scholarly journals Ebola outbreak brings to light an unforeseen impact of tsetse control on sleeping sickness transmission in Guinea

2018 ◽  
Author(s):  
Moïse Kagabadouno ◽  
Oumou Camara ◽  
Mamadou Camara ◽  
Hamidou Ilboudo ◽  
Mariame Camara ◽  
...  
Keyword(s):  
Vector Control ◽  
Human African Trypanosomiasis ◽  
Control Strategies ◽  
Tsetse Flies ◽  
Tsetse Control ◽  
Control Programs ◽  
Unique Framework ◽  
Protection Against Infection ◽  
The Impact ◽  
Disease Focus

AbstractIn addition to the thousands of deaths due the unprecedented ebola outbreak that stroke West Africa (2014-2016), national health systems in affected countries were deeply challenged impacting a number of diseases control programs. Here we describe the case of Human African Trypanosomiasis (HAT), a deadly neglected tropical disease due to a trypanosome transmitted by tsetse flies for which no vaccine nor chemoprophylaxis exists. Data are presented for the disease focus of Boffa in Guinea where a pilot elimination project combining medical screening and vector control was launched in 2012. During ebola, HAT active screening activities were postponed and passive surveillance also was progressively impaired. However, tsetse control using small insecticide impregnated targets could be maintained. The over two years disruption of screening activities led to a dramatic increase of HAT prevalence, from 0.7% in 2013 (21/2885) to 2% (69/3448) in 2016, reaching epidemic levels (>5%) in some villages. In deep contrast, control levels reached in 2013 (0.1%; 7/6564) were maintained in areas covered with impregnated targets as no cases were found in 2016 (0/799). In Boffa, ebola has thus incidentally provided a unique framework to assess the impact of current HAT control strategies. A first lesson is that the “screen and treat” strategy is fragile as rapid bursts of the disease may occur in case of disruption. A second lesson is that vector control reducing human-tsetse contacts, even implemented alone, is effective in providing a good level of protection against infection. This advocates for a greater attention being paid to the combination of tsetse control together with medical activities in aiming to reach the HAT elimination objective in Africa.

scholarly journals The economic impact and cost-effectiveness of combined vector-control and dengue vaccination strategies in Thailand: results from a dynamic transmission model

2020 ◽  
Vol 14 (10) ◽  
pp. e0008805
Author(s):  
Gerhart Knerer ◽  
Christine S. M. Currie ◽  
Sally C. Brailsford
Keyword(s):  
Public Health ◽  
Cost Effectiveness ◽  
Vector Control ◽  
Dengue Fever ◽  
Control Strategies ◽  
Cost Effective ◽  
Scenario Analyses ◽  
Life Years ◽  
The Cost ◽  
The Impact

Background and aims Dengue fever is a major public health problem in tropical/subtropical regions. Prior economic analyses have predominantly evaluated either vaccination or vector-control programmes in isolation and do not really consider the incremental benefits and cost-effectiveness of mixed strategies and combination control. We estimated the cost-effectiveness of single and combined approaches in Thailand. Methods The impacts of different control interventions were analysed using a previously published mathematical model of dengue epidemiology and control incorporating seasonality, age structure, consecutive infection, cross protection, immune enhancement and combined vector-host transmission. An economic model was applied to simulation results to estimate the cost-effectiveness of 4 interventions and their various combinations (6 strategies): i) routine vaccination of 1-year olds; ii) chemical vector control strategies targeting adult and larval stages separately; iii) environmental management/ public health education and awareness [EM/ PHEA]). Payer and societal perspectives were considered. The health burden of dengue fever was assessed using disability-adjusted life-years (DALYs) lost. Costs and effects were assessed for 10 years. Costs were discounted at 3% annually and updated to 2013 United States Dollars. Incremental cost-effectiveness analysis was carried out after strategies were rank-ordered by cost, with results presented in a table of incremental analysis. Sensitivity and scenario analyses were undertaken; and the impact and cost-effectiveness of Wolbachia was evaluated in exploratory scenario analyses. Results From the payer and societal perspectives, 2 combination strategies were considered optimal, as all other control strategies were dominated. Vaccination plus adulticide plus EM/ PHEA was deemed cost-effective according to multiple cost-effectiveness criteria. From the societal perspective, incremental differences vs. adulticide and EM/ PHEA resulted in costs of $157.6 million and DALYs lost of 12,599, giving an expected ICER of $12,508 per DALY averted. Exploratory scenario analyses showed Wolbachia to be highly cost-effective ($343 per DALY averted) vs. other single control measures. Conclusions Our model shows that individual interventions can be cost-effective, but that important epidemiological reductions and economic impacts are demonstrated when interventions are combined as part of an integrated approach to combating dengue fever. Exploratory scenario analyses demonstrated the potential epidemiological and cost-effective impact of Wolbachia when deployed at scale on a nationwide basis. Our findings were robust in the face of sensitivity analyses.

scholarly journals Patterns of epidemiology and control of onchocerciasis in West Africa

1997 ◽  
Vol 71 (2) ◽  
pp. 91-101 ◽  
Author(s):  
B. Boatin ◽  
D.H. Molyneux ◽  
J.M. Hougard ◽  
O.W. Christensen ◽  
E.S. Alley ◽  
...  
Keyword(s):  
West Africa ◽  
Vector Control ◽  
Control Strategies ◽  
Control Programme ◽  
Transmission Potential ◽  
The Public ◽  
And Control ◽  
Combined Impact ◽  
The Impact ◽  
Onchocerciasis Control

AbstractThis paper summarizes the work of the Onchocerciasis Control Programme (OCP) in West Africa, a programme which over a 22 year history has reduced the public health problems of blinding onchocerciasis in eleven countries of West Africa through vector control and, more recently, ivermectin distribution. The paper emphasizes the different approaches to control the programme has developed in the different parts of the programme area which have been determined by the epidemiology of the disease (savanna/forest form), the migratory characteristics of the vectors, intensity of the disease before commencement of treatment, the combined impact of vector control and ivermectin and the likelihood of infiltration of infective blackflies from outside the programme area. The programme has constantly monitored the impact of operations on the trends in prevalence, incidence, annual transmission potential, ocular morbidity and species of fly populations, and as a result, has identified areas where special interventions are required until the programme comes to an end in 2002. The paper illustrates the changes in intensity of infection as measured by community microfilarial load and annual transmission potential over the duration of the programme control activities. The paper also defines and justifies the control strategies in different areas and identifies areas for special interventions.

Toxicological Evaluation of Novel Butenolide Pesticide Flupyradifurone Against Culex quinquefasciatus (Diptera: Culicidae) Mosquitoes

2020 ◽  
Vol 57 (6) ◽  
pp. 1857-1863
Author(s):  
Mohamed Ahmed Ibrahim Ahmed ◽  
Christoph Franz Adam Vogel
Keyword(s):  
Culex Quinquefasciatus ◽  
Mosquito Control ◽  
Control Strategies ◽  
Synergetic Effect ◽  
Fourth Instar ◽  
Synergistic Action ◽  
Toxicological Evaluation ◽  
Control Programs ◽  
Octopamine Receptor ◽  
The Impact

Abstract The impact of increasing resistance of mosquitoes to conventional pesticides has led to investigate various unique tools and pest control strategies. Herein, we assessed the potency of flupyradifurone, a novel pesticide, on fourth instar larvae of Culex quinquefasciatus Say. Further, we evaluated the synergistic action of piperonyl butoxide (PBO) and the octopamine receptor agonists (OR agonists) chlordimeform (CDM) and amitraz (AMZ) on the toxicity of flupyradifurone in comparison with sulfoxaflor and nitenpyram to increase their toxicity on Cx. quinquefasciatus. Results demonstrated that flupyradifurone was the most potent pesticide followed by sulfoxaflor and nitenpyram. Further, the synergetic effect of PBO, CDM, and AMZ was significant for all selected pesticides especially flupyradifurone. However, AMZ had the most significant effect in combination with the selected pesticides followed by CDM and PBO. The toxicity of the pesticides was time-dependent and increased over time from 24, 48, to 72 h of exposure in all experiments. The results indicate that flupyradifurone is a promising component in future mosquito control programs.

scholarly journals A Review: Aedes-Borne Arboviral Infections, Controls and Wolbachia-Based Strategies

Vaccines ◽  
2021 ◽  
Vol 9 (1) ◽  
pp. 32
Author(s):  
Samson T. Ogunlade ◽  
Michael T. Meehan ◽  
Adeshina I. Adekunle ◽  
Diana P. Rojas ◽  
Oyelola A. Adegboye ◽  
...  
Keyword(s):  
Vector Control ◽  
Yellow Fever Virus ◽  
Control Strategies ◽  
Weather Conditions ◽  
Wolbachia Infection ◽  
Control Methods ◽  
Vector Population ◽  
Natural Hosts ◽  
Biological Methods ◽  
The Impact

Arthropod-borne viruses (Arboviruses) continue to generate significant health and economic burdens for people living in endemic regions. Of these viruses, some of the most important (e.g., dengue, Zika, chikungunya, and yellow fever virus), are transmitted mainly by Aedes mosquitoes. Over the years, viral infection control has targeted vector population reduction and inhibition of arboviral replication and transmission. This control includes the vector control methods which are classified into chemical, environmental, and biological methods. Some of these control methods may be largely experimental (both field and laboratory investigations) or widely practised. Perceptively, one of the biological methods of vector control, in particular, Wolbachia-based control, shows a promising control strategy for eradicating Aedes-borne arboviruses. This can either be through the artificial introduction of Wolbachia, a naturally present bacterium that impedes viral growth in mosquitoes into heterologous Aedes aegypti mosquito vectors (vectors that are not natural hosts of Wolbachia) thereby limiting arboviral transmission or via Aedes albopictus mosquitoes, which naturally harbour Wolbachia infection. These strategies are potentially undermined by the tendency of mosquitoes to lose Wolbachia infection in unfavourable weather conditions (e.g., high temperature) and the inhibitory competitive dynamics among co-circulating Wolbachia strains. The main objective of this review was to critically appraise published articles on vector control strategies and specifically highlight the use of Wolbachia-based control to suppress vector population growth or disrupt viral transmission. We retrieved studies on the control strategies for arboviral transmissions via arthropod vectors and discussed the use of Wolbachia control strategies for eradicating arboviral diseases to identify literature gaps that will be instrumental in developing models to estimate the impact of these control strategies and, in essence, the use of different Wolbachia strains and features.

scholarly journals Pest suppression by ant biodiversity is modified by pest biodiversity

2015 ◽  
Author(s):  
David J Gonthier ◽  
Ryan Kuesel ◽  
Ivette Perfecto
Keyword(s):  
Control Strategies ◽  
Pest Species ◽  
Predator Species ◽  
Control Programs ◽  
Pest Damage ◽  
Multiple Predator Species ◽  
Pest Suppression ◽  
Food Web Complexity ◽  
The Impact ◽  
Pest Risk

Agroecosystems are often complex ecosystems with diverse food webs. Changes in food web complexity may have important context-dependent consequences for pest control strategies. The success of predator introductions to suppress pests may depend on the diversity of pests. For crops with diverse pest assemblages, it is hypothesized that diverse predator communities are needed to suppress diverse pest assemblages below damaging levels. In this study, we compare the ability of ant predator monocultures and polycultures to suppress single- and diverse- (three species) pest assemblages in a coffee foodweb. We use a factorial experiment that compared treatments of predator and pest diversity to understand the impact of pest diversity on multiple predator effects. We show that predator polycultures enhanced pest risk relative to predator monocultures significantly more in the diverse-pest treatment relative to in the single-pest treatments for two of three pest species. Further, we show that pest diversity significantly reduced pest risk in all predator treatments except for the predator polyculture treatment. These results suggest that pest diversity may reduce the efficiency of single predator species at suppressing pest damage, but do not limit multiple predator species. This in turn leads to stronger effects of predator diversity with greater pest diversity. These results highlight the need to consider foodweb complexity, such as pest diversity, when designing and implementing biology control programs.

scholarly journals Bacteriome diversity of blackflies gut and association with Onchocerca volvulus, the causative agent of onchocerciasis in Mbam valley (Center Region, Cameroon)

2020 ◽  
Author(s):  
Arnauld Efon-Ekangouo ◽  
Hugues Nana-Djeunga ◽  
Guilhem Sempere ◽  
Joseph Kamgno ◽  
Flobert Njiokou ◽  
...  
Keyword(s):  
Vector Control ◽  
Bacterial Communities ◽  
Control Strategies ◽  
Onchocerca Volvulus ◽  
Parasitic Infections ◽  
Tsetse Flies ◽  
Protective Effects ◽  
River Blindness ◽  
Parasite Infestation

AbstractBackgroundVector control using larvicides is the main alternative strategy to address limits of preventive chemotherapy using ivermectin to fight onchocerciasis. However, it remains substantially limited by implementation difficulties, ecological concerns and resistance of vector populations. Therefore, efficient and environmentally safe alternative control strategies are still needed. This study explores the role of blackfly bacterial communities both on vector competence and refractoriness to O. volvulus infection in order to determine their potential as a novel vector control-based approach to fight onchocerciasis.Principal findingsA total of 1,270 blackflies were dissected and the infection rate was 10.1%, indicative of ongoing transmission of onchocerciasis in the surveyed communities. Sequencing process revealed 19 phyla and 210 genera, highlighting the diversity of gut blackflies bacterial communities. Wolbachia was the predominant genus with 70% of relative abundance of blackflies gut bacterial communities. Serratia sp and Acidomonas genera were significantly abundant among infected blackflies (p=0.043 and p=0.027, respectively), whereas other genera as Brevibacterium were associated with the absence of infection (p=0.008).Conclusion/SignificanceThis study revealed that blackfly native bacteria are potentially involved in infection by O. volvulus, either by facilitating or preventing the parasite infestation of the vector. These bacteria represent an interesting potential as a biological target for a novel approach of vector control to fight onchocerciasis.Author summaryStudies of arthropods involved in vector-borne diseases (tsetse flies, mosquitoes, and drosophila) demonstrated the importance of their native bacteria either to ease infection and transmission of human pathogenic microorganisms including parasites or on the contrary to induce host protective effects against these parasites. Indeed, some native bacteria of arthropod vectors are now recognized to be associated either with the resistance of their hosts to parasitic infections, or the reduction of their host’s viability in case of the parasite infestation, thus highlighting the potential of such bacteria to be used as biological tool for vector control strategies. However, such bacteria have never been described on blackfly, an arthropod transmitting Onchocerca volvulus, which is the parasite responsible of onchocerciasis commonly known as river blindness. This study aimed to fill this gap by investigating the bacterial diversity of blackfly bacteriome and describing the possible role of bacteria communities in susceptibility/resistance features of the blackflies to O. volvulus infection, and therefore their potential as biological targets or tool for vector control. The screening of these blackflies’ native bacteria during this study, highlighted some bacteria genera of interest with significant association either with the absence of O. volvulus in blackfly or with vector infection.

scholarly journals Pest suppression by ant biodiversity is modified by pest biodiversity

2015 ◽  
Author(s):  
David J Gonthier ◽  
Ryan Kuesel ◽  
Ivette Perfecto
Keyword(s):  
Control Strategies ◽  
Pest Species ◽  
Predator Species ◽  
Control Programs ◽  
Pest Damage ◽  
Multiple Predator Species ◽  
Pest Suppression ◽  
Food Web Complexity ◽  
The Impact ◽  
Pest Risk

Agroecosystems are often complex ecosystems with diverse food webs. Changes in food web complexity may have important context-dependent consequences for pest control strategies. The success of predator introductions to suppress pests may depend on the diversity of pests. For crops with diverse pest assemblages, it is hypothesized that diverse predator communities are needed to suppress diverse pest assemblages below damaging levels. In this study, we compare the ability of ant predator monocultures and polycultures to suppress single- and diverse- (three species) pest assemblages in a coffee foodweb. We use a factorial experiment that compared treatments of predator and pest diversity to understand the impact of pest diversity on multiple predator effects. We show that predator polycultures enhanced pest risk relative to predator monocultures significantly more in the diverse-pest treatment relative to in the single-pest treatments for two of three pest species. Further, we show that pest diversity significantly reduced pest risk in all predator treatments except for the predator polyculture treatment. These results suggest that pest diversity may reduce the efficiency of single predator species at suppressing pest damage, but do not limit multiple predator species. This in turn leads to stronger effects of predator diversity with greater pest diversity. These results highlight the need to consider foodweb complexity, such as pest diversity, when designing and implementing biology control programs.

scholarly journals Colonization of the tsetse fly midgut with commensal Enterobacter inhibits trypanosome infection establishment

2018 ◽  
Author(s):  
Brian L. Weiss ◽  
Michele A. Maltz ◽  
Aurélien Vigneron ◽  
Yineng Wu ◽  
Katharine Walter ◽  
...  
Keyword(s):  
Control Strategies ◽  
Vector Competence ◽  
Tsetse Fly ◽  
Sub Saharan Africa ◽  
Tsetse Flies ◽  
Wild Type ◽  
African Trypanosomes ◽  
Control Programs ◽  
Causative Agents ◽  
Sub Saharan

AbstractTsetse flies (Glossina spp.) vector pathogenic trypanosomes (Trypanosoma spp.) in sub-Saharan Africa. These parasites cause human and animal African trypanosomiases, which are debilitating diseases that inflict an enormous socio-economic burden on inhabitants of endemic regions. Current disease control strategies rely primarily on treating infected animals and reducing tsetse population densities. However, relevant programs are costly, labor intensive and difficult to sustain. As such, novel strategies aimed at reducing tsetse vector competence require development. Herein we investigated whether an Enterobacter bacterium (Esp_Z), which confers Anopheles gambiae with resistance to Plasmodium, is able to colonize tsetse and induce a trypanosome refractory phenotype in the fly. Esp_Z established stable infections in tsetse’s gut, and exhibited no adverse effect on the survival of individuals from either group. Flies with established Esp_Z infections in their gut were significantly more refractory to infection with two distinct trypanosome species (T. congolense, 6% infection; T. brucei, 32% infection) than were age-matched flies that did not house the exogenous bacterium (T. congolense, 36% infected; T. brucei, 70% infected). Additionally, 52% of Esp_Z colonized tsetse survived infection with entomopathogenic Serratia marcescens, compared with only 9% of their wild-type counterparts. These parasite and pathogen refractory phenotypes result from the fact that Esp_Z acidifies tsetse’s midgut environment, which inhibits trypanosome and Serratia growth and thus infection establishment. Finally, we determined that Esp_Z infection does not impact the fecundity of male or female tsetse, nor the ability of male flies to compete with their wild-type counterparts for mates. We propose that Esp_Z could be used as one component of an integrated strategy aimed at reducing the ability of tsetse to transmit pathogenic trypanosomes.Author SummaryTsetse flies transmit pathogenic African trypanosomes, which are the causative agents of socio-economically devastating human and animal African trypanosomiases. These diseases are currently controlled in large part by reducing the population size of tsetse vectors through the use of insecticides, traps and sterile insect technique. However, logistic and monetary hurdles often preclude the prolonged application of procedures necessary to maintain these control programs. Thus, novel strategies, including those aimed at sustainably reducing the ability of tsetse to transmit trypanosomes, are presently under development. Herein we stably colonize tsetse flies with a bacterium (Enterobacter sp. Z, Esp_Z) that acidifies their midgut, thus rendering the environment inhospitable to infection with two distinct, epidemiologically important trypanosome strains as well as an entomopathogenic bacteria. In addition to inducing a trypanosome refractory phenotype, colonization of tsetse with Esp_Z exerts only a modest fitness cost on the fly. Taken together, these findings suggest that Esp_Z could be applied to enhance the effectiveness of currently employed tsetse control programs.

scholarly journals Characterization of Anopheles gambiae D7 salivary proteins as markers of human–mosquito bite contact

2022 ◽  
Vol 15 (1) ◽  
Author(s):  
Brenda Oseno ◽  
Faith Marura ◽  
Rodney Ogwang ◽  
Martha Muturi ◽  
James Njunge ◽  
...  
Keyword(s):  
Antibody Response ◽  
Vector Control ◽  
Anopheles Gambiae ◽  
Control Strategies ◽  
Antibody Responses ◽  
Salivary Proteins ◽  
Igg Antibody ◽  
Biomarkers Of Exposure ◽  
The Impact

Abstract Background Malaria is transmitted when infected Anopheles mosquitoes take a blood meal. During this process, the mosquitoes inject a cocktail of bioactive proteins that elicit antibody responses in humans and could be used as biomarkers of exposure to mosquito bites. This study evaluated the utility of IgG responses to members of the Anopheles gambiae D7 protein family as serological markers of human–vector contact. Methods The D7L2, D7r1, D7r2, D7r3, D7r4 and SG6 salivary proteins from An. gambiae were expressed as recombinant antigens in Escherichia coli. Antibody responses to the salivary proteins were compared in Europeans with no prior exposure to malaria and lifelong residents of Junju in Kenya and Kitgum in Uganda where the intensity of malaria transmission is moderate and high, respectively. In addition, to evaluate the feasibility of using anti-D7 IgG responses as a tool to evaluate the impact of vector control interventions, we compared responses between individuals using insecticide-treated bednets to those who did not in Junju, Kenya where bednet data were available. Results We show that both the long and short forms of the D7 salivary gland antigens elicit a strong antibody response in humans. IgG responses against the D7 antigens reflected the transmission intensities of the three study areas, with the highest to lowest responses observed in Kitgum (northern Uganda), Junju (Kenya) and malaria-naïve Europeans, respectively. Specifically, the long form D7L2 induced an IgG antibody response that increased with age and that was lower in individuals who slept under a bednet, indicating its potential as a serological tool for estimating human–vector contact and monitoring the effectiveness of vector control interventions. Conclusions This study reveals that D7L2 salivary antigen has great potential as a biomarker of exposure to mosquito bites and as a tool for assessing the efficacy of vector control strategies such as bednet use. Graphical abstract

scholarly journals Estimating the impact of city-wide Aedes aegypti population control: An observational study in Iquitos, Peru

2018 ◽  
Author(s):  
R.C. Reiner ◽  
S.T. Stoddard ◽  
G.M. Vazquez-Prokopec ◽  
H. Astete ◽  
T.A. Perkins ◽  
...  
Keyword(s):  
Aedes Aegypti ◽  
Vector Control ◽  
Dose Response ◽  
Response Curve ◽  
Dose Response Curve ◽  
Ministry Of Health ◽  
Mosquito Abundance ◽  
Control Programs ◽  
The Impact ◽  
Neighborhood Level

AbstractDuring the last 50 years, the geographic range of the mosquito Aedes aegypti has increased dramatically, in parallel with a sharp increase in the disease burden from the viruses it transmits, including Zika, chikungunya, and dengue. There is a growing consensus that vector control is essential to prevent Aedes-borne diseases, even as effective vaccines become available. What remains unclear is how effective vector control is across broad operational scales because the data and the analytical tools necessary to isolate the effect of vector-oriented interventions have not been available. We developed a statistical framework to model Ae. aegypti abundance over space and time and applied it to explore the impact of citywide vector control conducted by the Ministry of Health (MoH) in Iquitos, Peru, over a 12-year period. Citywide interventions involved multiple rounds of intradomicile insecticide space spray over large portions of urban Iquitos (up to 40% of all residences) in response to dengue outbreaks. Our model captured significant levels of spatial, temporal, and spatio-temporal variation in Ae. aegypti abundance within and between years and across the city. We estimated the shape of the relationship between the coverage of neighborhood-level vector control and reductions in female Ae. aegypti abundance; i.e., the dose-response curve. The dose-response curve, with its associated uncertainties, can be used to gauge the necessary spraying effort required to achieve a desired effect and is a critical tool currently absent from vector control programs. We found that with complete neighborhood coverage MoH intra-domicile space spray would decrease Ae. aegypti abundance on average by 67% in the treated neighborhood. Our framework can be directly translated to other interventions in other locations with geolocated mosquito abundance data. Results from our analysis can be used to inform future vector-control applications in Ae. aegypti endemic areas globally.Author SummaryDespite the growing threat of arboviruses, there is a dearth of ‘best practices’ for the primary vector control tools used in the field. In the absence of cluster randomized control trials, evidence on the utility (or lack thereof) of vector control interventions must be gleaned from ongoing control programs. Motivated by 12 years of household-level Ae. aegypti abundance surveys and neighborhood-level space-spray campaign data from Iquitos, Peru, we developed a new framework to model mosquito abundance. In spite of significant spatial and temporal heterogeneity, we identified a statistically significant and practically important impact of the local Ministry of Health space-spray campaign, specifically, a reduction of mosquito abundance of 67% when coverage was optimal. Our framework can be directly applied to other locations with geolocated mosquito abundance data and our findings can be used to both optimize resources within Iquitos as well as inform future vector-control interventions in Ae. aegypti endemic areas globally.

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