Spatial Analysis of Malaria Transmission Parameters in the Rice Cultivation Area of Office Du Niger, Mali

Sogoba, Nafomon; Vounatsou, Penelope; Doumbia, Seydou; Bagayoko, Magaran; Touré, Mahamadou B.; Sissoko, Ibrahim; Traorè, Sékou F.; Touré, Yéya T.; Smith, T.

doi:10.4269/ajtmh.2007.76.1009

Cited by 14 publications

(10 citation statements)

References 21 publications

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“…The human blood index (HBI) was signi cantly higher in Dangassa than in the irrigated rice farming area of Koïla Bamanan. This observation has now become common in Mali as rice farming has been associated with lower HBI as demonstrated by many studies [33,41]. The same observation has been reported in Senegal [42].…”

Section: Density and Human Blood Indexsupporting

confidence: 64%

Indoor and outdoor malaria transmission in two ecological settings in rural Mali: Implications for vector control

Keïta

Doumbia²,

Sissoko³

et al. 2020

Preprint

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Background: Implementation and upscale of effective malaria vector control strategies necessitates understanding the multi-factorial aspects of transmission patterns. The primary aims of this study are to determine the vector composition, biting rates, trophic preference, and the overall importance of distinguishing outdoor versus indoor malaria transmission through a study at two communities in rural Mali. Methods: Mosquito collection was carried out between July 2012 and June 2016 at two rural Mali communities (Dangassa and Koïla Bamanan) using pyrethrum spray-catch and human landing catch approaches at both indoor and outdoor locations. Species of Anopheles (An.) gambiae complex were identified by polymerase chain reaction (PCR). Enzyme-Linked -Immuno-Sorbent Assay (ELISA) were used to determine the origin of mosquito blood meals and presence of Plasmodium (P.) falciparum sporozoite infections.Results: A total of 11,237 An. gambiae (s.l.) were collected during the study period (5,239 and 5,998 from the Dangassa and Koïla Bamanan sites, respectively). Of the 679 identified by PCR in Dangassa, An. coluzzii was the predominant species with 91.4% of the catch followed by An. gambiae (8.0%) and An. arabiensis (0.6%). At the same time in Koïla Bamanan, of 623 An. gambiae s.l., An. coluzzii accounted for 99% of the catch, An. arabiensis 0.8% and An. gambiae 0.2%. Human Blood Index (HBI) measures were significantly higher in Dangassa (79.4%; 95% Bayesian credible interval (BCI) [77.4, 81.4]) than in Koïla Bamanan (15.9%; 95% BCI [14.7, 17.1]). The human biting rates were higher during the second half of the night at both sites. In Dangassa, the sporozoite rate was comparable between outdoor and indoor mosquito collections. For outdoor collections, the sporozoite positive rate was 3.6% (95% BCI [2.1-4.3]) and indoor collections were 3.1% (95% BCI [2.4-5.0]). In Koïla Bamanan, the sporozoite rate was higher indoors at 4.3% (95% BCI [2.7-6.3]) compared with outdoors at 2.4% (95% BCI [1.1- 4.2]). In Dangassa, corrected entomological inoculation rates (cEIRs) using HBI were for indoor locations were 13.74 infective bites/person/month (ib/p/m; 95% BCI: 9.21—19.14] and were 18.66 [12.55—25.81] ib/p/m, outdoors locations. For Koïla Bamanan,cEIRs were 1.57 [2.34 —2.72] ib/p/m and 0.94 [0.43—1.64] ib/p/m for indoor and outdoor locations, respectively. EIRs were significantly higher at the Dangassa site than the Koïla Bamanan site. Conclusion: The findings in this work may indicate the occurrence of active, outdoor residual malaria transmission is comparable to indoor transmission in some geographic settings. The high outdoor transmission patterns observed here highlight the need for additional strategies to combat outdoor malaria transmission to complement traditional indoor preventive approaches such as long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) which typically focus on resting mosquitoes.

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Section: Density and Human Blood Indexsupporting

confidence: 64%

Indoor and outdoor malaria transmission in two ecological settings in rural Mali: Implications for vector control

Keïta

Doumbia²,

Sissoko³

et al. 2020

Preprint

Self Cite

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“…In other areas, An. funestus density has been shown to be subject to seasonal variations associated with rice growth periods [28]. …”

Section: Discussionmentioning

confidence: 99%

Low and seasonal malaria transmission in the middle Senegal River basin: identification and characteristics of Anopheles vectors

Ndiath¹,

Sarr

Gaayeb

et al. 2012

Parasites Vectors

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BackgroundDuring the last decades two dams were constructed along the Senegal River. These intensified the practice of agriculture along the river valley basin. We conducted a study to assess malaria vector diversity, dynamics and malaria transmission in the area.MethodsA cross-sectional entomological study was performed in September 2008 in 20 villages of the middle Senegal River valley to evaluate the variations of Anopheles density according to local environment. A longitudinal study was performed, from October 2008 to January 2010, in 5 selected villages, to study seasonal variations of malaria transmission.ResultsAmong malaria vectors, 72.34% of specimens collected were An. arabiensis, 5.28% An. gambiae of the S molecular form, 3.26% M form, 12.90% An. pharoensis, 4.70% An. ziemanni, 1.48% An. funestus and 0.04% An. wellcomei. Anopheles density varied according to village location. It ranged from 0 to 21.4 Anopheles/room/day and was significantly correlated with the distance to the nearest ditch water but not to the river.Seasonal variations of Anopheles density and variety were observed with higher human biting rates during the rainy season (8.28 and 7.55 Anopheles bite/man/night in October 2008 and 2009 respectively). Transmission was low and limited to the rainy season (0.05 and 0.06 infected bite/man/night in October 2008 and 2009 respectively). During the rainy season, the endophagous rate was lower, the anthropophagic rate higher and L1014F kdr frequency higher.ConclusionsMalaria vectors are present at low-moderate density in the middle Senegal River basin with An. arabiensis as the predominant species. Other potential vectors are An. gambiae M and S form and An. funestus. Nonetheless, malaria transmission was extremely low and seasonal.

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“…The INDEPTH-MTIMBA data, which was used in our application, is the most comprehensive entomological database in Africa. Bayesian spatio-temporal binomial and zero inflated negative binomial regression models were developed to produce monthly maps of EIR taking into account the malaria–climate relation and seasonality in transmission (35, 36, 59–61). …”

Section: Discussionmentioning

confidence: 99%

“…In addition, due to the amount of zeros which is larger than what can be generated by the standard distributions, the data are over/under dispersed and zero inflated (21, 29–32). Statistical analysis which accounts for these characteristics is essential to obtain unbiased estimates for the regression coefficients (33–36). …”

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confidence: 99%

Modelling heterogeneity in malaria transmission using large sparse spatio-temporal entomological data

Rumisha

Smith

Abdulla

et al. 2014

Global Health Action

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BackgroundMalaria transmission is measured using entomological inoculation rate (EIR), number of infective mosquito bites/person/unit time. Understanding heterogeneity of malaria transmission has been difficult due to a lack of appropriate data. A comprehensive entomological database compiled by the Malaria Transmission Intensity and Mortality Burden across Africa (MTIMBA) project (2001–2004) at several sites is the most suitable dataset for studying malaria transmission–mortality relations. The data are sparse and large, with small-scale spatial–temporal variation.ObjectiveThis work demonstrates a rigorous approach for analysing large and highly variable entomological data for the study of malaria transmission heterogeneity, measured by EIR, within the Rufiji Demographic Surveillance System (DSS), MTIMBA project site in Tanzania.DesignBayesian geostatistical binomial and negative binomial models with zero inflation were fitted for sporozoite rates (SRs) and mosquito density, respectively. The spatial process was approximated from a subset of locations. The models were adjusted for environmental effects, seasonality and temporal correlations and assessed based on their predictive ability. EIR was calculated using model-based predictions of SR and density.ResultsMalaria transmission was mostly influenced by rain and temperature, which significantly reduces the probability of observing zero mosquitoes. High transmission was observed at the onset of heavy rains. Transmission intensity reduced significantly during Year 2 and 3, contrary to the Year 1, pronouncing high seasonality and spatial variability. The southern part of the DSS showed high transmission throughout the years. A spatial shift of transmission intensity was observed where an increase in households with very low transmission intensity and significant reduction of locations with high transmission were observed over time. Over 68 and 85% of the locations selected for validation for SR and density, respectively, were correctly predicted within 95% credible interval indicating good performance of the models.ConclusionMethodology introduced here has the potential for efficient assessment of the contribution of malaria transmission in mortality and monitoring performance of control and intervention strategies.

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Spatial Analysis of Malaria Transmission Parameters in the Rice Cultivation Area of Office Du Niger, Mali

Cited by 14 publications

References 21 publications

Indoor and outdoor malaria transmission in two ecological settings in rural Mali: Implications for vector control

Indoor and outdoor malaria transmission in two ecological settings in rural Mali: Implications for vector control

Low and seasonal malaria transmission in the middle Senegal River basin: identification and characteristics of Anopheles vectors

Modelling heterogeneity in malaria transmission using large sparse spatio-temporal entomological data

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