[Malaria study in the cyclone risk zone: entomological , diagnostic and therapeutic approach in the southeastern region of Madagascar]. / Etude du paludisme en zone de risque cyclonique: approche entomologique, diagnostique et thérapeutique dans la région Sud-Est de Madagascar.

Madagascar is a tropical island affected by many natural disasters. The eastern coastal zone--an area of perennial malaria transmission--is regularly exposed to cyclones. Few malaria studies have been done in this area of Madagascar, and none have examined the potential relationship between malaria and natural disasters. A mobile team spent six weeks in the fields doing three lines of research: an entomological study by catching mosquitoes and determining their species: a therapeutic study of chloroquine (CQ) and sulphadoxine-pyrimethamine (SP) according to a 14 days WHO protocol and also a study of physician's diagnostic ability. Physicians were asked to make a presumptive clinical diagnosis of all febrile patients, and these results were compared to those obtained from blood smear examinations. The entomological study found three major vectors species: Anopheles gambiae, An. funestus and An. mascarensis. The therapeutic study showed that SP was 100% effective (n = 13) and only one case of CQ treatment failure was recorded (1/15). Finally the diagnostic study demonstrated that presumptive diagnosis of malaria based on the only clinical signs leads to an over-estimation of malaria frequency. Over 68% (102/149) of febrile patients were diagnosed by physicians to have malaria while only 52 (34.9%) were proven positive. Of the 47 patients diagnosed clinically as malaria-negative, 12 (25.5%) turned out to be positive. Outbreaks of malaria during or after natural disasters in Madagascar can be successfully treated with either CQ or SP, but compliance may be better with SP since it requires only one dose. Perhaps equally important in the context of natural disasters is to have the capacity to make a definitive diagnosis, and the dipsticks should be made available.

[Evaluation of the vectorial capacity of Anopheles arabiensis (Diptera:Culicidae) on the island of Réunion: an approach to the health risk of malaria importation in an area of eradication]. / Evaluation de la capacité vectorielle d'Anopheles arabiensis (Diptera: Culicidae) à l'île de La Réunion: une approche du risque sanitaire lié au paludisme d'importation en zone d'éradication.

Following intensive control measures, malaria was eradicated from La Réunion Island (Indian Ocean) in 1979. However, potential vectors remain in coastal areas and, each year Public Health Services detect some imported cases from surrounding countries. Anopheles arabiensis is the only species which can be responsible for local transmission though its brief life cycle and its exophilic and zoophilic behaviour were found to be key elements in maintaining the eradication status of the disease on the island. Its vectorial capacity was measured at different seasons and in different areas with a view to assessing the health risks due to imported malaria and suggesting a more pertinent strategy of vector control.

[Rice: source of life and death on the plateaux of Madagascar]. / Le riz source de vie et de mort sur les plateaux de Madagascar.

Since the 17th century, Europeans travelling in Madagascar described the contrast between the fever-free Plateau and the fever-ridden coasts. The former were inhabited by people of Asiatic origins and the latter by African migrants. At the end of the 18th century, "Merina" kings developed land irrigation and rice cultivation, using manpower from the coasts. Since then, rice has become a monoculture covering most of the arable lands of the Highlands. The first malaria epidemic occurred in the Tananarive area in 1878, and rapidly spread throughout the Plateau. The mortality rate was high. A second epidemic in 1895 may have been a resurgence of the previous one. Subsequently, malaria became meso-epidemic despite control measures, mainly consisting of larvivorous fishes, quinine treatment and prophylaxis. In 1949, an eradication program was launched based on DDT house-spraying and chloroquine prophylaxis in children. It was very successful on the Highlands where malaria disappeared, in 1962. Spraying was cancelled and only three small foci remained under surveillance. In 1987 and 1988, a malaria outbreak devastated the plateau. Subsequently, intensive spraying operations brought the situation under control by 1993. The main malaria vector on the Madagascar Highlands is An. funestus. More than 95% of its breeding sites are in the rice fields just before the harvest and afterwards in the fallow lands. The vector peak and the corresponding peak of malaria cases occur between February and May, depending on the farming calender. The second but less important vector, An. arabiensis, breeds in the rice fields just after seeding when the surface water is sunlit. Although rice fields remain the main source of this vector, it also breeds in rainwater pods and borow-pits. Malaria vectors on the plateau are products of human activities of rice cultivation, which is the basis of the economy. The epidemiological importance of rice fields varies greatly from one country to another. In Southeast Asia, the rice fields harbor several anopheline species most of which are only vectors of P. vivax. In West Africa where malaria is holoendemic, they produce large populations of An. gambiae; however, the malaria pattern is unaltered and remains at peak levels. In the dry areas of southern Madagascar, the vector An. funestus and meso-hyperendemic malaria are restricted to areas of cultivated rice. In West and Central Africa, An. funestus is never found in rice fields even though it is common in marshes. In Madagascar, this vector breeds in irrigated rice fields. Because it is practically impossible to control anophelines in rice fields by chemical, biological and ecological methods on the Highlands of Madagascar, house-spraying remains the best method for mass malaria control. Bed-nets impregnated with pesticides may offer an alternative, but their use is resisted by the local population.

[Malaria: research perspectives in medical entomology in Madagascar]. / Paludisme: perspectives des recherches en entomologie médicale a Madagascar.

The entomological studies on malaria in Madagascar had especially concerned the behavior of vectors in relation to insecticides. The cessation of spraying within the homes and the absence of chloroquine allowed a re-emergence of malaria on the Plateau in the 1980's. This phenomenon pointed out the heterogeneity of the transmission on the island. It was necessary to define the entomological characteristics of the four principal facies of transmission in Madagascar. These studies provided the services of public health with the epidemiological basis to organize the measures of the battle and prevention of malaria. In the very populated countryside of the Plateau, the nature of the vectors, their density and their vectorial competence present large local variations. The entomological studies search to define the different human and environmental factors which modulate the transmission and constitute the risk factors of epidemy. This micro-epidemiological approach will facilitate the analysis and comparison of the clinical and biological results obtained in the different residences. The research on medical entomology will equally enable the proposal of plans for the fight against malaria adapted to the different situations.

[Longitudinal study on malaria transmission and biology of vectors in the island of Sainte Marie, on the east coast of Madagascar, from 1988 to 1990]. / Etude longitudinale de la transmission du paludisme et de la biologie des vecteurs à l'île Sainte Marie, côte Est de Madagascar, de 1988 à 1990.

A 17-month longitudinal malaria survey was carried out in Sainte Marie Island, on the East Coast of Madagascar, from November 1988 to March 1990. During 706 man-nights of captures, 46401 mosquitoes belonging to 32 species were caught. Sporozoïte rates were calculated by Elisa. The malaria vectors were Anopheles gambiae sensu stricto, An. funestus and An. mascarensis. An. gambiae was the main vector. It was highly anthropophilic and partially exophilic. Transmission by this species mainly occurred from November to April, monthly sporozoïte antigene positivity rate varied from 0 to 3.85. The annual inoculation rate was about 100 infecting bites per man, in which 92 by Plasmodium falciparum. An. funestus intervened weakly in transmission. An. mascarensis, a malagasy endemic region anopheline is a newly discovered vector. The observed sporozoïte rate varied from 0.4 to 0.9 between September and March 1990. Parasite indexes in human fluctuated during the year from 64 to 80%. Because of the high level of transmission, recommendations for inhabitants and tourists are proposed.