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Prevention of malaria epidemics by vector control in Burundi highlands

Prevention of malaria epidemics by vector control in Burundi highlands. MSF UK Scientific day, 2007. Natacha Protopopoff, Dismas Baza, Michel Van Herp, Peter Maes, Wim Van Bortel, Tanguy Marcotty, Umberto D’Alessandro, Marc Coosemans. Introduction (1). Background

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Prevention of malaria epidemics by vector control in Burundi highlands

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  1. Prevention of malaria epidemics by vector control in Burundi highlands MSF UK Scientific day, 2007 Natacha Protopopoff, Dismas Baza, Michel Van Herp, Peter Maes, Wim Van Bortel, Tanguy Marcotty, Umberto D’Alessandro, Marc Coosemans

  2. Introduction (1) • Background • 2000 malaria epidemics (In Karuzi : 500 000 cases over a population of 300 000 people) • After the epidemics: • 4 years vector control activities implemented by MOH, MSF-B and ITM-Antwerp in Karuzi. • Evaluation by cross sectional surveys

  3. Limit +/-700 m +/-700 m Intervention Treated Valley Intervention non Treated Hill top Introduction (2) • Intervention description • 2002-2005: One round IRS/ year targeted in the valleys before the transmission period (More than 90% coverage).

  4. Introduction (3) • Intervention description • 2002: 2 LLIN distributed/household (total: 24000) • High net retention after distribution but quick decreased during following years.

  5. Limit +/-700 m +/-700 m Intervention Treated Valley Intervention non Treated Hill top Introduction (4) • Objectives • Reduction vectors density & transmission • Reduction of malaria prevalence • Protective effect of treated valleys on non treated hill tops

  6. Material and Methods (1) • Study design

  7. Material and Methods (2) • Study design • 2002-2006: 2 cross sectional surveys/year (3 and 9 months after IRS): total 9 surveys • Sample size: 25 clusters by area, 8 houses by cluster • Anopheles mosquitoes: indoor resting collection • Human population: blood slide collection (age group 1-9 y and >9)

  8. Results Anopheles density (1) -90%** -60%* -93%** -68%* -96%** -89%* -91%** -85%** % reduction between Intervention and Control valleys. * p<0.05, ** p<0.001

  9. Results Anopheles density (2) • Additional benefit of using net in the sprayed houses: reduction in Anopheles density of 77% (CI95%: 35-83, p=0.001) • No significant difference in Anopheles densitybetween hill tops of intervention and control areas despite a high reduction in the intervention treated valleys

  10. Results malaria transmission • The overall reduction on the infectious bites is 91.1% (CI95%: 67.9-97.6, p=0.001) in intervention valleys compared to control valleys. • Reduction of vectors density • Reduction of sporozoite rates among vectors in intervention valley (1.0%) compared to control valley (2.4%) (OR: 0.4 (CI95%: 0.2-0.8) p=0004) • No significant difference in malaria transmission between control and intervention hill tops

  11. Results malaria prevalence (1) Age group 1 to 9 years old -12% -57%* -49% -53%* -64%* -49% -43% -38% • % reduction ((1-OR)*100) between Intervention and Control valleys. • * p<0.05

  12. Results malaria prevalence (2) • Prevalence of malaria infection in infants (1 to 11 months) during survey 6 in the valleys * OR adjusted for age

  13. Surveys conclusions • IRS feasible in unstable political context • High impact on vectors with additional protective effect of nets • High impact on transmission • Moderate impact on prevalence • No reduction on intervention hill tops • Intervention focus on the higher risk areas: Higher anopheles density and malaria prevalence in the valleys than hill tops • From 2002-2006: Malaria cases didn’t reach epidemic threshold in Karuzi

  14. Lessons learnt • Collaboration with WHO, MOH & local authorities • Expertise product purchase, quality control • Standard tools (LLIN, pre-pack dose ready to use, Sprayers) • Implementation methodology (HR training, IRS, LLIN distribution vs dumping) • MSF internal precursor, • Other MSF large scale intervention (e.g.:Malaria: Sierra Leone, Kenya (Wadjir), Tchad, Indonesia ; Chagas: Nicaragua) • Essential VC requirement in medical infrastructures • Networking with specialists and suppliers

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