Trends in bednet ownership and usage and impact of bednets ... 2011/presentations... · and impact of bednets on malaria morbidity in the Kilifi HDSS: 2008 Victoriah Nyaga, Evasius

Trends in bednet ownership and usage and impact of bednets on malaria

morbidity in the Kilifi HDSS: 2008

Victoriah Nyaga, Evasius Bauni, Benjamin Tsofa, Abdisalan M. Noor, J. Anthony Scott, Laura L. Hammitt

Trends in bednet ownership and usage and impact of bednets on malaria

morbidity in the Kilifi HDSS: 2008-2010

Victoriah Nyaga, Evasius Bauni, Benjamin Tsofa, Abdisalan M. Noor, J. Anthony Scott, Laura L. Hammitt

Background

• Malaria remains a major cause of morbidity and mortalitymorbidity and mortality

• ITNs reduce morbidity and mortality in sub-Saharan Africa

Background

Malaria remains a major cause of morbidity and mortalitymorbidity and mortality

ITNs reduce morbidity and mortality in

‘90 ‘93 ‘02 ‘04 ’05 ’06 ‘09

Bednet Coverage and

Distribution in Kilifi District,

1990-

Coverage ~6%

ITN trial; nets distributed to ~30%

Subsidized ITNs available at retail outlets

Subsidized ITNs

Subsidized

‘90 ‘93 ‘02 ‘04 ’05 ’06 ‘09

Bednet Coverage and

Distribution in Kilifi District,

-2009

Nets free for pregnant women and U5; 50KSh for others

ITN trial; nets distributed to ~30%

available at retail outlets

ITNs for pregnant women and U5 at MCH

Subsidized ITNs for all at MoH clinics

Mass distribution campaign

and U5; 50KSh for others

Objectives

� Evaluate trends in bednet ownership and use in Kilifi HDSS

� Assess impact of bednet ownership and use on hospitalisation with malaria

Objectives

Evaluate trends in bednet ownership and

Assess impact of bednet ownership and use on hospitalisation with malaria

Kilifi HDSSKilifi HDSS

• Over 900 Km2

• Population of ~260,000

• ~10% live in Kilifi town, the

remainder live in rural areasremainder live in rural areas

• Economy: subsistence

farming

• Long rains: Apr-June

• Short rains: Oct-Nov

• U5 mortality rate: 41/1000

• Residents served by Kilifi

District Hospital

Linked surveillance systemsLinked surveillance systems

Methods

• Survey of bednet ownership and usage in the DSS

• Validation survey of randomly selected households

• Incidence of hospitalization with malaria in children at Kilifi District Hospital

Methods

Survey of bednet ownership and usage

Validation survey of randomly selected

Incidence of hospitalization with malaria in children at Kilifi District Hospital

Methods – Bednet Survey

• 3 questions asked of all residents in 3 HDSS enumeration rounds

• Oct 2008 – Feb 2009• Oct 2008 – Feb 2009

• Mar 2009 – Aug 2009

• June 2010 – Sept 2010

1.Do you own a bednet?

2.Do you usually sleep under a bednet?

3.Did you sleep under a bednet last night?

Bednet Survey

3 questions asked of all residents in 3 HDSS enumeration rounds

Feb 2009Feb 2009

Aug 2009

Sept 2010

Do you own a bednet?

Do you usually sleep under a bednet?

Did you sleep under a bednet last night?

Methods – Validation Survey

• 3 questions asked of all residents of 500 randomly selected households

• June 2009 – Sept 2009• June 2009 – Sept 2009

• Fieldworker entered household to assess

presence of net and net quality

• A hole was counted if a fieldworker could fit 2 fingers through it.

• Paired analysis comparing resident

response to survey to fieldworker

observation

Validation Survey

3 questions asked of all residents of 500 randomly selected households

Sept 2009Sept 2009

Fieldworker entered household to assess

presence of net and net quality

A hole was counted if a fieldworker could fit 2

Paired analysis comparing resident

response to survey to fieldworker

Methods –

Hospitalisation

• Incidence rate of hospital admission with slide-positive malaria in HDSS residents aged 0-13 years during each survey periods

• Rate ratios computed to compare incidence in bednet owners v non

• Analysis adjusted for age, sex and location of residence

– Malaria

Hospitalisation

Incidence rate of hospital admission with positive malaria in HDSS residents

13 years during each survey periods

Rate ratios computed to compare incidence in bednet owners v non-owners

Analysis adjusted for age, sex and location

ResultsResults

Bednet Ownership and Usage

in Kilifi HDSS

P<0.01 P<0.01

Bednet Ownership and Usage

in Kilifi HDSS

P<0.01

Bednet Ownership in Kilifi

HDSS by Age

Bednet Ownership in Kilifi

HDSS by Age

Bednet Use the Night Before

among Bednet Owners in Kilifi

HDSS by Age

Bednet Use the Night Before

among Bednet Owners in Kilifi

HDSS by Age

Validation exercise, N=2,983

• Net observed in 96.1% (95%CI: 93.3, 97.8) of those who reported to own a net.

• Net observed in 98.1% (95% CI: 95.7, 99.3) of • Net observed in 98.1% (95% CI: 95.7, 99.3) of those who reported to use a net the night prior to the survey.

• Net quality

• 0 holes: 18%

• 1-3 holes: 55%

• >3 holes: 27.2%

Validation exercise, N=2,983

Net observed in 96.1% (95%CI: 93.3, 97.8) of those who reported to own a net.

Net observed in 98.1% (95% CI: 95.7, 99.3) of Net observed in 98.1% (95% CI: 95.7, 99.3) of those who reported to use a net the night prior

Malaria admissions / 1000 cyfuMalaria admissions / 1000 cyfu

Scott, JAG et al, Lancet 2011

Incidence of hospital admission

with malaria in children <14 years

• Oct 2008 – Feb 2009• 85/100,000 child years (95%CI: 53, 137)

• Mar – Aug 2009• 120/100,000 child years (95%CI: 95, 153)

• June –Sept 2010 • 80/100,000 child years (95%CI: 67, 95)

Incidence of hospital admission

with malaria in children <14 years

85/100,000 child years (95%CI: 53, 137)

120/100,000 child years (95%CI: 95, 153)

80/100,000 child years (95%CI: 67, 95)

Impact of bednets on malaria

hospitalization in children <14Age Oct ’08 – Feb

‘09Mar – Aug ‘10

yrs RR 95%CI RR

Owned a

net

<5 0.42 0.15,

1.18

0.41

net 1.18

0-13 0.61 0.24,

1.57

0.56

Regular

net use

<5 0.41 0.14,

1.18

0.48

0-13 0.62 0.29,

1.61

0.60

Slept

under

net the

night

prior

<5 0.41 0.15,

1.13

0.44

0-13 0.59 0.23,

1.52

0.57

Impact of bednets on malaria

hospitalization in children <14Aug ‘10 Jun – Sept ‘10 Overall

95%CI RR 95%CI RR 95%CI

0.23,

0.71

0.57 0.34,

0.94

0.48 0.34,

0.680.71 0.94 0.68

0.34,

0.91

0.62 0.43,

0.92

0.60 0.45,

0.80

0.27,

0.84

0.56 0.34,

0.91

0.51 0.36,

0.72

0.36,

0.98

0.56 0.34,

0.82

0.58 0.44,

0.77

0.25,

0.78

0.72 0 42,

1.24

0.55 0.39,

0.80

0.35,

0.94

0.68 0.46,

1.00

0.64 0.47,

0.85

Impact of bednets on malaria

hospitalization in children <14Age Oct ’08 – Feb

‘09Mar – Aug ‘10

yrs RR 95%CI RR

Owned a

net

<5 0.42 0.15,

1.18

0.41

net 1.18

0-13 0.61 0.24,

1.57

0.56

Regular

net use

<5 0.41 0.14,

1.18

0.48

0-13 0.62 0.29,

1.61

0.60

Slept

under

net the

night

prior

<5 0.41 0.15,

1.13

0.44

0-13 0.59 0.23,

1.52

0.57

Impact of bednets on malaria

hospitalization in children <14Aug ‘10 Jun – Sept ‘10 Overall

95%CI RR 95%CI RR 95%CI

0.23,

0.71

0.57 0.34,

0.94

0.48 0.34,

0.680.71 0.94 0.68

0.34,

0.91

0.62 0.43,

0.92

0.60 0.45,

0.80

0.27,

0.84

0.56 0.34,

0.91

0.51 0.36,

0.72

0.36,

0.98

0.56 0.34,

0.82

0.58 0.44,

0.77

0.25,

0.78

0.72 0 42,

1.24

0.55 0.39,

0.80

0.35,

0.94

0.68 0.46,

1.00

0.64 0.47,

0.85

Impact of bednets on malaria

hospitalization in children <14Age Oct ’08 – Feb

‘09Mar – Aug ‘10

yrs RR 95%CI RR

Owned a

net

<5 0.42 0.15,

1.18

0.41

net 1.18

0-13 0.61 0.24,

1.57

0.56

Regular

net use

<5 0.41 0.14,

1.18

0.48

0-13 0.62 0.29,

1.61

0.60

Slept

under

net the

night

prior

<5 0.41 0.15,

1.13

0.44

0-13 0.59 0.23,

1.52

0.57

Impact of bednets on malaria

hospitalization in children <14Aug ‘10 Jun – Sept ‘10 Overall

95%CI RR 95%CI RR 95%CI

0.23,

0.71

0.57 0.34,

0.94

0.48 0.34,

0.680.71 0.94 0.68

0.34,

0.91

0.62 0.43,

0.92

0.60 0.45,

0.80

0.27,

0.84

0.56 0.34,

0.91

0.51 0.36,

0.72

0.36,

0.98

0.56 0.34,

0.82

0.58 0.44,

0.77

0.25,

0.78

0.72 0 42,

1.24

0.55 0.39,

0.80

0.35,

0.94

0.68 0.46,

1.00

0.64 0.47,

0.85

Limitations

• Net ownership was assumed to be the same throughout each period misclassification bias.misclassification bias.

• Analysis did not account for changes in access to the hospital, climatic changes, or bednet quality.

Limitations

Net ownership was assumed to be the same throughout each period – possible misclassification bias.misclassification bias.

Analysis did not account for changes in access to the hospital, climatic changes,

Conclusions

• Ownership and use increased over time MoH policy for highly subsidized/free ITNs at government clinics is working

• Ownership and usage • Ownership and usage the risk of malaria hospitalization among children

• Operational study provides quantitative data to support current policies

Conclusions

Ownership and use increased over time -MoH policy for highly subsidized/free ITNs at government clinics is working

Ownership and usage � 50% reduction in Ownership and usage � 50% reduction in the risk of malaria hospitalization among

Operational study provides quantitative data to support current policies

Acknowledgments

• Victoriah Nyaga

• Dr Laura Hammitt

• Dr Evasius Bauni• Dr Evasius Bauni

• Dr Benjamin Tsofa

• Dr. Anthony Scott

• HDSS enumerators

• KEMRI-Wellcome Trust

Acknowledgments

Wellcome Trust

Survey participants

Oct 08 – Feb 09

Count 237218Count 237218

Age yrs(IQR)

15(7,30)

Sex(Female) 53.23

Survey participants

Mar – Aug 09 Jun – Sep 10

245007 252017245007 252017

15(7,30) 15(7,31)

53.34 53.08