Background:
Among infectious syphilis cases, syphilitic ulcers most likely have the highest transmission efficiency, may be occult (asymptomatic oral/rectal/vaginal lesion), and often produce a negative or low (<=1:8 serologic) titer (STS). These factors may impact the effectiveness of traditional STD control, especially among men who have sex with men (MSM).



Objective:
To determine stage at diagnosis and duration of primary stage ulcers among MSM with syphilis in San Diego, CA, 2000-2005

Method:
Interview records were reviewed to determine ulcer duration among primary cases. For secondary cases, ulcer duration was estimated at 21 days.

Result:
During the 6 years, 478 cases of P&S syphilis (34% primary, 66% secondary) were reported; 361 (76%) were MSM. Compared to heterosexual men, MSM were 37% less likely to be diagnosed in the primary stage (34% [121/361] vs. 53% [34/64], rate ratio [RR] = 0.63, 95% CI = 0.48, 0.83, p < .01). Among MSM, those reporting receptive anal intercourse were 48% less likely to be diagnosed in the primary stage as other MSM (27% [68/249] vs. 52% [46/88], RR = 0.52, 95% CI = 0.39, 0.69, p < 0.001). Among MSM with P&S syphilis, mean duration of primary lesions before treatment was 20.2 days with MSM having a slightly longer duration than heterosexual men (20.3 days vs. 19.6 days, p = 0.06). The proportion of secondary cases reporting undiagnosed primary symptoms will be reported.


Conclusion:
Among MSM, occult primary lesions are probably often undiagnosed which very likely limits the community-level effectiveness of traditional case identification and partner services.

Implications:
Effectiveness of other biomedical approaches among MSM should be evaluated, such as symptom recognition education of MSM and clinicians, and frequent serologic testing, with physical examination for occult lesions among patients with an STS <=1:8 and no history of previous syphilis.