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Biomedical subjects

M Boussinesq

Publications and source records attributed to M Boussinesq.

At least 37 records · Page 2Linked to original sources
PubMed2001

A controlled prospective trial of the prophylactic effect of a single dose of ivermectin against Onchocerca volvulus.

A clinical trial was conducted in Cameroon in order to evaluate in humans the possible effect of a single dose of ivermectin (150 micrograms per kg) on the pre-adult stages of Onchocerca volvulus. The incidence of the skin microfilariae was measured in two groups of patients who initially had negative biopsies, and who were subsequently treated, immediately after the seasonal peak of transmission of O. volvulus, either with a combination of ivermectin + ferrous sulphate, or with ferrous sulphate alone. One year after the treatment, i.e. 14 months after the start of the transmission period, the proportion of patients with positive skin biopsies, and their mean microfilarial loads, did not differ significantly between the two groups. Thus a single dose of ivermectin does not seem to have any perceptible prophylactic effect against O. volvulus.

Adolescent↗
PubMed2001

Studies on the macrofilarial population of Onchocerca volvulus in hyper-endemic villages of the Central province of Cameroon.

The population structure of Onchocerca volvulus macrofilariae was studied in villages of central Cameroon where onchocerciasis is hyper-endemic. One nodule selected at random was removed from each of 576 adult males, and examined by histology. The numbers of male and female worms/nodule, and the status of the female worms (fecund, non-fecund, or dead) were recorded. The observations were analysed to evaluate whether the mean numbers of worms of each category varied in relation to the patient's age, the level of endemicity in his village, the anatomical localization of the nodule, the weight of the nodule, and the total number of palpable nodules harboured by the patient. The results obtained were very similar to those reported from West Africa. The mean numbers of dead female worms/nodule were relatively high in the villages with the lowest levels of endemicity. The mean numbers of fecund females and of live males were significantly higher in the nodules located around the knees. These results provide information which might be useful in modelling the population dynamics of O. volvulus, and also in the context of trials of any potentially macrofilaricidal drugs.

Adolescent↗
PubMed2001

Follow-up of Ascaris lumbricoides and Trichuris trichiura infections in children living in a community treated with ivermectin at 3-monthly intervals.

Ivermectin treatment was administered every 3 months over a 1-year period (April 1993-April 1994) to the whole eligible population of a village in South Cameroon where both Ascaris lumbricoides and Trichuris trichiura were hyper-endemic. A parasitological stool examination was performed before each treatment. Thirty children, aged 5-15 years, were not only found egg-positive for A. lumbricoides and/or T. trichiura before the first treatment but were also each treated and examined in each treatment round. Among these children, the intensity of infection with A. lumbricoides decreased significantly following the first treatment but thereafter remained steady. In contrast, the repeated ivermectin treatments had no significant impact on the intensity of the T. trichiura infections or on the prevalence of infection with T. trichiura or A. lumbricoides among the 30 children.

Adolescent↗
PubMed2001

Relationships between the prevalence and intensity of Loa loa infection in the Central province of Cameroon.

Ivermectin treatment may induce marked adverse effects in those harbouring > 8000 Loa microfilariae (mff)/ml of blood, individuals with > 30 000 Loa mff/ml being at risk of developing serious neurological reactions. It is thus necessary to delineate the geographical areas where such responses may occur. To determine if the simple measure of prevalence of Loa microfilaraemia would be appropriate to identify the communities at risk, the relationships between prevalence and intensity of Loa microfilaraemia were investigated in 67 villages in Cameroon. The prevalence recorded in the adult population was found to be closely related to each of the indicators of infection intensity investigated. For example, when the prevalences of Loa microfilaraemia in adults were 20%, 30% and 40%, approximately 5%, 9% and 16% of the adults had microfilarial loads exceeding 8000 mff/ml, respectively; the corresponding percentages of adults with > 30 000 mff/ml were about 1%, 3% and 5%-6%. Thus it seems that, in areas where loiasis is co-endemic, the monitoring procedure during large-scale ivermectin treatments for the control of onchocerciasis only needs to be strengthened in those communities where the prevalence of Loa microfilaraemia in adults exceeds 20%.

Adolescent↗
PubMed2001

[Hyperendemic loaiasis in the Tikar plain, shrub savanna region of Cameroon].

A survey on filariasis was conducted in the south-western part of the Adamaoua Province (Cameroon). In the Bankim district, located in the Tikar plain, the 10 surveyed villages were all hyperendemic for loiasis. The prevalence of microfilaraemia in adults exceeded 50% in four communities, and 5.4% of the adults had microfilarial loads above 30,000 microfilariae per ml blood. In the Banyo district, which is contiguous but located on the Adamaoua Plateau, five of the six villages examined were hypoendemic for loiasis. The considerable levels of endemicity recorded in the Tikar Plain, a region of pre-forest shrub savanna, are probably due to the presence of forest-galleries, favourable to the biology of Chrysops. Regarding onchocerciasis, the most affected villages were located south of the Tikar Plain, near the Mbam River. The low prevalence of hydroceles suggests that lymphatic filariasis is not endemic in this study area.

Adolescent↗
PubMed2001

[Entomologic study of loaiasis transmission in the Lekie area (Cameroon)].

A number of cases of Loa encephalopathy have been recorded after ivermectin treatment in the Lekie Division, an area of degraded forest located in central Cameroon. An entomological study was carried out in a village of this region between May 1999 and April 2000 to determine whether the high microfilarial loads of Loa found in the population, which can exceed 10,000 microfilariae per ml of blood, were related to high densities of vector populations. The Chrysops collected at 10 catching stations, using hand nets, by persons standing by a wood fire, were dissected to evaluate their level of infection with Loa. The vectorial densities were three-fold higher in the forest stations than in those located near the habitations (2307 and 725 bites per man per year, respectively). These values are lower than those reported from similar studies in Cameroon, Congo and Gabon. Measurement of Chrysops densities does not seem to be an appropriate tool to evaluate the level of endemicity of loiasis, and to delineate the areas where there is a risk of post-ivermectin Loa encephalopathies.

Animals↗
PubMed2000

Ocular findings after ivermectin treatment of patients with high Loa loa microfilaremia.

Hemorrhages in the palpebral conjunctiva (HPCs) have been recorded in patients living in an area endemic for loiasis who developed serious reactions after ivermectin treatment. A study was designed to evaluate the frequency of these lesions, and to identify risk factors associated with their appearance. The conjunctivae of 1,682 patients who complained of reactions were systematically examined. HPCs were found in 41 patients. The initial mean Loa loa microfilaremia in the individuals with HPCs was 14,900 microfilariae (mf) per mL, as compared with 14.5 mf/mL in the other patients. Mansonella perstans microfilaremia and male gender were also associated with HPCs. Post-treatment fundus examinations were performed on 37 patients, and a close relationship was found between the occurrence of HPCs and the presence of retinal lesions. The vascular pathological processes leading to the ocular lesions may be similar to those which occur at the cerebral level in patients harboring high L. loa microfilaremia who develop neurologic troubles after ivermectin treatment. Retinal lesions may represent a special feature of the Loa-related encephalopathies useful for differential diagnosis, and the HPCs may be useful as an alarm sign to identify those individuals who might develop serious reactions after ivermectin treatment.

Adolescent↗
PubMed2000

[Analysis of the prevention of post-ivermectin Loa loa encephalopathy by administration of initial low dose].

A number of cases of Loa-encephalopathy have been reported following ivermectin (Mectizan) treatment for onchocerciasis in patients with high Loa microfilaraemia. A possible explanation for these severe reactions is the formation of micro-emboli in small brain vessels as a result of massive paralysis of Loa microfilariae in the blood. This suggests that encephalopathy might be prevented by giving an initial low dose of ivermectin to induce a more gradual action on the Loa microfilariae. To test this hypothesis, a trial was conducted on 23 adult patients in Cameroon. Patients were divided into two groups. One group received the recommended dose of 150 micrograms/Kg. The other group received a lower dose of 50 micrograms/Kg (one 3 mg tablet of Mectizan). Blood smears were made daily from day 1 to 7 after treatment and then on days 15 and 30. Results showed no difference in the effect of the dosage level on Loa microfilaraemia. This finding suggests that an initial low dose of 3 mg Mectizan will not prevent encephalopathy following treatment for onchocerciasis.

Adult↗
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

Onchocerciasis modulates the immune response to mycobacterial antigens.

Chronic helminth infection induces a type-2 cellular immune response. In contrast to this, mycobacterial infections commonly induce a type-1 immune response which is considered protective. Type-2 responses and diminished type-1 responses to mycobacteria have been previously correlated with active infection states such as pulmonary tuberculosis and lepromatous leprosy. The present study examines the immune responses of children exposed to both the helminth parasite Onchocerca volvulus and the mycobacterial infections, Mycobacterium tuberculosis and M. leprae. Proliferation of peripheral blood mononuclear cells (PBMC) and production of IL-4 in response to both helminth and mycobacterial antigen (PPD) decreased dramatically with increasing microfilarial (MF) density. Although interferon-gamma (IFN-gamma) production strongly correlated with cellular proliferation, it was surprisingly not related to MF density for either antigen. IL-4 production in response to helminth antigen and PPD increased with ascending children's age. IFN-gamma and cellular proliferation to PPD were not related to age, but in response to helminth antigen were significantly higher in children of age 9-12 years than children of either the younger age group (5-8 years) or the older group (13-16 years). Thus, there was a MF density-related down-regulation of cellular responsiveness and age-related skewing toward type 2 which was paralleled in response to both the helminth antigen and PPD. This parasite-induced immunomodulation of the response to mycobacteria correlates with a previous report of doubled incidence of lepromatous leprosy in onchocerciasis hyperendemic regions. Moreover, this demonstration that helminth infection in humans can modulate the immune response to a concurrent infection or immunological challenge is of critical importance to future vaccination strategies.

Adolescent↗
PubMed1999

Genetic epidemiology of host predisposition microfilaraemia in human loiasis.

Evidence is accumulating from experimental and human studies that genetic factors are involved both in the control of infectious diseases and in the regulation of infection levels and clinical presentation. So far few studies have investigated the role of these genetic factors in human infection by the filarial parasite Loa loa. We present a segregation analysis on 74 nuclear families who live in the tropical rainforest of southern Cameroun and are exposed to homogeneous loiasis transmission. The results indicate that there is a genetic predisposition to be microfilaraemic and that predisposed subjects might be genetically unable to mount an efficient immune response against loiasis antigens. This individual susceptibility could explain at least in part why the prevalence of infection (microfilaraemic individuals) does not usually exceed 30% of the exposed population in hyperendemic regions. Further genetic studies, based on linkage analysis using both familial information and genetic markers, will help to identify the nature of the genetic factors predisposing to microfilaraemia.

Adolescent↗
PubMed1999

Effect of repeated ivermectin treatments on ocular onchocerciasis: evaluation after six to eight doses.

In 26 villages (1987 population 12,302), hyperendemic for savanna onchocerciasis in North Cameroon, ivermectin was distributed annually between 1987/89 and 1995. Each year until 1992, ophthalmologic examinations were performed before treatment. A final examination was made in 1995. The effects of ivermectin on ocular onchocerciasis were assessed by following (a) the ophthalmologic indices in three cohorts of males recruited before treatment in 1987, 1988 and 1989, who were treated and examined annually, and (b) the indices recorded yearly in the cross-section of males aged 15-19 years. The indices in 1995 from patients who had received up to eight doses were compared with those calculated before treatment in individuals of similar age. In the cohorts, the prevalences of microfilariae in the anterior chamber (MFAC) and of punctate keratitis (PK) recorded in 1995 were markedly reduced; there was a non-significant decrease in sclerosing keratitis (SK), and a significant worsening in the fundus indices in the cohorts. The cross-sectional analysis showed significant decreases in the prevalences of MFAC, PK and SK, and a significant increase in the mean visual acuity; there was no significant change in any fundus index. The findings suggest that repeated ivermectin treatment does not prevent the appearance of initial retinal lesions or the worsening of existing retinal lesions.

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↗