The throat is a major source of gonorrhoea infections in MSM

The throat is a major source of gonorrhoea transmission among men who have sex with men (MSM), according to Australian research published in Sexually Transmitted Infections. The study involved 60 male couples and showed a high prevalence of gonorrhoea infection in the throat and/or anus in the absence of urethral infection. The investigators suggest that transmission is occurring due to kissing, oral sex, rimming, or the use of saliva as lubricant for anal sex.

“Our key finding was that in the absence of urethral infection, when one man in a couple had throat gonorrhoea, his partner commonly had throat gonorrhoea (23%), and when one man in a couple had anal gonorrhoea his partner commonly had throat gonorrhoea (34%),” comment the investigators, who note these percentages are much higher than would be expected to occur by chance (3-6%).

They add: “Our data are not consistent with the conventional paradigm of gonorrhoea transmission between men, in which most gonorrhoea transmission is from the urethra to the throat and anus, and vice versa. Instead, our data are consistent with a new paradigm of gonorrhoea transmission in which the throat plays a central role in transmission to the partner’s throat, anus and urethra, presumably through infected saliva.”

If correct, the study’s findings will be of public health significance, requiring messaging to address gonorrhoea transmission in saliva.

Rates of gonorrhoea have increased significantly among MSM in recent years. Prevention strategies have focused on the use of condoms for anal sex. Symptoms of urethral gonorrhoea include a thick penile discharge and burning sensation when passing urine, typically occurring within days of infection. In most cases, these unpleasant symptoms will cause an individual to promptly seek treatment, therefore limiting the amount of time they remains infectious.

Could the high incidence and prevalence of gonorrhoea among MSM be due to transmission from the throat, especially as many infections in this site are asymptomatic? To see if this was the case, a group of researchers led by Dr Vincent Cornelisse designed a study involving MSM couples attending the sexual health clinic in Melbourne.

The study sample included 60 couples (120 men) in which at least one partner was diagnosed with gonorrhoea. All MSM at the clinic were screened for throat, anal and urethral gonorrhoea by NAAT (nucleic acid amplification test). Recruitment took place between 2015 and 2017.

The men had a median age of 30 years and gonorrhoea was diagnosed in 85 individuals. The throat was the most common site of infection (n = 63), followed by the anus (n = 48) and urethra (n = 25). Many individuals had multi-site infection, including ten men who had gonorrhoea in all three sites.

Consistent condom use for insertive and receptive anal sex was reported by 8% and 10% of patients respectively. A further 10% of men reported no recent insertive anal sex, with 11% saying they had had no receptive anal sex.

A total of 25 men had urethral gonorrhoea, of whom 72% had a partner with gonorrhoea in the throat and 76% had a partner with anal gonorrhoea.

There were 48 couples where either man had gonorrhoea of the throat (but neither had urethral infection), including eleven couples (23%) where both individuals had throat gonorrhoea. As men with urethral gonorrhoea have been excluded, the authors say that it is unlikely that the urethra is the source of infection.

Anal gonorrhoea was diagnosed in 48 men. Just over half (52%) had a partner with gonorrhoea in the throat. When the investigators excluded men with both anal and urethral gonorrhoea, 34% of men with anal gonorrhoea had a partner with gonorrhoea in the throat. When they excluded men with anal gonorrhoea whose partner had urethral gonorrhoea, 48% had a partner with throat gonorrhoea.

Of the 31 couples where either man had anal gonorrhoea (but neither had urethral infection), there were 15 couples (45%) where both men had anal infection. Couples where either man had infection in the throat were then excluded, leaving eight couples, including one where both men had anal infection.

“We observed high gonorrhoea positivity in the throat and anus if a man’s partner had urethral gonorrhoea,” note the authors. “Most cases of urethral gonorrhoea [88%] in our study were symptomatic and presented to our clinic within a few days of developing symptoms. This suggests that the direction of gonorrhoea transmission in these couples was likely from the throat or anus to the urethra.”

The authors assert that the “moderately” high prevalence of throat gonorrhoea among the partners of men with anal infection – even after excluding men with urethral infection – does not support conventional wisdom that the urethra is the main source of gonorrhoea infections in the throat and anus. “Instead, these data support direct transmission from the throat to anus,” the authors comment.

The investigators also highlight that when one man in a couple had throat gonorrhoea, there was a high chance that both men in the couple would have the infection at this site. They therefore suggest that transmission was occurring directly from throat to throat via kissing.

“Our data support a new paradigm of gonorrhoea transmission which suggests that the throat is a major source of gonorrhoea transmission between men,” conclude the authors. “Public health messaging may need to discuss the risk of gonorrhoea transmission during sexual activity that involves saliva. Also, a novel gonorrhoea prevention strategy is currently under investigation is the use of an antiseptic mouthwash to reduce the prevalence of throat gonorrhoea.”

A second study from the same research group provides further evidence to support the hypothesis. A total of 3677 MSM attending the Melbourne clinic completed surveys, reporting on numbers of sexual partners in the past three months:

• mean 4.3 partners who they had kissed but not had oral or anal sex with
• mean 5.0 partners they had kissed and had sex with
• mean 1.4 partners they had had oral or anal sex with, but not kissed.

Kissing-only and kissing-with-sex were associated with gonorrhoea in the throat, but sex-only was not. The adjusted odds for gonorrhoea in the throat were 1.46-fold for men with more than four kissing-only partners and 1.81-fold for men with more than four kissing-with-sex partners.