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Table 6 Comparative estimates of annual PfEIR using the two different methods [13], for malaria mosquitoes collected: indoors versus outdoors, in wet versus dry seasons, using different trapping methods, and in the different geographical zones of the study area

From: Dramatic decreases of malaria transmission intensities in Ifakara, south-eastern Tanzania since early 2000s

Attributes Category No. mosquitoes caught No. trap nights (no. traps per night * no. nights) Biting rate (no. mosquitoes/no. nights) No. sporozoites positive Sporozoite positive rate PfEIR by standard methoda PfEIR by alternative method a
Location Indoors 3801 1792 2.12 0 0 0 0
Outdoors 4394 1780 2.47 1 0.00023 0.205 0.205
Season Wet (December–May) 7604 1786 4.26 0 0 0 0
Dry (June–November) 591 1786 0.33 1 0.00169 0.204 0.204
Temperature Cool (June–September) 706 1190 0.59 1 0.00142 0.307 0.307
Hot (October–May) 7489 2382 3.14 0 0 0 0
Zones North and Western area (Viwanja Sitini and Ifakara Mjini) 853 1427 0.60 0 0 0 0
South and central areas (Lipangalala and Mlabani) 2379 1427 1.67 0 0 0 0
Eastern peri-urban areas (Katindiuka) 4963 714 6.95 1 0.00020 0.511 0.511
Trapping method HLC 5197 1200 4.33 1 0.00019 0.304 0.304
CDC light trap 1894 1192 1.59 0 0 0 0
Suna trap 1104 1180 0.94 0 0 0 0
Overall 8195 3572 2.29 1 0.000122 0.102 0.102
  1. aThe standard method calculates PfEIR as a product of sporozoites rates and human-biting rates; i.e., C*(Number of sporozoite positive mosquitoes/Number of mosquitoes tested) × (Number of mosquitoes collected/Number of trap nights) × 365(46), where, C is the relative efficiency coefficient for the relationship between CDC-light trap catches and human landing catches. The alternative method calculates PfEIR the ratio of sporozoite positive mosquitoes and number of nightly catches; i.e., C*(no of sporozoite positive mosquitoes/number of trap nights) × 365(14). Though the sporozoite rates are varied, the PfEIR estimates are same, primarily because all An. gambiae and An. funestus were analysed