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G De Sole

Publications and source records attributed to G De Sole.

At least 19 recordsLinked to original sources
PubMed1993

Distribution of onchocerciasis in selected river basins of four west African countries.

Detailed epidemiological mapping of eight river basins was conducted in four West African countries as part of an effort to identify the communities at risk of onchocercal blindness to guide a programme of large scale ivermectin distribution, attempting control of eye disease. The results show a surprising variability of pattern in the geographical distribution of intensity of onchocerciasis infections in the communities of the river basins investigated. These patterns were at time very different from what was expected on the basis of the available entomological and demographic information. The technique of detailed mapping proved very useful in achieving an excellent coverage of the communities at risk of onchocercal blindness where, so far, satisfactory treatment coverage has been attained for four consecutive yearly treatments.

Animals↗
PubMed1992

Distribution and severity of onchocerciasis in southern Benin, Ghana and Togo.

The Onchocerciasis Control Programme in West Africa has recently extended its operation in southern Benin, Ghana and Togo. To estimate the number of people infected and blinded by onchocerciasis and to describe the distribution and severity of the disease in the extension area, 99 villages were selected, using a stratified random sampling procedure, and surveyed. All the ecological and entomological information available was used in the sampling procedure and in the selection of 87 non-representative villages surveyed to confirm the findings. The study estimated that 590,468 people are infected and 11,715 blind from onchocerciasis out of a rural population of 1,878,234. The Pru, Asukawkaw and Mono river basins were areas with high risk of onchocercal blindness. The Oueme and Zou river basins in Benin and the mountainous areas between Ghana and Togo were classified as areas with medium risk of onchocercal blindness. The other parts of the study area presented low or no risk of onchocercal blindness. By detecting the river basins where villagers are at risk of onchocercal disease this study permits the selection of populations for disease control based on mass distribution of ivermectin, a microfilaricide.

Animals↗
PubMed1992

Onchocerca volvulus DNA probe classification correlates with epidemiologic patterns of blindness.

Onchocerciasis, or river blindness, results from infection with Onchocerca volvulus. The parasite is endemic to West Africa, in both rain forest and savanna bioclimes. Several lines of evidence suggest that different strains of the parasite exist in the rain forest and savanna. Furthermore, epidemiologic evidence indicates that ocular onchocerciasis is most severe in savanna regions. This has led to the hypothesis that there is a strain association with ocular pathology. To test this hypothesis, parasites from villages in which severe and mild onchocerciasis were endemic were classified with two strain-specific DNA probes. A strong correlation (P less than .001) was found between disease severity and probe recognition, supporting the hypothesis that pathogenicity is strain related. The results suggest that pFS-1 and pSS-1BT may be used to predict the pathogenic potential of parasite populations throughout much of West Africa.

Africa, Western↗
PubMed1992

Ocular onchocerciasis and the intensity of infection in the community. IV. The degraded forest of Sierra Leone.

To assess the pattern of onchocercal ocular disease and blindness in south Sierra Leone, ophthalmological surveys were carried out in 13 highly infected villages located in various river basins. The most important finding was the blinding potential of onchocerciasis in the degraded forest area where the prevalence of onchocercal blindness reached levels of up to 6%. This is remarkable since previous studies have claimed onchocerciasis in the forest to cause little blindness. Ocular onchocerciasis undoubtedly constitutes a problem of public health importance in south Sierra Leone. The rates of onchocercal ocular disease and blindness, however, were significantly lower than those found in savanna villages with similar levels of endemicity. The community pattern of ocular onchocerciasis was not significantly different from the classical pattern in the forest but this could be explained by the low endemicity levels in the forest villages studied. It is therefore not possible to deduce from this study whether the pattern of ocular onchocerciasis in south Sierra Leone is of the forest type, or a pattern on its own.

Adolescent↗
PubMed1991

Detailed epidemiological mapping of three onchocerciasis foci in West Africa.

Detailed epidemiological mapping of three isolated foci of hyperendemic blinding onchocerciasis was undertaken in three West African countries as part of community trials of ivermectin, a new microfilaricide for the treatment of human onchocerciasis. The results show that the geographical distribution of the prevalence and intensity of onchocerciasis infection in the community can be very different from what was expected on the basis of demographic and entomological information. The technique of detailed epidemiological mapping is an important tool for the identification of target populations for large scale ivermectin treatment of onchocerciasis. It is being used extensively in the Onchocerciasis Control Programme in West Africa.

Africa, Western↗
PubMed1991

Importance of migrants infected with Onchocerca volvulus in west African river valleys protected by 14 to 15 years of Simulium control.

A study was done to determine the importance of human migration from non-controlled endemic onchocerciasis foci to the river valleys that have been protected for the past 14 to 15 years by the vector control operations of the Onchocerciasis Control Programme in West Africa. The aim of the study was to assess the contribution of migrants to the prevalence and intensity of infection in villages from 5 major river valleys and their potential role in causing relapse of transmission once the vector is allowed to return. In Burkina Faso the migrant population varied from 0.0% to 18.1% of the village population, and averaged 4.9%. Migrants accounted only for 0.6% of the population in Ghanaian and Ivorian villages along the Black Volta river. The prevalence of infection was significantly higher in migrants (8.2%) than in non migrants (1.1%) in the surveyed villages in Burkina Faso, and 1.5% of migrants had infections with more than 16 microfilariae per snip as against 0.2% of non migrants. Nearly all infected migrants came from the south of the Côte d'Ivoire. The study shows that human migration has caused the importation of Onchocerca volvulus from non-controlled areas. However, the epidemiological importance of this phenomenon is limited because of the very small number of infected migrants per village while two-third of the infected migrants are believed to be infected with the less pathogenic forest strain of the parasite. Because migration patterns changes geographically and over time similar studies will be continued on a regular basis.

Animals↗
PubMed1991

Onchocerciasis distribution and severity in five West African countries.

The Onchocerciasis Control Programme in West Africa recently extended its operation to Guinea, Guinea-Bissau, the western part of Mali, Senegal and Sierra Leone. To estimate the number of people infected and blinded by the disease and to determine its distribution and severity in the extension area, 215 villages were selected, using a stratified random sampling procedure, and surveyed. All the relevant entomological information available at the time was used in the sampling procedure and in the selection of 92 non-representative villages that were surveyed to confirm the findings. In addition, the populations of 608 villages were examined to map out in detail the distribution of onchocerciasis in the areas at a high risk of onchocercal blindness. The study estimated that 1,475,367 people were infected and 23,728 were blinded from onchocerciasis out of a rural population of 4,464,183. The northern and western part of the study area and the lower Niger basin presented a low or no risk of onchocercal blindness. The upper Niger basin, the south-central part of Sierra Leone, and three small foci in the Gambia, Bakoye, and lower Niger river basins were areas with a high risk of onchocercal blindness. The other parts of the study area presented a medium risk of onchocercal blindness. By detecting the communities at risk of onchocercal disease this study permits the selection of populations for disease control based on mass distribution of ivermectin, a microfilaricide.

Gambia↗
PubMed1990

The predicted and observed decline in onchocerciasis infection during 14 years of successful control of Simulium spp. in west Africa.

In 55 villages from the well-protected central area of the Onchocerciasis Control Programme in West Africa (OCP), skin snip surveys have been carried out at regular intervals since the programme started, and the latest round of surveys was undertaken after 12-14 years of successful vector control. The observed trends in the prevalence and intensity of onchocerciasis infection in cohorts of adults were compared with the trends predicted using a host-parasite model. After 12-14 years of control the community microfilarial load (CMFL) was close to zero in all villages. During the last few years of control, the prevalence of infection declined at an accelerated rate, and this was predicted by the model. There was generally good agreement between observed and predicted trends. The predictions were based on an estimated average duration of infection of 10.4 years, which corresponds to a mean reproductive lifespan for Onchocerca volvulus of 9-9.5 years, and an upper limit of 15 years for 95% of the infections. Differences between the observed and predicted data included the trend in CMFL between the first and second surveys, which in 18 villages did not show the predicted decline. Furthermore, the observed final decline in prevalence was faster than predicted in the north-eastern part of the central OCP area. After 14 years of vector control, the level of onchocerciasis has fallen to such a low level that consideration is being given to ending larviciding.

Adult↗
PubMed1990

Migration studies in the onchocerciasis controlled areas of West Africa.

The possible impact of human migration from onchocerciasis endemic areas located beyond the borders of the "Onchocerciasis Control Programme in West Africa" to the area protected by this project was studied. The aim of this exercise was to assess the contribution of immigrants to the prevalence and intensity of infection of the human population protected by vector control activities and their potential role in generating transmission once the vector is allowed to repopulate the programme area. Data were collected in Southern Mali and the North, South, East and West of Burkina Faso. In Southern Mali a statistically significant difference in prevalence between migrants and non migrants was found only for migrants from Ivory Coast (p = 0.04). In Burkina Faso no statistically significant difference in prevalence and intensity of infection between migrant and non migrant was found with the exception of the villagers in the North, a marginal area for the parasite (p = 0.004). These findings suggest that immigrants will not constitute on important threat for the northern section of the well protected area of the Onchocerciasis Control Programme when the vector is allowed to repopulate the river valleys.

Adult↗
PubMed1990

Large scale ivermectin distribution and its epidemiological consequences.

Community trials were started to address questions concerning the safety of ivermectin during large scale treatment, its potential for transmission control, its effect in preventing ocular onchocercal disease, its acceptability and the organization of large scale treatment. A summary is presented of the major, latest results on the short-term epidemiological impact of large scale ivermectin treatment, as observed in eight community trials undertaken in the Onchocerciasis Control Programme in West Africa (OCP). Ivermectin treatment resulted in a 96%-99% reduction in the mean load of microfilariae (mf) in the skin in treated patients. The subsequent mf-repopulation of the skin was faster than in the clinical trials and after 12 months the mean loads had returned to more than 40% of the pre-treatment load. Ocular mf loads were also greatly reduced and a post-treatment regression of early lesions of the anterior segment of the eye was observed. The transmission of Onchocerca volvulus was reduced by some 60% during the first year after treatment in one trial but no additional reduction was observed after the second treatment round. These results, and other recent research findings, have been used to quantify an epidemiological model for the transmission and control of onchocerciasis. Preliminary results of computer simulations of the predicted long-term epidemiological impact of large scale ivermectin treatment indicate that ivermectin treatment may play a very important role in disease control but that it is unlikely to become a practical tool for transmission control in endemic foci. Ivermectin treatment appears to be the most appropriate method for control of recrudescence of infection in an area where the parasite reservoir has been virtually eliminated by vector control, such as in the core area of the OCP.

Africa, Western↗
PubMed1990

Epidemiological impact of vector control. I. Incidence and changes in prevalence and intensity of Onchocerca volvulus infection.

Since 1974, the Onchocerciasis Control Programme (OCP) has been engaged in a large scale attempt to control the savanna species of the vector of onchocerciasis in seven West African countries. The effect of the vector control effort has been measured by epidemiological evaluation. For this purpose 474 villages have been examined by means of skin snip surveys between 1975 and 1983 and of these, 184 have been retained to-date for follow-up surveys which have documented over the years the reduction of the parasite population. The latest results of the epidemiological evaluation clearly demonstrate an outstanding success of the vector control campaign. The parasite has been or is close to being eliminated from the hyperendemic foci of the core area of the Programme. Major improvements have been registered in the reinvaded areas located at the Western and Eastern borders of the Programme. A major improvement has been found along the river Marahoué, the only focus of the intermediate area between the savanna and the forest where at the previous survey, the endemic situation was still similar to the pre-control situation. The exceptions to this gratifying picture are foci along the Dienkoa and Kulpawn rivers, both located in the core area, where transmission has relapsed and several more years of an effective vector control will be needed to eliminate the local parasite population.

Adult↗
PubMed1990

Epidemiological impact of vector control. II. Changes in ocular onchocerciasis.

The impact of 10-11 years of successful vector control on ocular onchocerciasis was evaluated in the population of 13 villages in the central part of the Onchocerciasis Control Programme area. The prevalence of ocular microfilariae was found to have reduced remarkably and loads over 20 microfilariae in the anterior chamber of the eye or the cornea which was rampant before the start of vector control, were rare. Whilst limited change in the age specific prevalence of lesions of the posterior segment of the eye was recorded, significant reduction in the prevalence of lesions of the anterior segment of the eye was found. The small decrease in the age specific prevalence of lesions of the posterior segment of the eye was partly explained by a reduced occurrence of the type of lesions of the anterior segment of the eye which previously obstructed the effective view of the fundus during examination. The prevalence of blindness was found to have reduced by 40% and onchocercal blindness was no longer found below the age of 20 years. It was concluded that 10-11 years of successful vector control has effectively reduced the incidence of onchocercal eye lesions, the deterioration of the existing eye lesions and the risk of developing an onchocercal eye lesion as well as going blind to virtually nil.

Adolescent↗