become cancerous. This association arises because Lyme disease infections frequently persist in the skin, and B. burgdorferi can remain in tissues for prolonged periods. Sustained activation of the immune system in response to the infection leads to continuous B-cell multiplication, which can ultimately result in MALT lymphoma.⁴

Under normal circumstances, immune cell activity ceases once an infection clears. However, in Borrelia infections, B cells are continuously stimulated and proliferate in an uncontrolled manner, which is the mechanism by which cutaneous MALT lymphoma develops.⁴

Geographic Pattern of Association

Studies from Europe, particularly Germany, Austria, and Switzerland, have identified Borrelia burgdorferi DNA in 10 to 42% of cutaneous MALT lymphoma cases, typically detected using PCR. Strain types such as Borrelia afzelii and Borrelia garinii are more prevalent in Europe and have a greater propensity to infect the skin rather than the joints and nervous system. Furthermore, in some patients, skin lymphomas regressed or were visibly reduced following antibiotic treatment targeting Borrelia species.⁴

Diagnosis

Borrelia burgdorferi Detection

Early localised Borrelia infection can be diagnosed clinically by assessing symptoms. The characteristic erythema migrans rash is considered the most reliable diagnostic indicator when it follows known tick exposure.

Laboratory testing for Lyme disease is recommended in both the US and Europe. This is typically performed using antibody testing techniques such as enzyme-linked immunosorbent assay (ELISA) and western blotting. ELISA detects antibodies directed against Borrelia, the presence of which suggests active or prior infection. Western blotting serves as a confirmatory test to identify specific Borrelia proteins. However, a key limitation is that antibodies can persist in the body for years after infection, meaning a positive result does not always confirm active disease.⁵

Direct detection methods such as polymerase chain reaction (PCR) can also be employed. PCR detects Borrelia DNA in tissue samples including skin biopsies, synovial fluid, and cerebrospinal fluid, enabling site-specific diagnosis. In cases of suspected cutaneous MALT lymphoma, Borrelia testing typically includes PCR of skin biopsies alongside antibody testing to assess prior exposure.⁵

Treatment Options

Treatment of Lyme disease is guided by the stage of infection. Early localised infection is managed with first-line antibiotics such as doxycycline for approximately 10 to 21 days. Alternatives such as amoxicillin are available for those who cannot take doxycycline, including children under eight years of age and pregnant women.⁶

Treatment of cutaneous MALT lymphoma associated with Borrelia includes antibiotics such as doxycycline or penicillin, which can induce lymphoma regression. Where antibiotic therapy fails, additional options include radiotherapy for localised disease and immunotherapy with rituximab for disseminated or relapsing disease.⁷

The prognosis is generally favourable and often more successful than with other lymphoma subtypes. Cutaneous MALT lymphoma carries a high survival rate, particularly when treated early. Alongside antibiotic and oncological therapies, regular clinical review is strongly recommended, as skin examinations and repeat biopsies are valuable for guiding treatment decisions.⁶

Preventing Lyme Disease

Lyme disease can be prevented by considering environmental, seasonal, and personal risk factors. Caution is advised for those living in or travelling to endemic areas, including the north-eastern and north-central United States (such as New England and Wisconsin), Central and Eastern Europe, and parts of Asia. Individuals who participate in outdoor activities such as hiking, camping, hunting, or gardening should exercise particular vigilance, as ticks are commonly found in wooded, bushy, and grassy environments such as leaf litter, tall grass, and forests.⁸

Preventive measures include the use of tick repellents such as DEET to reduce tick contact, as well as wearing long sleeves and trousers during outdoor activities to minimise skin exposure.⁸

FAQs

What is Borrelia burgdorferi?

Borrelia burgdorferi is a spiral-shaped bacterium transmitted to humans through the bites of infected Ixodes ticks. It is the principal causative agent of Lyme disease.

How does Borrelia burgdorferi cause Lyme disease?

Following a tick bite, B. burgdorferi enters the skin and can spread via the bloodstream. Early clinical signs include the erythema migrans rash (the characteristic bullseye rash) and flu-like symptoms.

What is the early disseminated stage?

If not treated promptly, Lyme disease progresses to the early disseminated stage, in which the bacteria spread through the bloodstream and involve other areas of the body, including the heart, joints, and brain.

What is cutaneous MALT lymphoma?

Cutaneous marginal zone B-cell lymphoma is a subtype of MALT lymphoma. It is a low-grade B-cell cancer that arises in the skin, generally as a result of chronic immune system overactivation.

How is Borrelia burgdorferi linked to cutaneous MALT lymphoma?

Persistent Borrelia infections can drive continuous antigen stimulation of B cells, causing them to proliferate uncontrollably and form a lymphoma.

Which antibiotics are used in Borrelia-associated MALT lymphoma?

In some patients, cutaneous MALT lymphoma regresses following antibiotic therapy with doxycycline or amoxicillin.

Summary

Borrelia burgdorferi is a spiral-shaped bacterium transmitted to humans through the bites of Ixodes ticks, causing the tick-borne illness known as Lyme disease. The early localised infection is characterised by the erythema migrans rash and flu-like symptoms. When left untreated, the infection disseminates to other areas of the body, affecting the heart, joints, and brain, and may cause serious complications including irregular heartbeats, arthritis, memory loss, and meningitis.

Beyond these established complications, Borrelia infections have also been associated with the development of primary cutaneous MALT lymphoma. It is thought that chronic antigen stimulation arising from persistent Borrelia infection may trigger abnormal B-cell proliferation in the skin. The regression of some cases following Borrelia-targeted antibiotic therapy further supports a causal link between the two conditions.