Overturning a century of conventional wisdom, a study has confirmed the worst: throat gonorrhoea can be transmitted through tongue kissing.
Kissing had previously always been thought of as a low-risk activity for transmission of the infection. Aside from few case reports from 40 years ago, the public health message has consistently been that unprotected sex is largely responsible for the spread of gonorrhoea.
But research by the Melbourne Sexual Health Centre is upending that notion by demonstrating that tongue kissing increases the risk of gonorrhoea transmission in men who have sex with men (MSM).
With throat gonorrhoea rates increasing 130% between 2009 and 2015 in Australia, the revelation that kissing can also be risky may have major public health implications. The study, led by senior research fellow Dr Eric Chow, involved a survey of around 3,600 MSM attending a public sexual health centre in Melbourne.
The as-yet unpublished research findings were presented at the IUSTI Asia Pacific Sexual Health Congress in Auckland earlier this month.
In the study, men were asked to categorise their partners over the last three months into: kissing-only, sex-only and kissing-with-sex. “Sex” included oral sex and anal sex, as well as oro-anal sex (rimming). Most men had multiple partners over three months, with an average of 4.3 kissing-only partners, five kissing-with-sex partners and 1.4 sex-only partners. Around 6% of the men surveyed had oropharyngeal gonorrhoea. The median age was 30.
The researchers found that a man’s risk of getting throat gonorrhoea increased by 46% if he had four or more kissing partners, and increased 80% if he had four or more kissing-with-sex partners.
“We find that if you kiss your partners, regardless of whether you have sex with those partners, you have a higher risk of getting oropharyngeal gonorrhoea,” Dr Chow told The Medical Republic.
“If you only have sex with that partner but you didn’t kiss that partner, that is actually not associated with oropharyngeal gonorrhoea.”
We know from Dr Chow’s previous work that gonorrhoea can be cultured from saliva, which means the gonorrhoea in saliva is probably contagious.
And kissing as a form of transmission makes sense of another epidemiological fact: the relatively low rates of genital gonorrhoea in the population. If throat gonorrhoea were being transmitted by oral sex then we would expect to see a very high prevalence of gonorrhoea in the urethra as well, Dr Chow said.
“But we are seeing very low prevalence rates.” So how can men protect themselves against throat gonorrhoea?
A fail-safe method would be to abstain from kissing altogether, Dr Chow said, but survey results suggested that hardly anyone was prepared to do that. Another simple preventative method could be using mouthwash.
A recent RCT of around 60 MSM with oropharyngeal gonorrhoea showed that rinsing and gargling with an alcohol-containing mouthwash for a minute reduced the bacterial load.
Dr Chow is now conducting another RCT to investigate whether a daily mouthwash could prevent MSM from acquiring throat gonorrhoea.
“With the rise of antibiotic resistance to gonorrhoea we have very limited options for treatment,” he said. “So we probably need to find a new strategy in order to target oropharyngeal gonorrhoea infection. I have been leading a multiple site clinical trial to see whether daily mouthwash can prevent oropharyngeal gonorrhoea.
“This trial is happening in Sydney and Melbourne and … hopefully we will have some results early next year.”