Archives de l'Institut Pasteur de Madagascar最新文献

The "Institut Pasteur de Madagascar" virology laboratory is the National WHO Centre for Influenza surveillance in Madagascar. On this surveillance collaborate the Ministry of Health with 9 sentinel centres. In the present article, the authors relate the results of influenza surveillance in Antananarivo between 1995 and 2002. Among 6341 patients with nasal and/or pharyngeal swabs, influenza virus were isolated from 427 patients (6.7%): 307 (68.4%) influenza virus A (H3N2), 124 (27.1%) influenza virus B, 8 (4.0%) influenza virus A (H1N1). The virus had been continually spreading all year long. The weak and the strong points of the influenza sentinel surveillance are also discussed in order to ameliorate the collection processes of influenzal and respiratory morbidity data.

Enteroviruses, members of the family Picornaviridae, are responsible for a wide variety of diseases and represent a major public health hazard. Typing of non polio enterovirus (NPEV) infection is traditionally based on a serum neutralization assay. However, this method is time-consuming, labor-intensive, expensive, and may fail to identify antigenic variation. A new molecular typing involving partial sequencing of the genome has been recently developed. In this study, 46 NPEV strains were analyzed, including 37 antigenicaly "untypeable" viruses. Partial sequencing of the C-end of the viral capsid protein VP1 and pairwise identity with the prototype strains allow us to assign a serotype for all "untypeable" viruses. The results show a large number and wide variety of Coxsackieviruses A which belong to the HEV-C species and also Echoviruses and Coxsackieviruses B of the HEV-B species. This method may be useful to identify all NPEV serotypes in Madagascar and to assess the possible impact of circulating NPEV populations, as we enter the final stage of poliomyelitis eradication.

Since June 1997, a quarterly quality control of sputum smear exam for the tubercle diagnosis, depending on double reading of slides, was implemented between both central laboratories of the Mycobacteria National Reference Centre in Madagascar (mycobactoria laboratories of Institut Pasteur Madagascar [IPM] and Institut Hygiène Sociale [IHS]--Health Ministry). In 2000, four controls were done, in the course of which 240 slides were coloured by auramine, coming both from IPM and IHS, and another 80 slides from IHS were coloured by Ziehl-Neelsen. All the results were in agreement for the samples stained with auramine, while two false negatives were found for the samples stained with Ziehl-Neelsen. The maintenance of this quality control between the two laboratories is necessary to insure the reliability of their results and the controls that they make for the peripheral laboratories.

In 1994, prior to the Project of Development of the Plain of Antananarivo, an epidemiological survey was conducted in primary schools to assess the level of schistosomiasis. The results of stool examination by the Kato-Katz method demonstrated a prevalence of 4.3% among 6,169 randomized schoolchildren. The most infected four villages are located close the Mamba river. In 1999, after the realization of the project, another study had been done in the same Public Primary School to evaluate the evolution of schistosomiasis endemicity. 5,222 randomized pupils aged 5 to 16 years old took part in the study. The sex ratio was 1.4/1. The global prevalence was 1.8%. High prevalence are respectively notified in Antanandrano Primary school (23%) close to the Mamba river in the Northern part of the capitol and in Ambohitsoa Primary School (16.3%) located near the Mahazoarivo lac. Thus, between 1994 and 1999, a significant overall decrease in prevalence was observed (p < 10(-1)), although a few areas still have relatively high rates. Many factors may explain this improvement, including sanitary education, urbanization and a lack of conditions needed in the development of intermediate host. In addition, a high prevalence of ascaridiasis (79%) and trichocephalosis (67%) was observed. 4.3% of schoolchildren had been infected by Taenia sp. Schistosomiasis is hypoendemic in the plain of Antananarivo. The strategy against this disease must include an IEC programme, focusing in childhood exposure.

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.

Schistosomiasis is a major public health problem in Madagascar. The aim of the national control program is to reduce the morbidity in hyperendemic areas. A prospective study has been conducted in Morombe and Ampanihy to elaborate a simple method to identify Shistosoma haematobium hyperendemic communities. The study included 1,373 children from 5 to 15 years old in 17 primary schools. Moderate sensitivity and Negative Predictive Value, with high specificity and Positive Predictive Value of "blood in urine" and "Schistosomiasis" have been found. Those diagnosis values increase with age. The first symptom should be used in older children.

The first case of plague was introduced in Madagascar in 1898 in the east coast by way of boat from India. In 1921, plague reach the highlands and a large epidemic over the next twenty years. Until the beginning of the 80's, only of few case were identified, notified mostly in rural setting. However gradually it has re-emerged as a public health problem. Urban plague is located in the city of Antananarivo (resurgence in 1978 after 28 years of apparent silence) and in Mahajanga port (resurgence in 1991 after 63 years of silence). The reactivation of the Plague National Control Program from 1994 will allow better surveillance. The aim of this analysis is to update the epidemiological data on human plague in Madagascar based on reported cases obtained from the Central Lab of the Pasteur Institute of Madagascar from 1980 to 2001 (16,928 suspected cases of which 3,500 are likely positives or confirmed positives). The Plague season runs from October to March on the central highlands and July to November on the north-western coast. Sex-ratio male/female is 1.3/1, and the age-group of 5 to 25 years is more affected. The case fatality rate was 40% in the beginning of the 1980's, and decreased to 20% by the end of the 1990's. The percentage of case with pulmonary plague decrease from 15% to less than 5%. However, geographical extension is demonstrated: 4 districts in 1980, 30 districts in 1999 and 21 districts in 2001. In 2002, the diffusion of a new rapid test (reagent strip) in the primary health centres (CSB) in 42 endemic districts may help to decrease the morbidity and the letality due to plague and improve its control at the national level.

Tuberculosis during childhood is often due to Mycobacterium tuberculosis primo-infection. Tuberculosis is highly prevalent in Madagascar and most people are infected during childhood. Our objectives were to evaluate the primary resistance of M. tuberculosis and to determine the genotypes responsible for recent infection in the population. Thus we studied 142 isolated strains from 97 children (66 with pulmonary tuberculosis and 31 with extra-pulmonary tuberculosis) recruited in different health centers in Antananarivo from 1997 to 2000. Excepting one strain resistant to isoniazide, all strains were susceptible to the four antibiotics (streptomycin, isoniazid, ryfampicin and ethambutol). This result confirms the low rate of primary resistance reported during the two surveys in 1994-1995 and 1999-2000. 67 strains of 1997-2000 were typed with the genetic marker IS6110, 44 has been assigned to 13 clusters containing each 2 to 8 similar strains. Some IS6110 clusters have already been reported in 1994-1995. Some genotypes observed in 1994-1995 seemed to have disappeared in 1997-2000. (As the rate of the frequency of some genetic variants according to the period are more likely due to a difference in strain virulence). Since there is minimal antibiotic resistance versus M. tuberculosis in Madagascar, one can not explain the appearance or disappearance of certain variants because of drug resistance. Rather, this is due to the virulence of the various M. tuberculosis strains.