Determine the prevalence of neurosyphilis among adults presenting with meningoencephalitis to the national referral hospital in Lusaka, Zambia.

Neurosyphilis incidence is rising in North America, but little is known about its prevalence in sub-Saharan Africa.

Serum from a prospective cohort of adults presenting to the University Teaching Hospital in Lusaka, Zambia with signs and symptoms of meningoencephalitis was tested with treponemal pallidum haemagglutination (TPHA) tests.  Cerebrospinal fluids (CSF) samples corresponding to TPHA+ serum were tested with venereal diseases research lab (VDRL) tests, white cell count, protein, and tuberculosis culture and PCR.  Neurosyphilis was defined as a positive serum TPHA and (1) a positive CSF VDRL (definite neurosyphilis); (2) CSF pleocytosis and/or elevated CSF protein without evidence of tuberculosis (probable neurosyphilis); or (3) criteria for (2) with evidence of tuberculosis co-infection (possible neurosyphilis).  Participants were then dichotomized in two ways: group 1:  definite/probable vs possible/no neurosyphilis; and group 2:   definite/probable/possible versus no neurosyphilis.

Of 511 participants, 273 were male, mean age was 37 + 11 years, 88.5% were HIV+, and 50 (10%) were TPHA+. Neurosyphilis prevalence was 4.5% and 6.8% for groups 1 and 2, respectively. No statistical differences in demographic, clinical or laboratory characteristics were observed between individuals with neurosyphilis and those with other CNS infections, and both groups had a high but not significantly different one-year mortality of >20%. HIV+ participants with neurosyphilis were younger than HIV-uninfected participants with neurosyphilis (p <0.001), but there were no other significant demographic or clinical differences.

The prevalence of neurosyphilis among adults with meningoencephalitis presenting to the national referral hospital in Zambia is higher than that reported in studies conducted on other populations, and one-year mortality is high. Efforts to improve diagnosis and treatment of neurosyphilis are urgently needed to improve outcomes in sub-Saharan Africa.