Vector-focused Approaches to Curb Malaria Transmission in the Brazilian Amazon: An Overview of Current and Future Challenges and Strategies

In Brazil, malaria transmission is mostly confined to the Amazon, where substantial progress has been achieved towards disease control in the past decade. Vector control has been historically considered a fundamental part of the main malaria control programs implemented in Brazil. However, the conventional vector-control tools have been insufficient to eliminate local vector populations due to the complexity of the Amazonian rainforest environment and ecological features of malaria vector species in the Amazon, especially Anopheles darlingi. Malaria elimination in Brazil and worldwide eradication will require a combination of conventional and new approaches that takes into account the regional specificities of vector populations and malaria transmission dynamics. Here we present an overview on both conventional and novel promising vector-focused tools to curb malaria transmission in the Brazilian Amazon. If well designed and employed, these new vector-based approaches may improve the implementation of malaria-control programs, particularly in remote or difficult-to-access areas and in regions where existing interventions have been unable to eliminate disease transmission. However, much effort still has to be put on research expanding the knowledge of neotropical malaria vectors to set the steppingstones for the development of such innovative tools.

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Vector-Focused Approaches to Curb Malaria Transmission in the Brazilian Amazon: An Overview of Current and Future Challenges and Strategies

Tropical Medicine and Infectious Disease ◽

10.3390/tropicalmed5040161 ◽

2020 ◽

Vol 5 (4) ◽

pp. 161

Author(s):

Elerson Matos Rocha ◽

Ricardo de Melo Katak ◽

Juan Campos de Oliveira ◽

Maisa da Silva Araujo ◽

Bianca Cechetto Carlos ◽

...

Keyword(s):

Vector Control ◽

Malaria Transmission ◽

Malaria Control ◽

Disease Transmission ◽

Brazilian Amazon ◽

Malaria Vectors ◽

Anopheles Darlingi ◽

Control Programs ◽

Ecological Features ◽

Substantial Progress

In Brazil, malaria transmission is mostly confined to the Amazon, where substantial progress has been made towards disease control in the past decade. Vector control has been historically considered a fundamental part of the main malaria control programs implemented in Brazil. However, the conventional vector-control tools have been insufficient to control or eliminate local vector populations due to the complexity of the Amazonian rainforest environment and ecological features of malaria vector species in the Amazon, especially Anopheles darlingi. Malaria elimination in Brazil and worldwide eradication will require a combination of conventional and new approaches that takes into account the regional specificities of vector populations and malaria transmission dynamics. Here we present an overview on both conventional and novel promising vector-focused tools to curb malaria transmission in the Brazilian Amazon. If well designed and employed, vector-based approaches may improve the implementation of malaria-control programs, particularly in remote or difficult-to-access areas and in regions where existing interventions have been unable to eliminate disease transmission. However, much effort still has to be put into research expanding the knowledge of neotropical malaria vectors to set the steppingstones for the optimization of conventional and development of innovative vector-control tools.

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Community Knowledge, Perceptions, And Practices Regarding Malaria and Its Control In Jabi Tehnan District, Amhara Region, Northwest Ethiopia

10.21203/rs.3.rs-489446/v1 ◽

2021 ◽

Author(s):

Abebe Asale ◽

Zewdu Abro ◽

Bayu Enchalew ◽

Alayu Tesager ◽

Aklilu Belay ◽

...

Keyword(s):

Vector Control ◽

Malaria Control ◽

Community Education ◽

Indoor Residual Spraying ◽

Community Empowerment ◽

Malaria Episode ◽

Malaria Vectors ◽

Bed Nets ◽

Health Seeking ◽

Malaria Parasites

Abstract Background: Key program components of malaria control in Ethiopia include community empowerment and mobilization, vector control using long-lasting insecticidal nets (LLINs), indoor residual spraying (IRS), prompt diagnosis and treatment, and disease surveillance. However, the effectiveness of these interventions is often undermined by various challenges, including insecticide and drug resistance, the plasticity of malaria vectors feeding and biting behavior, and certain household factors that lead to misuse and poor utilization of LLINs. The primary objective of this study was to document households’ perceptions towards malaria and assess the prevalence of the disease and the constraints related to the ongoing interventions in Ethiopia (LLINs, IRS, community mobilization house screening). Method: The study was conducted in Jabi Tehnan district, Northwestern Ethiopi,a from November 2019 to March 2020. A total of 3,010 households distributed over 38 kebeles (villages) were randomly selected for socio-economic and demographic survey. Focus group discussions (FGDs) were conducted in 11 different health clusters taking into account agro-ecological differences. A total of 1,256 children under 10 years of age were screened for malaria parasites using microscopy in order to determine malaria prevalence. Furthermore, five-year malaria trend analysis was undertaken based on data obtained from the district health office to understand the disease dynamics.Result: Malaria knowledge in the area was high as all FGD participants correctly identified mosquito bites during the night as sources of malaria transmission. Delayed health seeking behavior remains a key behavioral challenge in malaria control as it took patients on average 4 days before reporting the case at the nearby health facility. On average households lost 2.53 working days per person-per malaria episode and theey spent US$ 18 per person perepisode. Out of the 1,256 randomly selected under 10 children tested for malaria parasites, 11 (0.89%) were found to be positive. Malaria disproportionately affected the adult segment of the population more, 50% of the total cases reported from households whose age was 15 and beyond. The second most affected group was the age group between 5 and 14 years followed by children under 10, with 31% and 14% burden,respectively.Conclusion: Despite the achievement of universal coverage in terms of LLINs access, utilization of vector control interventions in the area remained low.Using bed nets for unintended purposes remained a major challenge. Therefore, continued community education and communication work should be prioritised in the study area to bring about the desired behavioral changes.

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Optimising systemic insecticide use to improve malaria control

BMJ Global Health ◽

10.1136/bmjgh-2019-001776 ◽

2019 ◽

Vol 4 (6) ◽

pp. e001776 ◽

Cited By ~ 1

Author(s):

Hannah R Meredith ◽

Luis Furuya-Kanamori ◽

Laith Yakob

Keyword(s):

Vector Control ◽

Malaria Transmission ◽

Drug Administration ◽

Mass Drug Administration ◽

Companion Animals ◽

Malaria Vectors ◽

Systemic Insecticide ◽

Blood Concentrations ◽

Systemic Insecticides ◽

The Impact

BackgroundLong-lasting insecticidal nets and indoor residual sprays have significantly reduced the burden of malaria. However, several hurdles remain before elimination can be achieved: mosquito vectors have developed resistance to public health insecticides, including pyrethroids, and have altered their biting behaviour to avoid these indoor control tools. Systemic insecticides, drugs applied directly to blood hosts to kill mosquitoes that take a blood meal, offer a promising vector control option. To date, most studies focus on repurposing ivermectin, a drug used extensively to treat river blindness. There is concern that overdependence on a single drug will inevitably repeat past experiences with the rapid spread of pyrethroid resistance in malaria vectors. Diversifying the arsenal of systemic insecticides used for mass drug administration would improve this strategy’s sustainability.MethodsHere, a review was conducted to identify systemic insecticide candidates and consolidate their pharmacokinetic/pharmacodynamic properties. The impact of alternative integrated vector control options and different dosing regimens on malaria transmission reduction are illustrated through mathematical model simulation.ResultsThe review identified drugs from four classes commonly used in livestock and companion animals: avermectins, milbemycins, isoxazolines and spinosyns. Simulations predicted that isoxazolines and spinosyns are promising candidates for mass drug administration, as they were predicted to need less frequent application than avermectins and milbemycins to maintain mosquitocidal blood concentrations.ConclusionsThese findings will provide a guide for investigating and applying different systemic insecticides to achieve more effective and sustainable control of malaria transmission.

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Anopheline species, some of their habits and relation to malaria in endemic areas of Rondônia State, Amazon region of Brazil

Memórias do Instituto Oswaldo Cruz ◽

10.1590/s0074-02761989000400008 ◽

1989 ◽

Vol 84 (4) ◽

pp. 501-514 ◽

Cited By ~ 74

Author(s):

Ricardo Lourenço-de-Oliveira ◽

Anthony Erico da Gama Guimarães ◽

Monique Arlé ◽

Tereza Fernandes da Silva ◽

Márcia Gonçalves Castro ◽

...

Keyword(s):

Dominant Species ◽

Brazilian Amazon ◽

Amazon Region ◽

Malaria Vectors ◽

Anopheles Darlingi ◽

Anopheline Species ◽

Local Vector ◽

Endemic Areas

In view of recent studies incriminating several species of anophelines, besides Anopheles darlingi, as malaria vectors in the Brazilian Amazon, we performed an anopheline survey in four localities - Ariquemes, Cujubim, Machadinho and Itapoã do Oeste - in Rondônia, the most malarious State in the Country. Twenty species were found. An. darlingi was, by far, the dominant species and the only one whose density coincided with that of malaria. On human baits it was more numerous in the immediate vincinity of houses than indoors whre, however, it was almost the only species encountered. On both situations it fed mostly at sunset and during the first half of the night. It was less numerous far from houses and scarce inside the forest. Other species (An. triannulatus, An. evansae, An. albitarsis, An. strodei) appeared in appreciable numbers only in Ariquemes, both in areas with and without malaria. The remaining species were scanty. An. darlingi was confirmed as the primary local vector.

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WOMEN AND MALARIA—SPECIAL RISK AND APPROPRIATE CONTROL STRATEGY

PEDIATRICS ◽

10.1542/peds.96.1.117 ◽

1995 ◽

Vol 96 (1) ◽

pp. 117-117

Author(s):

R. Rueben

Keyword(s):

Pregnant Women ◽

Malaria Transmission ◽

Falciparum Malaria ◽

Malaria Control ◽

Rural Areas ◽

Control Strategies ◽

Current Control ◽

Control Measures ◽

Control Programs ◽

Utility Distribution

The factors that make pregnant women particularly vulnerable to morbidity and mortality with falciparum malaria and their relationship to current control strategies are reviewed. Pregnant women, particularly during their first pregnancy, are at greatest risk of severe falciparum malaria in areas of high and continuous malaria transmission and under conditions of unstable malaria in which they do not develop protective immunity. The author recommends chemoprophylaxis with chloroquine for pregnant women living in holoendemic and hyperendemic areas of Africa and Papua, New Guinea. Chloroquine is safe, but drug resistance has increasingly limited its utility, distribution is a formidable problem. In rural areas where poorly developed health care system are better developed and malaria transmission is less intense, the emphasis should be on early diagnosis and treatment. Women are potentially the key to the implementation of malaria control programs, yet recent studies indicate that underprivileged women frequently do not attend malaria clinics and are often missed in projects with passive surveillance. Additional research and community interventions are needed to enable women with malaria to obtain treatment and to involve them in malaria control measures at the village level.

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Malaria in migrant agricultural workers in western Ethiopia: entomological assessment of malaria transmission risk

10.21203/rs.3.rs-136085/v2 ◽

2021 ◽

Author(s):

Sisay Dugassa Lemma ◽

Mathew Murphy ◽

Sheleme Chibsa ◽

Yehualashet Tadesse ◽

Gedeon Yohannes ◽

...

Keyword(s):

Vector Control ◽

Malaria Transmission ◽

Anopheles Arabiensis ◽

Agricultural Development ◽

Transmission Risk ◽

Malaria Vectors ◽

Residential Housing ◽

Host Seeking ◽

Human Landing ◽

Western Ethiopia

Abstract Background Ethiopia has made great strides in malaria control over the last two decades. However, this progress has not been uniform and one concern has been reported high rates of malaria transmission in large agricultural development areas in western Ethiopia. Improved vector control is one way this transmission might be addressed, but little is known about malaria vectors in this part of the country. Methods To better understand the vector species involved in malaria transmission and their behaviour, human landing collections were conducted in Dangur woreda, Benishangul-Gumuz, between July and December 2017. This period encompasses the months with the highest rain and the peak mosquito population. Mosquitoes were identified to species and tested for the presence of Plasmodium sporozoites. Results The predominant species of the Anopheles collected was Anopheles arabiensis (1,733; i.e. 61.3% of the entire Anopheles), which was also the only species identified with sporozoites (Plasmodium falciparum and Plasmodium vivax). Anopheles arabiensis was collected as early in the evening as 18:00h-19:00h, and host-seeking continued until 5:00h-6:00h. Nearly equal numbers were collected indoors and outdoors. The calculated entomological inoculation rate for An. arabiensis for the study period was 1.41 infectious bites per month. More An. arabiensis were collected inside and outside worker’s shelters than in fields where workers were working at night. Conclusions Anopheles arabiensis is likely to be the primary vector of malaria in the agricultural development areas studied. High rates of human biting took place inside and outdoor near workers’ residential housing. Improved and targeted vector control in this area might considerably reduce malaria transmission.

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Response to Valle and Zorello Laporta: Clarifying the Use of Instrumental Variable Methods to Understand the Effects of Environmental Change on Infectious Disease Transmission

American Journal of Tropical Medicine and Hygiene ◽

10.4269/ajtmh.21-0218 ◽

2021 ◽

Author(s):

Andrew J. MacDonald ◽

Erin A. Mordecai

Keyword(s):

Environmental Change ◽

Malaria Transmission ◽

Disease Transmission ◽

Instrumental Variable ◽

Brazilian Amazon ◽

Zoonotic Diseases ◽

Infectious Disease Transmission ◽

Link Type ◽

The Face ◽

Original Approach

Identifying the effects of environmental change on the transmission of vectorborne and zoonotic diseases is of fundamental importance in the face of rapid global change. Causal inference approaches, including instrumental variable (IV) estimation, hold promise in disentangling plausibly causal relationships from observational data in these complex systems. Valle and Zorello Laporta recently critiqued the application of such approaches in our recent study of the effects of deforestation on malaria transmission in the Brazilian Amazon on the grounds that key statistical assumptions were not met. Here, we respond to this critique by 1) deriving the IV estimator to clarify the assumptions that Valle and Zorello Laporta conflate and misrepresent in their critique, 2) discussing these key assumptions as they relate to our original study and how our original approach reasonably satisfies the assumptions, and 3) presenting model results using alternative instrumental variables that can be argued more strongly satisfy key assumptions, illustrating that our results and original conclusion—that deforestation drives malaria transmission—remain unchanged.

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Insecticide Resistance and Its Intensity in Populations of Malaria Vectors in Colombia

BioMed Research International ◽

10.1155/2018/9163543 ◽

2018 ◽

Vol 2018 ◽

pp. 1-12 ◽

Cited By ~ 4

Author(s):

Lorena I. Orjuela ◽

Juliana A. Morales ◽

Martha L. Ahumada ◽

Juan F. Rios ◽

John J. González ◽

...

Keyword(s):

Insecticide Resistance ◽

Malaria Control ◽

Prevention And Control ◽

Malaria Prevention ◽

Malaria Vectors ◽

Anopheles Darlingi ◽

Frequent Monitoring ◽

Endemic Malaria ◽

Lambda Cyhalothrin ◽

And Control

Insecticide resistance in malaria vectors threatens malaria prevention and control efforts. In Colombia the three primary vectors, Anopheles darlingi, An. nuneztovari s.l., and An. albimanus, have reported insecticide resistance to pyrethroids, organophosphates, carbamates, and DDT; however, the insecticide resistance monitoring is not continuous, and the data on the prevalence of resistance is scarce and geographically limited. We describe the resistance levels and intensity of previously detected resistant populations among primary malaria vectors from the most endemic malaria areas in Colombia. The study was carried out in 10 localities of five states in Colombia. Bioassays were carried out following the methodology of CDC Bottle Bioassay using the discriminating concentration and in order to quantify the intensity the specimens were exposed to 2, 5, and 10X discriminating concentrations. Five insecticides were tested: deltamethrin, lambda-cyhalothrin, alpha-cypermethrin, permethrin, and DDT. The results provide evidence of low resistance intensity and resistance highly localized to pyrethroids and DDT in key malaria vectors in Colombia. This may not pose a threat to malaria control yet but frequent monitoring is needed to follow the evolution of insecticide resistance.

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Malaria in Migrant Agricultural Workers in Dangur District, Benishangul-gumuz, Ethiopia. Entomological Assessment of Malaria Transmission Risk

10.21203/rs.3.rs-136085/v1 ◽

2020 ◽

Author(s):

Sisay Dugassa Lemma ◽

Mathew Murphy ◽

Sheleme Chibsa ◽

Yehualashet Tadesse ◽

Gedeon Yohannes ◽

...

Keyword(s):

Vector Control ◽

Malaria Transmission ◽

Anopheles Arabiensis ◽

Agricultural Development ◽

Transmission Risk ◽

Malaria Vectors ◽

Residential Housing ◽

Host Seeking ◽

Human Landing ◽

Primary Vector

Abstract Background: Ethiopia has made great strides in malaria control. However, this progress has not been uniform and one concern has been reported high rates of malaria transmission in large agricultural development areas in western Ethiopia. Improved vector control is one way this transmission might be addressed, but little is known about malaria vectors in this part of the country. Methods: To better understand the vector species involved in malaria transmission and their behavior, human landing collections were conducted in Dangur woreda, Benishangul-Gumuz, between July and December 2017. Mosquitoes were identified to species and tested for presence of Plasmodium sporozoites. Results: The predominant species collected was Anopheles arabiensis (61.3% of all Anopheles), which was also the only species identified with sporozoites (P. falciparum and P. vivax). Anopheles arabiensis was collected as early in the evening as 18:00h-19:00h, and host-seeking continued until 5:00h-6:00h. Nearly equal numbers were collected indoors and outdoors. The calculated entomological inoculation rate for An. arabiensis for the study period was 1.41 infectious bites per month. More An. arabiensis were collected inside and outside worker’s shelters than in fields where workers were working at night. Conclusions: An. arabiensis is likely to be the primary vector of malaria in the agricultural development areas studied. High rates of human biting took place inside and outdoor near workers’ residential housing. Improved and targeted vector control in this area might considerably reduce malaria transmission.

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Biology, Epidemiology, and Public Health Significance of Malaria Disease Linked to Climate Changes

10.4018/978-1-6684-3686-8.ch089 ◽

2022 ◽

pp. 1787-1804

Author(s):

Moulay Abdelmonaim El Hidan ◽

Kholoud Kahime ◽

Aimrane Abdelmohcine ◽

Abdellatif Abbaoui ◽

Mohamed Echchakery ◽

...

Keyword(s):

Climate Change ◽

Malaria Transmission ◽

Disease Transmission ◽

Temporal Variations ◽

Malaria Vectors ◽

Climate Change Scenarios ◽

Health Issues ◽

Climate Conditions ◽

Health Significance ◽

Increasing Temperature

Malaria is a mosquito-borne infectious disease caused by obligate intraerythrocytic protozoa of the genus Plasmodium. As one of the most devastating global health issues, malaria is a sensitive disease to weather and climate conditions, in such a way the ongoing trends of increasing temperature and more variable weather could lead to malaria transmission spreading. Spatial and temporal variations in precipitation, temperature, and humidity that are projected to take place under different climate change scenarios will impact the biology and ecology of malaria vectors and subsequently the risk of disease transmission. Here, the authors review how climate and climate change may impact malaria transmission. They contrast ecological and behavioral characteristics of malaria vectors and parasites and how weather, climate, climate change, and socioeconomic factors may have very different impacts on their spatiotemporal occurrence and abundance and the resulting malaria risk.

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