Volume 9 Number 2 August 1995
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DiscussionThe overall pooled prevalence of RPR positivity seen in Ethiopian blood donors of the five regions (4.1% -12.2%) is comparable to rates seen in neighboring countries, including Somalia(12) and Tanzania(4). These high seroprevalence rates were obtained following prior health screening, including history of sexually transmitted diseases and sexual promiscuity , which are reasons for referral. Thus, the results represent underestimates for the actual prevalence of syphilis in the general population. For most Sexually transmitted diseases overall age specific morbidity rates are higher for men than for women(20). This has also been observed in our study. The overall prevalence in males was 4.5% while in females it was 3.0% (a M:F ratio of 1.5: 1.0). This is consistent with the male to female ratio of (1 :0.7) observed for HIV infection in blood donors(21). Differences in RPR seroreactivity rates in the two sexes were statistically significant indicating that gender is one determining factor for the acquisition of the disease. The reasons for the observed high and low prevalence centers are not apparent from the present study. The variations observed in RPR positivity rates are either due to wide variations in the prevalence of syphilis in the donor population, or factors related to the efficiency of health screening prior to blood donation by the centers in question. Table 1: Prevalence of RPR reactivity among Ethiopian Blood Donors in Selected Regions
Note: Data presented is from October 1987 to September 1989 inclusive for Addis Ababa and Janouary - June 1989 for the rest of the regions. Two major factors that could affect RPR positivity rates are reactives due to treponemas other than T. palladium and other disease states and conditions. No convincing serologic differences between. the pathogenic Treponemas have been discerned. False positivity can also be obtained in acute infections (such as malaria, infectious hepatitis, and others), immunization, autoimmune diseases, drug addiction (in about 25% of narcotic addicts) and diseases associated with hyperglobulinemia states such as leprosy(20). False seropositivity are unlikely to have affected the observed rates due to the thorough health screening prior to blood donations for the above. Even though yaws has been reported in Ethiopia (23), yaws and endemic syphilis are not expected to contribute much to the seroreactivity observed as Ethiopia is not a recognized African focus for these diseases(8,10). Thus, the serological findings probably reflect sexually acquired syphilis rather than non-venereal treponematoses. The observed peak RPR positivity :-ate in females 55-64 years of age could be due to the small sample size in both sexes in this age group. In the USA, peak incidence occurs in the age group of 15-34 years and 10% of people over the age of 70 years have false positive RPR results(22). However, due to paucity of observation (only 93 male and 6 female donors) in this age group, the role of aging should be taken with caution. Further studies are needed to clarify the above. The RPR test is the test of choice for donor screening and the most widely used non- treponema or reagin antibody test. However , the sensitivity of the test is variable in the various stages of the disease. A Zambian study using treponemal tests( II) in hospital patients and cOntrols have shown that the test showed a false negativity rate of 11%-14%, respectively, and a false positivity of 5% . This suggests that the actual prevalence of syphilis among Ethiopian blood donors may be higher than the rates obtained using the RPR test. Blood donor populations in Ethiopia more or less represent the adult urban general population(2l). The relatively high overall RPR positivity rates (about 3% in females and over 4% in males) obtained in adults with no apparent risk factors for syphilis, supports the previously reported high magnitude of syphilis in the adult urban population of Ethiopia. The interaction between syphilis and HIV infection occurs on a number of levels(20) It includes ( 1) the disproportional occurrence of HIV in persons with syphilis and vice versa, (2) the enhancement of the acquisition and transmission of HIV infection by syphilitic genital ulcers, and (3) the modification of the serologic response to syphilis, its natural course, and the ineffectiveness of standard therapy in HIV infected persons.
and its interaction with HIV infection, commitment of more health resources to the prevention and control of syphilis in Ethiopia is recommended. Prevention strategies to be adopted should include universal syphilis screening of blood (and the discard of reactive units) and notification of reactive donors with referral for further investigation and therapy. Routine syphilis screening of patients, and specially females in the sexually active age group who visit health institutions would 3Iso reduce the syphilis burden in the population. The study also provides base line-data for a quick evaluation of HIV control programs by systematically monitoring trends in syphilis serology. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||