Madagascar presents a large heterogeneity in terms of climate and altitude, which explains the uneven spread of malaria throughout the island. The capital, Antananarivo, counts more than one million inhabitants, altitude between 1250 and 1470 m, in an area where the transmission is low but malaria may cause deadly epidemic outbreaks. Numerous malaria cases are reported, without biological confirmation, and reliable data about urban malaria transmission are lacking. The " Institut Pasteur de Madagascar" together with the Malagasy Ministry of Health performed in 2003 a study about malaria transmission in Antananarivo. A prevalence survey of malaria among fever syndromes, with data collected from 43 urban dispensaries, showed that confirmed malaria cases represented only 2% of the total fever cases (15 cases out of 779 fever syndromes). The vast majority was imported from costal areas (13 cases out of 15), where malaria is hyperendemic. However, a local urban transmission was found for two patients and five other subjects identified during a proximity survey. Vectors A. arabiensis and A. funestus were found inside the patient houses, located in close proximity of flooded rice fields. Genetic analysis of P. falciparum strains allowed to distinguish three genotypes, aggregated by house. The analysis of parasite genome polymorphism proves here its validity for epidemic surveys in areas where malaria is unstable, with no premunition in the local urban population.

• Le present article presente le paludisme sur les Hautes Terres Centrales de Madagascar et les strategies pour ameliorer les composantes du programme national de lutte contre le paludisme. Pour la prise en charge du patient suspect d'acces palustre, l'utilisation des bandelettes de diagnostic rapide, la prise en charge precoce a domicile par la chloroquine pre-emballee et les reflexions sur les nouvelles combinaisons therapeutiques a base d'artemisinine sont discutees. Pour les mesures de prevention, l'alternance des pulverisations intra domiciliaires ciblees et generalisees dans la lutte antivectorielle, l'utilisation de moustiquaires impregnees d'insecticides, le passage au traitement preventif intermittent pour les groupes a risque, l'amelioration du systeme de surveillance et d'alerte epidemique par l'utilisation de la methode de Lot Quality Assurance Sampling pour l'investigation epidemiologique en cas de depassement du seuil d'alerte et la mise a disposition des bandelettes de diagnostic rapide sont etudies.

In the Madagascar Highlands, 0.76% of children from 168 random primary schools, and 19 of 150 families from 3 villages, had oval-shaped erythrocytes. Most harboured the deletion in the band 3 gene characteristic of South-East Asian ovalocytosis. This genetic trait supports the Indonesian origin of the Madagascar settlement.

RESUME : Cette etude evalue la prevalence et la densite des hemoparasites chez 387 oiseaux appartenant a 43 especes,et collectes sur 6 sites repartis dans differents milieux bio-climatiques de Madagascar. 139 (35,9%) se sont reveles porteurs d’au moins un hemoparasite avec par ordre de frequence Plasmodium et/ou Haemoproteus (19,9% des 387 oiseaux), microfilaires (13,7%), Leucocytozoon (11,1%) et Trypanosoma (1,0%). Pour analyser ces observations, nous avons envisage l’interaction de differentes variables environnementales (altitude, saison, site de capture) et propres a l’oiseau (âge, poids, sexe). Il est clair que certains parasites infectent preferentiellement certaines especes ou familles. Les plus gros oiseaux de sexe mâle presentent des prevalences et des densites d’hemoparasites significativement plus elevees, pour toutes especes d’oiseaux confondues. L’ensemble de ces observations permet de mieux comprendre l’interaction oiseau/parasite et souleve nombre de questions sur la pathogenicite de ces parasites et sur leur transmission vectorielle. Mots-cles : Hemoparasite - Oiseau - Plasmodium - Haemoproteus - Leucocytozoon - Trypanosoma - Microfilaire - Transmission vectorielle - Madagascar.

This study aims to evaluate the prevalence and density of haemoparasites in native Malagasy birds. Among the 387 birds, belonging to 43 species sampled at six localities in different bio-climatic zones of the island, 139 (35.9%) showed at least 1 hemoparasite with, by order of frequency, Plasmodium and/or Haemoproteus (19.9%), microfilariae (13.7% of 387 birds), Leucocytozoon (11.1%) and Trypanosoma (1.0%). An analysis to further elucidate these observations took into account the interaction of different environmental variables (altitude, season, site of collection) or aspects of the birds (age, weight, sex). There is evidence that some parasites preferentially infect some bird species or families. The largest male birds harboured the highest prevalences and densities of haemoparasite, regardless of species. These findings extend knowledge of bird/blood parasite relationships of Malagasy birds and provide interesting insights, especially concerning the pathogenicity of this type of parasitism and the parasite transmission by insect vectors.

A New Viral Agent, SEN Virus (SENV), Has Been Detected in Patients from Several Countries: The Pathogenic Role of SENV in Coinfections with Hepatitis B Virus or Hepatitis C Virus Should Be Investigated To the Editor-We read with interest the study of Shibata et al.[1] regarding the prevalence of a newly identified virus, SEN virus (SENV), among patients with liver disease and blood donors in Japan.We agree that SENV subtypes H and D have a global distribution since, in addition to the detection of the virus in Italy [2], the United States [3], Canada [4], and Japan [1], we detected SENV in patients from France and Brazil.In our study, the prevalence of SENV was higher among patients with chronic hepatitis of unknown etiology (9 [11%] of 80 patients); the prevalence was similar for samples from both France and Brazil.None of the 30 blood donors tested, however, appeared to be positive for SENV.Moreover, we analyzed sequential serum samples from 15 patients with acute hepatitis of unknown etiology, and none of the patients tested positive for SENV-H or SENV-D.Whether SENV is, in fact, a cause of liver disease remains an unanswered question.As the field of molecular biology advances, the discovery of new viruses raises the need for a valid set of criteria to verify that there is indeed a causal relationship between the presence of certain viruses and a poorer prognosis of liver disease [5] or between the presence of hepatitis G virus infection and a slower evolution of human immunodeficiency virus infection [6].Additional studies also are warranted to investigate whether patients with hepatitis C virus or hepatitis B virus (HBV) infections have a higher degree of liver damage when SENV is present.This could allow for the determination of whether coinfection with SENV can worsen the course of liver disease in such patients.In our experience [7], occult HBV infection occurs frequently in patients with liver disease of unknown etiology.The investigation of the prevalence and impact of coinfections with SENV and known hepatitis viruses would provide additional information for the assessment of the role of SENV in liver disease.

To establish a simple definition of a malaria attack based on blood parasite density and other explanatory covariates, a cohort study was conducted from 1993 to 1996 in the Madagascar highlands undergoing a low seasonal transmission of falciparum malaria. Using logistic regression, the explanatory variables found to be significantly related to the risk of fever are parasite density, age, season, and year. However, and in contrast with other studies, we found no evidence of a clear cutoff in parasite density values consistent with the concept of "pyrogenic threshold" despite a gradual increase of the risk of fever with increasing parasite density. Furthermore, the model evidenced an individual-dependent relationship at a given age. This point was in accordance with the immunological data recorded from the participants. The investigators conclude that the parasite density to distinguish malaria attacks from other causes of fever is not reliable in a context of low falciparum transmission.

To control the reappearance of malaria in the Madagascan highlands, indoor house-spraying of DDT was conducted from 1993 until 1998. Before the end of the insecticide-spraying programme, a surveillance system was set up to allow rapid identification of new malaria epidemics. When the number of suspected clinical malaria cases notified to the surveillance system exceeds a predetermined threshold, a parasitological survey is carried out in the community to confirm whether or not transmission of falciparum malaria is increasing. Owing to the low specificity of the surveillance system, this confirmation stage is essential to guide the activities of the control programme. For this purpose, Lot Quality Assurance Sampling (LQAS), which usually requires smaller sample sizes, seemed to be a valuable alternative to conventional survey methods. In parallel to a conventional study of Plasmodium falciparum prevalence carried out in 1998, we investigated the ability of LQAS to rapidly classify zones according to a predetermined prevalence level. Two prevalence thresholds (5% and 15%) were tested using various sampling plans. A plan (36, 2), meaning that at least 2 individuals found to be positive among a random sample of 36, enabled us to classify a community correctly with a sensitivity of 100% and a specificity of 94%. LQAS is an effective tool for rapid assessment of falciparum malaria prevalence when monitoring malaria transmission.

Following the severe malaria outbreak in the central highlands in Madagascar in 1986, a vector control program by use DDT pm 75 house-spraying has been implemented to operate in areas located at altitudes between 1000 and 1500 m. Early treatment with chloroquine has also been incorporated in the control program. To detect areas at particular high risk for malaria outbreak the Geographic Information System (GIS) has been applied and tested. The study has shown that the system can be used in malaria surveillance in order to identify areas in which an intense distribution of Anopheles funestus can be anticipated and, hence, targeted in spraying campaigns. The system may also be used to monitor changes in anti-malarial drug resistance, in addition, to control of other vector-born diseases.

The central region of Madagascar is a vast area of highlands (altitude 700-2000 m). Malaria transmission has re-established itself here since the last epidemic of 1985-90 and has caused the deaths of 40,000 persons according to the Minister of Health. To combat the main malaria vector in the region, Anopheles funestus, annual programmes of indoor house spraying of DDT were carried out between December 1993 and January 1998 in most rural areas at altitude 1000-1500 m. A parasitological and serological study was then conducted in the highland schools to evaluate the impact of the programme and set up a database on the region. Using a cluster-sampling method 2 independent selections were conducted (one of 130 sites, the other of 40 sites). During the study, 13,462 schoolchildren were examined, 71% living in sprayed villages. Parasite prevalence among schoolchildren declined as altitude increases, from 11% at 700-900 m to 0.4% at > 1500 m. Below 1500 m, the impact of the spraying on the prevalence of the parasite was very clear (an average decrease of from 20% to 2.7% below 1000 m and of from 4.5% without spraying to 0.8% at 1000-1500 m). Geographical analysis of the data showed that the marginal regions remained the most affected by malaria (especially outside spraying zones), and persistence of 'pockets of transmission' at 1000-1500 m, essentially in areas where spraying has never been used. In 9 schools, anti-Plasmodium antibodies were sought by indirect immunofluorescence on thick smears of parasitized red blood cells. The seroprevalence ranged from 22% to 63%, which suggests that the parasite is still circulating in the region. Even though our data show that vector control continues to be very successful in the Madagascan highlands, rapid reinfection could occur and must be monitored following spraying. To this end, the Minister for Health, with the support of the Italian Co-operation, has placed the region under epidemiological surveillance since 1997. An alert system for the timely detection of the sources of epidemics and the targeting of the antivectoral campaign is also in operation. Our study suggests that this strategy should be reinforced by the spraying of DDT in the marginal zones in order to consolidate the results obtained at higher altitudes.

Chloroquine is still the drug of choice for first-line treatment of uncomplicated malaria in Madagascar. However development and spread of chloroquine-resistance could compromise this therapeutic strategy in the future. The purpose of this 1997 study was to compare the efficacy of combined treatment using sulfadoxine and pyrimethamine and single-agent treatment using chloroquine for management of uncomplicated malaria. Study data were collected at four sites in coastal areas of Madagascar where transmission of malaria is perennial. Prevalence of malaria ranged from 15 p. 100 to 22 p. 100 in school children and from 24 p. 100 to 72 p. 100 in outpatient consulting spontaneously at community health centers. All four Plasmodium species affecting man were identified. Plasmodium falciparum was involved in 83 p. 100 of cases. In vivo testing of the susceptibility of Plasmodium falciparum to chloroquine was performed in 149 patients according to the standard simplified 7-day protocol of the WHO. The 35 tests in school children demonstrated no evidence of resistance. However type R1 + R2 resistance was noted in 17 of the 114 tests performed on outpatients, i.e. 14.9 p. 100. In vitro testing demonstrated chloroquine resistance in four of the 90 specimens tested, i.e. 4.4 p. 100. With regard to combined sulfadoxine/pyrimethamine treatment, 45 of 46 in vivo tests in outpatients showed no evidence of resistance. Combination treatment was more effective than single-agent treatment (p = 0.02) and could offer an effective alternative for future use.

Although the national policy for malaria control in Madagascar is to use chloroquine as the first line of treatment, mefloquine has been and is recommended to travellers to the country, both for malaria prevention and cure. The in-vitro susceptibility of Plasmodium falciparum to mefloquine was therefore assessed during a prospective surveillance study in various areas in Madagascar, including the tourist sites of Nosy-be and Sainte Marie. Of the 254 isolates of P. falciparum successfully tested, 232 (90.9%) were sensitive to mefloquine, 12 (4.7%) showed decreased susceptibility (40 nM < IC50 < 50 nM), and 10 (3.9%) were resistant (IC50 > 50 nM). Five (50%) of the resistant strains and nine (75%) of those with decreased susceptibility were from coastal areas or the two tourist sites. The drug pressure that could have induced the resistance observed could therefore be related to the donation of antimalarials, such as mefloquine, by tourists to local populations. The residents of the coastal areas take any donated drugs as self-medication, ignoring recommended doses and durations of treatment. This situation has two main consequences: (1) there is an urgent need to control the abusive and incorrect use of antimalarial drugs in Madagascar, to safeguard the effectiveness of chemotherapy in the future; and (2) these increases in resistance compromise the efficiency of the antimalarial chemoprophylaxis currently recommended to tourists. The use of mefloquine can no longer be considered as a guarantee of protection against malaria in coastal areas and other sites frequented by tourists.

Resistance of Plasmodium falciparum to chloroquine was first suspected in Madagascar in 1975 and later confirmed in vivo and in vitro. During the period from 1985 and 1990, the network of public health monitoring stations reported that 1% of the population living on the central Highlands of Madagascar died of malaria. Thereafter the National Malaria Control Program achieved good success by spraying homes with insecticide and reorganizing distribution of chloroquine in all villages. However data recorded between 1996 and 1998 indicates that, after four years of widespread chloroquine use, resistance to amino-4-quinolones is progressing in Madagascar. The tests described in this report were performed on patients with documented malaria included in cohorts and followed year round by a physician. The three villages studied were located along the borders of the highlands between the plateaus and coastal areas. In vivo tests showed that the incidence of chloroquine resistance was 0% in Mahakary, 32% in Ankazobe and 30% in Saharivo. Clinically, however, treatment was unsuccessful in only 16% and 8% of cases respectively. In vitro tests demonstrated chloroquine sensitivity in 79% of the 153 strains tested. No resistance to quinine or halofantrine was observed. In vitro tests indicated an onset of resistance to mefloquine. Although the success rate of chloroquine treatment is nearly 80%, spread of strongly chloroquine-resistant strains is a risk especially in subjects with mild immunity to malaria.