Important New Findings Regarding Lyme Bacteria- Part 1: Sexual Transmission
Keith Berndtson, MD
Two provocative studies on Lyme bacteria came out in the past month. Both are of great interest to those of us who follow the peer-reviewed literature on the microbiology of Lyme disease. This commentary addresses the one that appeared in December 2014 on sexual transmission of Lyme disease. The next installment will address exciting research that came out in January 2015 into the pleomorphic forms of Borrelia burgdorferi, or Bb, and what it means for diagnosis and treatment.
A study done by an international collaboration of eleven researchers titled, Culture and identification ofBorrelia spirochetes in human vaginal and seminal secretions, appeared in the open access journal F1000Research. This is the expanded version of an abstract on possible sexual transmission of Lyme disease in January of 2014.
Seminal and vaginal secretions were placed into BSK-H medium and cultured for four weeks. Microscopic examination was performed on spirochetes subjected to Dieterle silver staining and anti-Bb immunohistochemical staining. The team also ran molecular hybridization and PCR analyses. Each analysis included unblinded positive and negative controls.
All asymptomatic and seronegative controls produced no detectable spirochetes in their genetic secretions. Bb spirochetes were found in cultures from 11 of 13 subjects with Lyme disease, and in 12 of 13 Lyme disease subjects by light and darkfield microscopy. Molecular hybridization and PCR testing confirmed that the spirochetes were strains of Borrelia. All cultures were negative for Treponema species associated with syphilis.
Among three couples having unprotected sex, two showed identical strains of Borrelia burgdorferi. The third couple showed identical stains of Borrelia hermsii. The authors conclude that this ability to culture viable Borrelia spirochets from genital secretions suggests that Lyme disease could be transmitted by intimate contact from person to person.
Last year I trashed the press release that accompanied the preliminary abstract. I did so because the press release implied that the risk of catching Lyme disease in the bedroom was greater than the risk of catching it in the woods. The expanded article’s press release used more accurate wording: “We have taken Lyme disease out of the woods and into the bedroom.”
The expanded study clearly shows that patients with Lyme disease can contain viable Bb in their seminal or vaginal secretions. This finding deserves to draw a great deal of scientific attention. More work is needed to prove whether Lyme disease can be sexually transmitted, and if so, under what conditions.
Since this study implies that sexual transmission of Lyme disease is possible, it is of utmost importance that resources be allocated toward research that can derive a definitive answer to this question. Patients with Lyme disease need to know whether unprotected sex increases the risk of sexual transmission of Bb.
In the wake of last year’s preliminary abstract I pointed out that additional steps were needed to prove the sexual transmission of Lyme disease. I invoked Koch’s postulates as an historical reference on criteria for proving a microbe’s infectivity. The truth is, Koch’s postulates are too simple to grapple with the complexity of the situation.
The more nuanced Bradford Hill viewpoints for assessing biological causality are more useful than Koch’s postulates but they don’t take into account the complexity introduced by
1. Hormesis, where a small dose of toxin can trigger an aggressive, system-wide immune response)
2. Genetics, where differing HLA genotypes confer differing susceptibilities to disease.
3. Epigenetics, where lifestyle choices and environmental exposures can affect gene expression.
4. The relative pre-existing state of health or disease in a given host. In the case of sexual transmission of Lyme disease, the likelihood of transmitting the disease depends on the relative state of health or disease in the patient who has it, and in the uninfected person who engages in sexual activity with a person who has Lyme disease.
Our ways of assessing causality need to keep up with the complexity of our bodies and the environment around us, both in the exam room and in the courtroom.
We don’t know how many Bb spirochetes would be needed in a genital secretion to infect a given person. It might require far more than were found in the cultures performed in this study. We also don’t know enough about how sexual transmission of Bb in humans compares to tick-borne transmission in mammals.
The CDC revised its estimate of the annual incidence of Lyme disease in the United from 30,000 new cases annually to 300,000 thousand cases annually. Are all of these cases tick-borne? Can other blood-sucking arthropods transmit Lyme disease? What about mosquitoes? The public deserves clear answers to such questions.
Now they have a study that moves the ball forward on the possibility of sexual transmission of Lyme disease. This article forces us all to contend with what it really means. Are the Borrelia spirochetes cultured from the genital secretions of Lyme disease patients merely viable or are they actually infective and able to establish themselves in a new human host by means of sexual transmission.
Marianne Middelveen (the first author), Raphael Stricker (the senior author), and the rest of this international team of research collaborators should be congratulated for challenging the world scientific community to engage the question of the sexual transmissibility of Lyme disease and join the effort to find conclusive answers.