Malaria prevention during pregnancy in unstable transmission areas: the highlands of Madagascar.

Malaria transmission in Madagascar is highly variable from one region to the next, and the consequences of the disease on pregnant women and their foetuses are not fully documented. In midwestern Madagascar, the high-transmission lowlands in the west of the country meet the central plateaux, where malaria is unstable because of the high altitude and annual indoor spraying of DDT since 1993. We studied five of the region's main maternity clinics. We began by interviewing sample groups of women of childbearing age living within the vicinity of each clinic. This enabled us to determine the extent to which they had accessed and made use of available maternal health services during pregnancy and delivery, and, hence, to estimate the feasibility of boosting the prophylaxis. We then spent a whole year (from June 1996 to May 1997) observing deliveries at the five clinics in order to gauge the prevalence of placental infection and its consequences on birthweight in various transmission situations. Although only between 2 and 15% of the women said that they had taken prophylaxis during their previous pregnancy, the vast majority had benefited from preventive care: 97% had attended an antenatal visit on at least one occasion and 84% had had the assistance of medical or paramedical staff during delivery, even when their homes were situated relatively far away from the clinic (76%). In total, we observed 1637 deliveries with a mean placental malaria prevalence rate of 8.1%. Individual prevalence rates, however, were found to differ significantly between the maternity clinics situated in the east (minimum 2.1%) and west (maximum 26.2%) of the region. There were also marked variations in line with the seasonal fluctuations in entomological transmission. On the whole, a greater percentage of low birthweights (LBWs) was recorded at the lowland clinics than at the highland ones (17.1% vs. 9.7%), possibly because of the higher malaria infection rate in low altitude areas. On the other hand, the relative risk of LBW linked to placental infection was far greater in the highlands [4.9 (3.3-7.3)] than in the lowlands [1.9 (1.2-3.0)]. Although the rate of placental malaria among women inhabiting the country's central plateaux may be low, it means that transmission--and, hence, the risk of LBW because of placental infection--still persists in spite of the indoor DDT spraying programme. For maximum efficacy, we recommend a combination of vector control (extended to lower altitude areas outside the current OPID zone) and preventive care--i.e. individual chemoprophylaxis--for all highland women during pregnancy.

[Bancroftian filariasis in Madagascar: persistent endemicity]. / La filariose de Bancroft à Madagascar: une endémie persistante.

A major study was conducted to determine the prevalence of Bancroftian filariasis in 9 health districts located mainly on the east and north coast of Madagascar between 1995 and 1997. The study population included 2524 people 10 years or older. On the east and north coast, the incidence of microfilarial carriers varied depending on location from 7 p. 100 to 47 p. 100 in men and 3 p. 100 to 33 p. 100 in women. The highest incidences, i.e., around 33 p. 100 in both sexes, were observed in the southeastern districts of Ifanadiana, Manakara, and Vangaindrano. In the other districts on the east coast, the highest rates occurred mainly in men, i.e., 47 p. 100 in Vavatenina, 33 p. 100 in East Feneriva, and 33 p. 100 in Mahanoro. Only two districts on the west coast were studied, i.e., Marovoay where the incidence was zero and Ankazoabo where the prevalence was 4 p. 100 for men and 3 p. 100 for women. The results are compared with those of a study carried out in 1958. At 16.22 p. 100, chronic morbidity is relatively common in men but less disabling, i.e. mainly scrotal and member elephantiasis and hydroceles. Chronic morbidity was only 2.26 p. 100 in women, i.e. mainly member elephantiasis. Control of Bancroftian filariasis may be achievable by targeted use of drug prophylaxis and bednets in zones of high prevalence.

[Malaria in Antananarivo: evaluation of a post-epidemic situation]. / Le paludisme à Antananarivo: évaluation d'une situation post-épidémique.

Antananarivo has a population of close to one million inhabitants and is located in the highlands of Madagascar. The capital was, until some years ago, thought to be a malaria transmission-free zone. However, between 1985 and 1990, several malaria cases occurred in the suburbs of Antananarivo, along the Ikopa river (the Betsimitatatra Plain), suggesting that local transmission was occurring. Numerous malaria cases have since been reported by health workers each year, but there is insufficient epidemiological information about the cause and origin of the transmission, because cases are rarely confirmed by parasitological examination. The National Malaria Control Management in Madagascar has, after four years of intensive DDT spraying campaigns in the highlands, stopped this specific method of control. Epidemiological follow-up studies will be carried out to evaluate the effects on malaria transmission of this cessation of control measures. The transmission of malaria in Antananarivo was studied from 1995 to 1996. Patients from nine health centers in various suburbs of Antananarivo were included in the study, with the presence of fever used as the sole inclusion criterion. Children randomly selected from schools in the same area were included in a second study group. A blood sample was obtained from each participant to determine the parasite index and the prevalence of antibodies against P. falciparum. The splenic index was also determined. A second assessment was performed for the school children six months later, using the same markers of malaria infection. Nine hundred and thirty two patients from the health center group were referred for participation in the study. This represented 10% of all patients and 74% of the patients with fever. The school group included 1,545 children. The splenic index was similarly low (0.5%) in the health center and school groups, as was the overall parasite index (2.6% for the health center group and 0.8% in the school group). The prevalence of antibodies against P. falciparum was also low, but with a seasonal variation: 2.5% in June 1995 and 11.6% in January 1996. Almost all the cases confirmed by parasitological examination were due to the patient having stayed in an area with hyperendemic malaria or having been in contact with an individual who had been to an area with a high level of transmission. Our findings confirm that Antananarivo is now in a post-epidemic situation. Malaria cases are mostly associated with a history of travel in areas with high levels of malaria transmission, particularly the coastal regions of Madagascar. Nevertheless, a low level of transmission may persist and lead to further outbreaks of malaria in the future, due to the presence in the area of Anopheles arabiensis.

[The reconquest of the Madagascar highlands by malaria]. / La reconquête des Hautes Terres de Madagascar par le paludisme.

A strong malaria epidemic with a high mortality rate occurred on the Madagascar Highlands in 1986-88. Vector control and free access to antimalaria drugs controlled the disease. The authors have searched for the causes of the epidemic to propose a strategy avoiding such events. The Highlands on Madagascar were known as malaria free. In 1878 a very severe epidemic flooded all the country. Development of irrigated ricefields which house both An. arabiensis and An. funestus had created a new anthropic environment. Moreover manpower imported from malarious coastal areas for rice cultivation and also for building large temples, could have brought P. falciparum. After several outbreaks the disease became endemic up to 1949. In 1949 a malaria eradication programme based on DDT spraying and drug chemoprophylaxis and chemotherapy was launched. By 1960 malaria was eliminated and DDT spraying cancelled. Only 3 foci were kept under surveillance with irregular spraying until 1975. The prophylaxis and treatment centres ("centres de nivaquinisation") were kept open up to 1979. The catholic dispensary of Analaroa, 100 km N.E. of Tananarive, opened in 1971 and worked without interruption up to now. The malaria diagnosis has always been controlled by microscopy. Its registers are probably the more reliable source of information on malaria in the area. They show that malaria was already present on the Highlands in 1971 but at a low prevalence; in 1980 when the "centres de nivaquinisation" were closed the number of cases increased by three times the progressive increase of the number of cases became exponential from 1986 to 1988 which was the peak of the epidemic; malaria remained at a high level until the end of 1993; yearly DDT spraying since 1993 have decreased the number of malaria cases among the dispensary attendants by 90%. The epidemic peak of 1988 was well documented by the Pasteur Institute of Madagascar around Tananarive. Before the epidemic started it was observed a come back of An. funestus which had been previously eliminated of most of the villages by DDT spraying. More than an epidemic the malaria increase in 1988 was a reconquest by malaria of the land from which it had been eliminated in the years 1950. This episode became dramatic because the lack of immunity of the population and the shortage of medicaments. The global warming which was advocated to explain the epidemic has no responsibility because the temperature on the Madagascar Highlands has not changed during the last 30 years. Also the cyclones do not seem to have played any role. It is very likely that the gradual decline of control measures, first DDT spraying, later drug distributions, had the main responsibility in the Highlands drama. Everywhere An. funestus reached a high level during the time where the parasite reservoir was rebuilding. They synergised each other. These findings should be taken in account in drawing the strategy planning for the next years.

[Evolution of Plasmodium falciparum drug sensitivity in Madagascar from 1982 to 1993 and operational consequences]. / Evolution de la chimiosensibilité de Plasmodium falciparum a Madagascar de 1982 a 1993 et conséquences operationnelles.

Madagascar was one of the first African countries with reported chloroquine drug resistance of P. falciparum. Suspected as early as 1975, it was confirmed in 1981. Hereafter, regular tests in vivo and in vitro have been performed and allow for a study of drug resistance development. In 742 standard in vivo tests at the dose of 25 mg/kg of chloroquine that were executed between 1983 and 1993, R I resistance levels could be found in 8.5% of cases, R II was found in 8.2%. No resistance at R III levels was detected. The overall situation for in vitro is equally favorable. In 406 tests 78% of samples proved sensitive. The investigations undertaken by the Pasteur Institute of Madagascar, by the Institute for Tropical Medicine and Epidemiology in Paris and by the Unit of Epidemiological Surveillance within the Malagasy Ministry of Health raise a number of questions: Taking to account the various causes for imprecision in measurement and in evaluation (variations in parasite density, microscopic detection levels, bio-availability of the drug) of the groups of R I and R II how significant are the variations observed in numbers and proportions of resistance levels R I and R II? How important are the effects of auto-medication? Can they be correctly evaluated by Bergquist's test? How explain the low level of drug resistance in a country close to East Africa, in which chemoprophylaxis has been widely practiced and in which insufficient dosage for treatment is common? The absence of R III resistance in vivo permit for chloroquine to remain the first line treatment for malaria in Madagascar.(ABSTRACT TRUNCATED AT 250 WORDS)

[Epidemiological stratification of malaria in Madagascar]. / Stratification épidémiologique du paludisme à Madagascar.

Madagascar is considered as a sub-region of the Afrotropical geographical Region in spite of the high endemicity of 95% of the invertebrates. Nevertheless the three malaria vectors An. gambiae s.s., An. arabiensis and An. funestus are quite similar to those of the continental Africa. This support the hypothesis of their recent introduction. Plasmodium falciparum is the dominant parasite but the prevalence of P. vivax is not negligible. It is linked to the Asian component of the human population. P. malariae and P. ovale are of minor importance. The main epidemiological "facies" of Africa are found in Madagascar. The equatorial facies on the East Coast is characterized by a high transmission all year long. In the tropical facies on the West Coast transmission is seasonal (7 months at least). In both areas, malaria is stable and the inhabitants acquire a high immunity before the age of ten; most of the severe cases touch children below 10. The three vectors can be found but An. gambiae s.s. is dominant. In the exophilic southern facies the transmission is seasonal (two to four months). The only vector is An. arabiensis. Malaria is unstable and severe epidemics occur during the years of high rainfall. All age groups are vulnerable because the population is not immune in the Plateaux facies above 1,000 m., malaria is unstable. Severe epidemics occurred in 1987-1988. The vectors are An. Arabiensis and An. funestus. The occurrence of P. falciparum on the Plateaux seems linked to the development of irrigation of rice farming in the XIXth century. Most of the anopheles breeding places on the Plateaux are dependent on rice cultivation. Urban development has brought the inhabitants of the suburbs in close contact with rice fields. Despite the high number of anopheline bites the number of malaria cases remains by far lower than in the neighbouring rural areas. Regional migrations inside the island bring non-immune populations, from the south and the plateaux, in highly malarious areas of the coast, where the migrants are exposed to high risk. In spite of 40 years of uncontrolled use, chloroquine can still cure most, if not all, of malaria cases. Control measures appropriated to the different areas of Madagascar are discussed.

Epidemiologie du paludisme sur les hautes terres malgaches depuis 1878

Le paludisme est decrit sur les cotes malgaches depuis le XVIe siecle; mais la premiere epidemie liee a l'introduction de plasmodium falciparum n'est survenue sur les hautes terres qu'en 1878. La deuxieme epidemie; de 1896; a permis l'installation d'une transmission endemique jusqu'a la compagne d'eridication des annees 1950. L'arret progressif des activites antipaludiques dans les annees 1970 a permis une reinfestation progressive des hautes terres et la survenue d'une epidemie meurtriere de 1986 a 1988 qui redevient endemique depuis 1989. Ces trois epidemies ont en commun une repartition geographique heterogene; un mode de transmission instable et une tres forte morbidite-mortalite