Ecological niche model analysis
MAY, CONTRACTION
To complement entomological collections, species-distribution models were initially constructed and validated before the randomisation of study clusters to intervention groups, to predict the geographical extent of different malaria-vector species across the study area.A pilot entomological survey was done in May, 2018, before the start of the cRCT. A total of 202 households across 92 villages were sampled for one night each using a CDC light trap. Separate niche models were constructed for Species-occurrence data from the 2 years following LLIN distribution were used as test records for external validation of preintervention niche models to assess changes after intervention in the geographical distribution of major malaria-vector species in the different study groups. The test AUC value was compared with initial model accuracy metrics obtained using baseline test data, whereby no change in AUC values indicated stability in species occurrence (ie, minimal change in species distribution after intervention relative to the preintervention period), whereas a decrease in AUC values indicated a shift or contraction in species occurrence after intervention relative to the predicted preintervention niche. A threshold was then applied to dichotomise the predicted habitat suitability into presence or absence and the test omission rate was calculated for each model.