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M Boussinesq

Publications and source records attributed to M Boussinesq.

At least 19 recordsLinked to original sources
PubMed1999

Population biology of human onchocerciasis.

Human onchocerciasis (river blindness) is the filarial infection caused by Onchocerca volvulus and transmitted among people through the bites of the Simulium vector. Some 86 million people around the world are at risk of acquiring the nematode, with 18 million people infected and 600,000 visually impaired, half of them partially or totally blind. 99% of cases occur in tropical Africa; scattered foci exist in Latin America. Until recently control programmes, in operation since 1975, have consisted of antivectorial measures. With the introduction of ivermectin in 1988, safe and effective chemotherapy is now available. With the original Onchocerciasis Control Programme of West Africa coming to an end, both the new African Programme for Onchocerciasis Control and the Onchocerciasis Elimination Programme for the Americas, rely heavily on ivermectin self-sustained mass delivery. In consequence, the need for understanding the processes regulating parasite abundance in human and simuliid populations is of utmost importance. We present a simple mathematical framework built around recent analyses of exposure- and density-dependent processes operating, respectively, within the human and vector hosts. An expression for the basic reproductive ratio, R0, is derived and related to the minimum vector density required for parasite persistence in localities of West Africa in general and northern Cameroon in particular. Model outputs suggest that constraints acting against parasite establishment in both humans and vectors are necessary to reproduce field observations, but those in humans may not fully protect against reinfection. Analyses of host age-profiles of infection prevalence, intensity, and aggregation for increasing levels of endemicity and intensity of transmission in the Vina valley of northern Cameroon are in agreement with these results and discussed in light of novel work on onchocerciasis immunology.

Adolescent↗
PubMed1999

[The effect of ivermectin on the longevity of Simulium damnosum].

Studies on various blood-sucking arthropods have shown an increased mortality after feeding on hosts previously treated with ivermectin. We investigated in Cameroon the survival of blackflies (Simulium damnosum s.s. and S. sirbanum) fed on patients who had been treated at a dose of 150 micrograms/kg 3-13 days before the blood meal. The mortality rates were not significantly reduced when compared with those of flies fed on untreated individuals.

Adult↗
PubMed1998

Three probable cases of Loa loa encephalopathy following ivermectin treatment for onchocerciasis.

Over the past nine years, more than 12 million people exposed to Onchocerca volvulus infection have received at least one dose of ivermectin, almost all without serious adverse reactions. Since 1991, however, several cases with neurologic manifestations, including coma, have been reported after ivermectin treatment of persons infected with O. volvulus who also had concomitant Loa loa infection with very high microfilaremia (> 50,000 microfilariae/ml of blood). In 1995, four criteria were established to define probable cases of Loa encephalopathy temporally related to treatment with ivermectin (PLERI). The present paper describes three PLERI cases recorded in Cameroon and compares them with two others reported previously. Disorders of consciousness began 3-4 days after treatment. The objective neurologic signs were variable. The conditions improved favorably in three patients who benefited from early hospitalization and good nursing; their disorders of consciousness lasted only 2-3 days; the results of clinical examination became normal after one month and electroencephalographic abnormalities disappeared after 5-7 months. Conversely, late diagnosis and delay in proper management in two others probably led to worsening of the condition and to fatal outcome related to the usual complications of coma. In addition to these cases, patients w with high Loa microfilaremia also developed milder neurologic manifestations causing functional impairment lasting for at least one week after treatment. Before launching mass ivermectin distribution programs to control onchocerciasis in central Africa, communities in which the intensity of concomitant L. loa microfilaremia is high need to be identified, and specific educational measures and monitoring strategies should be developed and applied before they are treated.

Adolescent↗
PubMed1998

A cocktail of recombinant Onchocerca volvulus antigens for serologic diagnosis with the potential to predict the endemicity of onchocerciasis infection.

We report here the evaluation of the potential of a serologic test to determine the endemicity of onchocercal infection in hyper, meso, and hypoendemic communities by the detection of antibodies to a cocktail of recombinant antigens. Parasitologic parameters of infection prevalence and intensity were compared with serologic results. Infection prevalence by serology was consistently but not significantly higher than that defined by parasitology. Differences between the communities defined by microfilarial load (CMFL) and a measurement of Onchocerca volvulus-specific antibody levels (serologic index [SI]) were similar. When stratified by age, differences were more significant in the younger age groups. If a sentinel population of 5-15-year-old individuals was used to compare communities, all could be equally ranked by serologic and parasitologic parameters. The SI of the sentinel population gave a better distinction between each community than the SI of the whole and would be sufficiently sensitive to measure the changes in endemicity that would be required for onchocerciasis control programs.

Adolescent↗
PubMed1998

[The campaign against onchocerciasis in Africa: update].

Two methods are being used to control onchocerciasis. The first has a delayed effect and consists in reducing or interrupting transmission of Onchocerca volvulus by eradication of the vector at its most vulnerable developmental stage, i.e. the larval stage. The second method has more immediate effects and consists in mass treatment using ivermectin, the only widely available drug, to reduce the density of microfilariae (the pathogenic stage of the parasite) in the population. Both strategies have been implemented within the framework of two international programs: the Onchocerciasis Control Program (OCP) in West Africa, which started in 1974 and will continue until the end of 2002, and the African Program for Onchocerciasis Control (APOC), which was launched in 1995 and will last for 12 years. This article presents an overview of the efficacy of available control tools, as well as the objectives, strategies, organization, and results of the two ongoing control programs. Also dealt with are future perspectives of onchocerciasis control including monitoring techniques to maintain OCP gains, and research to develop new control tools and optimize the program efficacy.

Africa↗
PubMed1998

[Occurrence of onchocerciasis in subjects coming from non-endemic areas and migrating to a hyperendemic area].

The incidence of Onchocerca volvulus infection was measured from 1992-93 to 1995 in six villages of initially uninfected migrants who settled in 1991 in the Vina Valley (Cameroon), an area of ongoing transmission of onchocerciasis. The mean annual incidence (MAI) exceeded 20% in the three communities located in the first line, and fewer than 15 km from the hyperendemic areas of the Central African Republic. The MAI was lower than 16% in the second line communities. As these populations are particularly at risk of developing ocular complications from onchocerciasis, it is recommended that repeated ivermectin distributions be organized in the migrant villages of the Vina Valley.

Animals↗
PubMed1998

[Entomologic study on the transmission of onchocerciasis in a forest-savanna transition area of Cameroon].

An entomological study was conducted in the basin area of middle Sanaga (Cameroon) in order to document the pattern of onchocerciasis transmission in a region where a high prevalence of infection had been recorded in villages located 30 km from the main rivers. The main vector of O. volvulus was found to be S. squamosum s.s. No breeding site was found in the small tributaries of the Sanaga and Mbam Rivers, and the dispersal of S. damnosum s.l. in the area thus appeared to be particularly high. The highest blackfly population densities were recorded during the long rainy season, and a second peak of density occurred along the Mbam River during the short rainy season. A seasonal variation in dispersal patterns was found at three of the four transects studied. The transmission of Onchocerca volvulus in the area occurred principally between January and May (i.e. at the end of the long dry season and the beginning of the short rainy season). Vector control operations might well reinforce the effect of ivermectin distributions in this onchocerciasis focus.

Animals↗
PubMed1998

Geographical determinants of onchocerciasis transmission in a forest/savannah transition zone : two villages of the mbam focus

Mbam, a focus of onchocerciasis outbreaks, is located in the forest/savannah transition zone of Cameroon. Transmission of the disease in this area is similar to that sometimes observed in West Africa. Geographical factors affecting transmission must be identified to determine the areas for priority action. The locations of breeding sites for black flies (the vector of the disease) and factors favorable to their dispersion, the social behavior of these population and the way that she occupy space, must be investigated to identify areas in which the flies and man are in close contact. This geographical study shows that the closest contact between men and black flies occurs in cocoa plantations, due to the proximity of the breeding sites. The areas of closest contact for women and children are unknown, but their identification is important because women and children may be bitten by the flies during their daily activities.

Journal Article↗
PubMed1997

Onchocera volvulus: characterization of a highly immunogenic Gln-rich protein.

A pool of sera from individuals classified as putatively immune (PI) to Onchocerca volvulus infection was employed in the screening of a fourth-stage larval cDNA expression library. A highly immunogenic clone, encoding the Ov 53/80 protein, was identified. The full length cDNA of clone 4.21 contained 2527 nucleotides encoding 769 amino acids of which 100 are glutamine residues (13%). Antibodies raised against recombinant protein encoded by a partial cDNA sequence (clone 73-k) recognized a 53 and 80 kDa protein in O. volvulus larval and adult parasite extracts, respectively. The antibodies localized the native protein in the cuticle, hypodermis, secretory vesicles and in granules of the glandular esophagus of larvae and in the hypodermis and the cuticle of adult worms. The recombinant 73-k polypeptide (r73) was recognized by 90-100% of sera from PI and infected individuals from Liberia, but only by 67% of similar groups from Ecuador. r73 specific IgG2 and IgG3 levels in the PI from Liberia and Ecuador, respectively, were significantly lower than in the infected, whereas the r73 specific IgG1/IgG3 or IgG1/IgG2 in the PI and the infected individuals from Liberia or Ecuador, respectively, were similar. The IgG4 specific antibody response in the PI from Liberia and Ecuador were lower than in the infected. The T-cell proliferative responses to r73 in infected individuals from Cameroon were found to be inversely correlated with their levels of microfilariae.

Amino Acid Sequence↗
PubMed1997

Serious reactions after mass treatment of onchocerciasis with ivermectin in an area endemic for Loa loa infection.

BACKGROUND: In 1995, the World Bank launched an African Programme for Onchocerciasis Control to eliminate Onchocerca volvulus disease from 19 African countries by means of community-based ivermectin treatment (CBIT). Several cases of encephalopathy have been reported after ivermectin in people heavily infected with microfilariae of Loa loa (loiasis). We assessed the incidence of serious events in an area where onchocerciasis and loiasis are both endemic. METHODS: Ivermectin (at 150 micrograms/kg) was given to 17877 people living in the Lékié area of Cameroon. 50 microL samples of capillary blood were taken during the daytime before treatment from all adults (aged > or = 15 years), and the numbers of L loa and Mansonella perstans microfilariae in them were counted. Patients were monitored for 7 days after treatment. Adverse reactions were classified as mild, marked, or serious. Serious reactions were defined as those associated with a functional impairment that required at least a week of full-time assistance to undertake normal activities. We calculated the relative risk of developing marked or serious reactions for increasing L loa microfilarial loads. Risk factors for serious reactions were identified and assessed with a logistic regression model. FINDINGS: 20 patients (0-11%) developed serious reactions without neurological signs but associated with a functional impairment lasting more than a week. Two other patients were in coma for 2-3 days, associated with L loa microfilariae in cerebrospinal fluid. Occurrence of serious reactions was related to the intensity of pretreatment L loa microfilaraemia. The relative risk of developing marked or serious reactions was significantly higher when the L loa load exceeded 8000 microfilariae/mL; for serious reactions, the risk is very high (odds ratio > 1000) for loads above 50000 microfilariae/mL. INTERPRETATION: Epidemiological surveys aimed at assessing the intensity of infection with L loa microfilariae should be done before ivermectin is distributed for onchocerciasis control in areas where loiasis is endemic. In communities at risk, monitoring procedures should be established and adhered to during CBIT so that people developing serious reactions may receive appropriate treatment.

Adolescent↗
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↗
PubMed1997

Country-wide rapid epidemiological mapping of onchocerciasis (REMO) in Cameroon.

The prevalence of infection in local communities has been used as the basis for the country-wide repartition of onchocerciasis in Cameroon, following the principles for rapid epidemiological mapping of onchocerciasis (REMO) developed by the World Health Organization. The levels of endemicity were evaluated in 349 villages by rapid epidemiological assessment (REA), a method based on the examination of nodules in males aged > or = 20 years. An onchocerciasis map was then drawn from the epidemiological data which had been collected previously, from clinico-parasitological surveys based on the examination of skin snips, and the results of the REA surveys. The REMO surveys allowed the main onchocerciasis foci in Cameroon to be accurately delineated, and several small endemic areas which had never been reported before to be identified. The total 'at risk' population (i.e. those for which ivermectin treatment should be considered as urgent or highly desirable) was estimated by combining the epidemiological results and the demographical data available from an administrative census. Those at risk were estimated to number 3.5 million, representing about 50% of the total rural population in Cameroon.

Adult↗
PubMed1997

[Study of the distribution of human filariasis in West Province of Cameroon].

A clinical and parasitological survey of onchocerciasis and loiasis has been carried out in 38 communities in the West Province of Cameroon prior to the implementation of a mass ivermectin treatment. The highest endemicity levels of onchocerciasis were recorded in the villages located at an altitude below 1400 m, and whose inhabitants go down to the valleys for agricultural activities. Conversely, low endemicity levels were recorded in the most populated part of the study area, which is located at an altitude above 1400 m; in the latter communities, the residents cultivate the high ground not far from their houses and are thus less exposed to transmission of onchocerciasis. Despite relatively low microfilarial loads, the prevalences of nodules were fairly high; this demonstrates that in some epidemiological situations the latter indicator gives an erroneous indication of the intensity of infection in the population. The prevalence of loiasis is very low in most of the villages of the study area.

Agriculture↗
PubMed1997

[Human onchocerciasis in Africa].

Before the 1980s, the only available method for control of onchocerciasis was elimination of blackfly vector populations. This strategy was used with considerable success in the Onchocerciasis Control Programme in West Africa (OCP). The discovery of ivermectin, the first effective drug suitable for mass treatment of onchocerciasis, has revived international interest not only in fundamental research but also in development of new strategies to control onchocerciasis in the countries outside the OCP area. This report gives an overview of current parasitological, clinical, epidemiological and diagnostic data about onchocerciasis. Although little is known about the early development of Onchocerca volvulus in the human host, significant insight has been gained into the population dynamics of the parasite. The pathogenesis of cutaneous and ocular manifestations in onchocerciasis is now better understood. Epidemiological studies are under way to evaluate the extent of systemic manifestations. Recently developed diagnostic methods are more sensitive than conventional parasitological techniques. A new method for rapid assessment of endemic level has provided a detailed picture of the distribution of onchocerciasis. Species- and strain-specific DNA probes have been developed for identification of parasites in West Africa. New methods for quantifying disability allow evaluation of the socio-economic impact of the cutaneous and ocular complications of onchocerciasis.

Africa↗
PubMed1995

A new zoonosis of the cerebrospinal fluid of man probably caused by Meningonema peruzzii, a filaria of the central nervous system of Cercopithecidae.

A female fourth stage larva of Meningonema, probably of M. peruzzii Orihel et Esslinger, 1973, was recovered in Cameroon, from the cerebrospinal fluid of a patient harbouring Loa loa, but without any neurological signs. This observation is the first human case of Meningonema (Filarioidea Splendidofilariinae) which usually parasitizes the central nervous system of African Cercopithecinae. However, as indicated by Orihel and Esslinger, it seems probable that the perstans-like microfilariae described in cases of cerebral filariasis in Zimbabwe belonged to the same species.

Animals↗