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Abstract Novel insecticides are urgently needed to control insecticide-resistant populations of Anopheles malaria vectors. Broflanilide acts as a non-competitive antagonist of the gamma-aminobutyric acid receptor and has shown prolonged effectiveness as an indoor residual spraying product (VECTRON T500) in experimental hut trials against pyrethroid-resistant vector populations. This multi-centre study expanded upon initial discriminating concentration testing of broflanilide, using six Anopheles insectary colonies (An. gambiae Kisumu KCMUCo, An. gambiae Kisumu NIMR, An. arabiensis KGB, An. arabiensis SENN, An. coluzzii N’Gousso and An. stephensi SK), representing major malaria vector species, to facilitate prospective susceptibility monitoring of this new insecticide; and investigated the potential for cross-resistance to broflanilide via the A296S mutation associated with dieldrin resistance (rdl). Across all vector species tested, the discriminating concentration for broflanilide ranged between LC99 × 2 = 1.126–54.00 μg/ml or LC95 × 3 = 0.7437–17.82 μg/ml. Lower concentrations of broflanilide were required to induce complete mortality of An. arabiensis SENN (dieldrin-resistant), compared to its susceptible counterpart, An. arabiensis KGB, and there was no association between the presence of the rdl mechanism of resistance and survival in broflanilide bioassays, demonstrating a lack of cross-resistance to broflanilide. Study findings provide a benchmark for broflanilide susceptibility monitoring as part of ongoing VECTRON T500 community trials in Tanzania and Benin.

Objectives: Data on Rift Valley fever virus (RVFV) prevalence in urban settings and pastoral areas of Tanzania are scarce. We performed a cross-sectional study of RVFV seroprevalence and determinants in humans and animals from Ilala, Rufiji, and Sengerema districts of Tanzania. Methods: Blood samples from the study participants were tested for anti-RVFV immunoglobulin G (IgG) antibodies using an enzyme-linked immunosorbent assay. Logistic regression was used to determine association between exposure risk practices and RVFV seropositivity. Results: The study involved 664 humans, 361 cattle, 394 goats, and 242 sheep. The overall anti-RVFV IgG seroprevalence in humans and animals was 2.1% (95% confidence interval [CI] 0.01-0.04) and 9.5% (n = 95, 95% CI 0.08-0.12), respectively. Seroprevalence in humans in Rufiji, Ilala, and Sengerema was 3.0% (n = 225, 95% CI 0.01-0.06), 1.8% (n = 230, 95% CI-0.005- 0.04), and 1.4% (n = 209, 95% CI 0.01-0.04), respectively (P >0.05). Seroprevalence in animals in Sengerema, Rufiji, and Ilala was 12.1% (n = 40, 95% CI 0.09-0.16), 11.1% (n = 37, 95% CI 0.08-0.15), and 5.4% (n = 18, 95% CI 0.03-0.08), respectively (P = 0.006). Handling of carcasses increased the odds of RVFV seropositivity 12-fold (odds ratio 11.84, 95% CI 1.97-71.16). Conclusion: The study confirms previous occurrence of RVFV in multiple species in the study districts. Animal handling practices appear to be essential determinants of seropositivity.

Abstract Background Indoor residual spraying (IRS) is a major method of malaria vector control across sub-Saharan Africa. Effective control is being undermined by the rapid spread of insecticide resistance. There is major investment in development of new insecticides for IRS that possess novel modes of action, long residual activity, low mammalian toxicity and minimal cross-resistance. VECTRON™ T500, a new IRS product containing the active ingredient broflanilide as a 50% wettable powder (WP), has been shown to be efficacious against pyrethroid susceptible and resistant vector species on mud and concrete substrates in experimental hut (Phase II) trials. Methods A two-arm non-inferiority cluster randomized controlled trial (Phase III) will be undertaken in Muheza District, Tanga Region, Tanzania. VECTRON™ T500 will be compared to the IRS product Fludora® Fusion (clothianidin 50% WP + deltamethrin 6.25% WP). The predominant malaria vectors in the study area are pyrethroid-resistant Anopheles gambiae s.s., An. arabiensis and An. funestus s.s. Sixteen village clusters will be pair-matched on baseline vector densities and allocated to reference and intervention arms. Consenting households in the intervention arm will be sprayed with VECTRON™ T500 and those in the reference arm will be sprayed with Fludora® Fusion. Each month, CDC light traps will collect mosquitoes to estimate changes in vector density, indoor biting, sporozoite and entomological inoculation rates (EIR). Susceptibility to IRS active ingredients will be assessed using World Health Organisation (WHO) bottle bioassays. Target site and metabolic resistance mechanisms will be characterised among Anopheles field populations from both trial arms. Residual efficacy of both IRS products will be monitored for 12 months post intervention. Questionnaire and focus group discussions will explore factors that influence adherence, adverse effects and benefits of IRS. Discussion This protocol describes a large-scale non-inferiority evaluation of a novel IRS product to reduce the density and EIR of pyrethroid-resistant Anopheles vectors. If VECTRON™ T500 proves non-inferior to Fludora® Fusion, it will be considered as an additional vector control product for malaria prevention and insecticide resistance management. Trial registration: ClinicalTrials.gov, NCT05150808, registered on 26 November 2021. Retrospectively registered.

Experimental hut trials (EHTs) are used to evaluate indoor vector control interventions against malaria vectors in a controlled setting. The level of variability present in the assay will influence whether a given study is well powered to answer the research question being considered. We utilised disaggregated data from 15 previous EHTs to gain insight into the behaviour typically observed. Using simulations from generalised linear mixed models to obtain power estimates for EHTs, we show how factors such as the number of mosquitoes entering the huts each night and the magnitude of included random effects can influence study power. A wide variation in behaviour is observed in both the mean number of mosquitoes collected per hut per night (ranging from 1.6 to 32.5) and overdispersion in mosquito mortality. This variability in mortality is substantially greater than would be expected by chance and should be included in all statistical analyses to prevent false precision of results. We utilise both superiority and non-inferiority trials to illustrate our methodology, using mosquito mortality as the outcome of interest. The framework allows the measurement error of the assay to be reliably assessed and enables the identification of outlier results which could warrant further investigation. EHTs are increasingly playing an important role in the evaluation and regulation of indoor vector control interventions so it is important to ensure that these studies are adequately powered.

Abstract Background Long-lasting efficacy of insecticide-treated nets is a balance between adhesion, retention and migration of insecticide to the surface of netting fibres. ICON® Maxx is a twin-sachet ‘home-treatment kit’ of pyrethroid plus binding agent, recommended by the World Health Organization (WHO) for long-lasting, wash-fast treatment of polyester nets. While knitted polyester netting is widely used, fine woven polyethylene netting is increasingly available and nets made of cotton and nylon are common in Africa and Asia. It is important to investigate whether ICON Maxx is able to fulfill the WHO criteria of long-lasting treatment on a range of domestic fabrics to widen the scope for malaria protection. Methods This study was a controlled comparison of the bio-efficacy and wash-fastness of lambda-cyhalothrin CS, with or without binder, on nets made of cotton, polyethylene, nylon, dyed and undyed polyester. Evaluation compared an array of bioassays: WHO cone and cylinder, median time to knockdown and WHO tunnel tests using Anopheles mosquitoes. Chemical assay revealed further insight. Results ICON Maxx treated polyethylene and polyester netting met the WHO cone and tunnel test bio-efficacy criteria for LLIN after 20 standardized washes. Although nylon and cotton netting failed to meet the WHO cone and cylinder criteria, both materials passed the WHO tunnel test criterion of 80% mortality after 20 washes. All materials treated with standard lambda-cyhalothrin CS without binder failed to meet any of the WHO bio-efficacy criteria within 5 washes. Conclusion The bio-efficacy of ICON Maxx against mosquitoes on netting washed up to 20 times demonstrated wash durability on a range of synthetic polymer and natural fibres: polyester, polyethylene, nylon and cotton. This raises the prospect of making insecticide-binder kits into an effective approach for turning untreated nets, curtains, military clothing, blankets—and tents and tarpaulins as used in disasters and humanitarian emergencies—into effective malaria prevention products. It may provide a solution to the problem of reduced LLIN coverage between campaigns by converting commercially sourced untreated nets into LLINs through community or home treatment. It may also open the door to binding of non-pyrethroid insecticides to nets and textiles for control of pyrethroid resistant vectors.

Abstract Background ICON® Maxx (Syngenta) is an insecticide treatment kit of pyrethroid and binding agent for long-lasting treatment of mosquito nets. Interim recommendation for use on nets was granted by the World Health Organization (WHO) after successful evaluation in experimental huts following multiple washes. A full WHO recommendation is contingent upon demonstration of continued bio-efficacy after 3 years of use. Methods A household-randomized prospective study design was used to assess ICON Maxx-treated nets over 3 years in north-eastern Tanzania. Conventional treated nets (with lambda-cyhalothrin, but without binder) served as a positive control. At 6-monthly intervals, cross-sectional household surveys monitored net use and physical integrity, while cone and tunnel tests assessed insecticidal efficacy. Pyrethroid content was determined after 12 and 36 months. A parallel cohort of nets was monitored annually for evidence of net deterioration and attrition. Results After 12 months’ use, 97% of ICON Maxx-treated nets but only 67% of CTN passed the WHO efficacy threshold for insecticidal durability (> 80% mortality in cone or tunnel or 90% feeding inhibition in tunnel). After 24- and 36-months use, 67% and 26% of ICON Maxx treated nets met the cone criteria, respectively, and over 90% met the combined cone and tunnel criteria. Lambda-cyhalothrin content after 36 months was 17% (15.8 ± 4.3 mg/m2) of initial content. ICON Maxx nets were used year-round and washed approximately 4 times per year. In cross-sectional survey after 36 months the average number of holes was 20 and hole index was 740 cm2 per net. Cohort nets had fewer holes and smaller hole index than cross-sectional nets. However, only 15% (40/264) of cohort nets were not lost to follow-up or not worn out after 36 months. Conclusions Because more than 80% of nets met the WHO efficacy criteria after 36 months use, ICON Maxx was granted WHO full recommendation. Cross-sectional and cohort surveys were complementary and gave a fuller understanding of net durability. To improve net usage and retention, stronger incentives and health messaging should be introduced in WHO LLIN longitudinal trials. Untreated polyester nets may be made long-lastingly insecticidal in Africa through simple household treatment using ICON Maxx pyrethroid-binder kits.

Abstract Background The effectiveness of long-lasting insecticidal nets (LLIN), the primary method for preventing malaria in Africa, is compromised by evolution and spread of pyrethroid resistance. Further gains require new insecticides with novel modes of action. Chlorfenapyr is a pyrrole insecticide that disrupts mitochrondrial function and confers no cross-resistance to neurotoxic insecticides. Interceptor® G2 LN (IG2) is an insecticide-mixture LLIN, which combines wash-resistant formulations of chlorfenapyr and the pyrethroid alpha-cypermethrin. The objective was to determine IG2 efficacy under controlled household-like conditions for personal protection and control of wild, pyrethroid-resistant Anopheles funestus mosquitoes. Methods Experimental hut trials tested IG2 efficacy against two positive controls—a chlorfenapyr-treated net and a standard alpha-cypermethrin LLIN, Interceptor LN (IG1)—consistent with World Health Organization (WHO) evaluation guidelines. Mosquito mortality, blood-feeding inhibition, personal protection, repellency and insecticide-induced exiting were recorded after zero and 20 washing cycles. The trial was repeated and analysed using multivariate and meta-analysis. Results In the two trials held in NE Tanzania, An. funestus mortality was 2.27 (risk ratio 95% CI 1.13–4.56) times greater with unwashed Interceptor G2 than with unwashed Interceptor LN (p = 0.012). There was no significant loss in mortality with IG2 between 0 and 20 washes (1.04, 95% CI 0.83–1.30, p = 0.73). Comparison with chlorfenapyr treated net indicated that most mortality was induced by the chlorfenapyr component of IG2 (0.96, CI 0.74–1.23), while comparison with Interceptor LN indicated blood-feeding was inhibited by the pyrethroid component of IG2 (IG2: 0.70, CI 0.44–1.11 vs IG1: 0.61, CI 0.39–0.97). Both insecticide components contributed to exiting from the huts but the contributions were heterogeneous between trials (heterogeneity Q = 36, P = 0.02). WHO susceptibility tests with pyrethroid papers recorded 44% survival in An. funestus. Conclusions The high mortality recorded by IG2 against pyrethroid-resistant An. funestus provides first field evidence of high efficacy against this primary, anthropophilic, malaria vector.

Abstract Background Effective planning for disease prevention and control requires accurate, adequately-analysed, interpreted and communicated data. In recent years, efforts have been put in strengthening health management information systems (HMIS) in Sub-Saharan Africa to improve data accessibility to decision-makers. This study assessed the quality of routine HMIS data at primary healthcare facility (HF) and district levels in Tanzania. Methods This cross-sectional study involved reviews of documents, information systems and databases, and collection of primary data from facility-level registers, tally sheets and monthly summary reports. Thirty-four indicators from Outpatient, Inpatient, Antenatal care, Family Planning, Post-natal care, Labour and Delivery, and Provider-Initiated Testing and Counselling service areas were assessed. Indicator records were tracked and compared across the process of data collection, compilation and submission to the district office. Copies of monthly report forms submitted by facilities to the district were also reviewed. The availability and utilization of HMIS tools were assessed, while completeness and data accuracy levels were quantified for each phase of the reporting system. Results A total of 115 HFs (including hospitals, health centres, dispensaries) in 11 districts were involved. Registers (availability rate = 91.1%; interquartile range (IQR) 66.7–100%) and report forms (86.9%; IQR 62.2–100%) were the most utilized tools. There was a limited use of tally-sheets (77.8%; IQR 35.6–100%). Tools availability at the dispensary was 91.1%, health centre 82.2% and hospital 77.8%, and was low in urban districts. The availability rate at the district level was 65% (IQR 48–75%). Wrongly filled or empty cells in registers and poor adherence to the coding procedures were observed. Reports were highly over-represented in comparison to registers’ records, with large differences observed at the HF phase of the reporting system. The OPD and IPD areas indicated the highest levels of mismatch between data source and district office. Indicators with large number of clients, multiple variables, disease categorization, or those linked with dispensing medicine performed poorly. Conclusion There are high variations in the tool utilisation and data accuracy at facility and district levels. The routine HMIS is weak and data at district level inaccurately reflects what is available at the source. These results highlight the need to design tailored and inter-service strategies for improving data quality.

Bacterial larvicides Bacillus thuringiensis var. israelensis (Bti) and Bacillus sphaericus (Bs) have been used extensively for mosquito control. However, their efficacy varies greatly mainly due to factors related to target mosquitoes, larval habitat conditions, and inherent larvicide properties. We evaluated the efficacy of Bti (Bactivec®) and Bs (Griselesf®) for control of Anopheles gambiae complex, Culex quinquefasciatus and Aedes aegypti larvae under laboratory and semi-field conditions in northeastern Tanzania. Laboratory bioassays were conducted with five to six different concentrations of Bti and Bs, replicated four times and the experiment repeated on three different days. Larvae mortality was recorded at 24 or 48 h after the application of larvicide and subjected to Probit analysis. Laboratory bioassays were followed by semi-field trials to establish initial and residual activity of Bti and Bs. Semi-field trials were conducted in artificial larval habitats in the open sunlit ground and in “mosquito spheres”. These artificial larval habitats were colonized with mosquito larvae, treated with Bti and Bs, and the impact of treatments on mosquito larvae was monitored daily. Lethal concentration values that caused 50% and 95% mortalities of test larvae (LC50 and LC95) showed that An. gambiae complex and Cx. quinquefasciatus tested were highly susceptible to Bti and Bs under laboratory conditions. Likewise, larvae of Ae. aegypti were highly susceptible to Bti, with LC95 value as low as 0.052 mg/l. However, Ae. aegypti larvae were not susceptible to Bs under practical doses of laboratory settings. In semi-field trials, all treatment dosages for Bti provided 91.0–100% larval mortality within 24 h whereas Bs resulted in 96.8–100% larval mortality within the same time-frame. Bs had a more prolonged residual activity, with pupal reductions range of 55.7–100% for 9 days at all application rates while the corresponding pupal reduction with Bti was 15.4–100% for 5 days. Due to the low residual activity of Bti and Bs tested, weekly application at a maximum label rate would be appropriate to reduce mosquito larvae in natural larval habitats. Based on laboratory findings, Bs product tested would not be recommended for use in the control of Ae. aegypti.

Abstract Background Malaria control in Africa relies extensively on indoor residual spraying (IRS) and insecticide-treated nets (ITNs). IRS typically targets mosquitoes resting on walls, and in few cases, roofs and ceilings, using contact insecticides. Unfortunately, little attention is paid to where malaria vectors actually rest indoors, and how such knowledge could be used to improve IRS. This study investigated preferred resting surfaces of two major malaria vectors, Anopheles funestus and Anopheles arabiensis, inside four common house types in rural south-eastern Tanzania. Methods The assessment was done inside 80 houses including: 20 with thatched roofs and mud walls, 20 with thatched roofs and un-plastered brick walls, 20 with metal roofs and un-plastered brick walls, and 20 with metal roofs and plastered brick walls, across four villages. In each house, resting mosquitoes were sampled in mornings (6 a.m.–8 a.m.), evenings (6 p.m.–8 p.m.) and at night (11 p.m.–12.00 a.m.) using Prokopack aspirators from multiple surfaces (walls, undersides of roofs, floors, furniture, utensils, clothing, curtains and bed nets). Results Overall, only 26% of An. funestus and 18% of An. arabiensis were found on walls. In grass-thatched houses, 33–55% of An. funestus and 43–50% of An. arabiensis rested under roofs, while in metal-roofed houses, only 16–20% of An. funestus and 8–30% of An. arabiensis rested under roofs. Considering all data together, approximately 40% of mosquitoes rested on surfaces not typically targeted by IRS, i.e. floors, furniture, utensils, clothing and bed nets. These proportions were particularly high in metal-roofed houses (47–53% of An. funestus; 60–66% of An. arabiensis). Conclusion While IRS typically uses contact insecticides to target adult mosquitoes on walls, and occasionally roofs and ceilings, significant proportions of vectors rest on surfaces not usually sprayed. This gap exceeds one-third of malaria mosquitoes in grass-thatched houses, and can reach two-thirds in metal-roofed houses. Where field operations exclude roofs during IRS, the gaps can be much greater. In conclusion, there is need for locally-obtained data on mosquito resting behaviours and how these influence the overall impact and costs of IRS. This study also emphasizes the need for alternative approaches, e.g. house screening, which broadly tackle mosquitoes beyond areas reachable by IRS and ITNs.

Abstract Background The decline in malaria cases and vectors is major milestone in fighting against malaria. The efficacy of MAGNet long-lasting insecticidal nets (MAGNet LLIN), an alpha-cypermethrin incorporated long-lasting net, with the target dose ± 25% of 5.8 g active ingredient (AI)/kg (4.35–7.25 g AI/kg) was evaluated in six veranda-trap experimental huts in Muheza, Tanzania against freely flying wild population of Anopheles funestus. Methods MAGNet LLINs were tested against wild, free-flying, host-seeking An. funestus mosquitoes over a period of 6 weeks (total of 36 nights in the huts). MAGNet LLIN efficacy was determined in terms of mosquito mortality, blood-feeding inhibition, deterrence, induced exiting, personal protection, and insecticidal killing over 20 washes according to WHO standardized procedures. Efficacy was compared with reference to a WHOPES recommended approved LLINs (DuraNet) and to a net conventionally treated (CTN) treated with alpha-cypermethrin at WHO-recommended dose and washed to just before cut-off point. The efficacy of MAGNet was evaluated in experimental huts against wild, free-flying, pyrethroid-resistant An. funestus. The WHO-susceptibility method was used to detect resistance in wild Anopheles exposed to 0.75% permethrin. Mosquito mortality, blood-feeding inhibition and personal protection were compared between untreated nets and standard LLINs. Blood-feeding rates were recorded and compared between the 20 times washed; blood-feeding rates between 20 times washed MAGNet LLIN and 20 times washed WHOPES-approved piperonyl butoxide (PBO)/pyrethroid were not statistically different (p > 0.05). Results The results have evidently shown that MAGNet LLIN provides similar blood-feeding inhibition, exophily, mortality, and deterrence to the standard approved LLIN, thus meeting the WHOPES criteria for blood feeding. The significantly high feeding inhibition and personal protection over pyrethroid-resistant An. funestus recorded by both unwashed and 20 times washed MAGNet compared to the unwashed DuraNet, the WHOPES-approved standard pyrethroid-only LLIN provides proof of MAGNet meeting Phase II WHOPES criteria for a LLIN. Conclusion Based on this study, MAGNet has been shown to have a promising impact on protection when 20 times washed against a highly resistant population of An. funestus.

The success of long-lasting insecticidal nets (LLIN) as the primary method for preventing malaria is threatened by pyrethroid resistance in Anopheles vectors. New generation long-lasting nets incorporating PBO synergist (piperonyl butoxide) with pyrethroid are designed to control insecticide-resistant mosquitoes. The efficacy of Veeralin® PBO LLINs was evaluated in experimental huts against wild free-flying pyrethroid-resistant Anopheles funestus (s.l.). Mosquito mortality, blood-feeding inhibition and personal protection were compared between untreated nets, standard LLINs and PBO/pyrethroid combination nets. Blood-feeding rates recorded with 20-times washed Veeralin were not significantly different from those with 20-times washed PermaNet 3.0 LLIN, a WHO Pre-Qualification Team (PQT) approved PBO/pyrethroid LLIN. This provides evidence that Veeralin LLIN provides similar blood-feeding inhibition to the standard approved LLIN and thus meets WHO PQT criteria for blood-feeding. Results show significantly higher mortality for Veeralin PBO LLINs against pyrethroid-resistant Anopheles funestus (s.l.) compared to DuraNet, a WHO PQT approved standard pyrethroid-only LLIN, both when unwashed and washed 20 times. The improved efficacy over a standard pyrethroid-only LLIN can be attributed to the effect of PBO in the Veeralin LLIN, hence meeting the Vector Control Advisory Group (VCAG) criteria for a resistance breaking LLIN.

This study was carried out to determine the spatial variations in malaria mosquito abundance and human biting rate in five villages representing rice-irrigation and savannah ecosystems in Kilosa District, central Tanzania. The study involved five villages namely Tindiga and Malui (wetland/rice irrigation), Twatwatwa and Mbwade (dry savannah) and Kimamba (wet savannah). Indoor mosquitoes were sampled using Centers for Disease Control and Prevention light traps in three houses in each village. Anopheles gambiae s.l. molecular identification was carried out using polymerase chain reaction (PCR). A total of 936 female mosquitoes were collected. About half (46.9%) were malaria mosquitoes (Anopheles gambiae s.l.=28.6%; An. funestus= 18.3%). A total of 161 (60.1%) of the morphologically identified An. gambiae s.l. (268) and subjected to PCR analysis for speciation were genotyped as An. arabiensis. The An. funestus complex mosquitoes were composed of An. funestus funestus and An. rivulorum at the 5:1 ratio. On average, 17.9 Anopheles mosquitoes were collected per village per day. Two-thirds (62.8%) of the malaria mosquitoes were collected in Malui (rice agro-ecosystem) and the lowest number (2.3%) in Twatwatwa (dry savannah ecosystem). The biting rate per person per night for An. arabiensis+An. funestus s.s. was highest in Malui (46.0) and lowest in Twatwatwa (1.67). The parity rate of the An. funestus mosquitoes was lower compared to that of An. arabiensis and none of the mosquitoes was infected with malaria sporozoites. In conclusion, An. arabiensis is the most abundant malaria vector in Kilosa district and its variation is related to the ecological system. The heterogeneity in malaria mosquito abundance and human biting rate could be used to guide selection of locally appropriated control interventions.

BACKGROUND:In 2010, 2012, 2013 and 2014 dengue outbreaks have been reported in Dar es Salaam, Tanzania. However, there is no comprehensive data on the risk of transmission of dengue in the country. The objective of this study was to assess the risk of transmission of dengue in Dar es Salaam during the 2014 epidemic. METHODOLOGY/PRINCIPAL FINDINGS:This cross-sectional study was conducted in Dar es Salaam, Tanzania during the dengue outbreak of 2014. The study involved Ilala, Kinondoni and Temeke districts. Adult mosquitoes were collected using carbon dioxide-propane powered Mosquito Magnet Liberty Plus traps. In each household compound, water-holding containers were examined for mosquito larvae and pupae. Dengue virus infection of mosquitoes was determined using real-time reverse transcription polymerase chain reaction (qRT-PCR). Partial amplification and sequencing of dengue virus genome in infected mosquitoes was performed. A total of 1,000 adult mosquitoes were collected. Over half (59.9%) of the adult mosquitoes were collected in Kinondoni. Aedes aegypti accounted for 17.2% of the mosquitoes of which 90.6% were from Kinondoni. Of a total of 796 houses inspected, 38.3% had water-holding containers in their premises. Kinondoni had the largest proportion of water-holding containers (57.7%), followed by Temeke (31.4%) and Ilala (23.4%). The most common breeding containers for the Aedes mosquitoes were discarded plastic containers and tires. High Aedes infestation indices were observed for all districts and sites, with a house index of 18.1% in Ilala, 25.5% in Temeke and 35.3% in Kinondoni. The respective container indices were 77.4%, 65.2% and 80.2%. Of the reared larvae and pupae, 5,250 adult mosquitoes emerged, of which 61.9% were Ae. aegypti. Overall, 27 (8.18) of the 330 pools of Ae. aegypti were positive for dengue virus. On average, the overall maximum likelihood estimate (MLE) indicates pooled infection rate of 8.49 per 1,000 mosquitoes (95%CI = 5.72-12.16). There was no significant difference in pooled infection rates between the districts. Dengue viruses in the tested mosquitoes clustered into serotype 2 cosmopolitan genotype. CONCLUSIONS/SIGNIFICANCE:Ae. aegypti is the main vector of dengue in Dar es Salaam and breeds mainly in medium size plastic containers and tires. The Aedes house indices were high, indicating that the three districts were at high risk of dengue transmission. The 2014 dengue outbreak was caused by Dengue virus serotype 2. The high mosquito larval and pupal indices in the area require intensification of vector surveillance along with source reduction and health education.

BACKGROUND: Attractive toxic sugar bait (ATSB) sprayed onto vegetation has been successful in controlling Anopheles mosquitoes outdoors. Indoor application of ATSB has yet to be explored. The purpose of this study was to determine whether ATSB stations positioned indoors have the potential to kill host-seeking mosquitoes and constitute a new approach to control of mosquito-borne diseases. METHODS: Insecticides were mixed with dyed sugar solution and tested as toxic baits against Anopheles arabiensis, An. Gambiae s.s. and Culex quinquefasciatus in feeding bioassay tests to identify suitable attractant-insecticide combinations. The most promising ATSB candidates were then trialed in experimental huts in Moshi, Tanzania. ATSB stations were hung in huts next to untreated mosquito nets occupied by human volunteers. The proportions of mosquitoes killed in huts with ATSB treatments relative to huts with non-insecticide control treatments huts were recorded, noting evidence of dye in mosquito abdomens. RESULTS: In feeding bioassays, chlorfenapyr 0.5% v/v, boric acid 2% w/v, and tolfenpyrad 1% v/v, mixed in a guava juice-based bait, each killed more than 90% of pyrethroid-susceptible An. Gambiae s.s. and pyrethroid-resistant An. arabiensis and Cx. quinquefasciatus. In the hut trial, mortality rates of the three ATSB treatments ranged from 41-48% against An. arabiensis and 36-43% against Cx. quinquefasciatus and all were significantly greater than the control mortalities: 18% for An. arabiensis, 7% for Cx. quinquefasciatus (p

High coverage of conventional and long-lasting insecticide treated nets (ITNs and LLINs) in parts of E Africa are associated with reductions in local malaria burdens. Shifts in malaria vector species ratio have coincided with the scale-up suggesting that some species are being controlled by ITNs/LLINs better than others.Between 2005-2006 six experimental hut trials of ITNs and LLINs were conducted in parallel at two field stations in northeastern Tanzania; the first station was in Lower Moshi Rice Irrigation Zone, an area where An. arabiensis predominates, and the second was in coastal Muheza, where An. gambiae and An. funestus predominate. Five pyrethroids and one carbamate insecticide were evaluated on nets in terms of insecticide-induced mortality, blood-feeding inhibition and exiting rates.In the experimental hut trials mortality of An. arabiensis was consistently lower than that of An. gambiae and An. funestus. The mortality rates in trials with pyrethroid-treated nets ranged from 25-52% for An. arabiensis, 63-88% for An. gambiae s.s. and 53-78% for An. funestus. All pyrethroid-treated nets provided considerable protection for the occupants, despite being deliberately holed, with blood-feeding inhibition (percentage reduction in biting rates) being consistent between species. Veranda exiting rates did not differ between species. Percentage mortality of mosquitoes tested in cone bioassays on netting was similar for An. gambiae and An. arabiensis.LLINs and ITNs treated with pyrethroids were more effective at killing An. gambiae and An. funestus than An. arabiensis. This could be a major contributing factor to the species shifts observed in East Africa following scale up of LLINs. With continued expansion of LLIN coverage in Africa An. arabiensis is likely to remain responsible for residual malaria transmission, and species shifts might be reported over larger areas. Supplementary control measures to LLINs may be necessary to control this vector species.