Is There Lyme Disease in Mexico?

Lyme carditis may be underrecognized in Mexico.
A delayed diagnosis led to advanced heart block.
Recognition may prevent serious complications.

Lyme disease in Mexico remains controversial despite published reports documenting human infection, positive serologic testing, and Lyme carditis cases. A case report involving a 23-year-old woman with advanced heart block highlights the consequences of delayed recognition of Lyme carditis symptoms in regions where Lyme disease is not widely acknowledged.

Lyme carditis occurs when Borrelia burgdorferi affects the heart’s electrical conduction system. Patients may develop:

• chest pain,
• shortness of breath,
• dizziness,
• palpitations,
• lightheadedness,
• or atrioventricular (AV) block.

The authors describe the case of a 23-year-old woman who presented with dyspnea and chest pain. An electrocardiogram (ECG) revealed a third-degree AV block — a potentially life-threatening complication associated with Lyme carditis.

A temporary pacemaker was implanted. After an extensive evaluation for alternative causes of heart block, clinicians eventually tested the patient for Lyme disease.

While Lyme carditis symptoms can vary widely, the patient met the Centers for Disease Control and Prevention (CDC) two-tier Western blot criteria for Lyme disease.

Despite treatment with a three-week course of intravenous ceftriaxone, the woman ultimately required placement of a permanent pacemaker.

“At 3-month follow-up, she was still dependent on pacing,” wrote Carrizales-Sepulveda and colleagues. ¹

Delayed Recognition of Lyme Carditis Symptoms

The authors argued that the patient lived in a region where Lyme disease exposure may occur and had visited the hospital four weeks earlier with symptoms suggestive of Lyme carditis.

According to the CDC, a region may be considered endemic for Lyme disease if:

• at least two locally acquired confirmed cases have been reported, or
• infected tick vectors are established in the region.

However, Lyme disease remains controversial in parts of Mexico.

Officials have argued that “there is no convincing evidence that Borrelia burgdorferi is present in Mexico.”

READ MORE: Which treatment guidelines should you follow for Lyme carditis?

Evidence of Lyme Disease in Mexico

Despite ongoing skepticism, Carrizales-Sepulveda and colleagues reported measurable Lyme disease exposure in Mexico.

Using a two-tier approach with enzyme-linked immunosorbent assay (ELISA) followed by Western blot, investigators identified:

• 6.2% seroprevalence in northeastern Mexico
• 3.4% seroprevalence in Mexico City

The authors noted that these findings were often dismissed as false positives.

In addition, critics questioned whether the woman’s advanced AV block was truly caused by Lyme carditis or by another undiagnosed cardiac condition.

Can Lyme Disease Cause Heart Block?

Yes. Lyme carditis can interfere with the heart’s electrical conduction system and lead to varying degrees of AV block.

In severe cases:

• temporary pacing may be required,
• patients may experience syncope or collapse,
• and untreated Lyme carditis can become life-threatening.

Additional discussion can be found in:

• Patients can die when Lyme carditis is not treated
• Study identifies 189 children with Lyme carditis
• 17-year-old man dies from Lyme carditis

Clinical Takeaway

The Mexico case highlights how Lyme carditis symptoms may go unrecognized in regions where Lyme disease is considered uncommon or controversial.

Delayed diagnosis may increase the risk of:

• advanced heart block,
• pacemaker dependence,
• and potentially life-threatening complications.

Clinicians evaluating unexplained AV block should consider Lyme carditis in the differential diagnosis — even in regions where Lyme disease is not widely acknowledged.

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Dr. Daniel Cameron, MD, MPH
Lyme disease clinician with over 30 years of experience and past president of ILADS.

Symptoms • Testing • Coinfections • Recovery • Pediatric • Prevention