PubMed Health⌕ Search

Biomedical subjects

J Prod'hon

Publications and source records attributed to J Prod'hon.

At least 19 recordsLinked to original sources
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

[Epidemiologic study of the main human intestinal nematodes in the middle west of Madagascar].

An epidemiological study of human intestinal helminthiasis was conducted during July and August 1995, in the middle west of Madagascar, with 4571 adults and children ranging from six months to 90 years, in 61 communities between Betafo and Miandrivazo. Faecal examination utilising the MIF concentration method revealed that ascariasis was the dominant nematodosis in the middle west with high prevalences in the high-altitude communities. Ascaris lumbricoides prevalences increase among children and women. Interesting more than 50% of the pattern, ascariasis is a public health problem and its association with infant malnutrition is statistically significant. Hookworm infection prevalence is higher in low-altitude communities, it increases among adults. The Trichuris trichiura prevalences were lower than the prevalences of ascariasis and hookworm infection in all of the communities. Important variations of the prevalences of intestinal helminthiasis are observed essentially in relation with climatic conditions.

Adolescent↗
PubMed1995

Effect of repeated treatments with ivermectin on the incidence of onchocerciasis in northern Cameroon.

Mass treatments with ivermectin have been undertaken each year since 1987 in an area hyperendemic for onchocerciasis in northern Cameroon. The impact of these successive treatments on the incidence of infection in humans was evaluated by comparing the prevalence of skin microfilariae (PMF) and the mean microfilarial skin densities (MFD) observed in 1987 and 1992 in 5-7-year-old children who had never taken the drug but who were members of the treated communities. In 1992, the PMF and the MFD in children in this age group who never received ivermectin were reduced by 55% and 77%, respectively, in comparison with the values observed in 1987, before the first treatment round. These results reflect a pronounced reduction in the intensity of the transmission of Onchocerca volvulus in the treatment zone. The influence of the ivermectin treatment coverage in the human population, as well as the vectorial capacity and the dispersal of the vector blackflies, on the transmission of onchocerciasis is discussed.

Adolescent↗
PubMed1994

Density-dependent processes in the transmission of human onchocerciasis: intensity of microfilariae in the skin and their uptake by the simuliid host.

The transmission success of Onchocerca volvulus is thought to be influenced by a variety of regulatory or density-dependent processes that act at various points in the two-host life-cycle. This paper examines one component of the life-cycle, namely, the ingestion of microfilariae by the simuliid vector, to assess the relationship between intake of larvae and the density of parasites in the skin of the human host. Analysis is based on data from three areas in which onchocerciasis is endemic and includes published information as well as new data collected in field studies. The three areas are: Guatemala (Simulium ochraceum s.l.), West and Central Africa (savanna members of the S. damnosum complex), and South Venezuela (S. guianense). The data record experimental studies of parasite uptake by flies captured in the field and fed to repletion on locally infected subjects who harboured varying intensities of dermal microfilarial infection. Regression analyses of log transformed counts of parasite burdens ingested by the flies plotted against log transformed counts of microfilariae per mg of skin revealed little evidence for saturation in parasite uptake by the flies as the intensity in the human host increased. There was a positive and highly significant rank correlation between both variables for the three blackfly species. In an alternative analysis a model was fitted to data on prevalence of flies with ingested microfilariae (mff) versus dermal mean intensities. The model assumed an overdispersed distribution of the number of mff/fly and a given functional relationship between intake and skin load. The results of both approaches were consistent. It is concluded that parasite ingestion by the vector host is not strongly density dependent in the three geographical areas and ranges of dermal loads examined. It therefore appears that this transmission process is of reduced importance as a regulatory mechanism in the dynamics of parasite population growth.

Africa, Central↗
PubMed1993

[Long-term effect of a single dose of ivermectin on skin microfilarial density in an endemic onchocerciasis area of North Cameroon].

The long-term efficacy of a single dose of ivermectin (150 micrograms/kg) on skin microfilarial densities was evaluated by comparing parasite levels, before and after treatment, in 192 patients living in an area endemic for onchocerciasis in North Cameroon. A mass treatment with ivermectin has been undertaken in 1989 in two villages, where pretreatment community microfilarial loads (CMFL) were 5.5 and 25.1 microfilariae per snip. The parasitological examination carried out 32 months later showed that the microfilarial densities in the adults where only 24 and 51% of the initial values, respectively. In a third village, treated once in 1989 but located in an area where annual mass distributions of ivermectin have been undertaken since 1987, the mean microfilarial density 28 months after treatment was only 12% of the initial value. In 1992, the mean microfilarial load in children had decreased significantly in comparison with those of 1989 only in the village where the level of endemicity was initially the lowest. The rate of increase in the number of skin microfilariae after one dose of ivermectin is related with the pretreatment endemicity level. The impact of large-scale ivermectin treatments on the transmission of onchocerciasis enhances the long-term efficacy of this drug on the skin microfilarial densities.

Adult↗
PubMed1991

[Control of onchocerciasis with ivermectin: results of a mass campaign in northern Cameroon].

A mass chemotherapy campaign to treat onchocerciasis with ivermectin was carried out in northern Cameroon, in the North Vina valley, a savanna area that is part of the extended Vina-Pendé-Longone focus. More than 20,000 people aged five years and over were treated at least once and more than 30,000 treatments were distributed. One to four treatments were given at intervals of six months or one year. Clinical and parasitological examinations of representative samples of the treated population and full ophthalmological examinations of males aged 15 to 35 years were carried out before each treatment to assess the efficacy of the different protocols of treatment. Secondary effects were recorded daily during the week after administration of ivermectin in the whole population treated. The evolution of arterial blood pressure was monitored over seven days in about 300 adults living in the hyperendemic region. The impact of mass treatment on natural transmission of the disease was evaluated by daily capture and dissection of blackflies during the month before and the two months after treatment. All levels of onchocerciasis endemicity were represented in the study area (maximum community microfilarial load (CMFL), 300 microfilariae per biopsy). Six months and one year after the first treatment, loads were down by more than 90% and more than 60% respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1988

Characterization of an immunodominant Onchocerca volvulus antigen with patient sera and a monoclonal antibody.

Adult Onchocerca voluvlus and infective larvae, but not microfilariae contain an immunodominant antigen (33,000 and 21,000 Mr in females, 39,000, 33,000, and 21,000 Mr in males, 133,000 Mr in infective larvae) which is recognized by an Onchocerca-specific mAb. The component is part of the reproductive organs and muscles. 96.2% of onchocerciasis sera contained antibodies detectable by immunoblotting against it. Antigen purified by immunoaffinity chromatography was specifically recognized in immunoblots by onchocerciasis sera, but not by sera from other filarial infections. The high immunogenicity, the specificity, and the occurrence in infective larvae of this antigen indicate an immunodiagnostic potential and a possible role in the immunobiology of the parasite.

Animals↗
PubMed1988

Forest and savanna onchocerciasis: comparative morphometric histopathology of skin lesions.

A comparative study was made of skin biopsies from onchocerciasis patients living in the forest and in the savanna of West Africa. The lesions and their pathogenesis were similar in the two series of patients. An inflammatory reaction around the extra-lymphatic microfilariae was observed. But the localization of the microfilariae was slightly different: the mean distances between the microfilariae and the border of the basement membrane of the epidermis was approximately 115 microns in the forest and 138 microns in the savanna. Statistical analysis showed that the forest microfilariae were in the superficial parts of the dermis when the densities were low and in deep parts of the dermis when the densities were high. In the savanna, the phenomenon, although less clearly defined was reverse. The two situations were inverted when the density of microfilariae reached approximately 51 microfilariae per calibrated snip, which was seldom the case. Therefore, the most cases, microfilariae appeared to have been more superficial in the forest than the savanna.

Adolescent↗
PubMed1987

[Ivermectin and the reduction of the rate of infection of simuliids in a forest focus of human onchocerciasis].

Eight patients from a forest onchocercian area "Grandes rivières", in Ivory Coast, were treated with a single oral dose of ivermectin (12 mg). The density of dermic microfilariae was estimated at days 0, 7 and 180; the mean numbers of ingested microfilariae and of developing larvae in the vectors S. soubrense-S. sanctipauli, engorged on the treated patients were recorded. Comparisons were made with non treated patients, having a similar density of microfilariae than the 8 treated patients at day 7. Results confirm the reduction induced by ivermectin of the dermic microfilarial density and the resulting reduction of the infection of the simuliids. Furthermore 7 days after treatment, a new phenomenon is demonstrated: for a similar dermic microfilarial density, simuliids take up a number of microfilariae 100 times lower from treated than from untreated patients. To explain this phenomenon, it is suggested that ivermectin induces a change in the microfilarial distribution in the layers of the dermis. Six months after treatment, this low uptake of microfilariae by the vectors had disappeared, and the infection rate of the engorged similiids was much higher than at day 7 although the dermic microfilarial density was similar.

Animals↗
PubMedDate not supplied

Onchocerca volvulus: striking decrease in transmission in the Vina valley (Cameroon) after eight annual large scale ivermectin treatments.

The impact of repeated ivermectin treatments on the transmission of Onchocerca volvulus was evaluated in the Vina valley, northern Cameroon, by comparing the prevalence and intensity of infection observed in untreated 5-7 years old children living in the treated communities before and after 7-8 successive annual rounds of ivermectin treatment of the general population of those communities. The villages studied were Ngoumi and Babidan, where the initial community microfilarial loads (CMFL) were 83.7 and 216.4 microfilariae per skin snip, respectively. In 1995, after 8 annual treatments, the prevalence and intensity in Ngoumi had decreased by more than 90%, compared with the pretreatment values, and the prevalence continued to decrease between 1992 and 1995. In Babidan, after 7 annual treatments, the prevalence and intensity had also decreased significantly, but less than in Ngoumi. The study demonstrated that repeated treatments brought about a notable reduction in the transmission of O. volvulus in the Vina valley, despite unfavourable factors such as mean drug coverages below 60% and the good vectorial competence of Simulium damnosum s.s. and S. sirbanum.

Adult↗
PubMedDate not supplied

[Onchocerciasis chemotherapy. II. Evaluation of two therapeutic schemes on microfilarial density, utilising the association diethylcarbamazine and levamisole (author's transl)].

As the study of the association diethylcarbamazine-levamisole gave encouraging results on the dermal microfilarial density of Onchocerca volvulus (Leuckart, 1893), the authors followed it up in order to determine the optimum regimen for mass treatment. Two therapeutic schemes have been tested: A--Initial treatment: 14 days with the dayly dosis of respectively 200 mg of diethylcarbamazine and 120 mg of levamisole progressively reached in four days. After one year: a single dayly dosis of respectively 200 mg and 60 mg for five days. B--Initial treatment: 7 days with the same dosis as above. After one year: dayly dosis of respectively 200 mg and 60 mg for seven days. It appears that scheme A may be considered as the best baseline to achieve the optimum regimen for the mass treatment of onchocerciasis. The aim of such a treatment is to decrease the dermal microfilarial density to a level compatible with the patient good condition.

Adolescent↗