Table 4. Visceral leishmaniasis incidence rate before and after introduction of insecticide treated bed nets in Fulbaria upazila, Mymensingh district, Bangladesh compared to a contemporaneous control area without ITN distribution.

	Number of cases (Incidence Rate per 10,000 per year)		Rate change [After-Before]† (p value)	% reduction compared with control (p value)†
	Before intervention¶	After intervention¶
Intervention n = 37050	534 (144.13)	178 (48.04)	-96.09 (<0.0001)	-46.80 (<0.0001)
Control n = 34923	477 (136.59)	377 (107.95)	-28.63 (0.0006)
Total N = 71973	1011 (140.47)	555 (77.11)	-67.44 (<0.0001)
Rate Difference (I-C)	7.54 (0.3901)	-59.91 (<0.0001)	-67.45 (<0.0001)

*ITN = insecticide treated net, either a long lasting insecticide impregnated bed net or a KO TAB 1-2-3 self-impregnated net. Distributions were done in 2004, 2006 and 2008 respectively.

† Effect of intervention is calculated using difference-in-difference (DID) estimate, δ = (B–A)–(D–C), where A and B are the baseline value and post-intervention value for VL-affected HH per 1,000 HH/VL incidence per 10,000 persons in the intervention area respectively; C and D are the baseline value and post-intervention value for VL affected HH per 1,000 HH/VL incidence per 10,000 persons in the control area respectively. The effect of intervention is negative or positive if δ is negative or positive. Then the percentage reduction by intervention is calculated as [δ/A] × 100.

‡p values were calculated by Z statistic for pre- or post-rate differences between intervention and control areas.