Syphilis transmission

[curiouslg]

Dear Doctor,
I am a female who recently has been diagnosed with secondary syphilis. I am quite certain from whom I was infected. I have never had concurrent sexual partners & get tested between relationships.  

My question is this - 1 wk after what I now know was the primary chancre (misdiagnosed as eczema by my OB/GYN) appeared near the bottom of my vaginal opening / near the anus, a new partner performed oral sex on me for about 5 minutes. Partners mouth and tongue were near the clitoris only & therefore not near/on the chancre. It was not vigorous or arousing.  This was approximately 1 month after my exposure to the infected partner.

What is the likelihood of transmission (I know this has to be best guess) in this scenario based on your research of the bacteria and what you've seen in the clinic?

I have read on CDC that syphilis has been reported transmitted via oral sex in MSM only in about 1/3 of cases in a particular study but have not seen any reports of Female to Male transmission via oral. I have read the "UptoDate" material on syphilis as well which references studies from EW Hook (I presume the one from this forum), however, I would really like to understand your perspective here

[curiouslg]

Got it.

The 3-10% quote may be on the low side, I was unable via internet to access the full literature where the quote was taken from: {Eckert LO, Lentz GM (2007). Infections of the lower genital tract. In VL Katz et al., eds., Comprehensive Gynecology, 5th ed., pp. 569–606. Philadelphia: Mosby Elsevier} so I appreciate your POV on that as well.

Thanks again.

[Edward W Hook, MD]

First let me say that since the lesions of syphilis are painless, it is tough to be sure if there was lesion contact or not.  I would just be guessing as to the likelyhood of transmission and would guess that it would be somewhere between 10 and 20% at most in the instnace you describe but I must emphasize that such a guess is just that, a guess.  I can't do better than this.  The opinions of others are sure to vary.

I suspect the estimate you quote is on the low side.  EWH

[curiouslg]

I will rephrase

1) In your expert opinion, what is the likelihood of a female transmitting syphilis to a healthy male in 1 instance of limited 5 minute oral sex (tongue did not directly touch the primary lesion located near the bottom of vaginal opening)?  

2) How valid are these statistics?
Eckert LO, Lentz GM (2007). Infections of the lower genital tract. In VL Katz et al., eds., Comprehensive Gynecology, 5th ed., pp. 569–606. Philadelphia: Mosby Elsevier.
"syphilis is contagious whenever an open sore or skin rash is present. The risk of being infected with it from a single sexual encounter with an infected partner is approximately 3% to 10"

Thank you.

[Edward W Hook, MD]

I would guess that this person has been exposed, making their risk of infection somewhere in the neighborhood of 1 in #.  I hope this addresses your question, if not, please rephrase it. EWH

[curiouslg]

I will let this partner know either way, but for my own piece of mind, really curious what your educated guess is for this specific transmission scenario given known exposure.
Specific timeline

1) Sex with infected partner
2) 3 wks later, notice sore in genital (described above)
3) Immediately saw OBGYN, tested for all STDs but syphilis; diagnosed sore as eczema
4) 1 month after sex with infected partner (and after seeing obgyn); oral sex as above - exposed partner
5) Many months later (now), diagnosed with secondary syphilis

Thank you very much.

[curiouslg]

The new partner did perform brief oral sex on my before treatment as it was before I knew I had it due to misdiagnosis on the part of my OBGYN.  I was curious if the risk is different if his tongue was near the chancre vs on the chancre as was this situation.

[Edward W Hook, MD]

Welcome to the Forum.  Yes, I am that EW Hook and I'll try to help.

Determining the risk for syphilis transmission is based on data collected in studies more than 50 years ago which are probably not as methodologically strong as they would be if the studies were performed today.  At that time, partners to persons with primary and secondary syphilis were shown to have about a 1 in three chance of being infected.  The studies suggested that exposure to primary syphilis was more likely to led to infection than exposure to secondary syphilis (makes sense in that this infection is transmitted by direct lesion contact) and did not take into account the numbers of exposures to that partner.

Let me seek a little clarification.  Did your partner perform oral sex on you before you were treated for syphilis?  If so, your partner has been exposed.  If a lesion was present, their risk for infection is about 1 in three.  If no lesions was present, there is still risk but it is a bit harder to define what precisely the risk is.   Either way, if this exposure occurred prior to your treatment, it is important that your partner be tested and treated (either preventively if their test is negative or curatively if their test is positive).

I hope this addresses your question. EWH