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Biomedical subjects

V Robert

Publications and source records attributed to V Robert.

At least 109 records · Page 6Linked to original sources
PubMed1993

Importance of low dispersion of Anopheles gambiae (Diptera: Culicidae) on malaria transmission in hilly towns in south Cameroon.

The dispersion of Anopheles gambiae Giles s.l. from larval breeding places was examined in the towns of Yaounde and Edea, Cameroon. The study areas are characterized by hilly reliefs of approximately 40 m and by larval breeding places in the swampy valleys. Mosquito density was estimated by night-biting indoor catches carried out during 1 yr in three districts, with four collecting houses in each, along a transect from 0 (at the valley bottom) to 350 m (at the hilltop). In each district, the human-biting rate decreased gradually from valley bottom to hilltop. In two districts, the observed densities were zero at 200 and 250 m from breeding places. In the third district where the habitat is less dense, there was a 50% reduction in biting mosquitoes at 350 m from valley bottom. Our studies confirm that dense habitat in the urban area is associated with a low degree of vector dispersion. It emphasizes that slope is another factor which limits dispersion. These findings explain why malaria transmission is heterogenous (range, 0-45 infective bites per man per year) inside the districts and occurs mainly around swamps in the valleys. These data are important when considering the uncontrolled urbanization which is occurring in the undeveloped areas in the valleys.

Animals↗
PubMed1993

Anthropophilic mosquitoes and malaria transmission at Edea, Cameroon.

An entomological study was carried out during 1990 in the town of Edea in the south of Cameroon to study anthropophilic mosquitoes with special reference to malaria transmission. Man-biting mosquitoes were caught regularly during one night each month in two different districts: Bilalang which is a well planned suburb with 160 houses on a hill-top, provided with a piped water supply; and Pongo which is a densely urbanised suburb in a valley. From 188 man-nights 1030 mosquitoes were collected, comprising 700 Culex quinquefasciatus (68%), 262 Anopheles gambiae (25%) and others species (7%) belonging to the genus Anopheles, Mansonia, Culex and Aedes. The estimated annual biting rates of mosquitoes were 811 bites per man in Bilalang and 2,866 in Pongo. The estimated yearly malaria inoculation rates were 3.8 and 30.2 infective bites per man in Bilalang and Pongo, respectively. In different parts of Pongo district much variation existed; extreme values of the estimated yearly inoculation rate were zero and 86.3 in two houses 200 m apart, located on the top of a hill and in the bottom of a valley, respectively. This study is one of the first conducted on malaria transmission in a moderate sized African town; it shows that the mosquito populations are typically urban and differ greatly from rural ones.

Aedes↗
PubMed1993

[Yellow fever virus, dengue 2 and other arboviruses isolated from mosquitos, in Burkina Faso, from 1983 to 1986. Entomological and epidemiological considerations].

An arbovirus surveillance was carried out in Burkina Faso from 1983 to 1986. It was based on crepuscular catches of mosquitoes on human bait in some wooded areas and in one town. The total collection was 228 catches with an average of 8 men per catch. The total number of mosquitoes caught was 44,956 among which 32,010 potential vector of yellow fever; all these mosquitoes were analysed for arbovirology. In the south-western part of the country (region of Bobo-Dioulasso), surveillance was conducted each year from August to November, whilst the circulation of Aedes-borne arboviruses is well known to be favoured. In 1983, 1984 and 1986, seven strains of yellow fever virus were isolated in circumstances remarkably similar. They came from selvatic areas and never from the town. They concerned only Aedes (Stegomyia) luteocephalus which is the very predominant potential vector of yellow fever in the region. They were obtained in low figure, between 1 and 4 per year. They occurred from 27th of October to 21th of November. These observations confirm that the southern portion of the Sudan savanna zone of West Africa is the setting of a customary circulation of yellow fever virus and therefore belongs to the endemic emergence zone. In 1986, two strains of dengue 2 virus were isolated. One concerned Ae. luteocephalus from the selvatic area, the other Ae. (St.) aegypti from the heart of town. These data suggest two distinct cycles for dengue 2 virus, one urban and one selvatic, which could coexist simultaneously in the same region. In the south-eastern part of the country (region of Fada-N'Gourma) a yellow fever epidemic occurred between September and December 1983; its study has enable to precise their entomological aspects. The entomological inoculation rate of yellow fever virus has been evaluated to 22 infected bites per man during the month of october, for a man living close to forest gallery. 25 strains of yellow fever virus strains was isolated from Ae. (Diceromyia) furcifer which is the potential vector the most abundant in this region: the main role of this species in an epidemic was confirmed. An investigation in September 1984 had not permitted isolation of the virus therefore it is suspected that the large epizootic circulation of virus in 1983 has not been renewed the year after. In total 59 viral strains belonging to 10 different viruses were isolated from 9 species of mosquitoes.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1993

[Restructuring of the collagen network in hypertension: role of the angiotensin-aldosterone system].

UNLABELLED: Myocardial fibrosis as a consequence of systemic hypertension is a determinant factor in alteration of cardiac function. It has been postulated that this fibrous reaction is under the influence of an elevation of blood aldosterone. To gain further insight into the mechanisms that result in an accumulation of cardiac collagen, we used a model of aldosterone-salt-induced hypertension in rat. Uninephrectomized male Wistar rats weighting 200 g were perfused with 0.75 microgram/hr aldosterone and received 1% NaCl + 0.3% KCl in the drinking water for 2 months. RESULTS: 1) Arterial hypertension was evidenced as soon as 15 days and reached 40% at 2 months. 2) The left ventricle (LV) was hypertrophied by 45% at 2 months and its relative content in mRNA coding for the beta-isoform of the myosin heavy chain was increased by 142%. 3) The microscopic examination of hemalun-eosin stained LV showed a number of important foci of proliferating non-muscular cells, of inflammatory aspect. 4) The LV collagen concentration as measured by hydroxyproline assay was not changed whereas an histological study done on Sirius red-stained slides showed that the interstitial and perivascular collagen network was more important in treated rats. 5). The abundance of mRNAs coding for the alpha 1 chain of type I collagen was increased by 60%. Our results suggest that the fibrous response involves a pretranslational regulation of collagen synthesis.

Aldosterone↗
PubMed1993

Experimental infections of Anopheles gambiae with Plasmodium falciparum of naturally infected gametocyte carriers in Cameroon: factors influencing the infectivity to mosquitoes.

Factors which could influence the success of experimental infections of Anopheles gambiae with Plasmodium falciparum were investigated in Cameroon. 139 experimental infections with different gametocyte carriers were performed. 86 (62%) gave rise to mosquito infection after dissection of at least 20 mosquitoes. Among succeeding infections, the mean percentage of infected mosquitoes was 18.6% and mean oocyst load per positive midgut was 2.56. Only gametocyte density was identified as a factor which determined the success and the level of mosquito infection. No significant influence was found for sex and age of the gametocyte carrier, body-temperature, presence of asexual erythrocyte stages, rhesus factor, blood group and use of antimalarial drugs (chloroquine and amodiaquine).

ABO Blood-Group System↗
PubMed1993

Malaria transmission-blocking activity in the plasma of Plasmodium falciparum gametocyte carriers in Cameroon.

Experimental infections of Anopheles gambiae 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 by plasma from donors without previous malaria exposure. A lower mosquito-infection rate was observed in 50 out of 65 autologous plasma samples. The transmission was completely blocked in 8 infections, whilst belonging exposures to heterologous plasma led to infected mosquitoes. Evidence is shown that blood plasma factors of gametocyte carriers from a population living in a malaria-endemic area are able to reduce transmission capacity.

Adolescent↗
PubMed1993

[Notes on the phlebotomus of Aïr (Niger)].

238 phlebotomine sandfly belonging to seven species have been collected in four localities of Niger, in the Aïr mountain range. Phlebotomus bergeroti was the dominant species in animal bait and in collections inside dwellings. Some attention has to be paid to P. alexandri, a recognized vector of kala-azar elsewhere.

Animals↗
PubMed1993

[Comparison of catches by landings on humans and by CDC light traps for sampling of mosquitoes and evaluation of malaria transmission in South Cameroon].

The classical method to estimate the malaria transmission in an endemic area is based on the number and infectivity of human landing mosquitoes. To compare this method with CDC Miniature Light Trap a study was carried out in a forested area of South Cameroon. Light-trap and servant were placed in six different houses of the same village from 08 p.m. to 06 a.m. In average the human landing caught 29.9 anopheline females per night, while light-trap 52.4. The ratio of light-trap on human landing was 1.75 for Anopheles genus. This ratio varied with the species: 1.88 for An. nili and 0.54 for An. gambiae s.s. Light-trap showed disadvantages, especially the lack of steadiness and the fact that only 49.6% (n = 238) of potential vectors of malaria were in good standing for dissection of salivary glands. The authors concluded that human landing remained the most efficient method of catching for the estimation of human malaria transmission in the forested area of Africa. Nevertheless, the lower cost of light-trap is an important advantage.

Animals↗
PubMed1993

[Yellow fever epidemic in the extreme North of Cameroon in 1990: first yellow fever virus isolation in Cameroon].

Some two years ago, suspicious cases of yellow fever (YF) were reported in northern Cameroon. A deadly epidemic broke out during the second half of the rainy season (from 15 September to 22 December 1990) with 180 known cases, of which 125 died. The real figures could have been between 5000 and 20,000 cases with between 500 and 1000 deaths. The affected area was within the yellow fever belt, which is situated around latitude 11 degrees North and 14 degrees East. In this mountainous area (altitude, about 800 m) the rural inhabitants are scattered, with a high density of 200,000 people per 1000 km2. Investigations began at the start of the dry season and a strain of yellow fever virus was isolated for the first time in Cameroon. A study of 107 serum samples (23 families in 11 villages) was carried out by immunofluorescence and ELISA, which showed 20% IgM carriers for yellow fever virus and nothing for the three other flaviviruses, although these were largely present; there were up to 98% crossed reactions in IgG with dengue 2 and West Nile strains. The under-10 age group represented 63% of the IgM carriers. An entomological study was carried out at the same time. It permitted the capture of Aedes aegypti, A. furcifer, A. luteocephalus and the identification of numerous potential larval sites, at times still in the productive phase of A. aegypti which is considered to be the principal vector.(ABSTRACT TRUNCATED AT 250 WORDS)

Aedes↗
PubMed1992

Epidemiology of Plasmodium falciparum in a rice field and a savanna area in Burkina Faso. Comparative study on the acquired immunoprotection in native populations.

A longitudinal study, including entomological, parasitological, immunological and clinical data, was carried out in a rice field and a savanna village in Burkina Faso. In this study, the authors followed the evolution of several parasitological parameters in order to compare the level of immunoprotection in children of these two areas. In particular, the percentages of recently 'infected' or 'recovered' children were calculated, during the interval separating two consecutive surveys. In both areas, parasite densities quickly increased in children from 0 to 14 years old, immediately after the beginning of the transmission period. In savanna, during the rainy season (May-October), parasite densities decreased and the proportion of recently 'recovered' children from 0 to 4 years old (becoming parasitologically negative between two consecutive surveys) was very low. On the other hand, parasite densities decreased and the recovery rate was higher in children from 10 to 14 years old before the end of the rainy season, while the transmission was going on. In the rice field area, Plasmodium falciparum densities decreased only at the end of the transmission period (December) and had the same levels as those found in savanna, in spite of a lower inoculation rate. The second peak of transmission seemed neither to increase the proportion of recovered children, nor to boost the immunoprotection of these children.

Adolescent↗
PubMed1992

Anopheles nili as the main vector of human malaria in villages of southern Cameroon.

In villages near Sanaga river, in the forest zone of south Cameroon, Anopheles nili Theobald is the main species of mosquito regularly found biting man inside houses. Its densities are related to the flow level of the river. It is also the main malaria vector in terms of intensity and seasonal duration of transmission. The yearly malaria inoculation rate due to An. nili alone is 104 infective bites/man, varying between 3 infective bites/man in October and 20 in March. Anopheles gambiae Giles is a less important vector in the area but reached its peak in the dry season, when the Sanaga river is at its lowest level. These observations underline the influence of local ecology on malaria transmission and the need for entomological studies in each situation.

Animals↗
PubMed1992

Efficacy of insecticide impregnated bed-nets to control malaria in a rural forested area in southern Cameroon.

Due to current spreading of chemoresistant strains of Plasmodium falciparum malaria control must incorporate vector control programmes. Due to well known constraints house sprayings cannot be performed as before. Personal protection can be developed and a large scale use of insecticide treated bed-nets appeared to be very useful to reduce man-vector contact in Asia, South America and West and East Africa. No trial has been done in forest Central Africa where transmission is permanent. We performed such a trial in the southern part of Cameroon (using deltamethrin, at 25 mg/m2) and obtained similar data to those observed in The Gambia, Burkina Faso and Tanzania with a noteworthy reduction of both transmission and high parasitaemia of P. falciparum (respectively 78% and 75%) meaning a drop of malaria morbidity.

Animals↗
PubMed1992

[Feasibility of mosquito control using insecticide-impregnated bednets in rural areas of Cameroon].

The feasibility of using impregnated bednets in a malaria control strategy has been evaluated in a rural area of Cameroon. The benefit is well perceived by the population in terms of protection against nuisance but not in terms of prevention of the disease. The correct use of bednets is, however, unsatisfactory. The material should be adapted to the various sleeping accommodations, and efforts for education and information directed towards the potential users should be intensified.

Animals↗
PubMed1992

[Urban malaria in Yaounde (Cameroon). 2. Entomologic study in 2 suburban districts].

A one year entomological survey was carried out to precise the malaria vectors and the malaria transmission in Yaounde, the Cameroon capital (800,000 inhabitants). The study was done in two districts not yet fully urbanized: Nkol Bikok and Nkol Bisson. The latter is located at the periphery and has a pool. Anopheles gambiae was the only human malaria vector. Its agressivity for man depended on the urbanization of the district. Annual man biting rate was 284 in Nkol Bikok and 1,813 in Nkol Bisson. The densities were maximum in May-June and in October-November, corresponding to the end of the short and long rainy seasons. The presence of A. gambiae was permanent except in August-September in Nkol Bikok. In Nkol Bisson the density was higher in the houses near the pool. The yearly inoculation rate (h) was 14 in Nkol Bikok and 30 in Nkol Bisson. The vectorial transmission was observed in may in Nkol Bikok and during four months (June, August, January, February) in Nkol Bisson. These entomological data showed clearly that malaria transmission actually occurred in Yaounde and that the probability to receive at least one infected anopheline bite per year was very near to 1 for inhabitants unprotected against mosquito bites.

Animals↗