Assessing bed net damage: comparisons of three measurement methods for estimating the size, shape, and distribution of holes on bed nets.

BACKGROUND: Measuring the physical condition of long-lasting insecticidal nets (LLINs) under field conditions is of great importance for malaria control programmes to guide decisions on how frequently to replace LLINs. Current guidelines by the World Health Organization Pesticide Evaluation Scheme (WHOPES) propose a proportionate hole index (pHI) for assessing LLIN condition by counting the number of holes the size of a thumb, fist, head, and larger than a head. However, this method does not account for irregular hole shapes or exact hole sizes which could result in inaccurate decisions about when to replace LLINs. METHODS: LLINs were collected during a 2013 health facility-based malaria case control study in Machinga District, Malawi. To evaluate the accuracy of the pHI, the physical condition of 277 LLINs was estimated by the WHOPES method and then compared with two more thorough measurement methods: image analysis of digital photographs of each LLIN side; and for 10 nets, ruler measurements of the length, width, and location of each hole. Total hole counts and areas per net were estimated by each method, and detailed results of hole shapes and composite pictures of hole locations were generated using image analysis. RESULTS: The WHOPES method and image analysis resulted in similar estimates of total hole counts, each with a median of 10 (inter-quartile range (IQR) 4-24 and 4-23, respectively; p = 0.004); however, estimated hole areas were significantly larger using the WHOPES method (median 162 cm2, IQR 28-793) than image analysis (median 13 cm2, IQR 3-101; p < 0.0001). The WHOPES method classified fewer LLINs in 'good condition' compared to image analysis (42% vs 74%). The ruler method detected significantly more holes than image analysis did (p = 0.002) in 10 LLINs; however, total hole area was not significantly different (p = 0.16). Most holes were not circular but roughly 2-5 times longer in one direction. The lower quarter of LLIN sides was found to have the most holes. CONCLUSIONS: The WHOPES method overestimated total hole area, likely because holes are elongated rather than circular, suggesting further adjustments to the pHI formula may be warranted when considering LLIN replacement strategies.

Effect of the Expanded Program on Immunization Contact Method of data collection on health behaviors in Mali.

BACKGROUND: The Expanded Program on Immunization Contact Method (EPI-CM) is a proposed monitoring and program management tool for developing countries. The method involves health workers tallying responses to questions about health behaviors during routine immunizations and providing targeted counseling. We evaluated whether asking caretakers about health behaviors during EPI visits led to changes in those behaviors. METHODS: We worked in 2 districts in Mali: an intervention district where during immunization visits workers asked about 4 health behaviors related to bed net use, fever, respiratory disease, and diarrhea, and a control district where workers conducted routine immunization activities without health behavior questions. To evaluate the effect of EPI-CM, we conducted a cross-sectional household survey at baseline and 1 year postintervention. We used multivariate logistic regression to compare between districts the change over 1 year in 4 health behaviors: use of insecticide-treated nets, appropriate fever treatment, care-seeking for respiratory complaints, and appropriate diarrhea treatment. RESULTS: There were no significant differences between the 2 districts in the change in the 4 health behaviors when controlling for age, sex, maternal education and occupation, immunization history, and wealth. CONCLUSIONS: We found no evidence that EPI-CM increases healthy behaviors. Further evaluation of other potential benefits and costs of EPI-CM is warranted.

Validity of Expanded Program on Immunization Contact Method health behavior estimates in Mali.

BACKGROUND: In the developing world, household surveys provide high-quality health behavior data integral to public health program management. The Expanded Program on Immunization Contact Method (EPI-CM) is a proposed, less resource-intensive method in which health center staff incorporate health behavior questions into routine vaccination activities. No systematic evaluation of EPI-CM validity has yet been conducted. METHODS: We used concurrent household survey and EPI-CM to collect data on 4 infant health behaviors in Mali at 2 time points (8 total comparisons). Studied health behaviors were bednet use, obtaining care for fever, obtaining care for a respiratory complaint, and using oral rehydration solution for diarrhea. Household survey and EPI-CM estimates were considered equivalent if a 95% confidence interval about the difference in estimated proportions fell within the interval (-.10, .10). RESULTS: EPI-CM estimates were higher than household survey estimates for 7 of 8 unadjusted paired estimates; estimates of bednet use in 2009 met a priori equivalence criteria in a setting of high bednet use (90.5%). When we restricted household survey data to infants up-to-date on vaccinations, estimates for behaviors other than bednet use remained substantially different. CONCLUSIONS: We were unable to demonstrate that EPI-CM, as implemented, consistently produces data comparable with household survey data.

Improved equity in measles vaccination from integrating insecticide-treated bednets in a vaccination campaign, Madagascar.

OBJECTIVE: To evaluate the effect of integrating ITN distribution on measles vaccination campaign coverage in Madagascar. METHODS: Nationwide cross-sectional survey to estimate measles vaccination coverage, nationally, and in districts with and without ITN integration. To evaluate the effect of ITN integration, propensity score matching was used to create comparable samples in ITN and non-ITN districts. Relative risks (RR) and 95% confidence intervals (CI) were estimated via log-binomial models. Equity ratios, defined as the coverage ratio between the lowest and highest household wealth quintile (Q), were used to assess equity in measles vaccination coverage. RESULTS: National measles vaccination coverage during the campaign was 66.9% (95% CI 63.0-70.7). Among the propensity score subset, vaccination campaign coverage was higher in ITN districts (70.8%) than non-ITN districts (59.1%) (RR=1.3, 95% CI 1.1-1.6). Among children in the poorest wealth quintile, vaccination coverage was higher in ITN than in non-ITN districts (Q1; RR=2.4, 95% CI 1.2-4.8) and equity for measles vaccination was greater in ITN districts (equity ratio=1.0, 95% CI 0.8-1.3) than in non-ITN districts (equity ratio=0.4, 95% CI 0.2-0.8). CONCLUSION: Integration of ITN distribution with a vaccination campaign might improve measles vaccination coverage among the poor, thus providing protection for the most vulnerable and difficult to reach children.

Assessing bed net use and non-use after long-lasting insecticidal net distribution: a simple framework to guide programmatic strategies.

BACKGROUND: Insecticide-treated nets (ITNs) are becoming increasingly available to vulnerable populations at risk for malaria. Their appropriate and consistent use is essential to preventing malaria, but ITN use often lags behind ITN ownership. In order to increase ITN use, it is necessary to devise strategies that accurately identify, differentiate, and target the reasons and types of non-use. METHODS: A simple method based on the end-user as the denominator was employed to classify each individual into one of four ITN use categories: 1) living in households not owning an ITN; 2) living in households owning, but not hanging an ITN; 3) living in households owning and hanging an ITN, but who are not sleeping under one; and 4) sleeping under an ITN. This framework was applied to survey data designed to evaluate long-lasting insecticidal nets (LLINs) distributions following integrated campaigns in five countries: Togo, Sierra Leone, Madagascar, Kenya and Niger. RESULTS: The percentage of children <5 years of age sleeping under an ITN ranged from 51.5% in Kenya to 81.1% in Madagascar. Among the three categories of non-use, children living in households without an ITN make up largest group (range: 9.4%-30.0%), despite the efforts of the integrated child health campaigns. The percentage of children who live in households that own but do not hang an ITN ranged from 5.1% to 16.1%. The percentage of children living in households where an ITN was suspended, but who were not sleeping under it ranged from 4.3% to 16.4%. Use by all household members in Sierra Leone (39.9%) and Madagascar (60.4%) indicate that integrated campaigns reach beyond their desired target populations. CONCLUSIONS: The framework outlined in this paper provides a helpful tool to examine the deficiencies in ITN use. Monitoring and evaluation strategies designed to assess ITN ownership and use can easily incorporate this approach using existing data collection instruments that measure the standard indicators.

Prevalence of Chronic Hepatitis B Virus Infection among Children in Haiti, 2017.

In 2016, the World Health Assembly endorsed the Global Health Sector Strategy on Viral Hepatitis, which calls for elimination of hepatitis B virus (HBV) by 2030 (definition: ≤ 0.1% hepatitis B surface antigen [HBsAg] prevalence among children aged 5 years). The burden of chronic HBV infection among children in Haiti is unknown. We conducted a nationally representative cross-sectional serological survey among 5- to 7-year-old children based on a two-stage cluster design with two strata: West (includes metropolitan Port-au-Prince) and non-West (all other departments). We collected demographic, socioeconomic, and vaccination history data and tested for HBsAg using a rapid point-of-care test. We estimated HBsAg prevalence and evaluated the association of HBV infection with vaccination history, demographics, and socioeconomic characteristics. Of the 1,152 children, seven (0.5%, 95% CI: 0.2-1.2) were HBsAg positive. The HBsAg prevalence varied by region (West: 0.1%, 95% CI: 0.01-0.9; non-West: 0.7%, 95% CI: 0.2-1.9) (P = 0.1), gender (males: 0.7%, 95% CI: 0.2-2.4; females: 0.2%, 95% CI: 0.05-1.1) (P = 0.3), and caregiver's education level (none: 0.8%, 95% CI: 0.2-3.1; some or completed primary: 0.5%, 95% CI: 0.1-1.8; some secondary: 0.4%, 95% CI: 0.1-1.8; secondary and higher: 0.0%, 95% CI: 0-0), although the differences were not statistically significant. None of the HBsAg-positive children had documented vaccination with hepatitis B vaccine (HepB). Haiti's chronic HBV infection prevalence among children is low; however, it is above the elimination target. To reach elimination, Haiti needs to achieve high coverage with the three HepB doses and introduce a HepB birth dose.

Use of handheld computers with global positioning systems for probability sampling and data entry in household surveys.

We introduce an innovative method that uses personal digital assistants (PDAs) equipped with global positioning system (GPS) units in household surveys to select a probability-based sample and perform PDA-based interviews. Our approach uses PDAs with GPS to rapidly map all households in selected areas, choose a random sample, and navigate back to the sampled households to conduct an interview. We present recent field experience in two large-scale nationally representative household surveys to assess insecticide-treated bed net coverage as part of malaria control efforts in Africa. The successful application of this method resulted in statistically valid samples; quality-controlled data entry; and rapid aggregation, analyses, and availability of preliminary results within days of completing the field work. We propose this method as an alternative to the Expanded Program on Immunization cluster sample method when a fast, statistically valid survey is required in an environment with little census information at the enumeration area level.

Bed Net Durability Assessments: Exploring a Composite Measure of Net Damage.

BACKGROUND: The durability of Long Lasting Insecticidal Nets (LLINs) in field conditions is of great importance for malaria prevention and control efforts; however, the physical integrity of the net fabric is not well understood making it challenging to determine overall effectiveness of nets as they age. The 2011 World Health Organization Pesticide Evaluation Scheme (WHOPES) guidelines provide a simple, standardized method using a proportional hole index (PHI) for assessing net damage with the intent to provide national malaria control programs with guidelines to assess the useful life of LLINS and estimate the rate of replacement. METHODS: We evaluated the utility of the PHI measure using 409 LLINs collected over three years in Nampula Province, Mozambique following a mass distribution campaign in 2008. For each LLIN the diameter and distance from the bottom of the net were recorded for every hole. Holes were classified into four size categories and a PHI was calculated following WHOPES guidelines. We investigate how the size, shape, and location of holes influence the PHI. The areas of the WHOPES defined categories were compared to circular and elliptical areas based on approximate shape and actual measured axes of each hole and the PHI was compared to cumulative damaged surface area of the LLIN. RESULTS: The damaged area of small, medium, large, and extra-large holes was overestimated using the WHOPES categories compared to elliptical areas using the actual measured axes. Similar results were found when comparing to circular areas except for extra-large holes which were underestimated. (Wilcoxon signed rank test of differences p< 0.0001 for all sizes). Approximating holes as circular overestimated hole surface area by 1.5 to 2 times or more. There was a significant difference in the mean number of holes < 0.5 cm by brand and there were more holes of all sizes on the bottom of nets than the top. For a range of hypothetical PHI thresholds used to designate a "failed LLIN", roughly 75 to 80% of failed LLINs were detected by considering large and extra-large holes alone, but sensitivity varied by brand. CONCLUSIONS: Future studies may refine the PHI to better approximate overall damaged surface area. Furthermore, research is needed to identify whether or not appropriate PHI thresholds can be used to deem a net no longer protective. Once a cutoff is selected, simpler methods of determining the effective lifespan of LLINs can help guide replacement strategies for malaria control programs.

The risk of West Nile Virus infection is associated with combined sewer overflow streams in urban Atlanta, Georgia, USA.

BACKGROUND: At present, the factors favoring transmission and amplification of West Nile Virus (WNV) within urban environments are poorly understood. In urban Atlanta, Georgia, the highly polluted waters of streams affected by combined sewer overflow (CSO) represent significant habitats for the WNV mosquito vector Culex quinquefasciatus. However, their contribution to the risk of WNV infection in humans and birds remains unclear. OBJECTIVES: Our goals were to describe and quantify the spatial distribution of WNV infection in mosquitoes, humans, and corvids, such as blue jays and American crows that are particularly susceptible to WNV infection, and to assess the relationship between WNV infection and proximity to CSO-affected streams in the city of Atlanta, Georgia. MATERIALS AND METHODS: We applied spatial statistics to human, corvid, and mosquito WNV surveillance data from 2001 through 2007. Multimodel analysis was used to estimate associations of WNV infection in Cx. quinquefasciatus, humans, and dead corvids with selected risk factors including distance to CSO streams and catch basins, land cover, median household income, and housing characteristics. RESULTS: We found that WNV infection in mosquitoes, corvids, and humans was spatially clustered and statistically associated with CSO-affected streams. WNV infection in Cx. quinquefasciatus was significantly higher in CSO compared with non-CSO streams, and WNV infection rates among humans and corvids were significantly associated with proximity to CSO-affected streams, the extent of tree cover, and median household income. CONCLUSIONS: Our study strongly suggests that CSO-affected streams are significant sources of Cx. quinquefasciatus mosquitoes that may facilitate WNV transmission to humans within urban environments. Our findings may have direct implications for the surveillance and control of WNV in other urban centers that continue to use CSO systems as a waste management practice.

Rapid scale-up of long-lasting insecticide-treated bed nets through integration into the national immunization program during child health week in Togo, 2004.

In December 2004, Togo was the first country to conduct a nationwide free insecticide-treated net (ITN) distribution as part of its National Integrated Child Health Campaign. Community-based cross-sectional surveys were conducted one and nine months post-campaign as part of a multidisciplinary evaluation of the nationwide distribution of ITNs to children 9-59 months of age to evaluate ITN ownership, equity, and use. Our results demonstrated that at one month post-campaign, 93.1% of all eligible children received an ITN. Household ITN ownership and equity increased significantly post-campaign. Nine months post-campaign, 78.6% of households with a child eligible to participate in the campaign retained at least one campaign net. Use by eligible children was 43.5% at one month post-campaign (during the dry season) and 52.9% at nine months post-campaign (during the rainy season). Household ownership of at least one ITN increased from 8.0% pre-campaign to 62.5% one month post-campaign. Together, these findings demonstrate that in this setting, increased household ITN ownership, equity, and retention can be achieved on a national scale through free ITN distribution during an integrated campaign.