# Advanced Molecular and Microscopic Diagnostics Suggest Congenital Borrelia Transmission: A Case Report

## TL;DR

This case report suggests that Borrelia, the bacteria causing Lyme disease, may be transmitted from mother to child without a tick vector.

## Contribution

The study provides molecular and microscopic evidence of congenital Borrelia transmission in a human case.

## Key findings

- Intact spirochetes were found in placental tissue and were reactive to Borrelia antibodies.
- Borrelia DNA isolated from the placenta and later from the mother and child was identified as the same species.
- Viable spirochetes were cultured from the mother and child, supporting vector-free transmission.

## Abstract

Lyme disease is by far the most common arthropod-borne disease in the Northern Hemisphere. It is caused by certain Borrelia species that are primarily transmitted to hosts by Ixodid ticks; however, transplacental transmission of the spirochete in both animals and humans has been reported. Here, we report imaging of intact spirochetes in an archived placental tissue sample that is immunoreactive to Borrelia antibodies and from which Borrelia DNA was isolated. Both mother and child showed evidence of seroreactivity to Borrelia spp. in the years following the child’s birth, although neither individual tested positive by the conventional two-tiered serological algorithm. Cultivation of viable spirochetes from a vaginal swab of the mother and from the urine of the child some years later supports the possibility of vector-free transmission of Borrelia from mother to child. By amplifying several genomic loci from the DNA of cultured and non-cultured Borrelia from blood and body fluid samples of the mother and child, the Borrelia in both were identified as the same species, Borrelia burgdorferi sensu stricto, a strain specific to North America.