Etiologies of acute, persistent, and dysenteric diarrheas in adults in Bangui, Central African Republic, in relation to human immunodeficiency virus serostatus

A study of the etiologies of diarrhea in adults in relation to their human immunodeficiency virus (HIV) serostatus and number of CD4+ cells was carried out in the Central African Republic. In cases and controls, multi-parasitism was observed. Salmonella spp. were identified mainly during acute diarrhea, with 50% of the S. enteritidis isolated during the study being responsible for septicemia and/or urinary tract infection in immunodeficient patients. Enteroaggregative Escherichia coli (EAggEC) were the most frequently identified agent in HIV+ patients with persistent diarrhea; 42.8% of the patients with EAggEC as sole pathogens had bloody diarrhea, and these strains were negative for the presence of a virulence plasmid. Coccidia were found in those with acute and persistent diarrhea. Blood was observed in 53.3% of infections involving coccidia as the sole pathogen. Microsporidium spp. and Blastocystis hominis were found only in HIV+ patients with persistent diarrhea. Shigella spp., Campylobacter spp., and Entamoeba histolytica were found in HIV+ and HIV- dysenteric patients; bacteria resembling spirochetes that could not be cultivated were identified only in HIV+ cases with dysentery. Shiga-like toxin-producing E. coli O157:H- was isolated from two cases with hemolytic-uremic syndrome. Fungi were identified as the sole pathogen in 6.4% of the HIV+ patients with persistent diarrhea. Most of enteropathogenic bacteria identified were resistant to ampicillin and trimethoprim-sulfamethoxazole, remained susceptible to ampicillin plus clavulanic acid, and were susceptible to amikacin, gentamicin, and ciprofloxacin.

High prevalence in Central Africa of blood donors who are potentially infectious for human herpesvirus 8

BACKGROUND

In western countries, the transmission of human herpesvirus 8 (HHV-8) via blood transfusion has been recently postulated. In sub-Saharan African, the incidence of HHV-8-associated Kaposi's sarcoma and the seroprevalence for HHV-8 in autochthonous populations are high.

STUDY DESIGN AND METHODS

The aim of this study was to estimate the prevalence of blood donations potentially infectious for HHV-8 in the general adult population of Central Africa. Forty-nine blood donors at the Centre de Transfusion Sanguine in Bangui, the capital of the Central African Republic, were selected. Forty-five inpatients of Broussais Hospital, Paris, France, who were known to be seronegative for HIV and hepatitis B and C viruses and who had not received heart or kidney transplants, were chosen as a European "control" group for comparison. HHV-8 DNA sequences were detected in peripheral blood mononuclear cells by nested polymerase chain reaction using primer sets located in the HHV-8 open reading frame 26.

RESULTS

Eleven (22.5%; 95% CI: 12%-37%) of 49 blood donors were positive for HHV-8. Three (6%) were HIV-1 seropositive. Two (67%) of the 3 HIV-infected blood donors were also positive for HHV-8. All blood donors were apparently healthy; none was known to suffer from Kaposi's sarcoma. Only one (2.2%) control was carrying HHV-8 DNA on the peripheral blood mononuclear cells. The prevalence of HHV-8 was higher in blood donors from Bangui than in patients from Broussais Hospital.

CONCLUSIONS

HHV-8 infection is highly prevalent in an apparently healthy adult population from Central Africa, which raises concerns about HHV-8 transmission through transfusion in this setting.

Cross-reactions between the cytotoxic T-lymphocyte responses of human immunodeficiency virus-infected African and European patients

The great variability of protein sequences from human immunodeficiency virus (HIV) type 1 (HIV-1) isolates represents a major obstacle to the development of an effective vaccine against this virus. The surface protein (Env), which is the predominant target of neutralizing antibodies, is particularly variable. Here we examine the impact of variability among different HIV-1 subtypes (clades) on cytotoxic T-lymphocyte (CTL) activities, the other major component of the antiviral immune response. CTLs are produced not only against Env but also against other structural proteins, as well as some regulatory proteins. The genetic subtypes of HIV-1 were determined for Env and Gag from several patients infected either in France or in Africa. The cross-reactivities of the CTLs were tested with target cells expressing selected proteins from HIV-1 isolates of clade A or B or from HIV type 2 isolates. All African patients were infected with viruses belonging to clade A for Env and for Gag, except for one patient who was infected with a clade A Env-clade G Gag recombinant virus. All patients infected in France were infected with clade B viruses. The CTL responses obtained from all the African and all the French individuals tested showed frequent cross-reactions with proteins of the heterologous clade. Epitopes conserved between the viruses of clades A and B appeared especially frequent in Gag p24, Gag p18, integrase, and the central region of Nef. Cross-reactivity also existed among Gag epitopes of clades A, B, and G, as shown by the results for the patient infected with the clade A Env-clade G Gag recombinant virus. These results show that CTLs raised against viral antigens from different clades are able to cross-react, emphasizing the possibility of obtaining cross-immunizations for this part of the immune response in vaccinated individuals.

[Acute epidemic hemorrhagic conjunctivitis (AEHC) in Madagascar 1991]

An epidemic of A.E.H.C. was broken out everywhere in Madagascar during hot season from September 1990 to May 1991 with an important acuteness in February and March. Clinical symptoms are those of A.E.H.C. to enterovirus with some particularities. Virological study shows cytopathogenic effect of enterovirus and microbiology shows the existence of several bacterial germs particularly staphylococcus epidermidis. The discovery of two cases of streptococcus pneumonia and the absence of chlamydia trachomatis make the originality of our cases. The efficacy of the association antibiotic and steroids is spectacular.

Rift Valley fever epizootic in the central highlands of Madagascar

Between February and April 1991, unusual numbers of bovine abortion around Antananarivo (central highlands, Madagascar) were reported by official veterinary services. Rift Valley fever (RVF) virus isolations were made from sixteen aborted foetuses and one dead calf in different foci. Using monoclonal antibodies, the isolated viruses were found to be different from the 1979 RVF strains isolated in Madagascar from mosquitoes and human laboratory infection, and closer to African RVF strains. In a bovine population--previously characterized by a negative or very low RVF antibody prevalence--a high prevalence of IgM antibodies (264/994: 26.5% positive) was revealed; the IgM prevalence in recently aborting females varied from 40 to 91%. Among 994 human sera tested by IgG-IFA (immunofluorescent antibody assay) and IgM ELISA, 8.2% and 4.5%, respectively, proved positive. A total of 11,371 mosquitoes (61% Culex antennatus) were collected in the epizootic areas and tested without any virus isolation. Extensive studies were conducted to determine the geographical extension and the impact of this epidemic on the highly susceptible livestock and human populations.

Rift Valley fever on the east coast of Madagascar

In March 1990, a Rift Valley fever virus (RVFV) outbreak was suspected in the district of Fenerive on the east coast of Madagascar after an abnormally high incidence of abortions and disease in livestock. Sera from humans and cattle were tested for RVFV antibodies by immunofluorescence assay (IFA) and ELISA-IgM capture. Sera and mosquitoes collected in the same area were tested for virus isolation by tissue culture and suckling mouse intracerebral inoculation, and for antigen detection by an ELISA antigen capture assay. Among cattle from the area, RVFV antibody prevalence was 58.6% by IFA and 29.6% by ELISA-IgM. In contrast, human populations in the same area had a lower RVFV antibody prevalence, with 8.01% IFA and 5.4% IgM-positive sera. No RVFV antigen was detected and virus isolation was unsuccessful from the sera and mosquito pools tested. Different hypotheses concerning the emergence and diffusion of RVFV in this area and the occurrence of the outbreak are discussed.

Antigenic variations in West Nile virus strains isolated in Madagascar since 1978

The antigenic interrelationship between 52 Madagascan West Nile isolates and two prototype viruses (Eg101 and G2266) was assessed by an immunofluorescent technique using monoclonal antibodies. This analysis enabled us to define 5 groups of variants, 4 of which were closer to the Egyptian strain (Eg101) than to the Indian prototype (G2266). Groups II and V were dominant whereas strains of groups I and IV were less numerous. One strain belonging to group III was antigenically similar to the Indian strain. Antigenic variations were observed among viruses isolated from man, birds and different mosquito genera. Geographic variations were also observed. Exchanges exist between Madagascar and the African continent by means of migratory birds which seem to be instrumental in disseminating the virus and introducing the antigenic variants.

[Serological surveillance of West Nile virus infection in a village of the Central Highlands in Madagascar]

A serological survey on the frequency of West Nile virus antibodies has been carried out in a village near Antananarivo. IgG antibodies were searched for by enzyme-linked immunosorbent assay on 460 sera collected in December 1988 and on 494 sera collected in July 1989. The prevalence of West Nile virus antibodies varied from 13.4% to 21.8% between the beginning and the end of the rainy season. Seroconversion was observed in 14.7% of 354 paired serum samples collected in December and July which had been negative in December. The distribution of seropositive samples in the hamlets, and their frequency in relation to the presence of domesticated animals were analysed. Results show that West Nile virus circulates in the human population of the central highlands of Madagascar, which might account for the pseudo-influenza pathology observed in the region.

[Transmission cycles of the West-Nile virus in Madagascar, Indian Ocean]

Virological, serological and entomological research conducted in Madagascar since 1975, reveal the wide-spread presence of West-Nile virus on the island. This arbovirus has been isolated from humans, parrots and egrets. Vectors belong to the genus Culex (e.g. Cx. decens, Cx. quinquefasciatus, Cx. antennatus, Cx. univittatus), however the virus has also been isolated from Aedes and Anopheles. Serological tests carried out on over 1,600 human and almost 1,000 animal sera, revealed that human beings could be infected throughout the island. Other potential vertebrate hosts, apart from birds, are oxen and bats. Insectivores, rodents and lemurs are probably involved in the transmission cycles only to a very small extent.

[A sero-epidemiologic survey of HIV infection in Burundi between 1980 and 1981]

A retrospective investigation permitted us to show presence of HIV infection in Burundi between 1980 and 1981. 658 sera collected in healthy population of Burundi during this period have been tested for HIV1 and HIV2 with ELISA screening and western-blot analysis. Results completed with HIV1 antigen research show 29 patients infected with HIV1 (27 antibodies to HIV1 carriers, and 2 with HIV1 antigen). The epidemiological situation before finding HIV show high prevalence (4.4%) of HIV1 infection. No HIV2 was found. The epidemiology of HIV infection was dominated by high prevalence in urban areas (8.08%) but 2.82% of country people were infected, by frequence in man (5.94%) but 3.08% of women were carriers, and by heterosexual transmission. After this study HIV infection was more frequent and we have observed epidemiological modification (importance of vertical transmission). Frequent antigenic cross-reaction between HIV1 and HIV2 core proteins has been observed. Cross-reaction with other retrovirus is possible.