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Biomedical subjects

V Robert

Publications and source records attributed to V Robert.

At least 145 records · Page 8Linked to original sources
PubMed1988

[Control of malaria using mosquito nets impregnated with pyrethroids in Burkina Faso].

An experimental trial of malaria control was carried out in the village of Karangasso in the south-west Burkina Faso. It was based on the use by the whole population of deltamethrin impregnated bed nets at 25 mg/m2. During the first year pretreatment data on entomology, parasitology and pathological incidence of malaria were collected in the whole village. During the second year a quarter of the village with a population of 1,200 was chosen for the experiment and impregnated bed nets were given to everybody while the other quarter of the same population size was kept as a control area. Malaria transmission was reduced by 82% due to the decrease of both vector populations and sporozoitic indexes. It should be pointed out that this reduction in transmission was evaluated on non-protected catchers and consequently was underestimated for the villagers sleeping under nets. Parasitic index remained about the same but the mean parasitic load decreased significantly. Pathological incidence, based on the number of clinical malaria cases confirmed by blood examination, decreased by 59%. This trial shows that mass use of deltamethrin impregnated bed nets should be considered as a valuable tool for malaria control. The purchase of bed net is expensive but could be reduced sharply. The cost of the impregnation is very low regarding the residual effect which remains one year. The acceptance by the population was good.

Animals↗
PubMed1986

[Impact of building a dam on the transmission of malaria. Malaria survey conducted in southeast Mauritania].

In March during the dry season an investigation was conducted on the site of Foum Gleita dam in the Islamic Republic of Mauritania in order to study, one year after the filling of the dam, the epidemiological situation of local malaria at a clinico-parasitological, immunological and entomological level. No malarial transmission was observed in the 5th month of the dry season. So far, the damming of water has not led to the spread of anophelines which would have brought about malarial transmission not within the rainy season.

Adolescent↗
PubMedDate not supplied

Insecticide impregnation can restore the efficiency of torn bed nets and reduce man-vector contact in malaria endemic areas.

Three trials with torn bed nets impregnated with permethrin and deltamethrin were made under field conditions at the Soumousso Field Station and the Vallée du Kou rice-field area, both in Burkina Faso, and the Djoumouna fish pond area in the Congo Republic. Even a considerably torn correctly impregnated bed net could be an useful method for limiting human-anopheline contacts. But bed nets in poor condition, i.e. too little impregnated and too much torn, cannot protect the users against anopheline bites. Protection increases with insecticide concentration, but at a high dosage insecticide could have more a repellent than a killing effect. Therefore a balance has to be found for the optimum rate of insecticide treatment of bed nets to obtain a real reduction in malaria transmission and morbidity, in every epidemiological situation.

Animals↗
PubMedDate not supplied

Malaria transmission-blocking activity in experimental infections of Anopheles gambiae from naturally infected Plasmodium falciparum gametocyte carriers.

Experimental infections of anopheline mosquitoes were carried out with Plasmodium falciparum gametocytes from 65 naturally infected patients in Cameroon. A comparison was made between infections with blood containing autologous plasma and blood in which the plasma was replaced with plasma from a donor without previous malaria exposure. A lower infection rate was observed in 50 of 65 autologous plasma samples. Transmission was significantly blocked in 3 infections. This indicates that, in a population living in an area endemic for malaria, blood plasma factor(s) can reduce the transmission capacity of gametocyte carriers to mosquitoes.

Adolescent↗
PubMedDate not supplied

Use of monoclonal antibodies for the detection and quantitation of HIV1 core protein p25: comparative evaluation of in vitro HIV1 infection by immunofluorescence, antigen capture ELISA and reverse transcriptase assays.

A two-site enzyme linked immunosorbent assay (ELISA) was developed to detect and quantify the HIV1 core protein p25 in the cell-free supernatant from virus-infected CEM cell culture, and compared with other assays. The assay, based on a sandwich method, employs two monoclonal antibodies (mAb) directed against different epitopes on the p25 core protein of HIV1, one used for p25 antigen capture and the other as a biotinylated probe. This immunoassay is sensitive enough to detect as little as 30 pg/ml of recombinant p25, the range of sensitivity of commercial kits, and therefore compares favourably with the conventional reverse transcriptase assay. Moreover, several hundred assays can be monitored quite conveniently by this simple ELISA procedure, which represents a useful tool for detection of HIV1 replication in microculture systems and rapid screening of antiretroviral agents using the reference strain HIV1-BRU as a model system.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

Effect of gametocyte sex ratio on infectivity of Plasmodium falciparum to Anopheles gambiae.

Insectary-reared Anopheles gambiae were experimentally fed with the blood of 90 naturally infected human volunteers carrying gametocytes of Plasmodium falciparum. At least one mosquito was successfully infected in 74% of experiments. The probability that a gametocyte carrier was infective, the probability that a mosquito became infected, and the number of oocysts harboured were related to gametocyte density. The mean proportion of male gametocytes was 0.217 (i.e., 3.6 females for every male). Sex ratios differed significantly between gametocyte carriers. Variation in sex ratio was not related to the probability that a gametocyte carrier was infective. Among infective people whose sex ratio estimates were based on a reasonable number of gametocytes, sex ratio significantly predicted the proportion of infected mosquitoes and mean oocyst load, with infectivity rising as the proportion of the male gametocytes increased towards 50%. There was no indication that infectivity reached a peak at some intermediate sex ratio, as would be expected if random mating of gametes was the primary determinant of fertilization success. These results raise 2 interesting questions: why should higher sex ratios be more infective, and why is the observed population sex ratio lower than that which produces the greatest infectivity?

Animals↗
PubMedDate not supplied

Comparison of direct and membrane feeding methods to infect Anopheles arabiensis with Plasmodium falciparum.

Two standard methods are available to infect mosquitoes with malaria parasites: direct feeding through the skin of the gametocyte carrier, and membrane feeding. Anopheles arabiensis collected at larval stages and reared in an insectary were fed in parallel by feeding on Plasmodium falciparum gametocyte carriers and by membrane feeding on venous blood of the same gametocyte carriers. Infection of mosquitoes was assessed at Day 7 post bloodmeal by oocyst count of the mosquito midguts. The following parameters were not significantly different between the two methods: the percentage of gametocyte carriers infective for at least one mosquito (52.4% through the skin versus 57.1% through the membrane), the mean infection rate of mosquitoes (10.0% versus 11.3%), the geometric mean oocyst number per mosquito (2.51 versus 3.83). In conclusion, infection of mosquitoes by membrane feeding was similar to infection by direct feeding. Most of the volunteers preferred venipuncture to mosquito bites.

Animals↗
PubMedDate not supplied

[Climate variability and number of deaths attributable to malaria in the Niakhar area, Senegal, from 1984 to 1996].

There are a number of reasons why climate, in certain physical and social environments, could have an impact on the epidemiology of malaria. Events, such as floods or drought, are related to the number of malaria cases and deaths, both seasonally and interannually. At a smaller scale, this study analyses the relation between climate variability and the variability in the number of deaths attributable to malaria in Niakhar, Senegal. The Niakhar area has a population of 30,000 and has been under demographic surveillance system since 1984. The rainfall in this region is highly seasonal, with a rainfall maximum in August and almost no rain between October/November and May/June. In addition to this seasonal cycle, rainfall also varies greatly from year to year (interannual variation). Over the 13 years, there were 661 deaths attributed to malaria with a marked interannual variability (range from 23 to 100, with a median of 43). There was also a strong seasonality in mortality, with nearly all deaths (89.1%) occurring between August and December. The number of deaths peaks in October, two months after the rainfall peak. Standardised monthly values were calculated for each climatic series (rainfall, relative humidity, temperature) as well as standardised five-month and monthly values of the number of deaths attributed to malaria between August and December. Correlation coefficients were calculated between these standardised values. The correlation between the variability in August rainfall and the variability in the number of deaths attributed to malaria between August and December was positive and statistically significant (r = +0.61, p = 0.02). In addition, highly significant cross-correlations were found between monthly rainfall series and monthly mortality series at one- and two-month lag (r = + 0.43, p = 0.0004 for one-month lag; r = + 0.26, p = 0.03 for two-month lag). This correlation is somewhat lower than the correlation of August rainfall alone with August to December mortality, but the result adds confidence to the signal given the increased degrees of freedom in the analysis. Similar, but slightly weaker, results were found when precipitation data were replaced with surface humidity data. Results with temperature were less clear; while temperature could in some circumstances have a direct impact on malaria, in this case here it is possible that the weak negative correlation between malaria deaths and temperature arises mainly because precipitation is physically connected to both the indices, correlating positively with malaria and negatively with temperature. The availability of a continuous demographic and medical survey since 1984 in a region of highly variable rainfall has created a rare opportunity to analyse with some confidence a climate versus malaria relationship. The findings are consistent with our understanding of the proposed link between rainfall and conditions for the reproduction of the malaria vector, leading to a lag time (here of one to two months) between anomalies of rainfall and deaths attributable to malaria. These results may have practical implications in Sub-Saharan regions marked by a great seasonal and interannual variability in rainfall by providing a simple tool to forecast the impact of climate variability on malaria mortality.

Animals↗
PubMedDate not supplied

[Sylvatic yellow fever in Africa recent advances and present approach (author's transl)].

Recent works carried out in west and central Africa resulted in numerous yellow fever virus isolations from sylvatic mosquitoes in the forest-savanna transitional zone. This virus was also obtained from monkeys, whereas studies on sequence and duration of the observed epizootics permitted a previsional approach of the yellow fever mechanisms in the same belt, the epidemiological importance of which was stressed ("emergence zone"). In the same course of research and publications, the prevalent part of the involved mosquitoes as virus-reservoirs was constantly emphasized ("reservoir-vector"). Recent investigations on transovarial transmission and yellow fever isolations from male mosquitoes caught in the field, provide decisive support to such a conception. It can explain that epizootics may be locally observed several years in succession, despite the fact that yellow fever virus circulation seems to be fundamentally of a dynamic character. Yellow fever virus was recently obtained from ticks and tick-eggs.

Africa↗
PubMedDate not supplied

[Epidemic of yellow fever in the southeastern region of Upper Volta (October-December, 1983). Epidemiological study. Preliminary results].

An epidemic of yellow fever raged during the last three months of 1983 in South East of Upper Volta. It spread on about ten thousand square kilometers, in a bushy savanna area, affecting only populations living in contact with forest galleries, belonging especially to the peul ethnical group. The transmission of the virus was effected by sylvatic vectors, essentially Aedes furcifer. Serological tests showed that about 50 % of the population living in contact with forest galleries was affected, that is to say 15.000 to 17.500 people. The average death rate on the whole area was 4 % (800 to 1.700 deaths); the lethality rate was estimated between 6 and 10 % of affected people. On the whole, 54 strains of yellow fever virus were isolated from human blood samples, and 26 strains from batches of mosquitoes. We called this epidemic "intermediate sylvatic epidemic". The epidemic quickly decreased in the sylvatic area, owing to climatic conditions. A mass campaign of vaccinations prevented it from spreading to near urban centres. On this particular case, the thermostability on field of the vaccine 17D provided by the Institute Pasteur of Dakar was proved to be effective.

Adolescent↗