Dust and meningitis A multidisciplinary work Preliminary results I. JEANNE 1, A. DEFOSSEZ 2, JL RAJOT 3, K.KIARI 4, M. KALACHE 1, P. BOISIER 1 CERMES, ENSG, IRD-Niamey, SNIS ESA - AMMA-Eu - Institut Pasteur - Coopération française - ENSG
Seasonal meningitis Epidemic Meningitis Agent: bacterium Neisseria meningitidis Reservoir Asymptomatic carriage ++ Clinically infected cases Spread human to human Direct contact (respiratory droplets) > 1h, < 1m Co-infection World Meningitis belt Reported to WHO: 750 000 case (10 years), 7% FR Epidemics Niger 1995 Nigeria 1996 Burkina Faso 1996 97, 2002 Mali 1997
Risk Human population Immunity, asymptomatic carriage, density, promiscuity, movment, meeting, Bacterial population serogroups, serotypes and subtypes : virulence, circulation Environnemental favorable factors Seasonality +++ Mechanisms not demonstrated In Sahel : dust (quantity, quality, iron, shape), humidity, lancover,..? Start, expand or end drivers?
Meningitis and climate Question: are there typical atmospheric conditions prior to crossing an epidemic threshold? First : what about dust events? Available data : notified presumptive cases of meningitis from 1995 to 2005 Scale in time : week Scale in space : district Need : 1. To improve diagnosis and to assess the reliability of notifications 2. Weekly dust representation at district scale or below
Monthly distribution of tested CSF specimens (2003-2005) Ateier Santé Climat Novembre 2005 Number tested 1400 1200 1000 800 600 400 200 0 H. influenzae S. pneumoniae N. meningitidis Negative Jan Fev Mar Avr Mai Jun Jul Aou Sep Oct Nov Dec 2 779 negative among 4565 tested Month 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% 600 500 400 300 200 100 0 % Ng Nm Jan Fev Mar Avr Mai Jun Jul Aou Sep Oct Nov Dec
Dust MAPS ESA EPIDEMIO AMMA ESA, CERMES, JENA OPTRONIK, SILOGIC, IRD Niamey, ENSG, UMLV Weekly maximum IDDI Infrared Difference Dust Index (IDDI) [Legrand, 2001] : vizualisation of dust concentration in arid and semi arid areas. Infra red band METEOSAT 5,6 et 7. African Meningitis Belt of West Africa (~ 4500x2000 km) November April 1995 2005 Spatial resolution : 5 km Clouds masks
Type of data Data Scale in space Scale in time Validation Epidemiological Districts Weekly data (Monday to Sunday) Exhaustive Presumptive Microbiological Health centers Day of collection Diagnosed Not yet exhaustive Horizontal visibility DMN 14 Stations in Niger + 4 sites Argos Several measures per day Dust maps Pixel : 5 km Weekly (Monday to Sunday ~ 15 km Field validation
Dust maps preparation Temporal profile / week Characterization of events / soil level Extraction of Niger PCA / year District mean
Characterization of events Ateier Santé Climat Novembre 2005
Scales 1 Scale in time 10 annual mean values Scale in space Niger Ateier Santé Climat Novembre 2005
10-years mean Ateier Santé Climat Novembre 2005
Interpretation => the dust comes from North East => Southwestern districts: less dust => 2 areas with a lot of dust N Guigmi Agadez => 3 areas with few dust Lac Tchad Aïr Northeastern Highlands
Scales 2 Scale in time Weeks Scale in space Niger Ateier Santé Climat Novembre 2005
pixels (bleu) et cas (rose) 8 7 6 5 4 3 2 1 Poussières et méningites 0 1 9 17 25 33 41 49 57 65 73 81 89 97 105 113 Semaines (4 années de Nov 95 à Avril 99) Epidemic (95-96 & 96-97) or non-epidemic years (97-98 & 98-99) Dust peak each year Time lag between dust peaks and meningitis incidence curve slope
coefficient r de Spearman Determination of best fitted time lag between dust events and meningitis 0,6 0,5 0,4 0,3 0,2 0,1 0-0,1-0,2 0 2 4 6 8 10 délai poussières / méningites (semaines) Années 96-97 (épidémiques) Années 98-99
Habitants / km² Meningitis and population 10000 1000 100 10 1 0,1 Nombre de cas selon la densité des districts 0,01 0 2000 4000 6000 8000 Nombre de cas par district de 1993 à 1999 At district level (n = 38), incidence of meningitis well correlated to population density : Spearman R # 0,799, p highly significant
Scales 3 Scale in time Years Scale in space Districts Ateier Santé Climat Novembre 2005
Ateier Santé Climat Novembre 2005
Maradi region : attack rates nb cases/100,000 inhabitants 2003 2004 Population immunity is a key factor Usually, at least 3 years between two epidemics in a given population
Maradi region : spatial distribution of population (main towns and villages)
Scales 4 Scale in time Year Scale in space Health facilities (CSI) Ateier Santé Climat Novembre 2005
0 0-5 km 5-15 km 15-30 km 30 50 km 50 100 km > 100 km Ateier Santé Climat Novembre 2005
Cerebrospinal fluid N.meningitidis A positive 2003 2004 2005 Ateier Santé Climat Novembre 2005
Scales 5 Scale in time Weeks Scale in space Health facilities (CSI)
Data transmission via Argos Weekly report, Alert Environnemental and epidemiological data
Evolution hebdomadaire des cas ded paludisme et de la pluviometrie enregistrés au CSI de Bengou (GAYA) en 2004 40 35 30 25 20 15 10 5 0 40 42 44 46 49 53 1 3 6 8 11 14 16 18 20 22 24 26 28 30 32 34 36 38 Semaine cas pluviometrie 80 70 60 50 40 30 20 10 0 Ateier Santé Climat Novembre 2005 nbre de cas mm de pluie
1 site Finer spatial scale More complete data data collection S2E Argos: pilot study Niger et Burkina Faso MEDES MEDIAS CNES CLS IRSS - ProdiG Global fund : 40 sites for malaria control measures evaluation (2005-2006) AMMA : analysis climate-diseases (malaria, meningitis,..) 350 300 250 200 150 100 50 0 5 8 11 14 17 20 23 26 30 33 36 39 42 45 48 pluies cas palu 70 60 50 40 30 20 10 0 Fiability transmission Quicker data data diffusion and andanalysis
Next perspectives Health center scale Improve exhaustivity CSF collection Improve data transmission (44 Argos) Analysis Dust/Meningitis for the whole Niger using population, roads, etc. and other meteo parameters Analysis for other Sahel countries (AMMA-Africa?)...
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