Baseline susceptibility of a wild strain of main vectors of leishmaniasis to WHO-recommended insecticides in southeastern Iran.

BACKGROUND: In Iran, both cutaneous leishmaniases (CL) and visceral leishmaniases (VL) are endemic, recording one of the 10 highest CL prevalence in the world. Parasites are transmitted by the bite of infected Phlebotomus sand fly females. Several sand fly species have been identified as vectors in the studied region of Kerman province. Residual spraying to control adult sand flies, is the only way to decrease the spreading of the diseases but, following control treatment against malaria vectors in endemic areas in Iran, resistance or tolerance to insecticides emerged in some sand fly species. The objective of this study was to survey insecticides susceptibility levels of 3 vector species in wild sand fly populations in different foci of the diseases in Kerman province. Ph. sergenti, and Ph. papatasi respectively vectors of anthroponotic and zoonotic cutaneous leishmaniases and for the first time Ph. alexandri one of the anthroponotic visceral leishmaniases vector were tested against: deltamethrin 0.05%, malathion 5%, dichloro-diphenyl-trichloroethane (DDT) 4%. MATERIALS AND METHODS: In leishmaniases endemic areas species specific sand fly sites were selected in Kerman province, and specimens were collected by manual aspirators at different time intervals during the spring and summer 2019. All the susceptibility tests were performed according to the WHO tube test recommended procedure. RESULTS: Twenty five blood-fed female sand flies from the region's prevalent species were used in each pooled test replicates. All wild specimens died within 60 min of exposure to DDT 4%, malathion 5%, and deltamethrin 0.05%, but the mortality rate for Ph. papatasi exposed to malathion and DDT was 91.6% and 66.6%, respectively. CONCLUSION: According to current study results, Ph. sergenti and Ph. alexandri are highly susceptible to all the evaluated insecticides in the study areas. However, Ph. papatasi was susceptible to deltamethrin (100% mortality), possibly resistant or tolerant to malathion (91.6% mortality), and confirmed to be resistant to DDT (66.6% mortality).

Insecticidal efficacy against Phlebotomus perniciosus in dogs treated orally with fluralaner in two different parallel-group, negative-control, random and masked trials.

BACKGROUND: Dogs are the reservoir host of Leishmania infantum, the agent of zoonotic visceral leishmaniasis (VL), which is transmitted by the bite of phlebotomine sand flies. The sand fly Phlebotomus perniciosus is the main vector of zoonotic VL in the western Mediterranean region. Fluralaner has been shown to effectively kill this vector. The aim of this study was to evaluate the insecticidal efficacy of oral fluralaner in dogs bitten by P. perniciosus. METHODS: Two parallel-group, negative-controlled, randomized, masked laboratory trials with equivalent designs were performed in two different locations using two different pathogen-free laboratory-bred P. perniciosus strains for the challenge. In each trial, 12 purpose-bred beagles, initially ranked on natural attractiveness to sand flies, were randomly allocated to two groups (6 animals/group). Dogs in one group received fluralaner orally at the approved dose on day 0, and dogs in the control group were not treated. Each dog was subsequently exposed to an average of 70 unfed live sand fly females on days 1, 28, 56 and 84. Viability of blood-fed females was then evaluated for up to 96 h after exposure, and insecticidal efficacy was measured as the survival rate of flies fed on the fluralaner-treated dogs versus that of dogs in the control group. Significance was calculated for the proportion of live fed sand fly counts from treated versus control group dogs. RESULTS: Comparison of the survival proportions between treated and control groups showed that fluralaner insecticidal efficacy was highly significant in both trials (P < 0.001 or P < 0.01 in different assessments) through to day 56. In the first trial, efficacy reached 100% on days 1 and 28, and 99.1% on day 56; in the second trial, the insecticidal efficacy was 98.5, 100 and 85.9%, respectively on the same days. On day 84, efficacy was in the range of 53-57% (P < 0.05) in the first trial and 0% in the second trial. CONCLUSION: A single oral fluralaner administration to dogs under laboratory conditions results in strong and reproducible insecticidal efficacy against P. perniciosus for at least 8 weeks.

Statewide Efficacy Assessment of Insect Growth Regulators Against Aedes albopictus (Diptera: Culicidae) in Sabah, Malaysia: An Alternative Control Strategy?

The efficacy of three groups of insect growth regulators, namely juvenile hormone mimics (methoprene and pyriproxyfen), chitin synthesis inhibitors (diflubenzuron and novaluron), and molting disruptor (cyromazine) was evaluated for the first time, against Aedes albopictus Skuse (Diptera: Culicidae) larvae from 14 districts in Sabah, Malaysia. The results showed that all field populations of Ae. albopictus were susceptible towards methoprene, pyriproxyfen, diflubenzuron, novaluron, and cyromazine, with resistance ratio values ranging from 0.50-0.90, 0.60-1.00, 0.67-1.17, 0.71-1.29, and 0.74-1.07, respectively. Overall, the efficacy assessment of insect growth regulators in this study showed promising outcomes and they could be further explored as an alternative to conventional insecticides.

Recent trends in global insecticide use for disease vector control and potential implications for resistance management.

Insecticides have played a major role in the prevention, control, and elimination of vector-borne diseases, but insecticide resistance threatens the efficacy of available vector control tools. A global survey was conducted to investigate vector control insecticide use from 2010 to 2019. Out of 140 countries selected as sample for the study, 87 countries responded. Also, data on ex-factory deliveries of insecticide-treated nets (ITNs) were analyzed. Insecticide operational use was highest for control of malaria, followed by dengue, leishmaniasis and Chagas disease. Vector control relied on few insecticide classes with pyrethroids the most used overall. Results indicated that IRS programs have been slow to react to detection of pyrethroid resistance, while proactive resistance management using insecticides with unrelated modes of action was generally weak. The intensive use of recently introduced insecticide products raised concern about product stewardship regarding the preservation of insecticide susceptibility in vector populations. Resistance management was weakest for control of dengue, leishmaniasis or Chagas disease. Therefore, it will be vital that vector control programs coordinate on insecticide procurement, planning, implementation, resistance monitoring, and capacity building. Moreover, increased consideration should be given to alternative vector control tools that prevent the development of insecticide resistance.

Onchocerca volvulus transmission in the Mbam valley of Cameroon following 16 years of annual community-directed treatment with ivermectin, and the description of a new cytotype of Simulium squamosum.

BACKGROUND: The onchocerciasis focus surrounding the lower Mbam and Sanaga rivers, where Onchocerca volvulus is transmitted by Simulium damnosum s.l. (Diptera: Simuliidae), was historically the largest in the southern regions of Cameroon. Annual community-directed treatment with ivermectin (CDTI) has been taking place since 2000, but recent studies have shown that new infections are occurring in children. We aimed to investigate blackfly biting and O. volvulus transmission rates along the lower Mbam river 16 years after the formal onset of annual CDTI. METHODS: Black flies were collected for three consecutive days each month between July 2016 and June 2017 at two riverside villages and two inland sites situated 4.9 km and 7.9 km from the riverside. Specimens collected at each site were dissected on one of the three collection days each month to estimate parity rates and O. volvulus infection rates, while the remaining samples were preserved for pool screening. RESULTS: In total, 93,573 S. damnosum s.l. black flies were recorded biting humans and 9281 were dissected. Annual biting rates of up to 606,370 were estimated at the riverside, decreasing to 20,540 at 7.9 km, while, based on dissections, annual transmission potentials of up to 4488 were estimated at the riverside, decreasing to 102 and 0 at 4.9 km and 7.9 km, respectively. However, pool screening showed evidence of infection in black flies at the furthest distance from the river. Results of both methods demonstrated the percentage of infective flies to be relatively low (0.10-0.36%), but above the WHO threshold for interruption of transmission. In addition, a small number of larvae collected during the dry season revealed the presence of Simulium squamosum E. This is the first time S. squamosum E has been found east of Lake Volta in Ghana, but our material was chromosomally distinctive, and we call it S. squamosum E2. CONCLUSIONS: Relatively low O. volvulus infection rates appear to be offset by extremely high densities of biting black flies which are sustaining transmission along the banks of the lower Mbam river.

Efficacy and side effects of bio-fabricated sardine fish scale silver nanoparticles against malarial vector Anopheles stephensi.

Mosquitoes are a great menace for humankind since they transmit pathogenic organisms causing Malaria, Dengue, Chikungunya, Elephantiasis and Japanese encephalitis. There is an urgent need to discover new and novel biological tools to mitigate mosquito-borne diseases. To develop bioinsecticides through newly developed nanotechnology is another option in the present research scenario. In this study we synthesize and characterize sardine fish scales with silver nitrate by adopting various instrumental techniques such as UV- and FTIR-spectroscopy, energy-dispersive X-ray (EDAX), X-ray diffraction analyses (XRD) and scanning electron microscopy (SEM). Toxicity bioassays were conducted with young developmental stages of mosquito vectors. Significant mortality appeared after different life stages of mosquito vectors (young larval and pupal instars were exposed to the nanomaterials). LC50 values were 13.261 ppm for young first instar larvae and 32.182 ppm for pupae. Feeding and predatory potential of G. affinis, before and after exposure to nanoparticles against mosquito larval (I & II) instars of the mosquitoes showed promising results in laboratory experiments. Feeding potential of mosquito fish without nanoparticle treatment was 79.7% and 70.55% for the first and second instar larval populations respectively. At the nanoparticle-exposed situation the predatory efficiency of mosquitofish was 94.15% and 84.3%, respectively. Antioxidant enzymes like (SOD), (CAT), and (LPO) were estimated in the gill region of sardine fish in control and experimental waters. A significant reduction of egg hatchability was evident after nanoparticle application. It became evident from this study that the nano-fabricated materials provide suitable tools to control the malaria vector Anopheles stephensi in the aquatic phase of its life cycle. This finding suggests an effective novel approach to mosquito control.

Insecticidal efficacy of fluralaner (Bravecto®) against Triatoma brasiliensis, a major vector of Trypanosoma cruzi in Brazil.

BACKGROUND: Triatomines are responsible for the vector transmission of the protozoan parasite Trypanosoma cruzi, which causes Chagas disease. Triatoma brasiliensis is the main vector of the parasite in Brazil, and dogs are an important reservoir of the parasite. The aim of this study was to evaluate the insecticidal effect of fluralaner (Bravecto®) on T. brasiliensis after a blood meal in treated dogs. METHODS: Healthy mongrel dogs (n = 8) were recruited from the Zoonoses Control Center (ZCC) in the city of Natal, Rio Grande do Norte, Brazil, and randomized into two groups, a fluralaner (Bravecto®)-treated group (n = 4) and a control group (n = 4). Colony-reared third-, fourth- and fifth-instar nymphs of T. brasiliensis nymphs (n = 10) were allowed to feed on dogs from both groups for 30-40 min, once monthly, for up to 12 months. Bug mortality was observed up to 5 days after each blood meal. RESULTS: Mortality in triatomines which had a blood meal on fluralaner (Bravecto®)-treated dogs was 100% for up to 7 months after treatment, with mortality decreasing to 66.4% after 8 months, 57% after 9 months, 35% after 10 months, 10% after 11 months and 0% after 12 months. The mortality of triatomines that fed on non-treated control dogs was always ≤ 2.5%. CONCLUSIONS: Our results suggest that fluralaner (Bravecto®) treatment of dogs induces long-term mortality of T. brasiliensis after the blood meal. This is a potential approach to be used to control vector transmission of T. cruzi, the etiological agent of Chagas disease, especially in endemic areas.

The impact of insecticides and plant extracts on the suppression of insect vector (Bemisia tabaci) of Mungbean yellow mosaic virus (MYMV).

Mungbean yellow mosaic virus (MYMV) is an important constraint in successful production of mungbean (Vigna radiata L.) in many countries, including Pakistan. The MYMV spreads by insect vector whitefly (Bemisia tabaci Gennadius). The use of resistant cultivars is the most effective management tactics for MYMV. Twenty mungbean varieties/lines were screened against insect vector of MYMV under field condition in the current study. Resistance levels for varieties/lines were assessed through visual scoring of typical disease symptoms. Furthermore, the impacts of two insecticides 'Imidacloprid' and 'Thiamethoxam' and two plant extracts, i.e., neem (Azadirachta indica), and Eucalyptus (Eucalyptus camaldulensis) were tested on the suppression of whitefly. Field screening indicated that none of the tested varieties/lines proved immune/highly resistant, while significant variations were recorded among varieties/lines for resistance level. All varieties/lines were systemically infected with MYMV. The varieties 'AARI-2006' and 'Mung-14043' were considered as resistant to MYMV based on visual symptoms and the lowest vector population. These varieties were followed by 'NM-2006' and 'NL-31', which proved as moderately resistant to MYMV. All remaining varieties/lines were grouped as moderately to highly susceptible to MYMV based on visual symptoms' scoring. These results revealed that existing mungbean germplasm do not possess high resistance level MYMV. However, the lines showing higher resistance in the current study must be exploited in breeding programs for the development of resistant mungbean varieties/lines against MYMV. Imidacloprid proved as the most effective insecticide at all concentrations to manage whitefly population. Therefore, use of the varieties with higher resistance level and spraying Imidacloprid could lower the incidence of MYMV.

The efficacy of insecticide-treated window screens and eaves against Anopheles mosquitoes: a scoping review.

BACKGROUND: Female mosquitoes serve as vectors for a host of illnesses, including malaria, spread by the Plasmodium parasite. Despite monumental strides to reduce this disease burden through tools such as bed nets, the rate of these gains is slowing. Ongoing disruptions related to the COVID-19 pandemic may also negatively impact gains. The following scoping review was conducted to examine novel means of reversing this trend by exploring the efficacy of insecticide-treated window screens or eaves to reduce Anopheles mosquito bites, mosquito house entry, and density. METHODS: Two reviewers independently searched PubMed, Scopus, and ProQuest databases on 10 July, 2020 for peer-reviewed studies using insecticide-treated screens or eaves in malaria-endemic countries. These articles were published in English between the years 2000-2020. Upon collection, the reports were stratified into categories of biting incidence and protective efficacy, mosquito entry and density, and mosquito mortality. RESULTS: Thirteen out of 2180 articles were included in the final review. Eaves treated with beta-cyfluthrin, transfluthrin or bendiocarb insecticides were found to produce vast drops in blood-feeding, biting or mosquito prevalence. Transfluthrin-treated eaves were reported to have greater efficacy at reducing mosquito biting: Rates dropped by 100% both indoors and outdoors under eave ribbon treatments of 0.2% transfluthrin (95% CI 0.00-0.00; p < 0.001). Additionally, co-treating window screens and eaves with polyacrylate-binding agents and with pirimiphos-methyl has been shown to retain insecticidal potency after several washes, with a mosquito mortality rate of 94% after 20 washes (95% CI 0.74-0.98; p < 0.001). CONCLUSIONS: The results from this scoping review suggest that there is value in implementing treated eave tubes or window screens. More data are needed to study the longevity of screens and household attitudes toward these interventions.

Improved vector control of Triatoma infestans limited by emerging pyrethroid resistance across an urban-to-rural gradient in the Argentine Chaco.

BACKGROUND: The sustainable elimination of Triatoma infestans in the Gran Chaco region represents an enduring challenge. Following the limited effects of a routine pyrethroid insecticide spraying campaign conducted over 2011-2013 (first period) in Avia Terai, an endemic municipality with approximately 2300 houses, we implemented a rapid-impact intervention package to suppress house infestation across the urban-to-rural gradient over 2015-2019 (second period). Here, we assess their impacts and whether persisting infestations were associated with pyrethroid resistance. METHODS: The 2011-2013 campaign achieved a limited detection and spray coverage across settings (< 68%), more so during the surveillance phase. Following community mobilization and school-based interventions, the 2015-2019 program assessed baseline house infestation using a stratified sampling strategy; sprayed all rural houses with suspension concentrate beta-cypermethrin, and selectively sprayed infested and adjacent houses in urban and peri-urban settings; and monitored house infestation and performed selective treatments over the follow-up. RESULTS: Over the first period, house infestation returned to pre-intervention levels within 3-4 years. The adjusted relative odds of house infestation between 2011-2013 and 2015-2016 differed very little (adj. OR: 1.17, 95% CI 0.91-1.51). Over the second period, infestation decreased significantly between 0 and 1 year post-spraying (YPS) (adj. OR: 0.36, 95% CI 0.28-0.46), with heterogeneous effects across the gradient. Mean bug abundance also dropped between 0 and 1 YPS and thereafter remained stable in rural and peri-urban areas. Using multiple regression models, house infestation and bug abundance at 1 YPS were 3-4 times higher if the house had been infested before treatment, or was scored as high-risk or non-participating. No low-risk house was ever infested. Persistent foci over two successive surveys increased from 30.0 to 59.3% across the gradient. Infestation was more concentrated in peridomestic rather than domestic habitats. Discriminating-dose bioassays showed incipient or moderate pyrethroid resistance in 7% of 28 triatomine populations collected over 2015-2016 and in 83% of 52 post-spraying populations. CONCLUSIONS: The intervention package was substantially more effective than the routine insecticide spraying campaign, though the effects were lower than predicted due to unexpected incipient or moderate pyrethroid resistance. Increased awareness and diagnosis of vector control failures in the Gran Chaco, including appropriate remedial actions, are greatly needed.

An Overview on Target-Based Drug Design against Kinetoplastid Protozoan Infections: Human African Trypanosomiasis, Chagas Disease and Leishmaniases.

The protozoan diseases Human African Trypanosomiasis (HAT), Chagas disease (CD), and leishmaniases span worldwide and therefore their impact is a universal concern. The present regimen against kinetoplastid protozoan infections is poor and insufficient. Target-based design expands the horizon of drug design and development and offers novel chemical entities and potential drug candidates to the therapeutic arsenal against the aforementioned neglected diseases. In this review, we report the most promising targets of the main kinetoplastid parasites, as well as their corresponding inhibitors. This overview is part of the Special Issue, entitled "Advances of Medicinal Chemistry against Kinetoplastid Protozoa (Trypanosoma brucei, Trypanosoma cruzi and Leishmania spp.) Infections: Drug Design, Synthesis and Pharmacology".

Estimating the impact of Tiny Targets in reducing the incidence of Gambian sleeping sickness in the North-west Uganda focus.

BACKGROUND: Riverine species of tsetse (Glossina) transmit Trypanosoma brucei gambiense, which causes Gambian human African trypanosomiasis (gHAT), a neglected tropical disease. Uganda aims to eliminate gHAT as a public health problem through detection and treatment of human cases and vector control. The latter is being achieved through the deployment of 'Tiny Targets', insecticide-impregnated panels of material which attract and kill tsetse. We analysed the spatial and temporal distribution of cases of gHAT in Uganda during the period 2010-2019 to assess whether Tiny Targets have had an impact on disease incidence. METHODS: To quantify the deployment of Tiny Targets, we mapped the rivers and their associated watersheds in the intervention area. We then categorised each of these on a scale of 0-3 according to whether Tiny Targets were absent (0), present only in neighbouring watersheds (1), present in the watersheds but not all neighbours (2), or present in the watershed and all neighbours (3). We overlaid all cases that were diagnosed between 2000 and 2020 and assessed whether the probability of finding cases in a watershed changed following the deployment of targets. We also estimated the number of cases averted through tsetse control. RESULTS: We found that following the deployment of Tiny Targets in a watershed, there were fewer cases of HAT, with a sampled error probability of 0.007. We estimate that during the intervention period 2012-2019 we should have expected 48 cases (95% confidence intervals = 40-57) compared to the 36 cases observed. The results are robust to a range of sensitivity analyses. CONCLUSIONS: Tiny Targets have reduced the incidence of gHAT by 25% in north-western Uganda.

Chemical control and insecticide resistance status of sand fly vectors worldwide.

BACKGROUND: Phlebotomine sand flies are prominent vectors of Leishmania parasites that cause leishmaniasis, which comes second to malaria in terms of parasitic causative fatalities globally. In the absence of human vaccines, sand fly chemical-based vector control is a key component of leishmaniasis control efforts. METHODS AND FINDINGS: We performed a literature review on the current interventions, primarily, insecticide-based used for sand fly control, as well as the global insecticide resistance (IR) status of the main sand fly vector species. Indoor insecticidal interventions, such as residual spraying and treated bed nets are the most widely deployed, while several alternative control strategies are also used in certain settings and/or are under evaluation. IR has been sporadically detected in sand flies in India and other regions, using non-standardized diagnostic bioassays. Molecular studies are limited to monitoring of known pyrethroid resistance mutations (kdr), which are present at high frequencies in certain regions. CONCLUSIONS: As the leishmaniasis burden remains a major problem at a global scale, evidence-based rational use of insecticidal interventions is required to meet public health demands. Standardized bioassays and molecular markers are a prerequisite for this task, albeit are lagging behind. Experiences from other disease vectors underscore the need for the implementation of appropriate IR management (IRM) programs, in the framework of integrated vector management (IVM). The implementation of alternative strategies seems context- and case-specific, with key eco-epidemiological parameters yet to be investigated. New biotechnology-based control approaches might also come into play in the near future to further reinforce sand fly/leishmaniasis control efforts.

Phenotypic plasticity, canalisation and developmental stability of Triatoma infestans wings: effects of a sublethal application of a pyrethroid insecticide.

BACKGROUND: Triatomine control campaigns have traditionally consisted of spraying the inside of houses with pyrethroid insecticides. However, exposure to sublethal insecticide doses after the initial application is a common occurrence and may have phenotypic consequences for survivors. Here, using Triatoma infestans (the main vector of Chagas disease in the Southern Cone of South America) as a model species, we quantified the effects of exposure to a sublethal dose of pyrethroid insecticide on wing morphology. We tested if the treatment (i) induced a plastic effect (change in the character mean); (ii) altered environmental canalisation (higher individual variation within genotypes); (iii) altered genetic canalisation (higher variation among genotypes); and (iv) altered developmental stability (higher fluctuating asymmetry [FA]). METHODS: Each of 25 full-sib families known to be susceptible to pyrethroid insecticides were split in two groups: one to be treated with a sublethal dose of deltamethrin (insecticide-treated group) and the other to be treated with pure acetone (control group). Wings of the emerging adults were used in a landmark-based geometric morphometry analysis to extract size and shape measurements. Average differences among treatments were measured. Levels of variation among families, among individuals within families and among sides within individuals were computed and compared among treatments. RESULTS: Wing size and shape were affected by a sublethal dose of deltamethrin. The treated insects had larger wings and a more variable wing size and shape than control insects. For both wing size and shape, genetic variation was higher in treated individuals. Individual variations and variations in FA were also greater in deltamethrin-treated insects than in control ones for all full-sib families; however, the patterns of shape variation associated with genetic variation, individual variation and FA were different. CONCLUSIONS: Insects exposed to a sublethal dose of deltamethrin presented larger, less symmetrical and less canalised wings. The insecticide treatment jointly impaired developmental stability and genetic and environmental canalisation. The divergent patterns of shape variation suggest that the related developmental buffering processes differed at least partially. The morphological modifications induced by a single sublethal exposure to pyrethroids early in life may impinge on subsequent flight performance and consequently affect the dynamics of house invasion and reinfestation, and the effectiveness of triatomine control operations.

Towards an odour-baited trap to control Musca sorbens, the putative vector of trachoma.

Musca sorbens is a synanthropic filth fly that aggressively attacks people to feed from mucous membranes of the eyes, nose or mouth, from open sores, or from sweat. It has long been suspected that this fly contributes to the transmission of eye infections, particularly trachoma, and recent work has added to the evidence base that M. sorbens is a trachoma vector in Ethiopia. There are few options to control M. sorbens, largely due to a lack of evidence. Space spraying with insecticides is effective, but an environmentally sound and long-term sustainable solution would be better, for example, mass trapping. We tested commercially available and homemade trap types in a pilot (laboratory) study and three field studies. A homemade design, built from a bucket and two empty water bottles, baited with a commercially available lure, The Buzz, was found to be most effective. This trap caught 3848 M. sorbens over 26 trap 'events' (3- or 4-day periods); mean/median per 24 h 43.6 (standard deviation 137.10)/2.25 (IQR 0.25-12.67). The Buzz lure is cheap and effective for 4 weeks, and trap components cheap and locally available. Further studies are needed to understand the impact of this trap on local fly populations and the local transmission of trachoma.

Evaluation of improved coloured targets to control riverine tsetse in East Africa: A Bayesian approach.

BACKGROUND: Riverine tsetse (Glossina spp.) transmit Trypanosoma brucei gambiense which causes Gambian Human African Trypanosomiasis. Tiny Targets were developed for cost-effective riverine tsetse control, and comprise panels of insecticide-treated blue polyester fabric and black net that attract and kill tsetse. Versus typical blue polyesters, two putatively more attractive fabrics have been developed: Vestergaard ZeroFly blue, and violet. Violet was most attractive to savannah tsetse using large targets, but neither fabric has been tested for riverine tsetse using Tiny Targets. METHODS: We measured numbers of G. f. fuscipes attracted to electrified Tiny Targets in Kenya and Uganda. We compared violets, Vestergaard blues, and a typical blue polyester, using three replicated Latin squares experiments. We then employed Bayesian statistical analyses to generate expected catches for future target deployments incorporating uncertainty in model parameters, and prior knowledge from previous experiments. RESULTS: Expected catches for average future replicates of violet and Vestergaard blue targets were highly likely to exceed those for typical blue. Accounting for catch variability between replicates, it remained moderately probable (70-86% and 59-84%, respectively) that a given replicate of these targets would have a higher expected catch than typical blue on the same day at the same site. Meanwhile, expected catches for average violet replicates were, in general, moderately likely to exceed those for Vestergaard blue. However, the difference in medians was small, and accounting for catch variability, the probability that the expected catch for a violet replicate would exceed a Vestergaard blue equivalent was marginal (46-71%). CONCLUSION: Violet and Vestergaard ZeroFly blue are expected to outperform typical blue polyester in the Tiny Target configuration. Violet is unlikely to greatly outperform Vestergaard blue deployed in this way, but because violet is highly attractive to both riverine and savannah tsetse using different target designs, it may provide the more suitable general-purpose fabric.

Effectiveness of vector control methods for the control of cutaneous and visceral leishmaniasis: A meta-review.

Elimination of visceral leishmaniasis (VL) in Southeast Asia and global control of cutaneous leishmaniasis (CL) and VL are priorities of the World Health Organization (WHO). But is the existing evidence good enough for public health recommendations? This meta-review summarises the available and new evidence for vector control with the aims of establishing what is known about the value of vector control for the control of CL and VL, establishing gaps in knowledge, and particularly focusing on key recommendations for further scientific work. This meta-review follows the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) criteria, including (1) systematic reviews and meta-analyses (SRs/MAs) for (2) vector control methods and strategies and (3) for the control of CL and/or VL. Nine SRs/MAs were included, with different research questions and inclusion/exclusion criteria. The methods analysed for vector control can be broadly classified into (1) indoor residual spraying (IRS); (2) insecticide-treated nets (ITNs; including insecticide-impregnated bednets); (3) insecticide-treated curtains (ITCs; including insecticide-treated house screening); (4) insecticide-treated bedsheets (ITSs) and insecticide-treated fabrics (ITFs; including insecticide-treated clothing) and (5) durable wall lining (treated with insecticides) and other environmental measures to protect the house; (6) control of the reservoir host; and (7) strengthening vector control operations through health education. The existing SRs/MAs include a large variation of different primary studies, even for the same specific research sub-question. Also, the SRs/MAs are outdated, using available information until earlier than 2018 only. Assessing the quality of the SRs/MAs, there is a considerable degree of variation. It is therefore very difficult to summarise the results of the available SRs/MAs, with contradictory results for both vector indices and-if available-human transmission data. Conclusions of this meta-review are that (1) existing SRs/MAs and their results make policy recommendations for evidence-based vector control difficult; (2) further work is needed to establish efficacy and community effectiveness of key vector control methods with specific SRs and MAs (3) including vector and human transmission parameters; and (4) attempting to conclude with recommendations in different transmission scenarios.

Residual Malaria: Limitations of Current Vector Control Strategies to Eliminate Transmission in Residual Foci.

The transmission of Plasmodium parasites in residual foci is currently a major roadblock for malaria elimination. Human activities and behavior, along with outdoor biting mosquitoes with opportunistic feeding preferences are the main causes of the inefficacy of the main vector control interventions, long lasting insecticide-impregnated nets and insecticide residual spraying. Several strategies to abate or repel outdoor biting mosquito vectors are currently being researched, but the impact of insecticide resistance on the efficacy of these and current indoor-applied insecticides requires further assessment. Understanding the human, ecological and vector factors, determining transmission in residual foci is necessary for the design and implementation of novel control strategies. Vector control alone is insufficient without adequate epidemiological surveillance and prompt treatment of malaria cases, the participation of endemic communities in prevention and control is required. In addition, malaria control programs should optimize their structure and organization, and their coordination with other government sectors.

Insecticide susceptibility of Phlebotomus argentipes sandflies, vectors of visceral leishmaniasis in India.

OBJECTIVES: Indoor residual spraying (IRS) with insecticides is the main vector control intervention for the elimination of visceral leishmaniasis in India. After a change in IRS policy in 2015 due to widespread resistance of Phlebotomus argentipes to DDT, IRS with DDT was replaced with alpha-cypermethrin IRS in 2016. The objective of the present study was to evaluate the susceptibility of P. argentipes to DDT and its alternatives, namely malathion and pirimiphos-methyl (organophosphates); alpha-cypermethrin, deltamethrin, lambda-cyhalothrin and permethrin (pyrethroids), and bendiocarb and propoxur (carbamates), in support of visceral leishmaniasis elimination in India. METHODS: Phlebotomus argentipes sandflies were collected from the visceral-leishmaniasis endemic states of Bihar, Jharkhand and West Bengal. In the WHO tube tests, the phenotypic susceptibility of F1, 2-day old, non-blood fed females were determined against filter papers impregnated with DDT 4%, malathion 5%, pirimiphos-methyl 0.25%, alpha-cypermethrin 0.05%, deltamethrin 0.05%, lambda-cyhalothrin 0.05%, permethrin 0.75%, bendiocarb 0.1% and propoxur 0.1%, which were sourced from Universiti Sains Malaysia. The knockdown of sandflies after 1-h exposure and mortality at 24 h after the 1-h exposure period were scored. RESULTS: Mean mortality of P. argentipes 24 h after exposure in tube tests was 22.6% for DDT and ≥ 98% for other insecticide-impregnated papers tested. CONCLUSION: Phlebotomus argentipes continues to be highly resistant to DDT with no reversal of resistance after DDT's withdrawal from IRS. P. argentipes was fully susceptible to pyrethroid, organophosphate and carbamate insecticides tested. Regular monitoring is warranted for insecticide resistance management in sandfly vectors.

High pyrethroid/DDT resistance in major malaria vector Anopheles coluzzii from Niger-Delta of Nigeria is probably driven by metabolic resistance mechanisms.

Entomological surveillance of local malaria vector populations is an important component of vector control and resistance management. In this study, the resistance profile and its possible mechanisms was characterised in a field population of the major malaria vector Anopheles coluzzii from Port Harcourt, the capital of Rivers state, in the Niger-Delta Region of Nigeria. Larvae collected in Port-Harcourt, were reared to adulthood and used for WHO bioassays. The population exhibited high resistance to permethrin, deltamethrin and DDT with mortalities of 6.7% ± 2.4, 37.5% ± 3.2 and 6.3% ± 4.1, respectively, but were fully susceptible to bendiocarb and malathion. Synergist bioassays with piperonylbutoxide (PBO) partially recovered susceptibility, with mortalities increasing to 53% ± 4, indicating probable role of CYP450s in permethrin resistance (χ2 = 29.48, P < 0.0001). Transcriptional profiling revealed five major resistance-associated genes overexpressed in the field samples compared to the fully susceptible laboratory colony, Ngoussou. Highest fold change (FC) was observed with GSTe2 (FC = 3.3 in permethrin exposed and 6.2 in unexposed) and CYP6Z3 (FC = 1.4 in exposed and 4.6 in unexposed). TaqMan genotyping of 32 F0 females detected the 1014F and 1575Y knockdown resistance (kdr) mutations with frequencies of 0.84 and 0.1, respectively, while 1014S mutation was not detected. Sequencing of a fragment of the voltage-gated sodium channel, spanning exon 20 from 13 deltamethrin-resistant and 9 susceptible females revealed only 2 distinct haplotypes with a low haplotype diversity of 0.33. The findings of high pyrethroid resistance but with a significant degree of recovery after PBO synergist assay suggests the need to move to PBO-based nets. This could be complemented with carbamate- or organophosphate-based indoor residual spraying in this area.