Evaluation des risques de réémergence de l'épidémie du virus Chikungunya dans la vallée du Monastère de Mont Ngafula, RD Congo

Contexte et objectif. L'épidémie à virus Chikungunya est émergente, invalidante et mortelle qui sévi partout. Le virus Chikungunya est transmis à l'homme par la piqûre des insectes infectés du genre Aedes. A Kinshasa, le récent épisode de l'épidémie remonte à 4 années. L'objectif de la présente étude a été d'évaluer les risques de réémergence de l'épidémie du virus Chikungunya à Kinshasa Mont Ngafula. Méthodes. Il s'agissait d'une étude transversale menée à Mont Ngafula, dans laquelle 4 sites ont été sélectionnés à l'aide d'un plan d'échantillonnage à plusieurs degrés du 1er juin au 30 août 2021. Les larves et les nymphes des insectes ont constitué le matériel biologique de l'étude. Des variables environnementales (Température, pH, turbidité, Conductivité et Saturation en oxygène) ont été recueillies dans les gîtes larvaires. Une analyse de régression logistique multivariée a été effectuée pour identifier les prédicteurs de la densité des gîtes larvaires. Résultats. 400 ménages et 738 gîtes larvaires ont été explorés. Les indices entomologiques, indice récipient (IR), indice maison (IM) et indice de Breteau (IB) évalués étaient supérieurs aux critères et normes de l'OMS. La saturation en oxygène, la turbidité et la conductivité se sont avérées significativement associées à la densité des gîtes larvaires. Conclusion. Les risques de réémergence de l'épidémie de Chikungunya à Kinshasa sont réels. Une surveillance entomologique est nécessaire pour mettre en place des mesures de prévention et de contrôle de santé publique.

Piloting a new approach for capacity building in entomology and vector control at the level of national malaria control programmes

Following a survey of entomology capacity in the African Region in 1999; a commitment to strengthen capacity was made and the African Network on Vector Resistance to Insecticides (ANVR) was launched in 2000. Its aim was to facilitate Member States to build capacity in vector control and to collaborate with institutions to standardize methods and approaches. In 2006 ANVR assessed capacity with regard to national malaria control programmes. This assessment provided data on the capacity of countries across the Region to undertake vector surveillance. Recommendations to improve the situation followed and in 2007; through the Bill and Melinda Gates Foundation; a project to strengthen infrastructure and capacity was begun. This article outlines the impressive results of the project and its wider implications for adopting similar approaches across the Region

Transmission Dynamics of Malaria in Four Selected Ecological Zones of Nigeria in the Rainy Season

Background: Two of the problems of malaria parasite vector control in Nigeria are the diversity of Anopheline vectors and large size of the country. Anopheline distribution and transmission dynamics of malaria were therefore compared between four ecotypes in Nigeria during the rainy season. Methods: Polymerase chain reaction (PCR) was used in molecular identification after morphological identification microscopically. Enzyme linked immunorsorbent assay (ELISA) was used for the blood meal analysis and sporozoite detection. Results: Five species were identified out of 16;410 anophelines collected. An. gambiae s.s made up approximately 29.2-36.6of the population in each zone. All five species acted as vectors for P. falciparum . An. gambiae s.s had the highest sporozoite rate. The most infected mosquitoes were found in the rain forest. More blood meals were taken from bovids; except the savannah forest; where 73.3were on humans and Human Blood index (HBI) was 57.3. The Entomological inoculation rate (EIR) was a mean of 13.6 ib/p but was highest in the rainforest zone. Conclusions and limitations: This study demonstrates the complex distribution of anophelines and the considerable variations in the intensity of malaria transmission in Nigeria. We highlight the need to consider diverse epidemiological situations when planning countrywide control programmes

Mosquito larval habitats and public health implications in Abeokuta, Ogun State, Nigeria

Abstract: The larval habitats of mosquitoes were investigated in Abeokuta, Nigeria in order to determine the breeding sites of the existing mosquito fauna and its possible public health implications on the residents of the City. The habitats were sampled between August 2005 and July 2006 using plastic dippers and a pipette. The habitats were grouped as ground pools/ponds, gutters/open drains, tyres, domestic containers and treeholes/ leaf axils. Ten species of mosquitoes were encountered in the fi ve habitats namely Mansonia africana, M. uniformis, Culex quinquefasciatus, Aedes aegypti, Ae. albopictus, Ae. vittatus, Cx tigripes, Anopheles gambiae s.l., An. funestus and Eretmapodite clnysogaster. Ae. aegypti bred in all the habitats sampled while Cx quinquefasciatus bred in four habitats except tree holes/leaf axils. An. gambiae s.l and Ae. albopictus occurred in three habitats while other species bred only in one or two habitats. Ground pools and domestic containers recorded the highest number of species followed by gutters/open drains. Tree holes/leaf axils was the least preferred habitat with the lowest number of species occurrence. However, statistical analysis revealed non-signifi-cant difference in species occurrence in the fi ve habitats. The availability of the habitats to support the breeding of Aedes, Culex and Anopheles, which are known vectors of urban yellow fever, lymphatic fi lariasis and malaria suggest that the residents of Abeokuta City are at risk of mosquito-borne diseases. It is important that residents of the City are enlighten on the environmental factors that contribute to mosquito breeding and that the Government should institute proper sanitation measures to reduce mosquito breeding sites

Insecticide resistance in the Simulium damnosum S. L. vectors of human onchocerciasis: distributional, cytotaxonomic and genetical studies

Human onchocerciasis is a debilitating disease caused by the filarial parasite Onchocerca volvulus (Leukart). The parasite is transmitted by dipterous insects of the family Simuliidae. ln West Africa, transmission is by members of lhe Simulium damnosum (Theobald) species complex. The manifestations of the disease are mainly dermal, lymphatic and ocular, the most severe of which is blindness hence the common name 'river blindness'. The disease is found in parts of Latin America, the Yemen and Sub-Sahara Africa. lt affects some 17.7 million people world-wide with 500,000 severely visually disabled and some 27O,00O blind. ln West Af rica, which is the most affected area, there are over 5 million infected with onchocerciasis and about 148,000 blind. ln view of this, the Onchocerciasis Control Programme in West Africa (OCP), one of the biggest vector control operations covering parts of 11 countries was started in 1975 by the World Health Organization to control onchocerciasis as a disease of public health and socio-economic importance. The initial strategy of the OCP was the application of insecticides to the breeding sites of the insect vectors. ln the OCP, temephos an organophosphate insecticide (OP) was the only chemical used for the initial five years due to its selective mode of action. Resistance to temephos first appeared in 1980 in a population of S. soubrense/S.sanctipauli on the Bandama river in Southern Côte d'lvoire. Later, similar resistant populations of the same species were identified in other river basins in the C6te d'lvoire. ln 1981 Chlorphoxim, also an OP, was used as a replacement for temephos in areas where resistance to temephos had been detected but a similar pattern of resistance was soon detected against chlorphoxim Careful monitoring of resistance to temephos has shown that it has spread to all river basins and different species of the S. damnosum complex at one time or another within the OCP area. Resistance to insecticides demands that large quantities and more novel and toxic chemicals have to be used in the fight against insects and other arthropod pests. This has important economic, operational and environmental demands. ln the West African vector control programme mentioned above, a rotation of 6 insecticides is used to manage insecticide resistance. This strategy places a major constraint on the operations of the Programme (OCP) due to the logistic need of stocking insecticides in the field

Anaplasmosis in Uganda. II. Prevalence of bovine anaplasmosis

The prevalence of bovine anaplasmosis was studied in 320 Zebu cattle randomly selected from three regions of Uganda (central; south-western and north-western) using DOT-ELISA; Western immunoblotting; Rapid Card Agglutination Test (RCAT); Capillary Tube Agglutination Test (CAT); Complement Fixation Test (CFT); and parasitological techniques. Dried blood on Whatman filter paper no. 1 was eluated in PBS 0.05pc Tween 20 prior to testing at an initial dilution of 1:25. The incidence of parasitaemia ranged from 25pc in the central region to 35pc in the north-western region and the serological prevalence was lower in the central region and highest in the north-west. Prevalence rates assayed by DOT-ELISA and Western immunoblotting were 1.5-fold greater than those tested with RCAT and 3-fold greater than in CAT. The overall prevalence rates by DOT-ELISA and Western immunoblotting compared favourably with CFT data. The present data utilizing dried blood on filter papers indicate that there is a high prevalence of anaplasmosis in those regions of Uganda surveyed and it confirms our observations and those of others that collecting blood on filter papers is a suitable technique for large-scale screening and for seroepidemiological studies

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