Journal Article > ResearchFull Text
BMJ Glob Health. 2022 December 1; Volume 7 (Issue 12); e009674.; DOI:10.1136/bmjgh-2022-009674
Van Bortel W, Mariën J, Jacobs BKM, Sinzinkayo D, Sinarinzi P, et al.
BMJ Glob Health. 2022 December 1; Volume 7 (Issue 12); e009674.; DOI:10.1136/bmjgh-2022-009674
BACKGROUND
Long-lasting insecticidal nets (LLINs) are one of the key interventions in the global fight against malaria. Since 2014, mass distribution campaigns of LLINs aim for universal access by all citizens of Burundi. In this context, we assess the impact of LLINs mass distribution campaigns on malaria incidence, focusing on the endemic highland health districts. We also explored the possible correlation between observed trends in malaria incidence with any variations in climate conditions.
METHODS
Malaria cases for 2011—2019 were obtained from the National Health Information System. We developed a generalised additive model based on a time series of routinely collected data with malaria incidence as the response variable and timing of LLIN distribution as an explanatory variable to investigate the duration and magnitude of the LLIN effect on malaria incidence. We added a seasonal and continuous-time component as further explanatory variables, and health district as a random effect to account for random natural variation in malaria cases between districts.
RESULTS
Malaria transmission in Burundian highlands was clearly seasonal and increased non-linearly over the study period. Further, a fast and steep decline of malaria incidence was noted during the first year after mass LLIN distribution (p<0.0001). In years 2 and 3 after distribution, malaria cases started to rise again to levels higher than before the control intervention.
CONCLUSION
This study highlights that LLINs did reduce the incidence in the first year after a mass distribution campaign, but in the context of Burundi, LLINs lost their impact after only 1 year.
Long-lasting insecticidal nets (LLINs) are one of the key interventions in the global fight against malaria. Since 2014, mass distribution campaigns of LLINs aim for universal access by all citizens of Burundi. In this context, we assess the impact of LLINs mass distribution campaigns on malaria incidence, focusing on the endemic highland health districts. We also explored the possible correlation between observed trends in malaria incidence with any variations in climate conditions.
METHODS
Malaria cases for 2011—2019 were obtained from the National Health Information System. We developed a generalised additive model based on a time series of routinely collected data with malaria incidence as the response variable and timing of LLIN distribution as an explanatory variable to investigate the duration and magnitude of the LLIN effect on malaria incidence. We added a seasonal and continuous-time component as further explanatory variables, and health district as a random effect to account for random natural variation in malaria cases between districts.
RESULTS
Malaria transmission in Burundian highlands was clearly seasonal and increased non-linearly over the study period. Further, a fast and steep decline of malaria incidence was noted during the first year after mass LLIN distribution (p<0.0001). In years 2 and 3 after distribution, malaria cases started to rise again to levels higher than before the control intervention.
CONCLUSION
This study highlights that LLINs did reduce the incidence in the first year after a mass distribution campaign, but in the context of Burundi, LLINs lost their impact after only 1 year.
Journal Article > ResearchFull Text
Trop Med Int Health. 2008 December 1; Volume 13 (Issue 12); 1479-1487.; DOI:10.1111/j.1365-3156.2008.02164.x
Protopopoff N, Verhaeghen K, Van Bortel W, Roelants P, Marcotty T, et al.
Trop Med Int Health. 2008 December 1; Volume 13 (Issue 12); 1479-1487.; DOI:10.1111/j.1365-3156.2008.02164.x
OBJECTIVES AND METHODS: In Burundi, the occurrence of the knock down resistance (kdr) mutation in Anopheles gambiae sensu lato (s.l.) was determined for six consecutive years within the framework of a vector control programme. Findings were also linked with the insecticide resistance status observed with bioassay in An. gambiae s.l. and An. funestus.
RESULTS: The proportion of An. gambiae s.l. carrying the East Leu-Ser kdr mutation was 1% before the spraying intervention in 2002; by 2007 it was 86% in sprayed valleys and 67% in untreated valleys. Multivariate analysis showed that increased risk of carrying the kdr mutation is associated with spraying interventions, location and time. In bioassays conducted between 2005 and 2007 at five sites, An. funestus was susceptible to permethrin, deltamethrin and DDT. Anopheles gambiae s.l. remained susceptible or tolerant to deltamethrin and resistant to DDT and permethrin, but only when kdr allele carriers reached 90% of the population.
CONCLUSIONS: The cross-resistance against DDT and permethrin in Karuzi suggests a possible kdr resistance mechanism. Nevertheless, the homozygous resistant genotype alone does not entirely explain the bioassay results, and other mechanisms conferring resistance cannot be ruled out. After exposure to all three insecticides, homozygote individuals for the kdr allele dominate among the surviving An. gambiae s.l. This confirms the potential selection pressure of pyrethroids on kdr mutation. However, the high occurrence of the kdr mutation, even at sites far from the sprayed areas, suggests a selection pressure other than that exerted by the vector control programme.
RESULTS: The proportion of An. gambiae s.l. carrying the East Leu-Ser kdr mutation was 1% before the spraying intervention in 2002; by 2007 it was 86% in sprayed valleys and 67% in untreated valleys. Multivariate analysis showed that increased risk of carrying the kdr mutation is associated with spraying interventions, location and time. In bioassays conducted between 2005 and 2007 at five sites, An. funestus was susceptible to permethrin, deltamethrin and DDT. Anopheles gambiae s.l. remained susceptible or tolerant to deltamethrin and resistant to DDT and permethrin, but only when kdr allele carriers reached 90% of the population.
CONCLUSIONS: The cross-resistance against DDT and permethrin in Karuzi suggests a possible kdr resistance mechanism. Nevertheless, the homozygous resistant genotype alone does not entirely explain the bioassay results, and other mechanisms conferring resistance cannot be ruled out. After exposure to all three insecticides, homozygote individuals for the kdr allele dominate among the surviving An. gambiae s.l. This confirms the potential selection pressure of pyrethroids on kdr mutation. However, the high occurrence of the kdr mutation, even at sites far from the sprayed areas, suggests a selection pressure other than that exerted by the vector control programme.
Journal Article > ResearchFull Text
PLOS One. 2009 November 25; Volume 4 (Issue 11); e8022.; DOI:10.1371/journal.pone.0008022
Protopopoff N, Van Bortel W, Speybroeck N, Van Geertruyden JP, Baza D, et al.
PLOS One. 2009 November 25; Volume 4 (Issue 11); e8022.; DOI:10.1371/journal.pone.0008022
INTRODUCTION: Malaria is re-emerging in most of the African highlands exposing the non immune population to deadly epidemics. A better understanding of the factors impacting transmission in the highlands is crucial to improve well targeted malaria control strategies.
METHODS AND FINDINGS: A conceptual model of potential malaria risk factors in the highlands was built based on the available literature. Furthermore, the relative importance of these factors on malaria can be estimated through "classification and regression trees", an unexploited statistical method in the malaria field. This CART method was used to analyse the malaria risk factors in the Burundi highlands. The results showed that Anopheles density was the best predictor for high malaria prevalence. Then lower rainfall, no vector control, higher minimum temperature and houses near breeding sites were associated by order of importance to higher Anopheles density.
CONCLUSIONS: In Burundi highlands monitoring Anopheles densities when rainfall is low may be able to predict epidemics. The conceptual model combined with the CART analysis is a decision support tool that could provide an important contribution toward the prevention and control of malaria by identifying major risk factors.
METHODS AND FINDINGS: A conceptual model of potential malaria risk factors in the highlands was built based on the available literature. Furthermore, the relative importance of these factors on malaria can be estimated through "classification and regression trees", an unexploited statistical method in the malaria field. This CART method was used to analyse the malaria risk factors in the Burundi highlands. The results showed that Anopheles density was the best predictor for high malaria prevalence. Then lower rainfall, no vector control, higher minimum temperature and houses near breeding sites were associated by order of importance to higher Anopheles density.
CONCLUSIONS: In Burundi highlands monitoring Anopheles densities when rainfall is low may be able to predict epidemics. The conceptual model combined with the CART analysis is a decision support tool that could provide an important contribution toward the prevention and control of malaria by identifying major risk factors.
Conference Material > Poster
Ndayisaba R, Colombe S, Van Bortel W, Sinarinzi P, Nzomukunda Y, et al.
MSF Scientific Day International 2024. 2024 May 16; DOI:10.57740/ultcgK
Conference Material > Slide Presentation
Leclair C, Marien J, Sinzinkayo D, Abdelrahman A, Lampaert E, et al.
MSF Scientific Days International 2021: Research. 2021 May 19
Conference Material > Abstract
Leclair C, Marien J, Sinzinkayo D, Abdelrahman A, Lampaert E, et al.
MSF Scientific Days International 2021: Research. 2021 May 19
INTRODUCTION
In Burundi, malaria continues to be a major public health issue as the leading cause of health facility attendance, high levels of mortality and devastating malaria epidemics in highland areas. Since 2004, Burundi’s National Malaria Control Programme (PNILP) has developed an integrated malaria control strategy. Since 2016, Médecins Sans Frontières (MSF), in collaboration with the PNILP, has implemented integrated malaria control interventions within two malaria endemic health districts located in the central highlands and eastern border regions.
METHODS
We re-assessed epidemiological trends for malaria in Burundi to: (1) evaluate spatial heterogeneity and seasonality; (2) longitudinally describe trends in disease incidence for three epidemiological strata; and (3) assess the association between long-lasting insecticidal net (LLIN) mass distribution campaigns (MDC) and disease incidence. Analysis used malaria case data, routinely collected and reported weekly by PNILP from 2011- 2019. Malaria cases were converted into incidence rates, using existing population data, and expressed per 1000 population at risk. Health districts (n=47) were categorized into three different strata based upon geographic elevation and endemic channels, using the quartile method. A generalized additive mixed model (GAMM) was implemented in R to analyze time-series data.
ETHICS
This work met the requirements for exemption from MSF Ethics Review Board review, and was conducted with permission from Sebastian Spencer, Medical Director, Operational Centre Brussels, MSF.
RESULTS
From 2011-2016, seasonality and intensity of malaria transmission was heterogeneous across the three epidemiological strata. The median incidence (cases/1000 population) for health districts <1200m elevation was 6.0 (interquartile range, IQR, 4.3-8.5); for those 1200-1850m, incidence was 12.3 (IQR 8.0-17.6); and for those >1850m, incidence was 2.1 (IQR 1.1-6.3). In contrast to the observed incidence rates for health districts within the endemic channels at <1200m and >1850m, health districts within the endemic
channel at 1200-1850m showed marked seasonality, with a bimodal distribution. Health districts in these endemic channels, had peaks in median incidence of 17.6 cases/1000 and 15.1cases/1000 population in weeks 26 and 52, respectively. GAMM analysis suggested an increasing trend in malaria incidence over the period 2011—2019. The analysis further revealed that LLIN-MDC campaigns were associated with a rapid reduction in malaria incidence, but the epidemiological impact was attenuated after one year. Specifically, comparing malaria incidence in three health districts adjacent to MSF’s intervention area (1200-1850m channel), the 2017 LLIN-MCD was associated with a 44% reduction in clinical incidence one year post-distribution (RR 0.56, 95%CI 0.556-0.56), but no evidence for a reduction two years post-distribution was observed RR 1.10 (95%CI 1.092-1.099).
CONCLUSION
These findings highlight the effectiveness of LLIN as a malaria control intervention across different epidemiological strata in Burundi. However, the duration of functional effectiveness of LLIN is most definitely less than 3 years and may be shorter than one year in Burundi. The reasons underlying these finding are legion. Further operational research is needed to disentangle the dynamic interplay between operational, human behavioural, sociological, and entomological factors.
In Burundi, malaria continues to be a major public health issue as the leading cause of health facility attendance, high levels of mortality and devastating malaria epidemics in highland areas. Since 2004, Burundi’s National Malaria Control Programme (PNILP) has developed an integrated malaria control strategy. Since 2016, Médecins Sans Frontières (MSF), in collaboration with the PNILP, has implemented integrated malaria control interventions within two malaria endemic health districts located in the central highlands and eastern border regions.
METHODS
We re-assessed epidemiological trends for malaria in Burundi to: (1) evaluate spatial heterogeneity and seasonality; (2) longitudinally describe trends in disease incidence for three epidemiological strata; and (3) assess the association between long-lasting insecticidal net (LLIN) mass distribution campaigns (MDC) and disease incidence. Analysis used malaria case data, routinely collected and reported weekly by PNILP from 2011- 2019. Malaria cases were converted into incidence rates, using existing population data, and expressed per 1000 population at risk. Health districts (n=47) were categorized into three different strata based upon geographic elevation and endemic channels, using the quartile method. A generalized additive mixed model (GAMM) was implemented in R to analyze time-series data.
ETHICS
This work met the requirements for exemption from MSF Ethics Review Board review, and was conducted with permission from Sebastian Spencer, Medical Director, Operational Centre Brussels, MSF.
RESULTS
From 2011-2016, seasonality and intensity of malaria transmission was heterogeneous across the three epidemiological strata. The median incidence (cases/1000 population) for health districts <1200m elevation was 6.0 (interquartile range, IQR, 4.3-8.5); for those 1200-1850m, incidence was 12.3 (IQR 8.0-17.6); and for those >1850m, incidence was 2.1 (IQR 1.1-6.3). In contrast to the observed incidence rates for health districts within the endemic channels at <1200m and >1850m, health districts within the endemic
channel at 1200-1850m showed marked seasonality, with a bimodal distribution. Health districts in these endemic channels, had peaks in median incidence of 17.6 cases/1000 and 15.1cases/1000 population in weeks 26 and 52, respectively. GAMM analysis suggested an increasing trend in malaria incidence over the period 2011—2019. The analysis further revealed that LLIN-MDC campaigns were associated with a rapid reduction in malaria incidence, but the epidemiological impact was attenuated after one year. Specifically, comparing malaria incidence in three health districts adjacent to MSF’s intervention area (1200-1850m channel), the 2017 LLIN-MCD was associated with a 44% reduction in clinical incidence one year post-distribution (RR 0.56, 95%CI 0.556-0.56), but no evidence for a reduction two years post-distribution was observed RR 1.10 (95%CI 1.092-1.099).
CONCLUSION
These findings highlight the effectiveness of LLIN as a malaria control intervention across different epidemiological strata in Burundi. However, the duration of functional effectiveness of LLIN is most definitely less than 3 years and may be shorter than one year in Burundi. The reasons underlying these finding are legion. Further operational research is needed to disentangle the dynamic interplay between operational, human behavioural, sociological, and entomological factors.
Journal Article > ResearchFull Text
Am J Trop Med Hyg. 2008 July 1; Volume 79 (Issue 1); 12-18.
Protopopoff N, Van Bortel W, Marcotty T, Van Herp M, Maes P, et al.
Am J Trop Med Hyg. 2008 July 1; Volume 79 (Issue 1); 12-18.
In a highland province of Burundi, indoor residual spraying and long-lasting insecticidal net distribution were targeted in the valley, aiming also to protect the population living on the hilltops. The impact on malaria indicators was assessed, and the potential additional effect of nets evaluated. After the intervention--and compared with the control valleys--children 1-9 years old in the treated valleys had lower risks of malaria infection (odds ratio, OR: 0.55), high parasite density (OR: 0.48), and clinical malaria (OR: 0.57). The impact on malaria prevalence was even higher in infants (OR: 0.14). Using nets did not confer an additional protective effect to spraying. Targeted vector control had a major impact on malaria in the high-risk valleys but not in the less-exposed hilltops. Investment in targeted and regular control measures associated with effective case management should be able to control malaria in the highlands.