Kilimanjaro Christian Medical College
Impact of the combination of LLIN and IRS versus
LLIN alone on vector density and malaria
transmission in Northern Tanzania: A community
randomized Controlled Trial
Natacha Protopopoff, Alex Wright, Reginald Kavishe, Philippa West, Robinson Tigererwa,
Franklin W. Mosha, William Kisinza, Immo Kleinschmidt, Mark Rowland
Background
• ITN and IRS have been shown to be individually
effective in preventing malaria.
• Scale-up over the past decade in Africa
• Is there an additional benefit to using both
simultaneously?
• Evidence so far is ambivalent:
• Randomized control trial in Sudan/Gambia/Benin
no added effect
• Other trial e.g. Bioko added impact
Study area
• Rural district on west shore of lake
Victoria, Tanzania
• Altitude ranging from 1100-1600m
• Population of 425,000
• IRS since 2007 yearly round with
pyrethroid Lambda-cyhalothrin and
bendiocarb in 2012
• Prevalence 23% varying between 1%
to 62% in June 2011
• Two malaria transmission seasons
November/December and June/July
Study design
• Two arms clusters randomized control trial (50 clusters)
Arm A
Arm B
Year 1: Baseline
IRS +LLINs
IRS +LLINs
Year 2: Intervention
IRS+LLINs
LLINs
• Objective: To assess whether IRS with bendiocarb plus LLINs
provide added protection against malaria
• Outcomes
– Malaria prevalence and aneamia
– Entomological Inoculation Rate (EIR)
– Mosquito density
Trial timetable
Jan Feb Mar
XS 1
LLIN
IRS1
LLIN+
IRS
Baseline 2011
Intervention year 2012
Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
XS 2
XS A
XS B
XS C
Monthly Entomological XS = 7 rounds
Monthly Entomological XS = 12 rounds
LLIN
XS 1
IRS1
XS 2
Monthly Entomological XS = 7 rounds
LLIN
XS A
IRS2
XS B
XS C
Monthly Entomological XS = 12 rounds
IRS2
Net distribution to all population
IRS: Intervention - 2bendiocarb
IRS: Baseline - 1lambdacyhalothrin
Material & Methods
• CDC monthly light trap collection
– Each month
• 40 clusters (20 LLIN arm-20
LLIN+IRS arm)
• 8 houses randomly
selected/cluster/month
• One night collection
• Laboratory testing
– Detection of Sporozoite in Anopheles
collected (ELISA)
– Real time PCR Taq Man assay for species
identification
IRS coverage
• Coverage was assessed with household questionnaire
IRS
Intervention arm (LLIN + IRS) Control arm (LLIN)
% [95% CI], (N)
Baseline IRS 2011
Post Intervention
96.4% [94.2-97.8], (1120)
IRS (Dec11-Jan12)
89.3% [85.0-93.6], (634)
IRS (Apr12)
86.9% [80.9-93.0], (1271)
92.7% [89.6-95.0], (1062)
ITN coverage post
Control arm (LLIN)
% [95% CI], (N)
Intervention arm (LLIN + IRS)
% [95% CI], (N)
95.0% [92.5-96.7], (1060)
97.3% [96.2-98.1], (1119)
92.0% [89.8-94.3], (1917)
94.0% [91.6-96.3], (1914)
Houses with all bed covered 51.9% [46.3-57.5], (1917)
59.5%[55.6-63.4], (1914)
Baseline
Ownership (at least one net
own/household)
Post intervention
Ownership (at least one net
own/household)
Houses with all bed covered decrease from 61.3% [95%CI: 56.9-65.6] (Jan-Marc 2013)
to 41.9% [95%CI: 36.6-47.1] (Oct-Dec 2013)
Post intervention results
• 15,480 mosquitoes collected during these 12 rounds.
• 26.1% were identified as Anopheles
• Sporozoite rate 0.4% in Anopheles arabiensis (1/239)
LLIN arm
Outcome
%/
Mean
N
1904
3.4
1909
2.7
RR*=0.66 0.37-1.19 0.163
Mean gambiae s.l/HH 1892
1.7
1893
0.4
RR*=0.16 0.06-0.44 0.001
2.5%
717
1.8%
OR=0.73 0.21-2.54 0.607
0.2
RR*=0.01 0.00-0.01 <0.001
Mean Culex/HH
Sporozoite rate
EIR/month/hh
N
LLIN + IRS arm
3059
1.2
* Adjusted for baseline Anopheles density
%/
Mean
Ratio
95%CI
Pvalue
Baseline results
•
•
•
•
15,860 mosquitoes collected during the seven baseline rounds
45.3% were Anopheles
98.3% Anopheles gambiae s.l. and 0.2% Anopheles funestus.
81.4% (95%CI: 76.0-86.7) An.gambiae s.s. and 18.6% (95%CI: 13.323.9) An.arabiensis.
• Sporozoite rate in An.arabiensis 0% (N=187)
Outcome
LLIN arm
HH no.
%/
Mean
LLIN + IRS arm
HHno.
%/
Mean
Ratio
95%CI
Pvalue
Mean Culex/HH
Mean Ano gambiae
s.l/HH
1055
3.8
1120
2.7
RR=0.7 0.4-1.4
0.301
1055
3.1
1120
2.2
RR=0.7 0.1-4.4
0.708
Sporozoite rate
1359
1.7%
1466
2.9%
OR=1.7 1.0-2.8
0.048
1.3
RR=1.2 0.3-5.9
0.803
EIR/month/hh1
1
Post intervention result per round
IRS
Discussions & conclusion
• This trial shows that using IRS with Bendiocarb combined
with pyrethroid ITNs is beneficial compared to using ITNs
alone on anopheles density and EIR.
• Moderate coverage of LLIN
• High pyrethroid resistance observed in the area (mortality
11% in Anopheles exposed to permethrin)
• Difference in density observed over all the collection
round
• Arabiensis does not seems to have an important role in
malaria transmission
Thank you!
•
•
•
•
People of Muleba
Project team
RTI International
Muleba District
Medical Office
• Thank you for
listening
Kilimanjaro Christian Medical College
Baseline
Post intervention
Dec12
Nov12
Oct12
Sep12
Aug12
July12
June12
May12
Apr12
Mar12
Feb12
Jan12
Dec11
Nov11
Oct11
Sep11
Aug11
18.7
JunJul11
AprMay11
Average Anopheles per house
6.0
8.3
5.0
4.0
3.0
LLIN
LLIN+IRS
2.0
1.0
0.0