Multi-country evaluation of the durability of pyrethroid plus piperonyl-butoxide insecticide-treated nets: study protocol.

BACKGROUND: Mass distributions of long-lasting insecticidal nets (LLINs) have contributed to large reductions in the malaria burden. However, this success is in jeopardy due in part to the increasing pyrethroid-resistant mosquito population as well as low LLINs coverage in various areas because the lifespan of LLINs is often shorter than the interval between replenishment campaigns. New insecticide-treated nets (ITNs) containing pyrethroid and piperonyl-butoxide (PBO) have shown a greater reduction in the incidence of malaria than pyrethroid LLINs in areas with pyrethroid-resistant mosquitoes. However, the durability (attrition, bio-efficacy, physical integrity and chemical retainment) of pyrethroid-PBO ITNs under operational settings has not been fully characterized. This study will measure the durability of pyrethroid-PBO ITNs to assess whether they meet the World Health Organization (WHO) three years of operational performance criteria required to be categorized as "long-lasting". METHODS: A prospective household randomized controlled trial will be conducted simultaneously in Tanzania, India and Côte d'Ivoire to estimate the field durability of three pyrethroid-PBO ITNs (Veeralin®, Tsara® Boost, and Olyset® Plus) compared to a pyrethroid LLIN: MAGNet®. Durability monitoring will be conducted up to 36 months post-distribution and median survival in months will be calculated. The proportion of ITNs: (1) lost (attrition), (2) physical integrity, (3) resistance to damage score, (4) meeting WHO bio-efficacy (≥ 95% knockdown after 1 h or ≥ 80% mortality after 24 h for WHO cone bioassay, or ≥ 90% blood-feeding inhibition or ≥ 80% mortality after 24 h for WHO Tunnel tests) criteria against laboratory-reared resistant and susceptible mosquitoes, and insecticidal persistence over time will be estimated. The non-inferiority of Veeralin® and Tsara® Boost to the first-in-class, Olyset® Plus will additionally be assessed for mortality, and the equivalence of 20 times washed ITNs compared to field aged ITNs will be assessed for mortality and blood-feeding inhibition endpoints in the Ifakara Ambient Chamber Test, Tanzania. CONCLUSION: This will be the first large-scale prospective household randomized controlled trial of pyrethroid-PBO ITNs in three different countries in East Africa, West Africa and South Asia, simultaneously. The study will generate information on the replenishment intervals for PBO nets.

Household factors associated with access to insecticide-treated nets and house modification in Bagamoyo and Ulanga districts, Tanzania.

BACKGROUND: Insecticide-treated nets (ITNs) and house modifications are proven vector control tools, yet in most regions, full coverage has not been achieved. This study investigates household factors associated with access to ITNs and house modification in Tanzania. METHODS: Baseline cross-sectional survey data from previous studies on spatial repellants and indoor residual spray evaluation was analysed from 6757 households in Bagamoyo (60 km north of Dar es Salaam) and 1241 households in Ulanga (a remote rural area in southeast Tanzania), respectively. Regression models were used to estimate the associations between the outcomes: population access to ITNs, access to ITN per sleeping spaces, window screens and closed eaves, and the covariates household size, age, gender, pregnancy, education, house size, house modification (window screens and closed eaves) and wealth. RESULTS: Population access to ITNs (households with one ITN per two people that stayed in the house the previous night of the survey) was 69% (n = 4663) and access to ITNs per sleeping spaces (households with enough ITNs to cover all sleeping spaces used the previous night of the survey) was 45% (n = 3010) in Bagamoyo, 3 years after the last mass campaign. These findings are both lower than the least 80% coverage target of the Tanzania National Malaria Strategic Plan (Tanzania NMSP). In Ulanga, population access to ITNs was 92% (n = 1143) and ITNs per sleeping spaces was 88% (n = 1093), 1 year after the last Universal Coverage Campaign (UCC). Increased household size was significantly associated with lower access to ITNs even shortly after UCC. House modification was common in both areas but influenced by wealth. In Bagamoyo, screened windows were more common than closed eaves (65% vs 13%), whereas in Ulanga more houses had closed eaves than window screens (55% vs 12%). CONCLUSION: Population access to ITNs was substantially lower than the targets of the Tanzania NMSP after 3 years and lower among larger households after 1 year following ITN campaign. House modification was common in both areas, associated with wealth. Improved access to ITNs and window screens through subsidies and Behaviour Change Communication (BCC) strategies, especially among large and poor households and those headed by people with a low level of education, could maximize the uptake of a combination of these two interventions.

Comparing the new Ifakara Ambient Chamber Test with WHO cone and tunnel tests for bioefficacy and non-inferiority testing of insecticide-treated nets.

BACKGROUND: Insecticide-treated net (ITN) durability, measured through physical integrity and bioefficacy, must be accurately assessed in order to plan the timely replacement of worn out nets and guide procurement of longer-lasting, cost-effective nets. World Health Organization (WHO) guidance advises that new intervention class ITNs be assessed 3 years after distribution, in experimental huts. In order to obtain information on whole-net efficacy cost-effectively and with adequate replication, a new bioassay, the Ifakara Ambient Chamber Test (I-ACT), a semi-field whole net assay baited with human host, was compared to established WHO durability testing methods. METHODS: Two experiments were conducted using pyrethroid-susceptible female adult Anopheles gambiae sensu stricto comparing bioefficacy of Olyset®, PermaNet® 2.0 and NetProtect® evaluated by I-ACT and WHO cone and tunnel tests. In total, 432 nets (144/brand) were evaluated using I-ACT and cone test. Olyset® nets (132/144) that did not meet the WHO cone test threshold criteria (≥ 80% mortality or ≥ 95% knockdown) were evaluated using tunnel tests with threshold criteria of ≥ 80% mortality or ≥ 90% feeding inhibition for WHO tunnel and I-ACT. Pass rate of nets tested by WHO combined standard WHO bioassays (cone/tunnel tests) was compared to pass in I-ACT only by net brand and time after distribution. RESULTS: Overall, more nets passed WHO threshold criteria when tested with I-ACT than with standard WHO bioassays 92% vs 69%, (OR: 4.1, 95% CI 3.5-4.7, p < 0.0001). The proportion of Olyset® nets that passed differed if WHO 2005 or WHO 2013 LN testing guidelines were followed: 77% vs 71%, respectively. Based on I-ACT results, PermaNet® 2.0 and NetProtect® demonstrated superior mortality and non-inferior feeding inhibition to Olyset® over 3 years of field use in Tanzania. CONCLUSION: Ifakara Ambient Chamber Test may have use for durability studies and non-inferiority testing of new ITN products. It measures composite bioefficacy and physical integrity with both mortality and feeding inhibition endpoints, using fewer mosquitoes than standard WHO bioassays (cone and tunnel tests). The I-ACT is a high-throughput assay to evaluate ITN products that work through either contact toxicity or feeding inhibition. I-ACT allows mosquitoes to interact with a host sleeping underneath a net as encountered in the field, without risk to human participants.

Tanzania's human papillomavirus (HPV) vaccination program: Community awareness, feasibility, and acceptability of a national HPV vaccination program, 2019.

BACKGROUND: In April 2018, Tanzania introduced the human papillomavirus (HPV) vaccine nationally to 14-year-old girls, utilizing routine delivery strategies (i.e. vaccinating girls at health facilities and community outreach, including schools). We sought to assess awareness, feasibility, and acceptability of the HPV vaccination program among health workers and community-level stakeholders. METHODS: We conducted cross-sectional in-person surveys among health workers, school personnel, community leaders, and council leaders in 18 council areas across six regions of Tanzania in October-November 2019. Regions were purposively selected to provide demographic, geographic, and vaccination coverage variability; sub-regional levels used random or stratified random sampling. Surveys included questions on HPV vaccine training and knowledge, delivery strategy, target population, and vaccine and program acceptability. Descriptive analysis was completed for all variables stratified by respondent groups. RESULTS: Across the 18 councils, there were 461 respondents, including health workers (165), school personnel (135), community leaders (143), and council leaders (18). Over half of each respondent group (50-78%) attended a training or orientation on HPV vaccine. Almost 75% of the health workers and school personnel respondent groups, and less than half (45%) of community leaders correctly identified the target age group for HPV vaccine. Most (80%) of the health workers indicated HPV vaccination was available at health facilities and schools; most (79%) indicated that the majority of girls receive HPV vaccine in school. Approximately half (52%) of all respondents reported hearing misinformation about HPV vaccine, but 97% of all respondents indicated that HPV vaccine was either "very accepted" or "somewhat accepted" in their community. CONCLUSION: The HPV vaccination program in Tanzania was well accepted by community stakeholders in 18 councils; adequate knowledge of HPV vaccine and the HPV vaccination program was demonstrated by health workers and school personnel. However, continued technical support for integration of HPV vaccination as a routine immunization activity and reinforcement of basic knowledge about HPV vaccine in specific community groups is needed. The Tanzania experience provides an example of how this vaccine can be integrated into routine immunization delivery strategies and can be a useful resource for countries planning to introduce HPV vaccine as well as informing global partners on how to best support to countries in operationalizing their HPV vaccine introduction plans.