Impact of deltamethrin-impregnated bednets on biting rates of mosquitoes in Zaire.

In a rural area of Zaire, the whole population of a village was protected by deltamethrin-impregnated mosquitoes bednets. A similar village was observed as a control. Biting rates for mosquitoes were recorded in both villages. The principal man-biting species were Mansonia africana, Mansonia uniformis, and Aedes aegypti. In the village protected by the impregnated mosquito bednets, the number of Mansonia bites was reduced 96% indoors and at a lesser rate outdoors. Biting rates of Ae. aegypti dropped to 0 indoors, but the outdoor biting rate remained unchanged. It is concluded that the reduction in mosquito bites is not only caused by the repellent action of the deltamethrin but also by a reduction in mosquito numbers.

[Mosquito nets impregnated against malaria in Zaire]. / Moustiquaires imprégnées contre le paludisme au Zaïre.

On the Bateké plateau 60 km east of Kinshasa, Zaïre, where malaria is stable, three villages have been selected for a trial of malaria control using bednets impregnated with deltamethrin at 25 mg per square meter from February to November 1991. One village (3,000 inhabitants) has been provided 800 impregnated bednets and an other one (2,900 inhabitants) kept 800 non impregnated bednets. The third village (900 inhabitants) served as a control and has remained without nets. Anopheles gambiae was the main and nearly exclusive vector of malaria. Its biting density was reduced by 94% in the village protected by impregnated bednets and the inoculation rate dropped from 182 infective bites/man/year to 3.7 a decrease of 98%. The longevity of the vector expressed by its expectation of life decreased from 11.02 days to 3.64 days. In the village where inhabitants were protected by non impregnated nets, as well as in the control, the entomological indexes did not change. In the village protected with impregnated nets the malaria prevalence decreased by 50%, five months after the beginning of the experiment. The high parasitemia, above 10,000 and 20,000 parasites per mm3 decreased by 77% and 83% in the 0-7 year age group and by 67% and 65% in the 8-14 year group in the protected village. These high parasitemias are good markers of the clinical malaria risk. The experiment can be considered as very satisfactory on the point of view of public health.

[The culicidian fauna and its nuisance in Kinshasha (Zaire)]. / La faune culicidienne et sa nuisance à Kinshasa (Zaïre).

A public health study to inventory bloodsucking mosquitoes was conducted in Kinshasa and its regions. 20 culicidian species were represented by 7 Anopheles, 6 Culex, 5 Aedes and 2 Mansonia. In general, the number of bites/man/night (b/m/n) was in average 141.5 of Cx. quinquefasciatus, 60.1 of Cx. antennatus, 21.1 of M. africana, 16.3 of An. gambiae and 7.7 of M. uniformis. The nuisance is different from region to other. Culex quinquefasciatus is the most abundant and aggressive species in the urban area with an average of 400 b/m/n. In certain suburban zones, Culex antennatus is predominant, with aggression on the order of 176.5 b/m/n. The Anopheles gambiae complex is predominant in the semi-rural zone at the periphery of the city with 26.05 b/m/n. Other mosquitoes are equally implicated in their aggression and nuisance to man, in particular, Mansonia africana, Mansonia uniformis and Aedes aegypti. A geographical distribution map has been established for the preponderant species in Kinshasa.

Efficacy of Bacillus sphaericus against the malaria vector Anopheles gambiae and other mosquitoes in swamps and rice fields in Zaire.

The microbial control of Anopheles gambiae and other mosquitoes with a granular formulation of Bacillus sphaericus (Vectolex) was evaluated in rice fields and swamps, located around the suburban region of Kingabwa-village in Kinshasa, Zaíre. Ten treatment cycles with 15-day intervals were carried out with the same application rate, 10 kg/ha, during the dry season (May to September 1991). The treatments reduced larval populations of An. gambiae by 98% after 48 h, but repetitive applications were required every 15 days to maintain control. The persistence of B. sphaericus spores was more apparent in rice fields than in swamps. A significant reduction in nuisance biting by Culex quinquefasciatus and Mansonia uniformis was observed. For An. gambiae, a decrease of 13.6% in human biting was noted during the post-treatment period. The entomological inoculation rate was reduced from 0.238 to 0.143. The efficacy of B. sphaericus does not appear to offer outstanding potential for control of An. gambiae in rice fields and swamps and seems to be limited due to different factors tied to ecology and natural conditions in the fields.

Removal of gp160 induced bio-hazards for a safe AIDS vaccine candidate.

In the first AIDS vaccine trial, immunizing preparations were based on HIV-1 Env protein (gp160). Immunogenic properties of gp160 which trigger both a humoral and cellular immune response have since justified its use in various vaccine programs, both past and present. Many reports however have underlined deleterious effects on the immune system--anti-HIV-1 enhanced antibodies, anti-CD4 autoantibodies, and inhibition of T cell activation by HIV-1--particularly associated with the Env protein. The present study shows that gp160 presented in a biologically inactivated but immunogenic form, as used in our trial, could avoid these complications. Bio-hazards associated with gp160 which indeed could be removed by appropriate treatment of the native protein, should be taken into consideration in AIDS vaccine programs.

[HTLV-I retroviral variant in Zaire in patient with chronic neuromyelopathy. Nucleotidic sequence of the envelope gene]. / Variant retroviral HTLV-I au Zaïre chez un patient ayant une neuromyélopathie chronique. Séquence nucléotidique du gène d'enveloppe.

The oncoretrovirus HTLV-I is the etiological agent of adult T cell leukemia (ATL) and tropical spastic paraparesis/HLTV-I associated myelopathy (TSP/HAM). In contrast to the human lentiretroviruses, HIV-I and HIV-2, the causative agents of AIDS, HTLV-I is genetically very stable. We report here the molecular characterization of the envelope gene of an HTLV-I variant present in a TSP/HAM patient from Zaïre, raising the question of its relevance to disease or the ethnic and/or geographical origin of the patient.

[The Anopheles fauna and the transmission of human malaria in Kinshasa (Zaire)]. / La faune anophélienne et la transmission du paludisme humain a Kinshasa (Zaïre).

A longitudinal epidemiological study of malaria and its vectors was conducted in Kinshasa. 264 night-bite collections on human bait (1,056 man nights) and 384 collections of the house-resting fauna were carried out from April 1989 to October 1990. The anophelian fauna was identified and inventoried, 7 Anopheles species were found: Anopheles gambiae, An. funestus, An. paludis, An. hancocki, An. counstani, An. brunnipes, and An. nili. A single species, An. gambiae s. l. is responsible for the transmission of malaria, it represents 93.27% of the anopheline fauna. The average number of anophele bites man day was 16.28 bites/man/night, it varied between 1 b/m/n in urban area to 26.05 b/m/n in semi-rural area. The average of the sporozoite index for An. gambiae was 3.3%, but it varied from 0% in the urban area to 6.52% in the semi-rural area. The entomological inoculation rate (h) was 197 infective bites per year. This rate fluctuated from 1 infective bite each 128 nights in urban area to 1.7 infective night-bite in semi-rural area. Other epidemiological index were also determined: the level of daily survival rate (p = 8.75 days), the vectorial capacity of 17.97 and the Macdonald's stability 3.5 bites on man taken by a vector during its entire lifetime.

Field trials with Vectolex (Bacillus sphaericus) and Vectobac (Bacillus thuringiensis (H-14)) against Anopheles gambiae and Culex quinquefasciatus breeding in Zaire.

Under field conditions in Kinshasa, Zaire, an aqueous suspension of Bacillus thuringiensis (H-14), Vectobac (12-AS), lost most of its larvicidal activity at all concentrations after 48 h against Culex quinquefasciatus breeding in polluted gutter water and Anopheles gambiae breeding in clear water irrigation ponds. However, good control of Cx. quinquefasciatus was obtained using a granular formulation of B. sphaericus, Vectolex-G (ABG-6185), at concentrations of 10-30 kg/ha. High concentrations of Vectolex-G gave excellent control of An. gambiae breeding in irrigation ponds. The Vectobac-G was less active against An. gambiae than Vectolex-G, in spite of good dispersion of Vectobac-G particles.

[Seroprevalence of rubella in Kinshasa (Zaire)]. / Séroprévalence de la rubéole a Kinshasa (Zaïre).

A serosurvey of rubella was carried out by haemagglutination inhibition and IgM assay among 106 newborn infants (91% positive); 101 suckling infants aged 9-18 months (32.7% positive); 100 children aged 2-4 (58% positive); and 100 young girls 9-11 (68% positive), while 93% of mothers showed the presence of protective antibodies. These figures indicated that large numbers of women old enough to bear children are susceptible to infection with rubella, at least early in life. A vaccination programme is therefore recommended for one year-old children of both sexes and again for young girls prior to puberty.

[Epidemiological study of toxoplasmosis at Kinshasa and in lower Zaire]. / Etude épidémiologique de la toxoplasmose à Kinshasa et dans le Bas-Zaïre.

An epidemiological survey of human toxoplasmosis was carried out in urban Kinshasa and in rural Kwilu-Ngongo (Bas-Zaïre). First contact with Toxoplasma gondii occurred earlier in children from Kinshasa, but adults aged over 30 were more often carriers of IgG antibodies in Kwilu-Ngongo (65.5%) compared to those in Kinshasa (50.2%). In Zaire, nutritional diet and telluric contact seem to be very important.

Voluntary blood donor recruitment: a strategy to reduce transmission of HIV-1, hepatitis-B and syphilis in Kinshasa, Zaïre.

We evaluated the use of voluntary blood donor recruitment in Kinshasa, Zaïre, as a means of reducing transmission of HIV-1 and other infectious agents by blood transfusion. Between January 1, 1989, and April 7, 1989, 2,237 blood donors were enrolled in the study at the transfusion centre of the Mama Yemo Hospital. Each donor was tested for antibodies to HIV-1 confirmed by IFA and Western blot, Treponema pallidum, antibodies to hepatitis B virus (HBV) core antigen and screened for the presence of the HBV surface antigen. Test results were related to the data of the blood donors: age, sex, haematocrit, voluntary blood donor, family member donor, paid donor. The serological results of all donors for Anti-HIV-1. Anti-HBc, HBsAg and TPHA were 4.8%, 70.9%, 13.1% and 13.3% respectively. Lower seroprevalence rates were found among voluntary blood donors. However, only TPHA seroprevalence was significantly lower in voluntary blood donors (8.4%, 23/275) compared with paid donors (15.2%, 87/571) (p less than 0.01). A greater proportion of voluntary donors provides a store of blood which allows more extensive screening of blood for HIV-1 and other infectious diseases. Voluntary blood donor recruitment is critical for the provision of safe blood supplies in Kinshasa.

Detection of yellow fever viral RNA by nucleic acid hybridization and viral antigen by immunocytochemistry in fixed human liver.

Histopathologic examination of liver from patients with yellow fever is often not diagnostic. We therefore compared 2 virus-specific assays applicable to fixed liver, in situ nucleic acid hybridization and an immunocytochemical [alkaline phosphatase-antialkaline phosphatase (APAAP)] technique. Yellow fever structural gene sequences were detected by use of 35S-labeled negative-sense RNA probe (but not by immunocytochemistry) in 11 of 17 livers from children with fatal illness during the 1965 epidemic in Senegal. These fixed liver samples had been stored at ambient temperatures for 23 years. Both techniques were diagnostic on tissues collected 15-37 months before testing. Immunocytochemistry is a practical procedure for rapid specific diagnosis of liver stored for months, whereas RNA-RNA hybridization is a sensitive technique which can be applied to material stored for years.

[Anti-HIV2 antibody research in Kinshasa, Zaire]. / Recherche des anticorps anti-VIH2 a Kinshasa, Zaire.

880 suspect sera were analysed for HIV2 antibodies (ELISA, Western Blot) during the 2nd and 3rd trimester of 1988. Results show that Kinshasa is not yet an endemic zone for this virus. The authors recommend the use of a mixed test for diagnostics.

Persistent diarrhoea in Zairian AIDS patients: an endoscopic and histological study.

To determine the aetiology of persistent diarrhoea in African patients with acquired immunodeficiency syndrome (AIDS), 42 patients with human immunodeficiency virus (HIV) and persistent diarrhoea were enrolled in a microbiological, endoscopic, and histological study. Cryptosporidium was the intestinal parasite most often identified (30%); Isospora belli was found in 12% of the patients. Histological examination of the duodenal mucosa showed a non-specific inflammatory reaction in a significantly higher number of HIV-seropositive patients (82%) than HIV-seronegative controls without diarrhoea (52%) (p = 0.02). Lymphocytes were more likely to be found in inflammatory reactions in HIV-seropositive patients than in controls (p less than 0.0001). Pathogens were observed in histological sections of the duodenum of HIV-seropositive patients only (p = 0.002) and included cryptosporidia (four patients) Isospora belli (one), Strongyloides stercoralis (one), and Cryptococcus neoformans (one). On histological examination the rectal mucosa of HIV-seropositive patients and controls was similar, except eosinophils were more likely to be present in inflammatory reaction in HIV-seropositive patients (p = 0.05) and enteric pathogens were observed only in HIV-seropositive patients (cytomegalovirus inclusion bodies (one) and Schistosoma mansoni (two). The aetiology of persistent diarrhoea in most African AIDS patients remains unclear.

[Immunization against the human immunodeficiency virus in Zaire]. / Immunisation contre le virus de l'immunodéficience humaine au Zaïre.

The first experimental immunization of human against the AIDS retrovirus HIV-1 was started in a series of HIV seronegative healthy volunteers in november 1986. Priming used a vaccinia virus recombinant (V25) expressing Gp 160 env determinants of HTLV III B at the surface of infected cells. This priming which induced a weak immune reaction was performed on HIV seronegative French and Zaïrian individuals living in Zaïre (Kinshasa). These results prompted to boost the primary immune response. Four different protocols were used: slow drip intravenous infusion with paraformaldehyde fixed autologous cells infected with V25 (first protocol), repeated scarification with V25 for the second protocol. The third protocol used scarifications with fragment of Gp 120 env protein, and the fourth protocol used intramuscular injections of purified autologous cell membrane infected with V25. Results of the immune reaction obtained after these boosts: The three last protocols showed a cell mediated immunity (CMI) that not significantly enhanced in comparison with CMI obtained after V25 priming alone. Moreover, the sera showed low and variable neutralizing antibodies titers one to four months after boosting. By contrast boosting with V25 infected fixed cells (D.Z. individual) provide strong humoral and cellular group specific anamnestic immune response. Indeed, high levels of antibodies to viral envelope and neutralizing antibodies against divergent HIV-1 strains were observed. Group specific CMI and cell mediated cytotoxicity were enhanced by boosts. Skin-tests showed high mediated and delayed hypersensitivity to GP 160 in vivo. For the first time, these results show that an immune stage against HIV can be obtained in a man.

PIP: The 1st experimental immunization of humans against the AIDS retrovirus HIV-1 was begun in November 1986 among a group of HIV-seronegative healthy volunteers. A priming, involving a vaccine virus recombinant (V25) expressing Gp 160 env determinants of HTLV-III B at the surface of the infected cells was utilized. This priming, which induced a weak immune reaction, was performed on HIV-seronegative French and Zairian individuals living in Kinshasa, Zaire. These results prompted a boost to the primary immune response. 4 different protocols were used: the slow drip intravenous infusion with paraformaldehyde-fixed autologous cells infected with V25; repeated scarification with V25 for the 2nd protocol; scarifications with fragments of Gp 120 env protein; and intramuscular injections of purified autologous cell membrane infected with V25. The results of the immune reaction obtained after these boosts indicated the following: The last 3 protocols showed a cell- mediated immunity (CMI) that did not significantly enhance in comparison with CMI obtained after V25 priming alone. Moreover, the sera showed low and variable neutralizing antibody titers 1-4 months after boosting. By contrast, boosting with V25 infected fixed cells (D.Z.) provided strong humoral and cellular group specific anamnestic immune responses. Indeed, high levels of antibodies to viral envelope and neutralizing antibodies against divergent HIV-1 strains were observed. Group- specific CMI and cell mediated cytotoxicity were enhanced by boosts. Skin tests showed high mediated and delayed hypersensitivity to Gp 160 in vivo. For the 1st time, these results show that an immune state against HIV can be obtained in a man. (author's modified)

[Randomization of a population for a clinical trial of immunization against the human immunodeficiency virus (HIV)]. / Randomisation d'une population pour un essai clinique d'immunisation contre le virus de l'immunodeficience humaine (VIH).

Serum HIV antibodies has been investigated in different subpopulation from four different regions in Zäire by Elisa (Elavia Pasteur) and Western Blot. Seropositive prevalence differed from 2.4% (rural population) to 12.5% (urban population) according to the regions. When the group with 2.4% migrated to the area with 12.5% positives, after 8-12 months the number of seropositives in this group raised to 8%, showing an increase of 5.6% within one year. Such population is suitable for a large scale clinical trial (with anti-AIDS vaccine) to be performed on individuals with high risk of natural infection.

PIP: Major obstacles to development of a vaccine against the HIV infection have apparently been resolved by utilizing viral signals not directly from the virus or its products, but from membranes of infected cells. Evaluation of the level of protection provided by the vaccine requires a large scale clinical trial in a population with a high rate of infection. Screening studies have been conducted in different areas and in different subgroups in Zaire in order to identify such a group. A population living or working at a site some 30 km east of Kinshasa was studied between December 1986-March 1988, and a parallel study was conducted of persons residing in Kinshasa. Groups from 2 rural regions were also studied. The 1554 persons screened were divided into 8 groups based on their residence histories. Serum HIV antibodies were assessed by ELISA and Western Blot. The 4 groups composed of men living and working in Kinshasa or within a suburban radius of 30 km had a seroprevalence rate of 12.67%, with no significant difference by residence. A population of 136 pregnant women in the same locations had a seroprevalence rate of 12.5%, for a sex ratio of 1.1. A group of 71 persons studied in a provincial city of southern Zaire who had spent time in Kinshasa several years previously had a seroprevalence of 4.23%. A group of new arrivals to the Kinshasa vicinity from the provinces who had never previously resided in Kinshasa had a seroprevalence of 2.45%. The final group was also composed of new arrivals from the same provinces with no previous urban experience. Screening after 8-12 months in the city showed that their seropositive rate had increased from 2.45% to 8.00%. This increase of 5.6% within 1 year indicates that this group would be appropriate for a large scale clinical trial on individuals with high risk of natural infection.

Antigenic peptides recognized by T lymphocytes from AIDS viral envelope-immune humans.

T-lymphocyte immunity is likely to be an important component of the immune defence against the AIDS virus, because helper T cells are necessary for the antibody response as well as the cytotoxic response. We have previously predicted two antigenic sites of the viral envelope protein gp120 likely to be recognized by T lymphocytes, based on their ability to fold as amphipathic helices, and have demonstrated that these are recognized by T cells of mice immunized with gp120 (ref. 1). A peptide corresponding to one of these sites can also be induce immunity in mice to the whole gp120 protein. Because many clinically healthy seropositive blood donors have already lost their T-cell proliferative response to specific antigen, we tested the response to these synthetic peptides of lymphocytes from 14 healthy human volunteers who had been immunized with a recombinant vaccinia virus containing the AIDS viral envelope gene and boosted with a recombinant fragment. Eight of the 14 responded to one peptide, and four to the other peptide, not included in the boost. These antigenic sites recognized by human T cells may be useful components of a vaccine against AIDS. We also found a correlation between boosting with antigen-antibody complexes (compared to free antigen) and higher stimulation indices, suggesting a more effective method of immunization.

Comparison of the enzyme-linked immunosorbent assay (ELISA) with standard tests used to detect yellow fever virus antibodies.

The enzyme-linked immunosorbent assay (ELISA) was used to detect antibodies to yellow fever virus in 110 sera from patients living in an epidemic yellow fever area. The results were then compared with those obtained with the hemagglutination-inhibition (HI), complement-fixation (CF), neutralization (NT), and indirect immunofluorescence (IFA) tests. This ELISA, which used a type-specific antigen, showed the same results as the NT test and was found to be more sensitive and more specific than the HI and CF tests.