Dynamics of malaria vector composition and Plasmodium falciparum infection in mainland Tanzania: 2017-2021 data from the national malaria vector entomological surveillance.

BACKGROUND: In 2015, Tanzania National Malaria Control Programme (NMCP) established a longitudinal malaria vector entomological surveillance (MVES). The MVES is aimed at a periodical assessment of malaria vector composition and abundance, feeding and resting behaviours, and Plasmodium falciparum infection in different malaria epidemiological strata to guide the NMCP on the deployment of appropriate malaria vector interventions. This work details the dynamics of malaria vector composition and transmission in different malaria epidemiological strata. METHODS: The MVES was conducted from 32 sentinel district councils across the country. Mosquitoes were collected by the trained community members and supervised by the NMCP and research institutions. Three consecutive night catches (indoor collection with CDC light trap and indoor/outdoor collection using bucket traps) were conducted monthly in three different households selected randomly from two to three wards within each district council. Collected mosquitoes were sorted and morphologically identified in the field. Thereafter, the samples were sent to the laboratory for molecular characterization using qPCR for species identification and detection of P. falciparum infections (sporozoites). ELISA technique was deployed for blood meal analysis from samples of blood-fed mosquitoes to determine the blood meal indices (BMI). RESULTS: A total of 63,226 mosquitoes were collected in 32 district councils from January 2017 to December 2021. Out of which, 39,279 (62%), 20,983 (33%) and 2964 (5%) were morphologically identified as Anopheles gambiae sensu lato (s.l.), Anopheles funestus s.l., and as other Anopheles species, respectively. Out of 28,795 laboratory amplified mosquitoes, 13,645 (47%) were confirmed to be Anopheles arabiensis, 9904 (34%) as An. funestus sensu stricto (s.s.), and 5193 (19%) as An. gambiae s.s. The combined average entomological inoculation rates (EIR) were 0.46 (95% CI 0.028-0.928) for An. gambiae s.s., 0.836 (95% CI 0.138-1.559) for An. arabiensis, and 0.58 (95% CI 0.165-0.971) for An. funestus s.s. with variations across different malaria transmission strata. Anopheles funestus s.s. and An. arabiensis were predominant in the Lake and South-Eastern zones, respectively, mostly in high malaria transmission areas. Monthly mosquito densities displayed seasonal patterns, with two peaks following the rainy seasons, varying slightly across species and district councils. CONCLUSION: Anopheles arabiensis remains the predominant vector species followed by An. funestus s.s. in the country. Therefore, strengthening integrated vector management including larval source management is recommended to address outdoor transmission by An. arabiensis to interrupt transmission particularly where EIR is greater than the required elimination threshold of less than one (< 1) to substantially reduce the prevalence of malaria infection.

Perspectives of African stakeholders on gene drives for malaria control and elimination: a multi-country survey.

BACKGROUND: Gene drive modified mosquitoes (GDMMs) have the potential to address Africa's persistent malaria problem, but are still in early stages of development and testing. Continuous engagement of African stakeholders is crucial for successful evaluation and implementation of these technologies. The aim of this multi-country study was, therefore, to explore the insights and recommendations of key stakeholders across Africa on the potential of GDMMs for malaria control and elimination in the continent. METHODS: A concurrent mixed-methods study design was used, involving a structured survey administered to 180 stakeholders in 25 countries in sub-Saharan Africa, followed by 18 in-depth discussions with selected groups and individuals. Stakeholders were drawn from academia, research and regulatory institutions, government ministries of health and environment, media and advocacy groups. Thematic content analysis was used to identify key topics from the in-depth discussions, and descriptive analysis was done to summarize information from the survey data. RESULTS: Despite high levels of awareness of GDMMs among the stakeholders (76.7%), there was a relatively low-level of understanding of their key attributes and potential for malaria control (28.3%). When more information about GDMMs was provided to the stakeholders, they readily discussed their insights and concerns, and offered several recommendations to ensure successful research and implementation of the technology. These included: (i) increasing relevant technical expertise within Africa, (ii) generating local evidence on safety, applicability, and effectiveness of GDMMs, and (iii) developing country-specific regulations for safe and effective governance of GDMMs. A majority of the respondents (92.9%) stated that they would support field trials or implementation of GDMMs in their respective countries. This study also identified significant misconceptions regarding the phase of GDMM testing in Africa, as several participants incorrectly asserted that GDMMs were already present in Africa, either within laboratories or released into the field. CONCLUSION: Incorporating views and recommendations of African stakeholders in the ongoing research and development of GDMMs is crucial for instilling stakeholder confidence on their potential application. These findings will enable improved planning for GDMMs in Africa as well as improved target product profiles for the technologies to maximize their potential for solving Africa's enduring malaria challenge.

Opinions of key stakeholders on alternative interventions for malaria control and elimination in Tanzania.

BACKGROUND: Malaria control in Tanzania currently relies primarily on long-lasting insecticidal nets and indoor residual spraying, alongside effective case management and behaviour change communication. This study explored opinions of key stakeholders on the national progress towards malaria elimination, the potential of currently available vector control interventions in helping achieve elimination by 2030, and the need for alternative interventions that could be used to supplement malaria elimination efforts in Tanzania. METHODS: In this exploratory qualitative study, Focus group discussions were held with policy-makers, regulators, research scientists and community members. Malaria control interventions discussed were: (a) improved housing, (b) larval source management, (c) mass drug administration (MDA) with ivermectin to reduce vector densities, (d) release of modified mosquitoes, including genetically modified or irradiated mosquitoes, (e) targeted spraying of mosquito swarms, and (f) spatial repellents. RESULTS: Larval source management and spatial repellents were widely supported across all stakeholder groups, while insecticide-spraying of mosquito swarms was the least preferred. Support for MDA with ivermectin was high among policy makers, regulators and research scientists, but encountered opposition among community members, who instead expressed strong support for programmes to improve housing for poor people in high transmission areas. Policy makers, however, challenged the idea of government-supported housing improvement due to its perceived high costs. Techniques of mosquito modification, specifically those involving gene drives, were viewed positively by community members, policy makers and regulators, but encountered a high degree of scepticism among scientists. Overall, policy-makers, regulators and community members trusted scientists to provide appropriate advice for decision-making. CONCLUSION: Stakeholder opinions regarding alternative malaria interventions were divergent except for larval source management and spatial repellents, for which there was universal support. MDA with ivermectin, housing improvement and modified mosquitoes were also widely supported, though each faced concerns from at least one stakeholder group. While policy-makers, regulators and community members all noted their reliance on scientists to make informed decisions, their reasoning on the benefits and disadvantages of specific interventions included factors beyond technical efficiency. This study suggests the need to encourage and strengthen dialogue between research scientists, policy makers, regulators and communities regarding new interventions.

Adherence, Awareness, Access, and Use of Standard Diagnosis and Treatment Guideline for Malaria Case Management among Healthcare Workers in Meatu, Tanzania.

BACKGROUND: Effective case management is a vital component of malaria control and elimination strategies. However, the level of adherence to the malaria diagnostic test and treatment guideline is not known, particularly at Meatu district. Therefore, this study aimed at determining the adherence, awareness, access, and use of standard diagnosis and treatment guidelines among healthcare workers in Meatu district. METHOD: This was a descriptive cross-sectional study, which enrolled a total of 196 healthcare workers in Meatu district. Healthcare workers were sampled purposively to reach the required sample size. A structured questionnaire was used for data collection. RESULTS: Generally, 189 (96.4%) were aware of malaria treatment guidelines, while 148 (75.5%) had access and 98 (50.0%) used malaria treatment guidelines. One hundred and seven (54.6%) of all the healthcare workers adhered strictly to the diagnosis and national treatment guidelines. Ten (5.1%) partially adhered to the guideline when choosing antimalarials without confirmed malaria cases. Nonadherence to the prescription of recommended antimalarial drugs and laboratory confirmation was 79 (40.3%). CONCLUSION: Half of healthcare worker's adhere to malaria diagnostic test and treatment guidelines. Most the healthcare workers are aware of the malaria diagnostic test and treatment guidelines. Continued education and assessment of the personal attitudes towards malaria diagnostic test and treatment guidelines are recommended.

Healthcare workers knowledge and diagnostic practices: a need for dengue and chikungunya training in Moshi Municipality, Kilimanjaro Tanzania.

OBJECTIVE: Dengue and chikungunya virus diseases are becoming an increasingly important global health threats and are continuously expanding their geographical range. The study aims to investigate knowledge and diagnostic practice of dengue and chikungunya fever among healthcare workers in Moshi Municipality. RESULTS: Most of healthcare workers heard of chikungunya and dengue 146 (71.2%) and 203 (99%) respectively. Ninety-five (46.3%) and 152 (74.1%) had good knowledge regard chikungunya and dengue respectively. One hundred and twenty-two of HCWs 122 (59.5%) reported that there is no vaccination for dengue virus. Most HCWs 199 (97.0%) reported that the absence of diagnostic tool for dengue virus lead to difficult in managing the infection. The finding of this study showed that there is insufficient knowledge regarding chikungunya while knowledge regarding dengue is relatively fair. This calls for training regarding these infections.

Cross-sectional Survey on Antibiotic Prescription Practices Among Health Care Providers in Rombo District, Northern Tanzania.

BACKGROUND: Irrational and inappropriate antibiotic prescription is a worldwide phenomenon - increasing the threat of serious antibiotic resistance. A better understanding of health care providers' knowledge, attitudes, and prescription practices related to antibiotics is essential for formulating effective antibiotics stewardship programmes. The aim of the present study was to assess knowledge, attitudes, and prescription practices toward antibiotics among health care providers. METHODS: A descriptive cross-sectional study was conducted between March and June 2017 to assess knowledge, attitudes, and prescription practices toward antibiotics among health care providers in the Rombo district of northern Tanzania. A total of 217 health care providers were interviewed using a structured questionnaire. RESULTS: Over half of health care providers (n=111, 51.2%) strongly agreed that the inappropriate prescription of antibiotics puts patients at risk. More than half (n=112, 51.6%) reported that their decision to start antibiotic therapy was influenced by a patient's clinical condition, while 110 (50.7%) reported they were influenced by positive microbiological results in symptomatic patients. Almost two-thirds of the health care providers (n=136, 62.7%) reported that they had access to and used antibiotic therapy guidelines. Less than a quarter (n=52, 24.0%) received regular training and education in antibiotic prescription practice in their work place. CONCLUSION: Knowledge and prescription practice of antibiotics among health care providers was generally unsatisfactory. Training and education for health care providers is needed in the area of prescribing antibiotics.

Impact of non-pyrethroid insecticide treated durable wall lining on age structure of malaria vectors in Muheza, Tanzania.

OBJECTIVE: Malaria vectors control interventions are designed to cause immediate killing or shorten mosquito lives, therefore does not allow enough time for the development of the parasites to infective stage. The wall lining is new malaria vectors control intervention in Tanzania where its impact on age structure is not well known. Therefore this study aimed at determining the impact of non-pyrethroid durable wall lining on the age structure of malaria vectors. RESULTS: Higher proportions of An. gambiae sensu lato (57.1%, z = 2.66, P = 0.0077) and An. funestus (64.8%, z = 3.38, P = 0.001) were collected in the control clusters. Unexpectedly, significantly higher proportion of parous An. gambiae s. l. were collected in the intervention clusters (z = - 2.78, P = 0.0054). The wall lining intervention has demonstrated low impact on age structure of An. gambiae s. l., this call for further studies on the efficacy of the intervention.

Experimental hut evaluation of a novel long-lasting non-pyrethroid durable wall lining for control of pyrethroid-resistant Anopheles gambiae and Anopheles funestus in Tanzania.

BACKGROUND: A novel, insecticide-treated, durable wall lining (ITWL), which mimics indoor residual spraying (IRS), has been developed to provide prolonged vector control when fixed to the inner walls of houses. PermaNet® ITWL is a polypropylene material containing non-pyrethroids (abamectin and fenpyroximate) which migrate gradually to the surface. METHODS: An experimental hut trial was conducted in an area of pyrethroid-resistant Anopheles gambiae s.l. and Anopheles funestus s.s. to compare the efficacy of non-pyrethroid ITWL, long-lasting insecticidal nets (LLIN) (Interceptor®), pyrethroid ITWL (ZeroVector®), and non-pyrethroid ITWL + LLIN. RESULTS: The non-pyrethroid ITWL produced relatively low levels of mortality, between 40-50% for An. funestus and An. gambiae, across all treatments. Against An. funestus, the non-pyrethroid ITWL when used without LLIN produced 47% mortality but this level of mortality was not significantly different to that of the LLIN alone (29%, P = 0.306) or ITWL + LLIN (35%, P = 0.385). Mortality levels for An. gambiae were similar to An. funestus with non-pyrethroid ITWL, producing 43% mortality compared with 26% for the LLIN. Exiting rates from ITWL huts were similar to the control and highest when the LLIN was present. An attempt to restrict mosquito access by covering the eave gap with ITWL (one eave open vs four open) had no effect on numbers entering. The LLIN provided personal protection when added to the ITWL with only 30% blood-fed compared with 69 and 56% (P = 0.001) for ITWL alone. Cone bioassays on ITWL with 30 min exposure after the trial produced mortality of >90% using field An. gambiae. CONCLUSIONS: Despite high mortality in bioassays, the hut trial produced only limited mortality which was attributed to pyrethroid resistance against the pyrethroid ITWL and low efficacy in the non-pyrethroid ITWL. Hut ceilings were left uncovered and may have served as a potential untreated refuge. By analogy to IRS campaigns, which also do not routinely treat ceilings, high community coverage with ITWL may still reduce malaria transmission. Restriction of eave gaps by 75% proved an inadequate barrier to mosquito entry. The findings represent the first 2 months after installation and do not necessarily predict long-term efficacy.

The effectiveness of non-pyrethroid insecticide-treated durable wall lining to control malaria in rural Tanzania: study protocol for a two-armed cluster randomized trial.

BACKGROUND: Despite considerable reductions in malaria achieved by scaling-up long-lasting insecticidal nets (LLINs) and indoor residual spraying (IRS), maintaining sustained community protection remains operationally challenging. Increasing insecticide resistance also threatens to jeopardize the future of both strategies. Non-pyrethroid insecticide-treated wall lining (ITWL) may represent an alternate or complementary control method and a potential tool to manage insecticide resistance. To date no study has demonstrated whether ITWL can reduce malaria transmission nor provide additional protection beyond the current best practice of universal coverage (UC) of LLINs and prompt case management. METHODS/DESIGN: A two-arm cluster randomized controlled trial will be conducted in rural Tanzania to assess whether non-pyrethroid ITWL and UC of LLINs provide added protection against malaria infection in children, compared to UC of LLINs alone. Stratified randomization based on malaria prevalence will be used to select 22 village clusters per arm. All 44 clusters will receive LLINs and half will also have ITWL installed on interior house walls. Study children, aged 6 months to 11 years old, will be enrolled from each cluster and followed monthly to estimate cumulative incidence of malaria parasitaemia (primary endpoint), time to first malaria episode and prevalence of anaemia before and after intervention. Entomological inoculation rate will be estimated using indoor CDC light traps and outdoor tent traps followed by detection of Anopheles gambiae species, sporozoite infection, insecticide resistance and blood meal source. ITWL bioefficacy and durability will be monitored using WHO cone bioassays and household surveys, respectively. Social and cultural factors influencing community and household ITWL acceptability will be explored through focus-group discussions and in-depth interviews. Cost-effectiveness, compared between study arms, will be estimated per malaria case averted. DISCUSSION: This protocol describes the large-scale evaluation of a novel vector control product, designed to overcome some of the known limitations of existing methods. If ITWL is proven to be effective and durable under field conditions, it may warrant consideration for programmatic implementation, particularly in areas with long transmission seasons and where pyrethroid-resistant vectors predominate. Trial findings will provide crucial information for policy makers in Tanzania and other malaria-endemic countries to guide resource allocations for future control efforts. TRIAL REGISTRATION: NCT02533336 registered on 13 July 2014.

Susceptibility status of malaria vectors to insecticides commonly used for malaria control in Tanzania.

OBJECTIVE: The aim of the study was to monitor the insecticide susceptibility status of malaria vectors in 12 sentinel districts of Tanzania. METHODS: WHO standard methods were used to detect knock-down and mortality in the wild female Anopheles mosquitoes collected in sentinel districts. The WHO diagnostic doses of 0.05% deltamethrin, 0.05% lambdacyhalothrin, 0.75% permethrin and 4% DDT were used. RESULTS: The major malaria vectors in Tanzania, Anopheles gambiae s.l., were susceptible (mortality rate of 98-100%) to permethrin, deltamethrin, lambdacyhalothrin and DDT in most of the surveyed sites. However, some sites recorded marginal susceptibility (mortality rate of 80-97%); Ilala showed resistance to DDT (mortality rate of 65% [95% CI, 54-74]), and Moshi showed resistance to lambdacyhalothrin (mortality rate of 73% [95% CI, 69-76]) and permethrin (mortality rate of 77% [95% CI, 73-80]). CONCLUSIONS: The sustained susceptibility of malaria vectors to pyrethroid in Tanzania is encouraging for successful malaria control with Insecticide-treated nets and IRS. However, the emergency of focal points with insecticide resistance is alarming. Continued monitoring is essential to ensure early containment of resistance, particularly in areas that recorded resistance or marginal susceptibility and those with heavy agricultural and public health use of insecticides.

Microbial larvicide application by a large-scale, community-based program reduces malaria infection prevalence in urban Dar es Salaam, Tanzania.

BACKGROUND: Malaria control in Africa is most tractable in urban settlements yet most research has focused on rural settings. Elimination of malaria transmission from urban areas may require larval control strategies that complement adult mosquito control using insecticide-treated nets or houses, particularly where vectors feed outdoors. METHODS AND FINDINGS: Microbial larvicide (Bacillus thuringiensis var. israelensis (Bti)) was applied weekly through programmatic, non-randomized community-based, but vertically managed, delivery systems in urban Dar es Salaam, Tanzania. Continuous, randomized cluster sampling of malaria infection prevalence and non-random programmatic surveillance of entomological inoculation rate (EIR) respectively constituted the primary and secondary outcomes surveyed within a population of approximately 612,000 residents in 15 fully urban wards covering 55 km(2). Bti application for one year in 3 of those wards (17 km(2) with 128,000 residents) reduced crude annual transmission estimates (Relative EIR [95% Confidence Interval] = 0.683 [0.491-0.952], P = 0.024) but program effectiveness peaked between July and September (Relative EIR [CI] = 0.354 [0.193 to 0.650], P = 0.001) when 45% (9/20) of directly observed transmission events occurred. Larviciding reduced malaria infection risk among children < or =5 years of age (OR [CI] = 0.284 [0.101 to 0.801], P = 0.017) and provided protection at least as good as personal use of an insecticide treated net (OR [CI] = 0.764 [0.614-0.951], P = 0.016). CONCLUSIONS: In this context, larviciding reduced malaria prevalence and complemented existing protection provided by insecticide-treated nets. Larviciding may represent a useful option for integrated vector management in Africa, particularly in its rapidly growing urban centres.

Interdependence of domestic malaria prevention measures and mosquito-human interactions in urban Dar es Salaam, Tanzania.

BACKGROUND: Successful malaria vector control depends on understanding behavioural interactions between mosquitoes and humans, which are highly setting-specific and may have characteristic features in urban environments. Here mosquito biting patterns in Dar es Salaam, Tanzania are examined and the protection against exposure to malaria transmission that is afforded to residents by using an insecticide-treated net (ITN) is estimated. METHODS: Mosquito biting activity over the course of the night was estimated by human landing catch in 216 houses and 1,064 residents were interviewed to determine usage of protection measures and the proportion of each hour of the night spent sleeping indoors, awake indoors, and outdoors. RESULTS: Hourly variations in biting activity by members of the Anopheles gambiae complex were consistent with classical reports but the proportion of these vectors caught outdoors in Dar es Salaam was almost double that of rural Tanzania. Overall, ITNs confer less protection against exophagic vectors in Dar es Salaam than in rural southern Tanzania (59% versus 70%). More alarmingly, a biting activity maximum that precedes 10 pm and much lower levels of ITN protection against exposure (38%) were observed for Anopheles arabiensis, a vector of modest importance locally, but which predominates transmission in large parts of Africa. CONCLUSION: In a situation of changing mosquito and human behaviour, ITNs may confer lower, but still useful, levels of personal protection which can be complemented by communal transmission suppression at high coverage. Mosquito-proofing houses appeared to be the intervention of choice amongst residents and further options for preventing outdoor transmission include larviciding and environmental management.