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PubMedDate not supplied

[Historical aspects of the risk factors of Schistosoma intercalatum schistosomiasis].

Bilharziosis is a considerable public health problem. It is caused by many species of schistosoma, four of which have wide geographical distribution: Schistosoma mansoni, S. haematobium, S. japonicum and S. intercalatum. The recently discovered S. intercalatum is limited to central and west Africa. Its spread is progressive and its pathogenicity is not completely known. S. intercalatum bilharziosis is usually manifested in the form of dysentery. The physiopathologic explanation of this clinical manifestation is less clear. Immunopathologically, the formation of an inflammatory granuloma constitutes the origin of its symptoms. This is due to many biological factors including delayed hypersensitivity reactions. All cellular immunity changes will facilitate the appearance of symptoms. Our aim has been to show the importance of malnutrition as a pathogenic factor of S. intercalatum bilharziosis. The initial research hypothesis was as follows: malnutrition plays a role in the evolution of a patient from an asymptomatic state of infection to a symptomatic state of illness. We carried out the study in the suburbs of Bata, in Equatorial Guinea. The inhabitants of Ncolombong, essentially rural immigrants, comprised our study population. Following their consent, we recruited individuals less than 45 years of age who had not taken praziquantel during the last 12 months. We included a total of 297 patients. Our study was a case-control, matching on sex and age. A case was defined as an infected patient with acute or chronic diarrhea occurring within the last month' preceding the stool sample analysis. All cases were retained after exhaustive screening of the study population. Each case (group 1) was matched with one or several asymptomatic infected patients (group 2) and two or several asymptomatic noninfected patients chosen at random (group 3). The definition of malnutrition was as follows: weight/height < or = 90% for children less than 15 years of age or weight/height < or = 90% with a corporal mass index < or = 20 for children more than 15 years of age. Two logistical regression models were performed in order to distinguish pathogenic from infection factors. Among the confusion bias identified, none of the helminthiasis in Bata are risk factors. The risk factors of the infection have been searched with an interrogatory. The bias caused by the interviewer is minimized because all the team staff were trained for a week before the beginning of the study. Apart from malnutrition, the other causes of cellular immunodeficiency do not seem to have any relationship with the development of symptoms. The logistical model of infection identified the classical risk factors of infection: river leisures (OR = 3.97, CI 95%: 1.86-8.47), poor or average quality of walls of the house (OR = 2.53, CI 95%: 1.15-5.58), lack of water well (OR = 2.08, CI 95%: 1.08-4). Our study could not show any relationship between malnutrition and bilharziosis. The nutritional state does not play a significative role in the infection or development of the disease. Nevertheless, the nutritional state of the host probably influences other host or parasite factors. As a result, we still don't know its influence on ADCC (Antibody Dependent Cellular Mediated Cytotoxicity) mechanisms, on adult parasite adaptation and the efficiency of laying of eggs which affects the parasitological charge. We haven't found any relationship between parasitological load and appearance of symptoms. The parasitological load indirectly reflects the efficiency of the laying and nothing proves that it is correlated with the intensity of delayed type hypersensibility reactions. In the logistical model of the disease, a stay of more than 2 months in an endemic area (OR = 0.14, CI 95%: 0.03-0.76) and a poor or average quality of walls of the house decreased the risk (OR = 0.31, CI 95%: 0.11-0.85). This result permits us to suppose that there is a tolerance to schistosomian antigens by cellular immunity

Acute Disease↗
PubMed1993

Further data on the compatibility between Schistosoma intercalatum (lower Guinea strain) and Bulinus forskalii: epidemiological consequences.

A study of the compatibility between Schistosoma intercalatum from Cameroon and its potential vectors Bulinus forskalii from Cameroon, Equatorial Guinea, Ivory Coast and Niger has been carried out. As compatibility test, the snail infection test, completed by an histological study, was used. Snail infection experiments showed that all the populations of B. forskalii we tested are very good potential vectors, with infection rates ranging between 76.5 and 93%. The histological study revealed no defense reaction in the snails, which confirms the perfect compatibility of the B. forskalii populations we studied. In an epidemiological perspective, this study confirms the ever present risk of extension of S. intercalatum parasitosis in Africa.

Animals↗
PubMed1996

HIV-1 subtype O: epidemiology, pathogenesis, diagnosis, and perspectives of the evolution of HIV.

HIV-1 subtype O is a new HIV variant originating in the West-Central African region, with highest prevalences in countries such as Cameroon, Equatorial Guinea and Gabon. Detection of antibodies to HIV-1 subtype O can pose problems in unmodified ELISA tests, and confirmation of anti-HIV-1 subtype O in immunoblot may give false negative results in some specimens. Nucleic acid-based assays designed for HIV-1 detection do not amplify or detect sequences from HIV-1 subtype O. In their env sequences, HIV-1 subtype O strains show a higher heterogeneity than the classical HIV-1 subtypes, leading to the conclusion that HIV-1 subtype O has been introduced into the human population only recently. Further, unidentified subtypes are also likely to exist.

Acquired Immunodeficiency Syndrome↗
PubMed1993

Detection of genetic diversity within snail intermediate hosts of the genus Bulinus by using random amplified polymorphic DNA markers (RAPDs).

A polymerase chain reaction-based polymorphic assay procedure (RAPD) was used to study the genetic diversity of intermediate host snails within the genus Bulinus. Genetic differentiation was detected between two closely related species: Bulinus globosus and Bulinus umbilicatus. Evidence is presented demonstrating the potential of RAPD markers for differentiating populations of B. forskalii from different countries (Cameroon, Equatorial Guinea and Ivory Coast) or from the same country (Cameroon). RAPDs may be also used to identify offspring from cross- and self-fertilized hermaphrodite bulinid snails. RAPDs provide a cost-effective and routine method for genetic studies of snails transmitting schistosomiasis and for the evaluation of diversity between snail populations.

Animals↗
PubMed1986

An outbreak of Plasmodium vivax malaria among heroin users in Spain.

We report the first outbreak of induced malaria among heroin users in Spain, and the first one caused by Plasmodium vivax in Europe. Five drug addicts from Madrid, who had never travelled to endemic areas, were admitted to hospital with fever and splenomegaly. Four had P. vivax malaria with low parasitaemia, ranging from 1 to 3% red blood cells. The fifth case was considered a "seropositive contact" because he had fever and positive malaria indirect fluorescent antibody test but negative blood smear. The source of infection was a young drug addict, who had often travelled to Equatorial Guinea. Another heroin user with a diagnosis of malaria refused to be admitted to our hospital for further study. All had shared contaminated injection equipment. Treatment with chloroquine was effective and none had recrudescence of malaria during a mean follow-up of six months. Drug addicts with unexplained fever may have been infected by malaria transmitted by sharing injections.

Adolescent↗
PubMedDate not supplied

Quantitative determination of circulating anodic and cathodic antigens in serum and urine of individuals infected with Schistosoma intercalatum.

Circulating anodic and cathodic Schistosoma antigens (CAA and CCA) have been determined by enzyme immunoassays in serum and urine of 60 individuals infected with S. intercalatum in Equatorial Guinea. The median egg output was 29 eggs/g of faeces (range 3-840). The egg output strongly correlated with concentrations of serum CAA (p = 0.47) and urine CAA (p = 0.42) (P < 0.001 for both); the later 2 quantities were also correlated with each other (p = 0.44, P < 0.001). All except 3 infected individuals had detectable amounts of serum CAA and/or urine CCA, a sensitivity of 95% for these 2 tests combined. Urine CAA was detected in 43% of patients. Serum CCA was detected in all infected individuals; however, no significant correlation was obtained between serum CCA levels and egg output in the stools of individual patients. This is the first study to demonstrate CCA in specimens of patients infected with S. intercalatum. The detection of CCA in urine is a new, non-invasive diagnostic method for S. intercalatum infection.

Adolescent↗
PubMed2003

The African cherry (Prunus africana): can lessons be learned from an over-exploited medicinal tree?

For the last 35 years, the African cherry (Prunus africana (Hook. f.) Kalm.) has been used in the treatment of benign prostatic hyperplasia and other disorders. The bark, from which the treatment is derived, is entirely wild-collected. The major exporters of bark include Cameroon, Madagascar, Equatorial Guinea, and Kenya. Groupe Fournier of France and Indena of Italy produce 86% of the world's bark extract, both for their own products and for the free market. Worldwide exports of dried bark in 2000 have been estimated at 1350-1525 metric tons per year, down from its peak of 3225 tons in 1997. Bark extracts (6370-7225 kg per year) are worth an estimated $4.36 million US dollars per year. In 2000, Plantecam, the largest bark exporter in Africa, closed its extraction factory in Cameroon, due to complex ecological, social, and economic factors. Wild-collection is no longer sustainable (and probably never was) where harvest seriously affects morbidity and mortality rates of harvested populations. Since 1995, it has been included in CITES Appendix II as an endangered species. In this paper, alternatives to wild-collection to meet future market demand are investigated, including conservation practices, enrichment plantings, small- and large-scale production, and protection of genetic resources. The species is at the beginning of a transition from an exclusively wild-collected species to that of a cultivated medicinal tree.

Africa↗
PubMed2005

Protective correlates against HIVs may have evolved in human populations in the areas of historic occurrence of primate-to-man transmissions of SIVs ancestral to HIVs: studies in these populations may provide crucial insights for treatment and prevention of HIV infection.

Recent findings suggest that Human Immunodeficiency Viruses, HIV-1 and 2, might have been transmitted to humans from particular primate species. It is thought that some Simian Immunodeficiency Viruses (SIVs), from which HIVs presumably originated, existed in their primate hosts for ages. Behavioral characteristics increasing the probability of contact between these primates and humans (such as keeping monkeys for pets, hunting monkeys for food, improper handling of the monkey meat, etc.) documented in some African countries could have facilitated cross-species transmissions (CSTs) of HIVs. As it has been shown, multiple CSTs took place for both HIVs (1 and 2) and then, in a globalizing world, these local events led to the pandemic. Here, it is brought forward that in the regions of epizooty of SIVs closely related to HIVs, some human populations might have had exposure history to these viruses dating back hundreds years. Lacking the important framework for further spread provided by nowadays globalization, these CSTs could have led to isolated local HIV outbreaks limited to particular tribes or groups. The infections could have extinguished some populations while on the other hand provided evolutionary pressure to select for mechanisms protective for HIV infection and/or disease. Thus, here it is hypothesized that in the areas of the habitat of primates infected with SIVs, from which HIVs are thought to be originated, there could be historically exposed populations which might possess biological correlates of protection from HIVs. Current knowledge on the distribution of primates hosting HIV-related SIVs suggests that epidemiological, primatological, anthropological and molecular biological studies in the areas of Cameroon, Gabon, both Congos and Equatorial Guinea (for HIV-1) and Guinea-Bissau, Senegal, Guinea, Ivory Cost, Sierra Leone and Liberia (for HIV-2) could lead to the discoveries of correlates of protection against HIVs. It is also hypothesized that virology studies in the same areas might reveal less virulent and/or infective viruses which could provide insights in the HIV pathogenesis and vaccinology.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

Antibody prevalence against haemorrhagic fever viruses in randomized representative Central African populations.

Between 1985 and 1987, 5,070 randomly selected persons living in 6 central African countries (Cameroon, Central African Republic, Chad, Congo, Equatorial Guinea and Gabon) were checked for serological evidence of haemorrhagic fever. Rural and urban areas were studied, including ecoclimatic zones ranging from dry savana to tropical rain forest. Virus-reactive antibodies were found with all antigens tested, and the global prevalence of positive sera was distributed as follows: Crimean-Congo haemorrhagic fever virus, 0.22%; Rift Valley fever virus, 0.18%; Ebola virus, 12.40%; Marburg virus, 0.39%; Lassa virus, 0.06%; and Hantaan virus, 6.15%. A significant variation in antibody prevalence was observed within the study regions. Association between the viruses was not observed.

Africa, Central↗
PubMed2003

Schistosoma intercalatum: an endangered species in Cameroon?

Despite the extremely wide distribution of both intermediate (snail) and definitive hosts, the species Schistosoma intercalatum has a highly restricted distribution in parts of West Africa (Cameroon, Equatorial Guinea, Gabon, Nigeria, Democratic Republic of Congo and São Tomé). Recent studies showed that the epidemiology of this species is very dynamic, including invasions and extinctions. This article reviews the epidemiology of S. intercalatum in Cameroon, where the species is endangered, and analyses its overall status in Africa. The possible reasons for the limited distribution of S. intercalatum are discussed.

Animals↗
PubMed1997

Molecular population studies of Simulium damnosum s.l. (Diptera: Simuliidae) using a novel interspersed repetitive DNA marker.

Simulium damnosum s.l., the vector of West African onchocerciasis, has been the target of a major insect control initiative for the past 20 years. However, attempts to study the migration patterns of reinvading infective flies into controlled areas have been restricted by the lack of suitable genetic markers. Here, the results of the first population-level study of S. damnosum s.l. using a repetitive DNA marker, pSO11, are presented. Sequence analysis of pSO11 revealed a complex internal pattern of repetition and an open reading frame with 56.8 per cent similarity to a mouse retrotransposon protein. Combined with an interspersed genomic distribution, the internal structure of pSO11 suggested that it represents the 5' half of a transposable element. The genomic diversity of the sequence was analysed using Southern blot analysis of genomic DNA. Data were collected from 475 individuals from the island of Bioko (in Equatorial Guinea), Cameroon, Côte d'Ivoire and Sierra Leone. The results indicate that pSO11 is useful as an indicator of genomic diversity and that the experimental design used here permits comparison of an approximately random sample of chromosomal loci. Making this assumption, estimates of homozygosity based on pSO11 diversity were used to study inter- and intraspecific variability. The results indicate that pSO11 is potentially useful for studying population-level processes in S. damnosum s.l.

Animals↗
PubMed2001

Host specificity and incidence of Trypanosoma in some African rainforest birds: a molecular approach.

Studies of host-parasite interactions in birds have contributed greatly to our understanding of the evolution and ecology of disease. Here we employ molecular techniques to determine the incidence and study the host-specificity of parasitic trypanosomes in the African avifauna. We developed a polymerase chain reaction (PCR)-based diagnostic test that amplified the small subunit ribosomal RNA gene (SSU rRNA) of Trypanosoma from avian blood samples. This nested PCR assay complements and corroborates information obtained by the traditional method of blood smear analysis. The test was used to describe the incidence of trypanosomes in 479 host individuals representing 71 rainforest bird species from Cameroon, the Ivory Coast and Equatorial Guinea. Forty-two (59%) of these potential host species harboured trypanosomes and 189 individuals (35%) were infected. To examine host and geographical specificity, we examined the morphology and sequenced a portion of the SSU rRNA gene from representative trypanosomes drawn from different hosts and collecting locations. In traditional blood smear analyses we identified two trypanosome morphospecies, T. avium and T. everetti. Our molecular and morphological results were congruent in that these two morphospecies had highly divergent SSU rRNA sequences, but the molecular assay also identified cryptic variation in T. avium, in which we found seven closely allied haplotypes. The pattern of sequence diversity within T. avium provides evidence for widespread trypanosome mixing across avian host taxa and across geographical locations. For example, T. avium lineages with identical haplotypes infected birds from different families, whereas single host species were infected by T. avium lineages with different haplotypes. Furthermore, some conspecific hosts from geographically distant sampling locations were infected with the same trypanosome lineage, but other individuals from those locations harboured different trypanosome lineages. This apparent lack of host or geographical specificity may have important consequences for the evolutionary and ecological interactions between parasitic trypanosomes and their avian hosts.

Africa↗
PubMed2001

Increased trypanolytic activity in sera of sleeping sickness patients after chemotherapy.

We tested sera from patients previously treated for human African trypanosomiasis, from patients infected with trypanosomes, and from individuals never diagnosed with African trypanosomiasis living in the Trypanosoma brucei gambiense sleeping sickness focus of Mbini in Equatorial Guinea for their trypanolytic activity against bloodstream forms of T. b. rhodesiense expressing a metacyclic and bloodstream variant surface glycoprotein (VSG). Nearly 80% of the sera from treated patients showed high trypanolytic activity against trypanosomes expressing a metacyclic VSG. The trypanolytic activity of part of these sera was mediated by IgM while that of the other part was antibody-independent. On the other hand, only 40% of the sera exhibited high trypanolytic activity against trypanosomes expressing a bloodstream VSG which also was almost completely abolished by heat-inactivation. In contrast, most sera from infected and negative individuals displayed only low to moderate trypanolytic activity against either trypanosomes expressing a metacyclic or a bloodstream VSG. These results suggest that trypanolytic activity of sera increases after African sleeping sickness and is directed against trypanosomes expressing metacyclic VSG.

Animals↗
PubMed2000

The use of PCR in the diagnosis of hyper-reactive malarial splenomegaly (HMS).

Between August 1997 and September 1998, 14 cases of hyper-reactive malarial splenomegaly (HMS) were diagnosed in the Instituto de Salud Carlos III in Madrid, Spain. These cases, from Equatorial Guinea and Cameroon, were identified using the diagnostic criteria established by Y. M. Fakunle in 1981: gross splenomegaly; high levels of anti-malarial antibodies; IgM in serum at least two standard deviations above the local mean; and clinical and immunological response to antimalarial treatment. Although malarial parasites were only detected in the Giemsa-stained blood films of four of the cases, these four and four others were found to have the DNA of such parasites in their blood when tested using a method based on a semi-nested, multiplex PCR. These result indicate that malarial parasitaemias may be more prevalent in HMS than is usually recognized.

Adult↗
PubMed1997

Prevalences of Loa loa microfilaraemia throughout the area endemic for the infection.

Several cases of encephalopathy recorded in Cameroon since 1991 were in patients with very high, coincident, Loa loa microfilaraemias who had been treated with ivermectin for onchocerciasis. There was thus an urgent need to identify those areas where loiasis is hyperendemic, and where specific monitoring procedures should be developed if large-scale ivermectin treatment of onchocerciasis is to be implemented. In the present review, the available data on Loa endemicity are detailed and maps showing the prevalence of Loa microfilaraemia throughout the area endemic for the infection are presented. By superimposing these maps on those which show where onchocerciasis is meso- or hyper-endemic, it is now possible to identify several areas, in south-eastern Nigeria, southern and central Cameroon, the south of the Central African Republic, Equatorial Guinea, Gabon, and the north and west of the Democratic Republic of the Congo (ex-Zaire), where ivermectin treatment, although indicated, is most likely to lead to adverse reactions because of L. loa infections. Additional surveys, to delineate the areas highly infected with L. loa more accurately, are required.

Adolescent↗
PubMed2002

Revisiting sub-Saharan African countries' drug problems: health, social, economic costs, and drug control policy.

This article takes an international perspective on the drug problem in sub-Saharan Africa. This analysis borrows ideas from physical and economic geography as a heuristic device to conceptualize the global narcoscapes in which drug trafficking occurs. Both the legitimate and the illegal drug trade operate within the same global capitalist system and draw on the same technological innovations and business processes. Central to the paper's argument is evidence that sub-Saharan African countries are now integrated into the political economy of drug consumption due to the spill-over effect. These countries are now minor markets for "hard drugs" as the result of the activities of organizations and individual traffickers that use Africa as a staging point in their trade with Europe and the United States. As a result, sub-Saharan African countries have drug consumption problems that were essentially absent prior to 1980, along with associated health, social, and economic costs. The emerging drug problem has forced African countries to develop their own drug control policy. The sub-Saharan African countries mentioned below vary to some extent in the level of drug use and misuse problems: Burundi, Comoros, Djibouti, Eritrea, Ethiopia, Kenya, Madagascar, Malawi, Mauritius, Mozambique, Reunion, Rwanda, Seychelles, Somalia, Tanzania, Uganda, Zambia, Angola, Cameroon, Central African Republic, Chad, Congo, Congo (Zaire), Equatorial Guinea, Gabon, Sao Tome and Principe, Botswana, Lesotho, Namibia, South Africa, Swaziland, Benin, Burkina Faso, Cape Verde, Cote d'Ivoire, Gambia, Ghana, Guinea, Guinea Bissau, Liberia, Mali, Mauritania, Niger, Nigeria, Senegal, Sierra Leone, and Togo. As part of this effort, African countries are assessing the health, social, and economic costs of drug-use-related problems to pinpoint methods which are both effective and inexpensive, since their budgets for social programs are severely constrained. Many have progressed to the point of adopting anti-drug laws or legislation, or of establishing a drug control agency. They are also cooperating regionally to coordinate drug control measures and working with the Organization of African Unity (OAU). In addition, almost all the sub-Saharan African countries are signatories to all United Nations drug conventions. Since the drug problem in Africa has international origins, it will take concerted international cooperation and coordinated effort to combat the "social cancer" of drugs.

Africa South of the Sahara↗
PubMed2002

Evaluation of HIV type 1 group O isolates: identification of five phylogenetic clusters.

HIV-1 group O strains have a level of genetic diversity similar to that of strains in group M; however, group O has not been readily classified into genetic subtypes. Phylogenetic classification of group O has been hindered by the limited sequence information available. To facilitate phylogenetic analysis, we sequenced the gag p24 (693 nt), pol p32 (864 nt), and env gp160 (approximately 2700 nt) genes from 39 group O-infected specimens. These specimens include 32 plasma samples collected in Cameroon between 1996 and 1999, 2 specimens collected in the United States, and 5 infections previously isolated in Equatorial Guinea. Phylogenetic analysis of HIV-1 group O sequences resulted in the identification of five clusters that are maintained across gag, pol, and env, generally supported by high bootstrap values, and approximately equidistant from each other. In addition to the group O clusters, several isolates branch independently and are equidistant from the other group O isolates. Cluster I comprises greater than 50% of the group O isolates and is a diverse set of isolates that is subdivided into subclusters. The average intra-, sub-, and intercluster distances for group O are similar to the corresponding distances for group M subtypes. The five group O clusters have characteristics similar to those of group M subtypes. Thus the data presented may form the basis for classification of group O into subtypes. However, full-length genomes representing each group O cluster will be required to formalize a group O subtype classification.

Amino Acid Sequence↗