Evidence of strain structure in Plasmodium falciparum var gene repertoires in children from Gabon, West Africa

Existing theory on competition for hosts between pathogen strains has proposed that immune selection can lead to the maintenance of strain structure consisting of discrete, weakly overlapping antigenic repertoires. This prediction of strain theory has conceptual overlap with fundamental ideas in ecology on niche partitioning and limiting similarity between coexisting species in an ecosystem, which oppose the hypothesis of neutral coexistence. For Plasmodium falciparum, strain theory has been specifically proposed in relation to the major surface antigen of the blood stage, known as PfEMP1 and encoded by the multicopy multigene family known as the var genes. Deep sampling of the DBLα domain of var genes in the local population of Bakoumba, West Africa, was completed to define whether patterns of repertoire overlap support a role of immune selection under the opposing force of high outcrossing, a characteristic of areas of intense malaria transmission. Using a 454 high-throughput sequencing protocol, we report extremely high diversity of the DBLα domain and a large parasite population with DBLα repertoires structured into nonrandom patterns of overlap. Such population structure, significant for the high diversity of var genes that compose it at a local level, supports the existence of "strains" characterized by distinct var gene repertoires. Nonneutral, frequency-dependent competition would be at play and could underlie these patterns. With a computational experiment that simulates an intervention similar to mass drug administration, we argue that the observed repertoire structure matters for the antigenic var diversity of the parasite population remaining after intervention.

Immunoglobulin response to the low polymorphic Pf113 antigen in children from Lastoursville, South-East of Gabon

Pf113 is a P. falciparum putatively GPI-anchored protein that has been so far localized at the surface of merozoites, suggesting it could interact with RBC surface during merozoite invasion. Previous studies conducted in Papua New Guinea and in Kenya have revealed that this protein is recognized by natural antibodies in individuals living in malaria-endemic areas and is associated with protective immunity in malaria, further supporting the potential of Pf113 for the development of anti-malaria vaccines. However, in Central Africa, no study on the immunogenicity of this protein has been conducted. Here, we report the characterization of the Pf113 immune response in 103 children by Enzyme-Linked Immunoabsorbent Assay (ELISA), using a recombinant form of Pf113 expressed in Escherichia coli, together with the study of the Pf113 polymorphism, after amplification and sequencing of 40 field isolates. Data showed that almost 51% of the studied individuals had positive antibody responses to the recombinant Pf113 protein, and that IgG subclass response was dominated by IgG3 (84%) followed by IgG1 (50%). Surprisingly the prevalence of IgG4 was 92%. In addition, gene analysis in field isolates from this region indicated that Pf113 was not highly polymorphic, in particular regarding high-activity binding peptides (HABPs). Our data reinforce the idea that Pf113 may be considered for inclusion in multicomponent blood-stage vaccines.

Molecular epidemiological study of adenovirus infecting western lowland gorillas and humans in and around Moukalaba-Doudou National Park (Gabon)

Adenoviruses are widespread in human population as well as in great apes, although the data about the naturally occurring adenovirus infections remain rare. We conducted the surveillance of adenovirus infection in wild western lowland gorillas in Moukalaba-Doudou National Park (Gabon), in order to investigate naturally occurring adenovirus in target gorillas and tested specifically a possible zoonotic transmission with local people inhabiting the vicinity of the park. Fecal samples were collected from western lowland gorillas and humans, and analyzed by PCR. We detected adenoviral genes in samples from both gorillas and the local people living around the national park, respectively: the overall prevalence rates of adenovirus were 24.1 and 35.0 % in gorillas and humans, respectively. Sequencing revealed that the adenoviruses detected in the gorillas were members of Human mastadenovirus B (HAdV-B), HAdV-C, or HAdV-E, and those in the humans belonged to HAdV-C or HAdV-D. Although HAdV-C members were detected in both gorillas and humans, phylogenetic analysis revealed that the virus detected in gorillas are genetically distinct from those detected in humans. The HAdV-C constitutes a single host lineage which is compatible with the host-pathogen divergence. However, HAdV-B and HAdV-E are constituted by multiple host lineages. Moreover, there is no evidence of zoonotic transmission thus far. Since the gorilla-to-human transmission of adenovirus has been shown before, the current monitoring should be continued in a broader scale for getting more insights in the natural history of naturally occurring adenoviruses and for the safe management of gorillas' populations.

Seroprevalence of Toxocara spp. in a rural population in Central African Gabon

Toxocara spp. are zoonotic parasites with global distribution infecting humans by incidental ingestions of eggs shed in feces of dogs or cats. High seroprevalences have been reported from several regions of Africa, however data from the Central African region remain limited. Although several clinical entities caused by larvae of Toxocara spp. have been described, the public heath impact of this infection has so far often been neglected. This study was conducted to estimate the prevalence in a rural central African population. The population based study was performed in volunteers in a rural region of Gabon. A two-step testing approach was applied using an ELISA as screening test and a Western Blot (immunoblot) as confirmatory assay. Basic demographic data and risk factors were collected and compared between seropositive and negative participants. In total, 199 out of 332 serum samples were tested positive for Toxocara spp. antibodies (59.9%). After standardization for age to the overall Gabonese population seroprevalence was 53.6% (95% CI 48.2-59.0%). There was a trend towards higher seroprevalence in participants with agricultural activity. Seroprevalence of antibodies against Toxocara spp. is high in this rural population in Gabon. These results are comparable with previous reports from other sub-regions of Africa and add to our understanding of the epidemiology of toxocariasis in Africa. Given the high prevalence of toxocariasis in tropical regions, it may be speculated that clinically relevant presentations (e.g. visceral or ocular larva migrans syndrome) may occur in considerable numbers. A formal assessment of the burden of disease and the public health impact of human toxocariasis is therefore warranted.

High Frequency of Trypanosoma congolense Savannah Type (Kinetoplastida: Trypanosomatidae) Among Tsetse Flies (Diptera: Glossinidae) in a Historic Trypanosoma Foci in North-Eastern Gabon: Preliminary Study [corrected]

Human African trypanosomiasis became a neglected disease after the 1960s, when case numbers dropped dramatically. It again became a public health problem in sub-Saharan Africa at the end of the 1990s, when new cases were reported, notably in Central Africa, and specifically in Gabon, where historic foci existed and new cases have been reported. Therefore, the present study reports on an entomological survey conducted in May 2012 to determine the pathogenic trypanosome infection rate in tsetse flies and characterize the diversity of Trypanosoma species in the Ivindo National Park (INP) in northeastern Gabon. Nine Vavoua traps were used to catch tsetse over a 7-days period. All tsetse flies captured were identified to species, dissected, and trypanosome species identified using polymerase chain reaction (PCR). In total, 160 tsetse flies were analyzed, including Glossina palpalis palpalis, Glossina fusca congolense, and Glossina tachinoïdes The trypanosome infection rate of the flies was 6.3 and 31.9% using microscopy and PCR, respectively. The species identified were Trypanosoma congolense savannah type, Trypanosoma brucei brucei, Trypanosoma brucei gambiense, Trypanosoma vivax, and Trypanosoma congolense forest type. Trypanosoma risk index was 0.75 and 7.05 for humans and for animals, respectively. This study illustrates the diversity of Trypanosoma species infecting the tsetse flies in the INP. The simultaneous occurrence of Trypanosoma and tsetse from the palpalis group may suggest that the reservoirs of African animal trypanosomiasis should be carefully monitored in this area.

Genital shedding of herpes simplex virus type 2 in childbearing-aged and pregnant women living in Gabon

The prevalence of genital shedding of herpes simplex virus (HSV)-2 and related risk factors was evaluated in a prospective population of 355 women attending the Maternity Joséphine Bongo, in Libreville, Gabon. We found a high prevalence (66%) of HSV-2 seropositivity, with a high proportion, 14%, of women harbouring HSV-2 DNA shedding in their genital secretions. HSV-2 genital shedding was positively associated with previous episodes of genital blisters, current genital ulcer, current genital blister, HIV seropositivity and HSV-2 seropositivity. The high prevalence of HSV-2 in childbearing-aged population indicates that young women living in Gabon are at high risk for HIV acquisition in HIV-seronegative women sexually exposed to HIV, for HIV transmission in HIV-infected women co-infected by HSV-2 and finally for HSV-2 vertical transmission during pregnancy.

Cerebro-meningeal infections in HIV-infected patients: a study of 116 cases in Libreville, Gabon

BACKGROUND

Cerebro-meningeal pathology is common in human immunodeficiency virus (HIV) infection and the aetiology is often difficult to ascertain with certainty.

OBJECTIVE

To describe the major suspected and identified causes of meningeal or encephalitic syndromes in HIV infection in Libreville, Gabon.

METHODS

A descriptive study using clinical records of patients hospitalised in the Department of Medicine in the Military Hospital of Libreville (Gabon) between January 2006 and May 2010. Clinical features were evaluated using multivariable logistic regression to evaluate association with the outcome of a clinical improvement or death.

RESULTS

The most frequent neurological symptoms were reduced level of consciousness (54.3%), headache (55.2%), motor deficit (38.7%), and convulsions (36.2%). Cerebral toxoplasmosis represented 64.7% of diagnoses, followed by cryptococcal neuromeningitis in 12.9% of cases. Tuberculoma was diagnosed in 4 cases and lymphoma in 2 cases. In 9.5% of cases, no aetiology was determined. Toxoplasmosis treatment led to clinical improvement in 69.3% of cases with suspected cerebral toxoplasmosis. Overall mortality was 39.7%.

CONCLUSION

The diagnosis of neurological conditions in HIV positive patients is difficult, particularly in a low-resource setting. A trial of treatment for toxoplasmosis should be initiated first line with all signs of neurological pathology in a patient infected with HIV.

Marked Rise in the Prevalence of Asymptomatic Plasmodium falciparum Infection in Rural Gabon

Control strategies implemented a decade ago led to a marked reduction in the prevalence of malaria in many countries. In Dienga, southeastern Gabon, the prevalence of microscopic P. falciparum infection was 7% in 2003, close to the pre-elimination threshold of 5%. The aim of this work was to determine the prevalence of P. falciparum infection in the same community a decade later. A cohort of 370 individuals aged from 3 to 85 years living in Dienga was investigated for P. falciparum infection; during six passages (P) in 15-month period. Demographic data were collected, along with behaviors and attitudes towards malaria. Plasmodium infection was diagnosed by microscopy (ME), followed by PCR to detect submicroscopic infection. The prevalence of P. falciparum infection in P1, P2, P3, P4, P5 and P6 was respectively 43.5% (25.1% ME+, 18.4% PCR+); 40.9% (27.0% ME+, 13.9% PCR+), 52.7% (26.1% ME+, 26.6% PCR+); 34.1% (14.1% ME+, 20% PCR+), 57.7% (25.4.% ME+, 32.3% PCR+); and 46.2% (21.4% ME+, 24.8% PCR+) with an overall average of 45.9% (95%CI [37.0–54.7], 23.2% ME+ and 22.7% PCR+). P4 and P5 prevalences were statically different throughout the six passages. Microscopic prevalence was significantly higher than that observed ten years ago (23% [n = 370] vs 7% [n = 323], p < 0.001). Asymptomatic infections were the most frequent (96%). Gametocytes were detected in levels ranging from 5.9% to 13.9%. Insecticide-treated nets, indoor residual insecticides, and self-medication were used by respectively 33.2% (95%CI [29.0–37.4]), 17.7% (95%CI [15.5–19.9]) and 12.1% (95%CI [10.6–13.6]) of the study population. A near-threefold increase in P. falciparum infection has been observed in a rural area of southeastern Gabon during a 10-year period. Most infections were asymptomatic, but these subjects likely represent a parasite reservoir. These findings call for urgent reinforcement of preventive measures.

Possible Role of Rickettsia felis in Acute Febrile Illness among Children in Gabon

Infection is widespread but most prevalent among young, rural residents with fever.

Rickettsia felis has been reported to be a cause of fever in sub-Saharan Africa, but this association has been poorly evaluated in Gabon. We assessed the prevalence of this bacterium among children <15 years of age in 4 areas of Gabon; the locations were in urban, semiurban, and rural areas. DNA samples from 410 febrile children and 60 afebrile children were analyzed by quantitative PCR. Overall, the prevalence of R. felis among febrile and afebrile children was 10.2% (42/410 children) and 3.3% (2/60 children), respectively. Prevalence differed among febrile children living in areas that are urban (Franceville, 1.3% [1/77]), semiurban (Koulamoutou, 2.1% [3/141]), and rural (Lastourville, 11.2% [15/134]; Fougamou, 39.7% [23/58]). Furthermore, in a rural area (Fougamou), R. felis was significantly more prevalent in febrile (39.7% [23/58]) than afebrile children (5.0% [1/20]). Additional studies are needed to better understand the pathogenic role of R. felis in this part of the world.

Testing the accuracy ratio of the Spatio-Temporal Epidemiological Modeler (STEM) through Ebola haemorrhagic fever outbreaks

Mathematical modelling is an important tool for understanding the dynamics of the spread of infectious diseases, which could be the result of a natural outbreak or of the intentional release of pathogenic biological agents. Decision makers and policymakers responsible for strategies to contain disease, prevent epidemics and fight possible bioterrorism attacks, need accurate computational tools, based on mathematical modelling, for preventing or even managing these complex situations. In this article, we tested the validity, and demonstrate the reliability, of an open-source software, the Spatio-Temporal Epidemiological Modeler (STEM), designed to help scientists and public health officials to evaluate and create models of emerging infectious diseases, analysing three real cases of Ebola haemorrhagic fever (EHF) outbreaks: Uganda (2000), Gabon (2001) and Guinea (2014). We discuss the cases analysed through the simulation results obtained with STEM in order to demonstrate the capability of this software in helping decision makers plan interventions in case of biological emergencies.

Haemosporidian Parasites of Antelopes and Other Vertebrates from Gabon, Central Africa

Re-examination, using molecular tools, of the diversity of haemosporidian parasites (among which the agents of human malaria are the best known) has generally led to rearrangements of traditional classifications. In this study, we explored the diversity of haemosporidian parasites infecting vertebrate species (particularly mammals, birds and reptiles) living in the forests of Gabon (Central Africa), by analyzing a collection of 492 bushmeat samples. We found that samples from five mammalian species (four duiker and one pangolin species), one bird and one turtle species were infected by haemosporidian parasites. In duikers (from which most of the infected specimens were obtained), we demonstrated the existence of at least two distinct parasite lineages related to Polychromophilus species (i.e., bat haemosporidian parasites) and to sauropsid Plasmodium (from birds and lizards). Molecular screening of sylvatic mosquitoes captured during a longitudinal survey revealed the presence of these haemosporidian parasite lineages also in several Anopheles species, suggesting a potential role in their transmission. Our results show that, differently from what was previously thought, several independent clades of haemosporidian parasites (family Plasmodiidae) infect mammals and are transmitted by anopheline mosquitoes.

Broad Range of Hepatitis B Virus (HBV) Patterns, Dual Circulation of Quasi-Subgenotype A3 and HBV/E and Heterogeneous HBV Mutations in HIV-Positive Patients in Gabon

Integrated data on hepatitis B virus (HBV) patterns, HBV genotypes and mutations are lacking in human immunodeficiency virus type 1 (HIV-1) co-infected patients from Africa. This survey was conducted in 2010-2013 among 762 HIV-1-positive adults from Gabon who were predominantly treated with 3TC-based antiretroviral treatment. HBV patterns were identified using immunoassays detecting total antibody to hepatitis B core antigen (HBcAb), hepatitis B surface antigen (HBsAg), IgM HBcAb, hepatitis B e antigen (HBeAg), antibody to HBsAg (HBsAb) and an in-house real-time PCR test for HBV DNA quantification. Occult hepatitis B (OBI) was defined by the presence of isolated anti-HBc with detectable serum HBV DNA. HBV genotypes and HBV mutations were analyzed by PCR-direct sequencing method. Seventy-one (9.3%) patients tested positive for HBsAg, including one with acute hepatitis B (0.1%; 95% CI, 0.0%-0.2%), nine with HBeAg-positive chronic hepatitis B (CHB) (1.2%; 95% CI, 0.6%-2.2%), 16 with HBeAg-negative CHB (2.1%; 95% CI, 1.2%-3.3%) and 45 inactive HBV carriers (5.9%; 95% CI, 4.4%-7.8%). Sixty-one (8.0%; 95% CI, 6.2%-10.1%) patients showed OBI. Treated patients showed similar HBV DNA levels to those obtained in untreated patients, regardless of HBV patterns. Around 15.0% of OBI patients showed high (>1,000 UI/mL) viremia. The mutation M204V/I conferring resistance to 3TC was more common in HBV/A (47.4%) than in HBV/E isolates (0%) (P = .04). Our findings encouraged clinicians to promote HBV vaccination in patients with no exposure to HBV and to switch 3TC to universal TDF in those with CHB.

Diabetes in Sub-Saharan Africa: Distribution Based on Social Status in Libreville (Gabon)

OBJECTIVE

Many researchers continue to believe that urbanization is a major contributor to diabetes. We seek to demonstrate that the social status associated with urbanization has an impact on the prevalence of diabetes in Libreville, Gabon in sub-Saharan Africa.

METHODS

Our study was conducted in Libreville, the capital of Gabon; the city has a population of 397,000. Our study analyzed data from the registries of patients hospitalized in 2013 in the main diabetes center in Libreville.

RESULTS

The results revealed that, for 2013, 798 patients were hospitalized with diabetes at a prevalence of .2%. We found differences (P<.05) between women (423) and men (375). Mean age for women was 52.02 years and 48.88 years for men. The number of existing cases hospitalized was significantly more than new cases. All levels of society were represented in our study: students (42); military (36); administratives (99); technicians (180); unemployed (295); and retired (146). The results showed that the unemployed (36%), particularly women (29.40%) are most affected by diabetes.

CONCLUSIONS

Our results show the impact of social status on the increase of diabetes in Libreville. We found that urbanization, associated with insecurity especially in women, had an effect on the prevalence of diabetes in Libreville. These results indicate that, apart from the non-modifiable factors (age, race, ethnicity), insecurity is a modifiable factor that should be taken into account.

High Rate of Simian Immunodeficiency Virus (SIV) Infections in Wild Chimpanzees in Northeastern Gabon

The emergence of HIV-1 groups M, N, O, and P is the result of four independent cross-species transmissions between chimpanzees (cpz) and gorillas (gor) from central/south Cameroon and humans respectively. Although the first two SIVcpz were identified in wild-born captive chimpanzees in Gabon in 1989, no study has been conducted so far in wild chimpanzees in Gabon. To document the SIVcpz infection rate, genetic diversity, and routes of virus transmission, we analyzed 1458 faecal samples collected in 16 different locations across the country, and we conducted follow-up missions in two of them. We found 380 SIV antibody positive samples in 6 different locations in the north and northeast. We determined the number of individuals collected by microsatellite analysis and obtained an adjusted SIV prevalence of 39.45%. We performed parental analysis to investigate viral spread between and within communities and found that SIVs were epidemiologically linked and were transmitted by both horizontal and vertical routes. We amplified pol and gp41 fragments and obtained 57 new SIVcpzPtt strains from three sites. All strains, but one, clustered together within a specific phylogeographic clade. Given that these SIV positive samples have been collected nearby villages and that humans continue to encroach in ape's territories, the emergence of a new HIV in this area needs to be considered.

Clinical, environmental, and serologic surveillance studies of melioidosis in Gabon, 2012-2013

Burkholderia pseudomallei and B. thailandensis are in the soil; a novel B. pseudomallei sequence type causes lethal septic shock.

Burkholderia pseudomallei, an environmental gram-negative bacillus, is the causative agent of melioidosis and a bio-threat agent. Reports of B. pseudomallei isolation from soil and animals in East and West Africa suggest that melioidosis might be more widely distributed than previously thought. Because it has been found in equatorial areas with tropical climates, we hypothesized that B. pseudomallei could exist in Gabon. During 2012–2013, we conducted a seroprevalance study in which we set up microbiology facilities at a large clinical referral center and prospectively screened all febrile patients by conducting blood cultures and testing for B. pseudomallei and related species; we also determined whether B. pseudomallei could be isolated from soil. We discovered a novel B. pseudomallei sequence type that caused lethal septic shock and identified B. pseudomallei and B. thailandensis in the environment. Our data suggest that melioidosis is emerging in Central Africa but is unrecognized because of the lack of diagnostic microbiology facilities.

Effect of Antihelminthic Treatment on Vaccine Immunogenicity to a Seasonal Influenza Vaccine in Primary School Children in Gabon: A Randomized Placebo-Controlled Trial

Background

Helminth infections are a major public health problem, especially in the tropics. Infected individuals have an altered immune response with evidence that antibody response to vaccination is impaired. Hence, treatment of helminth infections before vaccination may be a simple intervention to improve vaccine immunogenicity. In the present study we investigated whether a single-dose antihelminthic treatment influences antibody responses to a seasonal influenza vaccine in primary school children living in Gabon, Central Africa.

Methods

In this placebo-controlled double-blind trial conducted in Gabon the effect of a single-dose antihelminthic treatment with 400 mg albendazole versus a placebo one month prior to immunization with a seasonal influenza vaccine was investigated. Antiviral antibody titers against all three vaccine strains were assessed by haemagglutination inhibition (HI) test at baseline (Day 0; vaccination) and four weeks (Day 28) as well as 12 weeks (Day 84) following vaccination. Vaccine-specific memory B-cell response was measured at Day 0 and Day 84 by vaccine-specific Enzyme-linked Immunospot (ELISpot) assay. The trial is registered with the Pan African Clinical Trials Registry (PACTR) (PACTR201303000434188).

Results

98 school children aged 6–10 years were randomly allocated to receive either antihelminthic treatment or placebo and were vaccinated one month after the treatment. The prevalence of helminths at baseline was 21%. Vaccine-specific HI titers against at least one of the three vaccine strains increased at Day 28 and Day 84 in all participants. HI titers against both influenza A strains as well as memory B-cell response were modestly higher in the antihelminthic treated group compared to the placebo group but the difference was not statistically significant. Total but not specific IgA was elevated in the antihelminthic treated group compared to the control group at Day 28.

Conclusion

In our setting antihelminthic treatment had no significant effect on influenza vaccine immunogenicity. A trend towards better antiviral and vaccine immunogenicity in the antihelminthic treated group encourages studies to be conducted with alternative treatment schedules or in populations with a higher helminth burden.

Helminth infections are a major health problem in the tropics and most affected are children. The parasites are able to influence the immune system from a T-helper 1 type response to a T-helper 2 type response. There is evidence that in infected individuals the immune response following vaccination is impaired. Thus pre-treatment with a single-dose of an antihelminthic treatment before vaccination could be a simple and cost-effective intervention to improve vaccine efficacy. In the present study we investigated whether a single-dose antihelminthic treatment with albendazole influences the vaccine outcome to a seasonal influenza vaccine in primary school children living in Gabon, Central Africa. We observed a trend towards a higher anti-viral antibody titer after vaccination in the pre-treated group compared to the placebo control group, albeit not statistical significant. Furthermore we detected a higher concentration of total IgA but not of vaccine-specific IgA. In conclusion, our findings show subtle effects of antihelminthic pre-treatment but are not conclusive enough to recommend a single-dose of albendazole before vaccination to improve vaccine immunogenicity but encourage to conduct further studies in endemic areas with other treatment regiments.

Impact of Anti-Retroviral Treatment and Cotrimoxazole Prophylaxis on Helminth Infections in HIV-Infected Patients in Lambaréné, Gabon

Background

Foci of the HIV epidemic and helminthic infections largely overlap geographically. Treatment options for helminth infections are limited, and there is a paucity of drug-development research in this area. Limited evidence suggests that antiretroviral therapy (ART) reduces prevalence of helminth infections in HIV-infected individuals. We investigated whether ART exposure and cotrimoxazole preventive therapy (CTX-P) is associated with a reduced prevalence of helminth infections.

Methodology and Principal Findings

This cross-sectional study was conducted at a primary HIV-clinic in Lambaréné, Gabon. HIV-infected adults who were ART-naïve or exposed to ART for at least 3 months submitted one blood sample and stool and urine samples on 3 consecutive days. Outcome was helminth infection with intestinal helminths, Schistosoma haematobium, Loa loa or Mansonella perstans. Multivariable logistic regression was used to assess associations between ART or CTX-P and helminth infection. In total, 408 patients were enrolled. Helminth infection was common (77/252 [30.5%]). Filarial infections were most prevalent (55/310 [17.7%]), followed by infection with intestinal helminths (35/296 [11.8%]) and S. haematobium (19/323 [5.9%]). Patients on CTX-P had a reduced risk of Loa loa microfilaremia (adjusted odds ratio (aOR) 0.47, 95% CI 0.23-0.97, P = 0.04), also in the subgroup of patients on ART (aOR 0.36, 95% CI 0.13-0.96, P = 0.04). There was no effect of ART exposure on helminth infection prevalence.

Conclusions/Significance

CTX-P use was associated with a decreased risk of Loa loa infection, suggesting an anthelminthic effect of antifolate drugs. No relation between ART use and helminth infections was established.

The geographical distribution of helminth infections, which are highly prevalent in many areas, overlaps considerably with regions of high HIV sero-prevalence. The highest burden of infection is found in resource-poor settings, making it unattractive for the pharmaceutical industry to invest. Limited available treatment options and drug-resistance are increasing problems for soil-transmitted helminths, whereas for some other helminth infections, such as for the blood-dwelling microfilariae, effective and safe treatment options are still far from being optimal. Limited evidence suggests antihelminthic effects of antiretroviral therapy (ART) in HIV-infected individuals. We aimed to investigate whether ART or cotrimoxazole preventive treatment (CTX-P) reduces prevalence of helminth infection in HIV-infected individuals attending a primary HIV clinic in a semi-rural area in Gabon. The most important finding of our study was that the use of CTX-P was associated with a reduced prevalence of Loa loa microfilaremia. ART use was not associated with a reduced prevalence of helminth infections. Additional studies are needed to assess the effects of CTX on helminth infections, as this might be a promising safe and effective drug adding to the limited repertoire of anthelminthic drugs.

Delay Between First HIV-Related Symptoms and Diagnosis of HIV Infection in Patients Attending the Internal Medicine Department of the Fondation Jeanne Ebori (FJE), Libreville, Gabon

BACKGROUND

HIV-infected patients (pts) in Africa are often diagnosed at very advanced stages of disease. They seek relief using traditional medicine or religious beliefs. General practitioners (GPs) are often consulted first. Once the HIV diagnosis has been made, concomitant use of alternative and allopathic medicine is also frequent.

OBJECTIVE

To describe the delay between presentation of HIV-related symptoms and diagnosis, the first physician consulted, and the use of traditional medicine or religion as an alternative or complement to allopathic medicine in HIV-infected patients.

METHOD

Patients followed for HIV infection at Fondation Jeanne Ebori were retrospectively interviewed to trace their therapeutic itinerary.

RESULTS

150 pts were interviewed. There were 63% females, mean age was 39 years, median CD4 count was 242 cells/microL (102-394), CDC stage A/B/C was 32%/40%/28%, and 57% had very low income. Religious affiliations were Catholic (52%), Protestant (21%), Muslim (3%), "progressive" Church (16%), and none (7%). The median time elapsed between their first symptoms and HIV diagnosis was 124 (20-292) days. The first person consulted was a traditional healer (5%), GP (61%), or private clinics (23%). Traditional healers were consulted for initiation rites in 23%, cure of disease in 90%, or sorcery in 20%. Once allopathic medicine was started, concomitant alternative therapy occurred in 25 (17%) for traditional medicine and 4 (3%) for faith healing. Resort to traditional healer (odds ratio [OR] 2.6, p = .02) and to faith healing (OR 3.1, p = .048) were risk factors for diagnosis delay.

CONCLUSION

Many factors related to patients, the health system, and culture or society are detrimental to an early diagnosis of HIV infection in Gabon. Increasing awareness of the risk of HIV infection throughout the general population and hope and trust in western medicine in patients and non-HIV-specialist physicians, as well as suppression of social stigma, could shorten the delay before diagnosis. Better communication between allopathic physicians and traditional or faith healers could also improve the care of HIV-infected patients.

Genital Mycoplasma infections and their resistance phenotypes in an African setting

We investigated the antimicrobial susceptibilities of mycoplasmas in Gabonese men and women. A total of 1,332 men and women were included in the study. Sperm, urine, ureteral or vaginal swabs were collected from the subjects. Mycoplasmas identification and antimicrobial susceptibility to azithromycin, clarithromycin, erythromycin, josamycin, pristinamycin, doxycycline, tetracycline, ofloxacin and ciprofloxacin were tested using the Mycoplasma IST 2 kit. 794 subjects were positive for Mycoplasma. Respectively, 1.6 % and 82.24 % of subjects were singly infected with M. hominis and Ureaplasma urealyticum and 15.87 % had a mixed infection. M. hominis isolates were resistant to erythromycin and had an intermediate (I) to resistant (R) profile to azithromycin and clarithromycin. 84.6 % of M. hominis strains were sensitive (S) to josamycin and pristinamycin. 30.8 % and 92.3 % of M. hominis strains were sensitive to tetracycline and doxycycline, respectively. 76.9 and 84.6 % of M. hominis isolates were sensitive to ciprofloxacin and ofloxacin, respectively. The sensitivity rates of U. urealyticum strains were 45.23 %, 47.7 %, 63.84 %, 90.8 % and 92 % for azithromycin, erythromycin, clarithromycin, pristinamycin and josamycin, respectively. U. urealyticum strains showed 62.2 % and 79.7 % sensitivity to tetracycline and doxycycline, respectively. The resistance rates to azithromycin, clarithromycin and erythromycin for samples with mixed infection were 72.8 %, 84.7 % and 85.6 %, respectively. Josamycin and pristinamycin were 81.5 % effective on samples with mixed infection. The sensitivity rates of samples with mixed infection to tetracycline, doxycycline, ciprofloxacin and ofloxacin were 32 %, 69.6 %, 8.9 % and 18.5 %, respectively. Sub-Saharan Africa needs to use antibiotics rationally, as falling to do so would compromise the management of infectious diseases.

β-Hemolytic streptococcal throat carriage and tonsillopharyngitis: a cross-sectional prevalence study in Gabon, Central Africa

BACKGROUND

Group A streptococcus (GAS) and possibly other β-hemolytic streptococci (BHS) account for a considerable morbidity and mortality burden in African populations; however, disproportionately little is known about the epidemiology of BHS in sub-Saharan Africa. This study assessed the prevalence of GAS, group G streptococcus (GGS) and group C streptococcus (GCS) carriage and tonsillopharyngitis in a Central African population.

METHODS

A prospective cross-sectional study was performed to assess the prevalence of and risk factors for BHS carrier status and tonsillopharyngitis in children and adults in Gabon.

RESULTS

The overall BHS carrier prevalence was 135/1,005 (13.4%); carrier prevalence of GAS, GGS, and GCS was 58/1,005 (5.8%), 50/1,005 (5.0%), and 32/1,005 (3.2%), respectively. Streptococcal carriage was associated with school and pre-school age (adjusted OR 2.65, 95% CI 1.62-4.36, p = 0.0001 and 1.90, 95% CI 1.14-3.17, p = 0.0141, respectively). Participants residing in urban areas were less likely carriers (OR 0.52, p = 0.0001). The point-prevalence of BHS-positive tonsillopharyngitis was 1.0% (9/1,014) and 15.0% (6/40) in school children with sore throat.

CONCLUSIONS

Non-GAS exceeded GAS throat carriage and tonsillopharyngitis suggesting a yet underestimated role of non-GAS streptococci in BHS diseases.

[Epidemiology of upper gastrointestinal bleeding in Gabon]

The department of internal medicine of the military hospital of Gabon managed 92 cases of upper gastrointestinal bleeding from April 2009 to November 2011. The frequency of these hemorrhages in the department was 8.2%; they occurred most often in adults aged 30-40 years and 50-60 years, and mainly men (74%). Erosive-ulcerative lesions (65.2%) were the leading causes of hemorrhage, followed by esophageal varices (15.2%). These results underline the importance of preventive measures for the control of this bleeding.

Zika virus in Gabon (Central Africa)--2007: a new threat from Aedes albopictus?

Background

Chikungunya and dengue viruses emerged in Gabon in 2007, with large outbreaks primarily affecting the capital Libreville and several northern towns. Both viruses subsequently spread to the south-east of the country, with new outbreaks occurring in 2010. The mosquito species Aedes albopictus, that was known as a secondary vector for both viruses, recently invaded the country and was the primary vector involved in the Gabonese outbreaks. We conducted a retrospective study of human sera and mosquitoes collected in Gabon from 2007 to 2010, in order to identify other circulating arboviruses.

Methodology/Principal Findings

Sample collections, including 4312 sera from patients presenting with painful febrile disease, and 4665 mosquitoes belonging to 9 species, split into 247 pools (including 137 pools of Aedes albopictus), were screened with molecular biology methods. Five human sera and two Aedes albopictus pools, all sampled in an urban setting during the 2007 outbreak, were positive for the flavivirus Zika (ZIKV). The ratio of Aedes albopictus pools positive for ZIKV was similar to that positive for dengue virus during the concomitant dengue outbreak suggesting similar mosquito infection rates and, presumably, underlying a human ZIKV outbreak. ZIKV sequences from the envelope and NS3 genes were amplified from a human serum sample. Phylogenetic analysis placed the Gabonese ZIKV at a basal position in the African lineage, pointing to ancestral genetic diversification and spread.

Conclusions/Significance

We provide the first direct evidence of human ZIKV infections in Gabon, and its first occurrence in the Asian tiger mosquito, Aedes albopictus. These data reveal an unusual natural life cycle for this virus, occurring in an urban environment, and potentially representing a new emerging threat due to this novel association with a highly invasive vector whose geographic range is still expanding across the globe.

Not previously considered an important human arboviral pathogen, the epidemic capacity of Zika virus (ZIKV, a dengue-related flavivirus) was revealed by the Micronesia outbreak in 2007, which affected about 5000 persons. Widely distributed throughout tropical areas of Asia and Africa, ZIKV is transmitted by a broad range of mosquito species, most of which are sylvatic or rural, Aedes aegypti, an anthropophilic and urban species, being considered the main ZIKV epidemic vector. In a context of emerging arbovirus infections (chikungunya (CHIKV) and dengue (DENV)) in Gabon since 2007, we conducted a retrospective study to detect other, related viruses. In samples collected during the concurrent CHIKV/DENV outbreaks that occurred in the capital city in 2007, we detected ZIKV in both humans and mosquitoes, and notably the Asian mosquito Aedes albopictus that recently invaded the country and was the main vector responsible for these outbreaks. We found that the Gabonese ZIKV strain belonged to the African lineage, and phylogenetic analysis suggested ancestral diversification and spread rather than recent introduction. These findings, showing for the first time epidemic ZIKV activity in an urban environment in Central Africa and the presence of ZIKV in the invasive mosquito Aedes albopictus, raise the possibility of a new emerging threat to human health.

Malaria in pregnancy in rural Gabon: a cross-sectional survey on the impact of seasonality in high-risk groups

BACKGROUND

Malaria remains one of the most important infectious diseases in pregnancy in sub-Saharan Africa. Whereas seasonal malaria chemoprevention is advocated as public health intervention for children in certain areas of highly seasonal malaria transmission, the impact of seasonality on malaria in pregnancy has not yet been investigated for stable, hyper-endemic transmission settings of Equatorial Africa. The aim of this study was to investigate the influence of seasonality on the prevalence of malaria in pregnancy in Gabon.

METHODS

The study was conducted at a rural district hospital in Gabon between January 2008 and December 2011. At first antenatal care visits demographic data, parity, age, and gestational age of pregnant women were documented and thick blood smears were performed for the diagnosis of malaria. Seasonality and established risk factors were evaluated in univariate and multivariate analysis for their association with Plasmodium falciparum infection.

RESULTS

1,661 pregnant women were enrolled in this study. Participants presenting during high transmission seasons were at significantly higher risk for P. falciparum infection compared to low transmission seasons (adjusted odds ratio [AOR] 1.91, 95% confidence interval [CI] 1.39-2.63, p < 0.001). Established risk factors including parity (AOR 0.45, CI 0.30-0.69, p < 0.001 for multipara versus paucipara) and age (AOR, CI and p-value for women aged 13-17, 18-22, 23-27 and ≥ 28 years, respectively: AOR 0.59, CI 0.40-0.88; AOR 0.57, CI 0.34-0.97; AOR 0.51, CI 0.29-0.91) were significant risk factors for P. falciparum infection. High-risk groups including nulli- and primipara and younger women aged 13-17 years showed a disproportionately increased risk for malaria in high transmission seasons from 17% to 64% prevalence in low and high transmission periods, respectively.

CONCLUSION

Seasonal variations lead to important differences in the risk for P. falciparum infection in pregnancy in the setting of central African regions with stable and hyper-endemic malaria transmission. The seasonal increase in malaria in pregnancy is most pronounced in high-risk groups constituted by young and pauciparous women. The evaluation of tailored seasonal prevention strategies for these high-risk populations may, therefore, be warranted.

Childhood tuberculosis in Lambaréné, Gabon: tuberculosis control in its infancy?

Central Africa is a region highly affected by the tuberculosis (TB) pandemic; however, data on local epidemiology are scarce. In the quest for gearing up towards tailored interventions, assessment of local baseline situations is mandatory. We conducted a retrospective study of 62 children registered in the TB register of a hospital in Lambaréné, Gabon. The evaluation revealed a discrepancy between the TB burden and the commitment to control TB. Extrapolation of the incidence suggests an unexpectedly high childhood TB burden, assuming that the official overall TB incidence is an underestimate of the true TB burden in Gabon.

Mapping monkeypox transmission risk through time and space in the Congo Basin

Monkeypox is a major public health concern in the Congo Basin area, with changing patterns of human case occurrences reported in recent years. Whether this trend results from better surveillance and detection methods, reduced proportions of vaccinated vs. non-vaccinated human populations, or changing environmental conditions remains unclear. Our objective is to examine potential correlations between environment and transmission of monkeypox events in the Congo Basin. We created ecological niche models based on human cases reported in the Congo Basin by the World Health Organization at the end of the smallpox eradication campaign, in relation to remotely-sensed Normalized Difference Vegetation Index datasets from the same time period. These models predicted independent spatial subsets of monkeypox occurrences with high confidence; models were then projected onto parallel environmental datasets for the 2000s to create present-day monkeypox suitability maps. Recent trends in human monkeypox infection are associated with broad environmental changes across the Congo Basin. Our results demonstrate that ecological niche models provide useful tools for identification of areas suitable for transmission, even for poorly-known diseases like monkeypox.

Is there a suburban sleeping sickness in Libreville?

BACKGROUND

The transmission of sleeping sickness occurs primarily in rural areas, and exposed populations are those living from rural activities such as agriculture, fishing, animal husbandry or hunting. However, urban and suburban foci are more and more reported in T. b. gambiense areas. In Libreville town, sleeping sickness cases are regularly diagnosed. In order to investigate about the establishment of a transmission cycle of that disease, we have carried out an entomological survey in two quarters in the vicinity of the town.

METHODS

Vavoua traps were set out in all suitable biotopes for tsetse flies during four days and examined twice a day. Flies were collected, identified and dissected.

RESULTS

Two species of Glossina were caught: G. palpalis palpalis (90.58%) and G. caliginea (9.42%). A total infection rate of 9.37% was observed after dissection of all non-teneral flies captured.

CONCLUSION

These results suggest the establishment of a trypanosomiasis transmission cycle in the area. No salivary gland was found infected. Given that infected persons are regularly detected, we can think about the existence of a suburban sleeping sickness focus in Libreville. More analysis is needed concerning the identification of human trypanosomes and the origin of Glossina blood meals that may confirm the existence of that focus.

Anopheles moucheti and Anopheles vinckei are candidate vectors of ape Plasmodium parasites, including Plasmodium praefalciparum in Gabon

During the last four years, knowledge about the diversity of Plasmodium species in African great apes has considerably increased. Several new species were described in chimpanzees and gorillas, and some species that were previously considered as strictly of human interest were found to be infecting African apes. The description in gorillas of P. praefalciparum, the closest relative of P. falciparum which is the main malignant agent of human malaria, definitively changed the way we understand the evolution and origin of P. falciparum. This parasite is now considered to have appeared recently, following a cross-species transfer from gorillas to humans. However, the Plasmodium vector mosquito species that have served as bridge between these two host species remain unknown. In order to identify the vectors that ensure ape Plasmodium transmission and evaluate the risk of transfer of these parasites to humans, we carried out a field study in Gabon to capture Anopheles in areas where wild and semi-wild ape populations live. We collected 1070 Anopheles females belonging to 15 species, among which An. carnevalei, An. moucheti and An. marshallii were the most common species. Using mtDNA-based PCR tools, we discovered that An. moucheti, a major human malaria vector in Central Africa, could also ensure the natural transmission of P. praefalciparum among great apes. We also showed that, together with An. vinckei, An. moucheti was infected with P. vivax-like parasites. An. moucheti constitutes, therefore, a major candidate for the transfer of Plasmodium parasites from apes to humans.

Phylogeography, risk factors and genetic history of hepatitis C virus in Gabon, central Africa

BACKGROUND

The epidemiological and molecular characteristics of hepatitis C virus (HCV) infection in the general population have been poorly investigated in Africa. The aim of this study was to determine the prevalence, genotype distribution and epidemic history of HCV in the Gabonese general population.

METHODS/PRINCIPAL FINDINGS

A total of 4042 sera collected from adults in 220 villages in all nine administrative areas of the country were screened for antibodies to HCV. HCV NS5B region sequencing was performed for molecular characterization and population genetic analyses. Of 4042 tested sera, 455 (11.2%) were positive. The seroprevalence of HCV varied significantly by administrative area, with the highest rate in Ogooué-Lolo province (20.4%) and the lowest in Ogooué-Maritine province (3.7%). History of parenteral injections, past hospital admission and age over 55 years were independent risk factors for HCV infection (p<0.0001). Phylogenetic analyses showed that 91.9% of the strains were genotype 4 (HCV-4), 5.7% genotype 1 and 2.2% genotype 2. HCV-4 strains were highly heterogeneous, with more than eight subtypes; subtype 4e predominated (57.3%). Coalescence analyses indicated that subtype 4e was the oldest, with an estimated most recent common ancestor of 1702 [95% CI, 1418-1884]. The epidemic profile indicated that it spread exponentially during the first part of the 20th century, probably by iatrogenic transmission.

CONCLUSIONS/SIGNIFICANCE

These results confirm the endemicity of HCV subtype 4e in Gabon and show that its spread is due to a cohort effect, with previous, possibly iatrogenic events. More extensive epidemiological studies are needed to better characterize the route of transmission and the dissemination of HCV in Gabon.

[Epidemiological and diagnostic featurers of colorectal cancer in Libreville, Gabon]

OBJECTIVE

The purpose of this study was to determine the epidemiological profile of colorectal cancer in Gabon and to describe its clinical and laboratory features.

MATERIAL AND METHODS

This retrospective monocentric descriptive study was based on all cases of colorectal cancers managed at the Libreville Hospital Center during the 10-year period from September 1996 to September 2006. Study endpoints included epidemiological characteristics, anatomoclinical forms and diagnostic methods.

RESULTS

A total of 51 cases were included. Mean patient age at time of diagnosis was 48 years. The sex ratio was 1.3 with a female predominance. Mean duration of symptoms ranged from 6 months to 1 year. Abdominal pain and digestive disturbances were the most common manifestations. Lower digestive-tract endoscopy was performed in 49 patients. The tumor was located at rectosigmoid junction in 80% of cases. Lieberkühnian adenocarcinoma accounted for 98% of cases.

CONCLUSION

Initially described in industrialized countries, colorectal cancer is now being reported in developing regions, even though data from the literature and Gabonese cancers register (1984-93) indicate otherwise. It often involves young adults. The rectum was the most frequent site in this study. Delayed diagnosis is the main reason for poor prognosis. Education to improve awareness of early clinical signs as well improvement of diagnostic facilities should allow early detection and better prognosis of colorectal cancer in Africa.

Epidemiology of concomitant infection due to Loa loa and Mansonella perstans in Gabon

BACKGROUND

The filarial parasites Loa loa and Mansonnella perstans are endemic in the central and western African forest block. Loa loa is pathogenic and represents a major obstacle to the control of co-endemic filariae because its treatment can cause fatal complications such as encephalitis.

METHODOLOGY/PRINCIPAL FINDINGS

4392 individuals aged over 15 years were studied both by direct examination and a concentration technique. The overall prevalence rates were 22.4% for Loa loa microfilaremia, 10.2% for M. perstans microfilaremia, and 3.2% for mixed infection. The prevalence of both filariae was higher in the forest ecosystem than in savannah and lakeland (p<0.0001). The intensity of microfilariae (mf) was also higher in the forest ecosystem for both parasites. The prevalence and intensity of microfilaria were both influenced by age and gender. Correlations were found between the prevalence and intensity of Loa loa microfilariae (r = 0.215 p = 0.036), and between the prevalence of Loa loa and the prevalence of individuals with microfilaria >8000 mf/ml (r = 0.624; p<0.0001) and microfilariae >30 000 mf/ml (r = 0.319, p = 0.002). In contrast, the prevalence of pruritis and Calabar swellings correlated negatively with the prevalence of Loa loa microfilaria (r = -0.219, p = 0.032; r = -0.220; p = 0.031, respectively). Pruritis, Calabar swellings and eye worm were not associated with L. loa mf intensity (r = -0.144, p = 0.162; r-0.061, p = 0.558; and r = 0.051, p = 0.624, respectively), or with the prevalence or intensity of M. perstans microfilariae.

CONCLUSIONS/SIGNIFICANCE

This map of the distribution of filariae in Gabon should prove helpful for control programs. Our findings confirm the spatial uniformity of the relationship between parasitological indices. Clinical manifestations point to a relationship between filariae and allergy.

[Abdominal pregnancy in Libreville from 1999 to 2009]

INTRODUCTION

Abdominal pregnancy (AP) is defined as the implantation and development of the fertilised egg in the cavity of peritoneum. It causes severe perinatal morbity and mortality.

OBJECTIVE

Underline the epidemiologic, diagnostic, therapeutic and prognostic aspects of the AP.

METHODOLOGY

Retrospective study conducted at Maternité Joséphine Bongo (maternity hospital) and at the Centre Hospitalier de Libreville (hospital centre) from January 1999 to December 2009 on 19 cases of abdominal pregnancies.

RESULTS

The frequency of AP in Libreville is one per 4447 deliveries (0.2 ‰) and one per 141 tubal ectopic pregnancies (0.7%). The mean age was 30.5 ± 7.2 years old and the mean parity 2.7 ± 1.7. The mean term of occurrence was 24.3 weeks of amenorrhoea (WA) with extremes at 14 and 39 WA. The diagnosis was made in the face of abdominal and pelvic pains in all the patients and an amenorrhoea in 11 cases (57%). It was confirmed by ultrasound scan in 14 cases (73.7%) and further to a laparotomy in five (26.3%) patients. We had two live births at 39 and 38 WA with respective birth weights of 2,380 and 2,550 g. Expulsion of the placenta was complete in seven (36.8%) cases. Five (26.3%) patients experienced hemorrhagic complications.

CONCLUSION

AP is a rare pathology. Its diagnosis beyond of the second quarter is difficult with an often-pejorative foetal forecast.

[Clinical and radiological features of tuberculosis during HIV infection in Libreville, Gabon]

OBJECTIVE

The purpose of this report is to describe the clinical and radiological features of tuberculosis during HIV infection.

MATERIALS AND METHODS

This retrospective comparative study was based on review of patients treated between 2006 and 2010 in the Department of Medicine of the Military Hospital in Libreville, Gabon. A total of 156 patients with all types of tuberculosis were included, i.e., a study group of 78 tuberculosis patients co-infected with HIV and a control group of 78 seronegative tuberculosis patients. Analysis was carried out on demographic, clinical and radiological data. RESULTS. Most patients in both groups were male. Mean patient age was 37.1 +/- 10.3 in the seropositive group and 29.5 +/- 11.5 in the seronegative group. Deterioration in general health was quantitatively higher in the seropositive group. Tuberculosis was confined to the lungs in 41% of patients co-infected with HIV and 55% of seronegative patients. Chest x-rays showed more extensive cavitation in seronegative patients. Mixed pulmonary and extrapulmonary disease was observed in 20.5% of seropositive patients and 10.3% of seronegative patients. The CD4 lymphocyte rate was not statistically different between patients with pulmonary versus extrapulmonary tuberculosis. CONCLUSION. Tuberculosis during HIV infection often has an atypical or banal clinical presentation. Radiological findings may be non-distinctive or even normal. For this reason, diagnosis of tuberculosis may be difficult.

[Ebola and Marburg hemorrhagic fever viruses: update on filoviruses]

The Ebola and Marburg viruses are the sole members of the Filoviridae family of viruses. They are characterized by a long filamentous form that is unique in the viral world. Filoviruses are among the most virulent pathogens currently known to infect humans. They cause fulminating disease characterized by acute fever followed by generalized hemorrhagic syndrome that is associated with 90% mortality in the most severe forms. Epidemic outbreaks of Marburg and Ebola viruses have taken a heavy toll on human life in Central Africa and devastated large ape populations in Gabon and Republic of Congo. Since their discovery in 1967 (Marburg) and 1976 (Ebola), more than 2,300 cases and 1,670 deaths have been reported. These numbers pale in comparison with the burden caused by malnutrition or other infectious disease scourges in Africa such as malaria, cholera, AIDS, dengue or tuberculosis. However, due to their extremely high lethality, association with multifocal hemorrhaging and specificity to the African continent, these hemorrhagic fever viruses have given rise to great interest on the part not only of the international scientific community but also of the general public because of their perceived potential as biological weapons. Much research has been performed on these viruses and major progress has been made in knowledge of their ecology, epidemiology and physiopathology and in development of vaccine candidates and therapeutic schemes. The purpose of this review is to present the main developments in these particular fields in the last decade.

High prevalence of the amphibian chytrid pathogen in Gabon

Amphibian chytridiomycosis is an infectious disease caused by the fungus Batrachochytrium dendrobatidis (Bd) that is implicated in the worldwide decline and extinction of amphibians. Africa has been proposed as a potential source for the global expansion of Bd, yet the distribution of Bd across the continent remains largely unexplored. Using quantitative polymerase chain reaction (qPCR), we screened for the presence of Bd in 166 adult anurans from two national parks in Gabon (Monts de Cristal and Ivindo). Bd was detected in 20 of the 42 species and was present at all three sites surveyed (two in Monts de Cristal, and one in Ivindo) with high prevalence (19.6%-36.0%). Both national parks were Bd-positive at all elevations and across habitat types, though no dead or dying frogs were encountered. To our knowledge, this study presents the first evidence of Bd in Gabon and the first record of infection for 19 of the 20 species that were Bd-positive. Documenting the distribution and virulence of Bd across Africa will be essential for understanding the dynamics of amphibian chytridiomycosis across the globe.

Entomological patterns in the human African trypanosomiasis focus of Komo Mondah, Gabon

BACKGROUND

The incidence of sleeping sickness is still considerable in the Komo Mondah focus, in spite of case-detection strategy. A combined strategy that associated both mass screening and vector control is effective for the control of the disease. In the perspective of a targeted vector control in main transmission sites, we have carried out an entomological survey in the epicentre of the focus.

OBJECTIVES

To determine tsetse flies distribution, human-fly contact point and eventually risk factors for acquisition of the disease.

METHODS

"Vavoua" traps were set for Glossina in four biotopes selected after an interview of HAT patients concerning their working places. Tsetse were captured and dissected. DNA from organs was analysed by PCR for trypanosome infections. The origin of blood meals was determined by ELISA.

RESULTS

The focus is infested by three species of Glossina: G. palpalis palpalis (1149: 91.85%) found in all biotopes; G. fuscipes fuscipes (85: 6.79%) and G. caliginea (17: 1.36%) found in water spots and landing stages. They are infected by three subgenera of trypanosomes and only G. palpalis palpalis is infected by human trypanosomes. G. fuscipes fuscipes is infected by T. brucei sl and G. caliginea is not infected. Flies are absent at the periphery of houses except in one village. Only 29.20% of blood meals were from humans. Landing stages built in swamp mangrove are presenting the higher index of epidemiological risk and populations are exposed to the disease when they go to the area for taking their fishing boats.

CONCLUSION

Swamp mangrove would be targeted in priority during a vector control campaign.

Human fatal zaire ebola virus infection is associated with an aberrant innate immunity and with massive lymphocyte apoptosis

BACKGROUND

Ebolavirus species Zaire (ZEBOV) causes highly lethal hemorrhagic fever, resulting in the death of 90% of patients within days. Most information on immune responses to ZEBOV comes from in vitro studies and animal models. The paucity of data on human immune responses to this virus is mainly due to the fact that most outbreaks occur in remote areas. Published studies in this setting, based on small numbers of samples and limited panels of immunological markers, have given somewhat different results.

METHODOLOGY/PRINCIPAL FINDINGS

Here, we studied a unique collection of 56 blood samples from 42 nonsurvivors and 14 survivors, obtained during the five outbreaks that occurred between 1996 and 2003 in Gabon and Republic of Congo. Using Luminex technology, we assayed 50 cytokines in all 56 samples and performed phenotypic analyses by flow cytometry. We found that fatal outcome was associated with hypersecretion of numerous proinflammatory cytokines (IL-1β, IL-1RA, IL-6, IL-8, IL-15 and IL-16), chemokines and growth factors (MIP-1α, MIP-1β, MCP-1, M-CSF, MIF, IP-10, GRO-α and eotaxin). Interestingly, no increase of IFNα2 was detected in patients. Furthermore, nonsurvivors were also characterized by very low levels of circulating cytokines produced by T lymphocytes (IL-2, IL-3, IL-4, IL-5, IL-9, IL-13) and by a significant drop of CD3+CD4+ and CD3+CD8+ peripheral cells as well as a high increase in CD95 expression on T lymphocytes.

CONCLUSIONS/SIGNIFICANCE

This work, the largest study to be conducted to date in humans, showed that fatal outcome is associated with aberrant innate immune responses and with global suppression of adaptive immunity. The innate immune reaction was characterized by a "cytokine storm," with hypersecretion of numerous proinflammatory cytokines, chemokines and growth factors, and by the noteworthy absence of antiviral IFNα2. Immunosuppression was characterized by very low levels of circulating cytokines produced by T lymphocytes and by massive loss of peripheral CD4 and CD8 lymphocytes, probably through Fas/FasL-mediated apoptosis.

[Lupus, corticosteroid treatment and opportunistic infection: 26 cases in Gabon]

Opportunistic infection is frequent in lupus patients. Susceptibility is inherent in the lymphopeniant nature of the disease and enhanced by the use of immune-suppressing agents (alone or in combination) for optimal disease control. The purpose of this retrospective series of lupus patients diagnosed based on the criteria of the American College of Rheumatology (ACR) was to assess the frequency of opportunistic infection in a high-risk epidemiological area. A total of 26 patients (24 women, 2 men) with a mean age of 28.8 years were identified. Systematic review carried infectious before the steroid and in light of the local endemicity (HBs Ag, hepatitis C serology, HIV + Rx Thorax IDR) coupled with blood cultures was non-contributory, without waking the tank or during the introduction treatment. With a mean follow-up of 3.6 years (range, 0.83 to 9.91), only one case of tuberculosis was observed with fatal outcome. Our study indicates that the prevalence of opportunistic infections in the Lupus under treatment in a high-risk area for infectious diseases was low. This finding suggests that the risk of infectious complications secondary to corticosteroid therapy in sub-Saharan zone is acceptable provided that surveillance is performed on a regular basis.

High prevalence of both humoral and cellular immunity to Zaire ebolavirus among rural populations in Gabon

To better understand Zaire ebolavirus (ZEBOV) circulation and transmission to humans, we conducted a large serological survey of rural populations in Gabon, a country characterized by both epidemic and non epidemic regions. The survey lasted three years and covered 4,349 individuals from 220 randomly selected villages, representing 10.7% of all villages in Gabon. Using a sensitive and specific ELISA method, we found a ZEBOV-specific IgG seroprevalence of 15.3% overall, the highest ever reported. The seroprevalence rate was significantly higher in forested areas (19.4%) than in other ecosystems, namely grassland (12.4%), savannah (10.5%), and lakeland (2.7%). No other risk factors for seropositivity were found. The specificity of anti-ZEBOV IgG was confirmed by Western blot in 138 individuals, and CD8 T cells from seven IgG+ individuals were shown to produce IFN-gamma after ZEBOV stimulation. Together, these findings show that a large fraction of the human population living in forested areas of Gabon has both humoral and cellular immunity to ZEBOV. In the absence of identified risk factors, the high prevalence of "immune" persons suggests a common source of human exposure such as fruits contaminated by bat saliva. These findings provide significant new insights into ZEBOV circulation and human exposure, and raise important questions as to the human pathogenicity of ZEBOV and the existence of natural protective immunization.

[Intermittent claudication: sign of epidemiological transition in Gabon]

Africa is in the midst of an epidemiological transition characterized by an increase in degenerative illnesses, in particular cardiovascular disease, and a decrease in infectious illnesses. In this context it is of critical importance to develop simple and effective low-cost tools to identify subjects at high risk for cardiovascular events. Screening for subclavian artery stenosis (SAS) could provide a useful risk indicator. The prevalence of SAS in the general population over the age of 40 years in Gabon is 5.1 %, which is close to prevalence values observed in industrialized countries. Presence of SAS has been associated with hypertension (OR: 5.79, 95% CI: 2.21-15.2; p < 0.05) and male gender (OR 2.34, 95% CI: 1.13-4.83; p < 0.05). These data confirm the epidemiological shift towards cardiovascular diseases and suggest that screening for SAS could be useful to identify subjects at high risk for cardiovascular events who could benefit from preventive strategies.

[Prevalence of illegal abortions in Libreville Hospital, Gabon]

The objectives of this study were to determine the prevalence of illegal abortion in Libreville and to describe abortive methods used. It is a cross sectional and descriptive survey carried out at the maternity hospital of Libreville (MHL) during one year, from 1 January 2008 to 31 December 2008. 750 abortions were performed during this period and 651 cases were illegal abortions. Prevalence was of 86.7%. The women undergoing illegal abortion were most often pupils (67.1%), with an average age of 22.4 +/- 5.3 years old and a mean parity of 1.2 +/- 1.50. The average gestational term was of 7.4 +/- 1.9 weeks. Misoprostol (63.1%) was the most frequent abortive product used. 2 maternal deaths were notified. Prevalence of illegal abortions is increasing at the MHL. Up to now, misoprostol is the most frequent abortive product used.

Aedes albopictus mosquito: the main vector of the 2007 Chikungunya outbreak in Gabon

The primary vector at the origin of the 2007 outbreak in Libreville, Gabon is identified as Aedes albopictus, trapped around the nearby French military camp. The Chikungunya virus was isolated from mosquitoes and found to be identical to the A226V circulating human strain. This is the first field study showing the role of the recently arrived species Aedes albopictus in Chikungunya virus transmission in Central Africa, and it demonstrates this species' role in modifying the epidemiological presentation of Chikungunya in Gabon.

[Maternal mortality in Libreville, Gabon: assessment and challenges]

OBJECTIVE

To analyze the course over time of the rates and causes of maternal mortality in Libreville, Gabon.

MATERIAL AND METHODS

This prospective descriptive study covers the 6-year period from January 1, 2001, to December 31, 2006. It was performed at the Libreville Hospital Center (LCH) maternity ward, the leading obstetrical care facility in the country. A maternal mortality registry began recording deaths on January 1, 2001. All maternal deaths are listed there, and a department meeting focusing on the death is organized after each. In this study, we analysed the epidemiologic characteristics, circumstances and cause of each death.

RESULTS

In all, 136 women died. Their mean age was 25 +/- 5 years with a range of 16 to 41 years. Mean parity was 4 +/- 3, and ranged from 1 to 7. Most of the women were not employed (86%), but had at least some secondary schooling (88%). There were 126 cases (93%) of intrapartum deaths. They occurred more often at night (72% versus 28% during the day) and during the week (77% versus 23% on weekends). The maternal mortality rate was cut in half between 2000 and 2006 (p<0.005), dropping from 444 to 248 per 100 000 live births. Hemorrhages and eclampsia were the two principal causes of mortality.

CONCLUSION

Faster access to care and improvement in the quality of emergency obstetrical care are essential conditions for reducing maternal mortality.

Community-acquired pneumonia in children in Lambarene, Gabon

Community-acquired pneumonia (CAP) accounts for more than two million deaths per year in children < 5 years of age. Recognition of pathogens is vital for guiding antibiotic treatment. In Gabon, no epidemiologic data on childhood CAP were available to help guide antibiotic therapy. We conducted a prospective, hospital-based, cross-sectional survey at the Albert Schweitzer Hospital, Lambarene, Gabon, to assess the importance of atypical organisms (Chlamydia pneumoniae, Mycoplasma pneumoniae, Bordetella pertussis, and Legionella pneumophila) and Streptococcus pneumoniae in the etiology of CAP in children by means of real-time polymerase chain reaction, cell culture, and serology. Collectively, atypical bacteria accounted for 11% of cases with a special emphasis on B. pertussis, accounting for 6% of cases. Clinical differentiation of atypical from typical pneumonia in children remains challenging. Molecular diagnostic methods offer fast and highly sensitive diagnostic tools and would be able to help guide antimicrobial therapy in rural areas where follow-up is difficult.