Non-Hodgkin lymphoma in Gabon and its relation to HTLV-I.

A case-control study was performed in Libreville, Gabon, to determine whether a relationship can be established between the relatively high proportion of non-Hodgkin lymphoma (NHL) among all cancer cases and the high seroprevalence rate of HTLV-I observed, and to discover whether cases of adult T-leukemia/lymphoma (ATLL) related to HTLV-I exist in Gabon. From November 1987 to April 1989, a total of 32 patients with NHL were recruited; 6 were infants with Burkitt's lymphoma and 26 were adults with NHL. Each patient was matched with 2 asymptomatic controls for age, sex and ethnic group. HTLV-I serology was done by ELISA and Western blot. Comparison of the groups was done by chi-square analysis. None of the 6 infants with Burkitt's lymphoma and none of their controls had antibodies to HTLV-I. Of the 26 patients with NHL, 7 (26.9%) had HTLV-I antibodies. Among the 52 controls, the HTLV-I rate was 13.4% (n = 7). There was no difference between cases and controls (Fisher's exact test, p = 0.16). Among the 26 NHL, 4 cases fitted the criteria of ATLL and were HTLV-I-positive; 3 others who were positive for HTLV-I were a woman with lymphoblastic gastric NHL and 2 old men with an unclassified lymphoma. From the results of this limited series it is not possible to state that there is an association between NHL and HTLV-I infection. Nevertheless, cases of ATLL related to HTLV-I are reported from this area. Based on the HTLV-I seroprevalence rates reported in Gabon, the estimated incidence rate of ATL among seropositive people in Gabon appears much lower than in Japan. Different explanations can be proposed, but under-diagnosis of ATLL is probably one of the main factors.

Prevalence of HTLV-I and HTLV-II infection in Gabon, Africa: comparison of the serological and PCR results.

A cluster sampling survey was performed in 1989 in Libreville, Gabon, to determine HTLV-I and HTLV-II prevalence and to compare the efficacy of polymerase chain reaction (PCR) and serology in detecting HTLV-I and HTLV-II infections. A total of 322 sera from adults were tested by ELISA and by Western blot (WB). The WB patterns were interpreted according to WHO criteria and those of the manufacturer. PCR analysis using primer pairs in the gag and pol region, with a specific probe for HTLV-I and HTLV-II, was performed on the lymphocytes of the 322 adults. In addition, 134/322 samples were re-tested with tax primers, in a second laboratory. Using WHO criteria, 8/322 (2.5%) samples were positive on WB and 25 were indeterminate; with the criteria of the kit, 26/322 (8.1%) were positive and 7 were indeterminate by WB. By PCR, 13 (4%) samples were positive, including 12 for HTLV-I (3.7%) and one for HTLV-II (0.3%). All 8 seropositive samples (by the WHO criteria) were positive by PCR, as were 4 out of 25 indeterminate samples. Only one out of 289 seronegative samples was positive by PCR. In contrast, only 12/26 positive samples by the kit criteria were confirmed by PCR. These results confirm the relatively high HTLV-I/II seroprevalence observed in Gabon. HTLV-I infection is preponderant, but HTLV-II is also present. The WHO criteria for WB give a better fit with PCR results than the kit criteria for WB. In the absence of a specific confirmatory test and based on the uncommon "seronegative" HTLV-I/II infection, the indication for PCR appears limited to the positive WB samples (to differentiate HTLV-I and II infection) and to the indeterminate WB samples.

Isolation and partial characterization of an HIV-related virus occurring naturally in chimpanzees in Gabon.

Two cases of wild-born chimpanzees which were positive for HIV-1 antibodies were observed in Gabon. These animals were never experimentally exposed to HIV-1 and had no history of inoculation with human blood products. A retrovirus was isolated from one of these chimpanzees. Several of the viral proteins from this virus, designated SIVcpz-GAB-1 (simian immunodeficiency virus from chimpanzee), differed in molecular weight from the known corresponding HIV/SIV proteins. The major gag protein of SIVcpz migrated on SDS-PAGE with a relative molecular mass of 25.5 and the outer membrane proteins were 110, 155 and 185 kD, respectively. SIVcpz did not induce severe cytopathic effects in human and chimpanzee lymphocytes. Antigenically, SIVcpz seems to be closer to HIV-1 than to HIV-2 and the other SIVs. Nucleic acid hybridization experiments appear to indicate that the virus is different from HIV-1 and HIV-2.

Seroepidemiological survey of HTLV-I infection among randomized populations of western central African countries.

Between 1987 and 1988, a survey to determine the distribution of HTLV-I infection was conducted in a representative population of adults, living in southern Chad, Cameroon, and Equatorial Guinea. Populations studied were selected by the cluster sampling technique. Sera were tested for IgG antibodies to HTLV-I by ELISA. ELISA-positive sera were retested by Western blot. The study comprised 2,301 adults, all apparently healthy. Crude prevalence rates range from 0.5 to 11.8%. We found three clearly different areas of HTLV-I seroprevalence rates. An area of low seropositivity in southern Chad and northern Cameroon (0.5-2.0%), an area of moderate seropositivity in the savannah region of Ngaoundere, Cameroon (4.2%) and in Bata, Equatorial Guinea (6.5%), and lastly an area of high seropositivity (8.6-11.8%) in the equatorial forest area of Equatorial Guinea and southern Cameroon. HTLV-I seroprevalence rates increased with age up to 12.6% after 40 years old in the areas of high seropositivity. There was no difference between male and female age-adjusted prevalence rates in all of the areas studied.

Epidemiology of HTLV-I in Gabon (Western Equatorial Africa).

In 1986 a survey to determine the distribution of HTLV-I infection was conducted in Gabon in a representative sample of adults and children. Five samples were taken in adults and 2 samples in children living in urban and rural areas. Samples were taken by the cluster sampling technique, i.e., clusters of randomly selected households. Sera were tested for IgG antibodies to HTLV-I by ELISA. ELISA-positive sera were retested by Western blot. The study comprised 1,874 adults and 684 children, all apparently healthy. In the adults the crude prevalence rates of anti-HTLV-I antibodies ranged from 5.0% in urban areas to 10.5% in the southern province. In rural areas, the age-adjusted prevalence rate (9.1%) was significantly higher than in urban areas (5.0%) (p less than 0.01). In children there was no significant difference between urban (2.4%) and rural (2.0%) prevalence rates. Prevalence increased with age but was not related to sex. This survey shows that HTLV-I infection is common in Gabon but varies considerably by region.

Urogenital Chlamydia trachomatis in Gabon: an unrecognised epidemic.

Samples from 218 men with urethritis, 517 women with pelvic pain or pelvic pain and vaginal discharge, 218 women consulting for infertility, and 598 postpartal women were screened for Chlamydia trachomatis by culture and direct immunofluorescence. Chlamydiae were detected in 18% (39/218) of the men, 18% (45/252) of women with vaginal discharge, 14% (38/265) of those with pelvic pain, 10% (21/218) of infertile, and 10% (59/598) of postpartal women. A chlamydial prevalence of 18% (41) was observed in 229 postpartal women aged under 21, whereas only 5% (10) of 360 postpartal women over 21 had C trachomatis. In the other clinical groups, an age related decrease in prevalence was noted in women over 25. The direct immunofluorescence test correlated well with culture. The small difference in isolation between symptomatic and postpartal women indicates that women in this population do not seek medical attention for chlamydial infections and expose themselves to chlamydial salpingitis and infertility.

PIP: Health workers took urethral samplers from 218 men with urethritis and 1850 women to screen for Chlamydia trachomatis using culture and immunofluorescence. All the men and women presented themselves at the Hospital Provincial de Franceville in semirural Gabon. 18% of men, 18% of women with vaginal discharge, 14% of women with pelvic pain, 10% of infertile women, and 10% of postpartum women tested positive for C. trachomatis infection. Postpartum women less than 21 years old had a significantly higher chlamydial prevalence than did older postpartum women (18 vs. 5%; p .05). Chlamydial prevalence among 21-25 year old postpartum women was significantly lower than among same age women presenting with other conditions (5% vs. 15% for infertile women, 21% for women with pelvic pain, and 2% for women with vaginal discharge; p .01). Except for postpartum women, older than 25 chlamydia prevalence decreased after age 25. The sensitivity of immunofluorescence ranged from 77% for infertile women to 93% for postpartum women. Its specificity ranged from 97% for women with discharge or pelvic pain to 100% for men. Thus, the direct immunofluorescence test corresponded well with culture. The isolation rates for asymptomatic women neared those of symptomatic women, indicating that most women with C. trachomatis infections have no or very mild symptoms and do no seek medical attention. This most likely jeopardizes their fertility.

[Seroprevalence of syphilis in urban and semi-rural populations of Gabon]. / Séroprévalence de la syphilis dans des populations urbaines et semi-rurales du Gabon.

The seroprevalence of syphilis was studied in an urban and a semi-rural community in Gabon by a cluster sampling technique. The crude prevalence rate of treponemal infection in the semi-rural population was estimated to be 13.3 +/- 5.0% and in the urban population 19.4 +/- 4.6%. The age-adjusted prevalence rate was significantly higher in the urban than in the semi-rural population. In both areas, it was significantly higher in men than in women. No significant difference was observed according to age. These high rates indicate the need for a control program for sexually transmitted diseases.