An epidemic of Neisseria gonorrhoeae in a Somali orphanage.

Neisseria gonorrhoeae was isolated from 53 young females (6-14 years old) in a Somali orphanage. A male guardian was found to be the effective transmitter having sexually abused the children. All the bacterial isolates were of the same serogroup WI and the same serovar Aedih. This presents an unusual example of a tight geographic cluster of infected people which is often characteristic of gonorrhoea epidemics.

PIP: The physician of an orphanage in Afgoye, 30 km from Mogadishu, Somalia, noticed vaginal discharge in 95 of the 500 girls at the orphanage in September 1987. A Somali-Italian investigative team took vaginal specimens from the 95 girls. Laboratory personnel isolated Neisseria gonorrhoea in 56% of the 95 6-14 year old females (53) who all lived in 2 adjacent dormitories. They found that all the bacterial isolates were of the N. gonorrhoea WI serogroup and Aedih serovar. The physician prescribed penicillin treatment for all the girls. Contact tracing revealed that a male guardian was the source of gonorrhea. Some children had already accused him of sexually abusing them. Orphanage officials had transferred him 1 week before the arrival of the investigative team. His room had been very near to the 2 dormitories for only a few weeks before the investigative team arrived. In this short time, his sexual abuse effected this cluster of infections. This supports the present theory of gonorrhea epidemiology that a core group of infectious people are most likely responsible for most, if not all, of the continuing endemicity of gonorrhea. The infection rate was in range of the estimated probability of transmission (50-70%) during sexual intercourse from an infectious male to a female. The results showed that high resolution typing of gonococci has in addition to its scientific value a more practical value; forensic medicine and illustration that gonorrhea consists of smaller microepidemics.

Chlamydia trachomatis, infertility, and population growth in sub-Saharan Africa.

In sub-Saharan Africa, Neisseria gonorrhoeae and Chlamydia trachomatis are common infections. These pathogens are also the major causes of post-salpingitis tubal infertility, and infertility is a frequent problem in this region. A mathematical model, recently devised to estimate the effect of gonococcal infection on population growth, was used to estimate the potential effect of chlamydial infection on population growth. The model predictions for chlamydial infection were compared with those previously reported for gonococcal infection. The model predicts that both infections may be exerting severe effects on population growth at realistic prevalence rates of infection. The model also predicts that N. gonorrhoeae produces a steeper reduction in population growth than does C. trachomatis because its transmission dynamics result in a higher force of infection (incidence rate) at any given prevalence of infection. Large scale changes in the epidemiology of these infections can be expected to occur in sub-Saharan Africa because of improved sexually transmitted disease (STD) diagnosis and treatment services as a component of AIDS prevention. Changes in the epidemiology of gonococcal and chlamydial infection are predicted to result in accelerated population growth unless STD control programs are linked to effective contraception programs.

PIP: Researchers applied estimates of Chlamydia trachomatis transmission and disease parameters to a compartmental mathematical model of heterosexual, sexually transmitted disease (STD) transmission to determine the potential effect of chlamydia infection via its link to tubal infertility on population growth in sub-Saharan Africa. Epidemiologic parameters included transmission efficiency, salpingitis rate per cervical infection, tubal fertility rate per salpingitis episode, and average duration of infectivity. Sexual behavior parameters were sexual partner change and networks of sexual mixing. Demographic parameters consisted of a constant mortality rate (.02/year), a mean life expectancy (50 years), age of menarche (15 years), age of menopause (45 years), and maximum potential fertility rate. The mathematical model estimated that as the probability of infertility due to chlamydia infection increases, population growth falls almost linearly at various values of basic reproductive rates. In fact, 10% decline in population growth accompanies a 10% chlamydia prevalence. When the researchers applied estimates of gonorrhea transmission to the model, they learned that a 10% prevalence of gonorrhea results in a 30% reduction in population growth, indicating that gonorrhea has more of an effect on population growth than does chlamydia infection. Gonorrhea has higher transmissibility and shorter duration of infectivity than chlamydia infection, resulting in a higher incidence rate at any given prevalence of infection. Improved diagnosis and treatment of STDs as a result of AIDS prevention programs should result in considerable changes in the epidemiology of gonorrhea and chlamydia infection. These changes will likely speed up population growth unless STD control programs are integrated with effective family planning programs.