Impact of promoting longer-lasting insecticide treatment of bed nets upon malaria transmission in a rural Tanzanian setting with pre-existing high coverage of untreated nets

Table 1 The estimated malaria transmission intensity attributable to the Anopheles gambiae complex and Anopheles funestu s, computed for each village separately and the 2008 overall average

Species	Idete	Namawala	Overall
Sporozoite prevalence (S; %)
A. gambiae complex	0.22	0.33	0.32
No. tested by ELISA	1,858	3,148	5,006
A. funestus	2.13	<0.09	1.71
No. tested by ELISA	422	105	527
Biting rate (B; b/p/n)
A. gambiae complex	33.51	89.66	60.90
A. funestus	2.40	1.05	1.74
No. of trap nights	916	732	1,648
Entomological inoculation rate (EIR; ib/p/y)
A. gambiae complex	26.3	124.8	71.1
A. funestus	18.7	0.3	10.8
Total	45.0	125.1	81.9
Proportion parous
A. gambiae complex	0.45	0.54	0.51
No. dissected	353	736	1,089
*A. gambiae* complex sibling species proportion
A. arabiensis	0.87	0.84	0.86
A. gambiae	0.12	0.15	0.14
No. PCR amplifications	1,481	2,599	4,080
Bed net usage (%) ^a
Untreated	41.0	47.3	44.8
Treated	47.0	46.6	46.8
Overall	87.9	94.0	91.5
No. of bed net users	4,112	6,551	10,663

S = no. of sporozoite positive mosquitoes/no. of mosquitoes tested
B = no. of mosquitoes collected/no. of trap nights/calibration factor of 0.30 for A. gambiae complex and 0.68 for A. funestus; and EIR = S × B × 365
^a Calculated as the percentage of people who slept under a bed net the previous night; bed nets were considered to be treated if insecticide had been applied in the previous 12 months

ISSN: 1475-2875