Determining areas that require indoor insecticide spraying using Multi Criteria Evaluation, a decision-support tool for malaria vector control programmes in the Central Highlands of Madagascar

BACKGROUND: The highlands of Madagascar present an unstable transmission pattern of malaria. The population has no immunity, and the central highlands have been the sites of epidemics with particularly high fatality. The most recent epidemic occurred in the 1980s, and caused about 30,000 deaths. The fight against malaria epidemics in the highlands has been based on indoor insecticide spraying to control malaria vectors. Any preventive programme involving generalised cover in the highlands will require very substantial logistical support. We used multicriteria evaluation, by the method of weighted linear combination, as basis for improved targeting of actions by determining priority zones for intervention. RESULTS: Image analysis and field validation showed the accuracy of mapping rice fields to be between 82.3% and 100%, and the Kappa coefficient was 0.86 to 0.99. A significant positive correlation was observed between the abundance of the vector Anopheles funestus and temperature; the correlation coefficient was 0.599 (p < 0.001). A significant negative correlation was observed between vector abundance and human population density: the correlation coefficient was -0.551 (p < 0.003). Factor weights were determined by pair-wise comparison and the consistency ratio was 0.04. Risk maps of the six study zones were obtained according to a gradient of risk. Nine of thirteen results of alert confirmed by the Epidemiological Surveillance Post were in concordance with the risk map. CONCLUSION: This study is particularly valuable for the management of vector control programmes, and particularly the reduction of the vector population with a view to preventing disease. The risk map obtained can be used to identify priority zones for the management of resources, and also help avoid systematic and generalised spraying throughout the highlands: such spraying is particularly difficult and expensive. The accuracy of the mapping, both as concerns time and space, is dependent on the availability of data. Continuous monitoring of malaria transmission factors must be undertaken to detect any changes. A regular case notification allows risk map to be verified. These actions should therefore be implemented so that risk maps can be satisfactorily assessed

Outbreak of Dengue and Chikungunya Fevers, Toamasina, Madagascar, 2006

An outbreak of dengue-like syndrome occurred in Toamasina from January through March 2006. Dengue type l or chikungunya viruses were detected in 38 of 55 patients sampled. Aedes albopictus was the only potential vector collected. Of 4,242 randomly selected representative residents interviewed retrospectively, 67.5% reported a dengue-like syndrome during this period

Longitudinal survey of malaria morbidity over 10 years in Saharevo (Madagascar): further lessons for strengthening malaria control

<p>Abstract</p> <p>Background</p> <p>Madagascar has been known for having bio-geo-ecological diversity which is reflected by a complex malaria epidemiology ranging from hyperendemic to malaria-free areas. Malaria-related attacks and infection are frequently recorded both in children and adults living in areas of low malaria transmission. To integrate this variability in the national malaria control policy, extensive epidemiological studies are required to up-date previous records and adjust strategies.</p> <p>Methods</p> <p>A longitudinal malaria survey was conducted from July 1996 to June 2005 among an average cohort of 214 villagers in Saharevo, located at 900 m above the sea. Saharevo is a typical eastern foothill site at the junction between a costal wet tropical area (equatorial malaria pattern) and a drier high-altitude area (low malaria transmission).</p> <p>Results</p> <p>Passive and active malaria detection revealed that malaria transmission in Saharevo follows an abrupt seasonal variation. Interestingly, malaria was confirmed in 45% (1,271/2,794) of malaria-presumed fevers seen at the health centre. All four <it>Plasmodia </it>that infect humans were also found: <it>Plasmodium falciparum</it>; <it>Plasmodium vivax</it>, <it>Plasmodium malariae </it>and <it>Plasmodium ovale</it>. Half of the malaria-presumed fevers could be confirmed over the season with the highest malaria transmission level, although less than a quarter in lower transmission time, highlighting the importance of diagnosis prior to treatment intake. <it>P. falciparum </it>malaria has been predominant (98%). The high prevalence of <it>P. falciparum </it>malaria affects more particularly under 10 years old children in both symptomatic and asymptomatic contexts. Children between two and four years of age experienced an average of 2.6 malaria attacks with <it>P. falciparum </it>per annum. Moreover, estimated incidence of <it>P. falciparum </it>malaria tends to show that half of the attacks (15 attacks) risk to occur during the first 10 years of life for a 60-year-old adult who would have experienced 32 malaria attacks.</p> <p>Conclusion</p> <p>The incidence of malaria decreased slightly with age but remained important among children and adults in Saharevo. These results support that a premunition against malaria is slowly acquired until adolescence. However, this claims for a weak premunition among villagers in Saharevo and by extension in the whole eastern foothill area of Madagascar. While the Malagasy government turns towards malaria elimination plans nowadays, choices and expectations to up-date and adapt malaria control strategies in the foothill areas are discussed in this paper.</p

Geographical and environmental approaches to urban malaria in Antananarivo (Madagascar)

<p>Abstract</p> <p>Background</p> <p>Previous studies, conducted in the urban of Antananarivo, showed low rate of confirmed malaria cases. We used a geographical and environmental approach to investigate the contribution of environmental factors to urban malaria in Antananarivo.</p> <p>Methods</p> <p>Remote sensing data were used to locate rice fields, which were considered to be the principal mosquito breeding sites. We carried out supervised classification by the maximum likelihood method. Entomological study allowed vector species determination from collected larval and adult mosquitoes. Mosquito infectivity was studied, to assess the risk of transmission, and the type of mosquito breeding site was determined. Epidemiological data were collected from November 2006 to December 2007, from public health centres, to determine malaria incidence. Polymerase chain reaction was carried out on dried blood spots from patients, to detect cases of malaria. Rapid diagnostic tests were used to confirm malaria cases among febrile school children in a school survey.</p> <p>A geographical information system was constructed for data integration. Altitude, temperature, rainfall, population density and rice field surface area were analysed and the effects of these factors on the occurrence of confirmed malaria cases were studied.</p> <p>Results</p> <p>Polymerase chain reaction confirmed malaria in 5.1% of the presumed cases. Entomological studies showed <it>An. arabiensis </it>as potential vector. Rice fields remained to be the principal breeding sites. Travel report was considered as related to the occurrence of <it>P. falciparum </it>malaria cases.</p> <p>Conclusion</p> <p>Geographical and environmental factors did not show direct relationship with malaria incidence but they seem ensuring suitability of vector development. Absence of relationship may be due to a lack of statistical power. Despite the presence of <it>An. arabiensis</it>, scarce parasitic reservoir and rapid access to health care do not constitute optimal conditions to a threatening malaria transmission. However, imported malaria case is suggestive to sustain the pocket transmission in Antananarivo.</p

Données récentes sur la sensibilité d'Anopheles arabiensis et d'Anopheles funestus aux pyréthrinoïdes et au DDT sur les Hautes Terres Centrales de Madagascar; résultats préliminaires montrant une absence de la mutation Kdr chez An. arabiensis

International audienceThe data indicate a decrease in the efficiency of α-cypermethrin 0.025% (Tkd99 = 21 mn) and of DDT 4% (Tkd99 = 191.5 mn) on An. arabiensis in Analamiranga. Neverthelesss, the effectiveness of permethrin 0.250% has been notified. In Soanierana, α-cypermethrin 0.025% was effective against An. arabiensis, whilst the ineffectiveness of the DDT 4% (Tkd99= 116 mn) in Andranonahoatra was observed. In Alasora, a fall in the effectiveness of α-cypermethrin 0.025% (Tkd99 = 21 mn) and the resistance to DDT 4% (Tkd99 = 6894 mn) was noted. No kdr mutation was detected on the kd gene of An. arabiensis resistant to the α-cypermethrin 0.025% and to DDT 4%, collected in Alasora. An. funestus collected in the district of Miandrivazo is susceptible to pyrethroids and to DDT. To conclude, in the Malagasy Central Highlands, An. arabiensis is ordinary sensitive to pyrethroid and poorly sensitive, or even resistant to DDT (as observed in Antananarivo plain). However, An. funestus remains sensitive to all tested insecticides; this observation is crucial because this anopheles vector is the first target of the campaigns of indoor spraying insecticides.RESUME : Anopheles arabiensis et Anopheles funestus sont les vecteurs principaux du paludisme sur les Hautes Terres Centrales de Madagascar. Dans le cadre des CAID (Campagnes d'Aspersions Intradomicilaires) d'insecticide, ces deux espèces de moustiques ont été ou sont encore en contact depuis plusieurs années avec des insecticides. Le suivi de la sensibilité de ces deux vecteurs aux insecticides est essentiel pour les directives de lutte anti-vectorielle. Cet article rapporte des études faites entre 2000 et 2003 sur :-des tests de sensibilité d'An. arabiensis et l'observation de l'effet knock down contre cinq papiers imprégnés de pyréthrinoïdes (α-cyperméthrine 0,025%, cyfluthrine 0,150%, deltaméthrine 0,050% et perméthrine 0,250%) et de DDT 4% dans trois villages du Moyen-Ouest (district de Tsiroanomandidy) et dans un village de la plaine d'Antananarivo;-des tests de sensibilité d'An. funestus dans un village du district de Miandrivazo contre quatre papiers imprégnés de pyréthrinoides (cyfluthrine 0,150%, deltaméthrine 0,050% et λ-cyhalothrine 0,050%) et de DDT 4%;-les résultats préliminaires sur l'absence d'une éventuelle mutation kdr, responsable de la résistance au DDT et aux pyréthrinoïdes, chez une population d'An. arabiensis de la plaine d'Antananarivo résistante au DDT. Les populations d'An. arabiensis du Moyen-Ouest et de la plaine d'Antananarivo montrent une baisse de sensibilité, voire une résistance au DDT 4%; cette baisse de sensibilité a été confirmée par l'allongement du Temps kd 99. Aucune mutation de type kdr n'a été mise en évidence parmi les anophèles résistants. Ces anophèles sont sensibles à la perméthrine (0,250%) et montrent une légère, mais néanmoins surprenante, baisse de sensibilité à un autre pyréthrinoïde, l'α-cyperméthrine. Dans le district de Miandrivazo, An. funestus reste parfaitement sensible aux pyréthrinoïdes et au DDT. En conclusion, sur les Hautes Terres Centrales de Madagascar, An. arabiensis est généralement sensible aux pyréthrinoïdes et peu sensible, voire résistant au DDT (comme dans la plaine d'Antananarivo). Au contraire, An. funestus est sensible à tous les insecticides testés; cette observation est essentielle puisque c'est An. funestus qui est la cible prioritaire des CAID

Données récentes sur la sensibilité d'Anopheles arabiensis et d'Anopheles funestus aux pyréthrinoïdes et au DDT sur les Hautes Terres Centrales de Madagascar; résultats préliminaires montrant une absence de la mutation Kdr chez An. arabiensis

International audienceThe data indicate a decrease in the efficiency of α-cypermethrin 0.025% (Tkd99 = 21 mn) and of DDT 4% (Tkd99 = 191.5 mn) on An. arabiensis in Analamiranga. Neverthelesss, the effectiveness of permethrin 0.250% has been notified. In Soanierana, α-cypermethrin 0.025% was effective against An. arabiensis, whilst the ineffectiveness of the DDT 4% (Tkd99= 116 mn) in Andranonahoatra was observed. In Alasora, a fall in the effectiveness of α-cypermethrin 0.025% (Tkd99 = 21 mn) and the resistance to DDT 4% (Tkd99 = 6894 mn) was noted. No kdr mutation was detected on the kd gene of An. arabiensis resistant to the α-cypermethrin 0.025% and to DDT 4%, collected in Alasora. An. funestus collected in the district of Miandrivazo is susceptible to pyrethroids and to DDT. To conclude, in the Malagasy Central Highlands, An. arabiensis is ordinary sensitive to pyrethroid and poorly sensitive, or even resistant to DDT (as observed in Antananarivo plain). However, An. funestus remains sensitive to all tested insecticides; this observation is crucial because this anopheles vector is the first target of the campaigns of indoor spraying insecticides.RESUME : Anopheles arabiensis et Anopheles funestus sont les vecteurs principaux du paludisme sur les Hautes Terres Centrales de Madagascar. Dans le cadre des CAID (Campagnes d'Aspersions Intradomicilaires) d'insecticide, ces deux espèces de moustiques ont été ou sont encore en contact depuis plusieurs années avec des insecticides. Le suivi de la sensibilité de ces deux vecteurs aux insecticides est essentiel pour les directives de lutte anti-vectorielle. Cet article rapporte des études faites entre 2000 et 2003 sur :-des tests de sensibilité d'An. arabiensis et l'observation de l'effet knock down contre cinq papiers imprégnés de pyréthrinoïdes (α-cyperméthrine 0,025%, cyfluthrine 0,150%, deltaméthrine 0,050% et perméthrine 0,250%) et de DDT 4% dans trois villages du Moyen-Ouest (district de Tsiroanomandidy) et dans un village de la plaine d'Antananarivo;-des tests de sensibilité d'An. funestus dans un village du district de Miandrivazo contre quatre papiers imprégnés de pyréthrinoides (cyfluthrine 0,150%, deltaméthrine 0,050% et λ-cyhalothrine 0,050%) et de DDT 4%;-les résultats préliminaires sur l'absence d'une éventuelle mutation kdr, responsable de la résistance au DDT et aux pyréthrinoïdes, chez une population d'An. arabiensis de la plaine d'Antananarivo résistante au DDT. Les populations d'An. arabiensis du Moyen-Ouest et de la plaine d'Antananarivo montrent une baisse de sensibilité, voire une résistance au DDT 4%; cette baisse de sensibilité a été confirmée par l'allongement du Temps kd 99. Aucune mutation de type kdr n'a été mise en évidence parmi les anophèles résistants. Ces anophèles sont sensibles à la perméthrine (0,250%) et montrent une légère, mais néanmoins surprenante, baisse de sensibilité à un autre pyréthrinoïde, l'α-cyperméthrine. Dans le district de Miandrivazo, An. funestus reste parfaitement sensible aux pyréthrinoïdes et au DDT. En conclusion, sur les Hautes Terres Centrales de Madagascar, An. arabiensis est généralement sensible aux pyréthrinoïdes et peu sensible, voire résistant au DDT (comme dans la plaine d'Antananarivo). Au contraire, An. funestus est sensible à tous les insecticides testés; cette observation est essentielle puisque c'est An. funestus qui est la cible prioritaire des CAID

Study on the movement of Rattus rattus and evaluation of the plague dispersion in Madagascar.

International audiencePlague affects mainly the rural areas in the central highlands of Madagascar. Rattus rattus is the main rodent host of Yersinia pestis in these localities. Since the introduction of plague, endemic foci have continued to expand, and spatiotemporal variability in the distribution of human plague has been observed. To assess the movements of R. rattus and evaluate the risk of dispersion of the disease, a field study at the scale of the habitats (houses, hedges of sisals, and rice fields) in the plague villages was carried out during high and low seasons of plague transmission to humans. The systemic oral marker Rhodamine B was used to follow rats' movements. Baits were placed in different habitats, and trapping success was carried out once a month for 3 months after the bait distribution. Plague indicators (reservoirs' abundance, flea index, Y. pestis prevalence in fleas, and Y. pestis antibody prevalence in rats) were determined. The highest abundance of rats and marking efficiency were observed in the sisal hedges and the rice fields. Marked rats were captured most commonly near the points where baits were initially placed. The main movements of rats were observed between the houses and sisal hedges. Major differences were observed between the seasons of high and low plague transmission. During the season of low plague transmission, rats were more abundant in the sisal hedges and rice fields, with rats moving from the houses to the rice fields. During the high plague transmission season, rats moved from the hedges of sisal to the rice fields. Important indicators of vector abundance and plague transmission were higher during the high plague transmission season. The three study habitats were the risk areas for plague transmission, but the risk appeared highest in the houses and sisals. Rats' movements according to the season were likely directed by the availability of food