Antigen test - Anopheles Database

Geographic Distribution and Ecological Characteristics of Dominant Malaria Vectors in the Americas

An increasing knowledge of the global risk of malaria shows that the nations of the Americas have the lowest levels of Plasmodium falciparum and P. vivax endemicity worldwide, sustained, in part, by substantive integrated vector control. Despite these comparatively low levels of malaria endemicity, mosquito-borne transmission remains an important public health concern in several areas of the region.

The maintenance of effective malaria prevention strategies requires continuous monitoring of mosquito vector populations and a detailed understanding of their geographical distribution. Changes in environmental conditions, climate, land use and human activities can influence mosquito habitats and potentially modify the distribution of malaria vectors.

To help maintain and better target these efforts, knowledge of the contemporary distribution of each of the dominant vector species (DVS) of human malaria is needed, alongside a comprehensive understanding of the ecology and behaviour of each species.

Understanding where dominant malaria vectors occur is essential for identifying areas potentially exposed to malaria transmission. However, geographical distribution alone is not sufficient. Information about mosquito ecology, breeding habitats, feeding behaviour and environmental preferences is also necessary to develop appropriate vector surveillance and control strategies.

1. Compilation of Contemporary Malaria Vector Distribution Data

2. Distribution of the Nine Dominant Vector Species in the Americas

The results for the nine DVS of the Americas are described in detail here.

Nearly 6000 occurrence records were gathered from 25 countries in the region and were complemented by a synthesis of published expert opinion range maps, refined further by a technical advisory group of medical entomologists.

The compilation of occurrence records from multiple countries provides a substantial geographical dataset for examining the distribution of malaria vectors throughout the Americas.

However, occurrence records do not always provide complete information about the actual geographical range of a species. Some regions may have been more intensively surveyed than others, while remote areas may have limited entomological documentation.

To address these limitations, the occurrence database was complemented by published expert opinion range maps.

These maps provide additional information based on previously established knowledge of mosquito distribution. Their refinement by a technical advisory group of medical entomologists also introduces expert assessment into the geographical analysis.

Combining field-based occurrence information with expert knowledge helps improve the representation of the potential distribution of dominant malaria vectors.

3. Environmental and Climate Variables Associated with Anopheline Ecology

A suite of environmental and climate variables of suspected relevance to anopheline ecology were also compiled from open access sources.

Environmental and climatic conditions play an important role in determining the distribution and abundance of mosquito populations. Different Anopheles species may have distinct ecological requirements related to temperature, rainfall, humidity, vegetation and the availability of suitable aquatic habitats.

These factors can influence mosquito development, survival, reproduction and geographical distribution.

For example, rainfall and surface water availability can affect the formation and persistence of mosquito breeding habitats. Temperature can influence larval development and adult mosquito activity, while vegetation and land-use characteristics may contribute to habitat suitability.

The integration of environmental and climatic variables with mosquito occurrence records provides a way to investigate the relationship between ecological conditions and species distribution.

Using open access environmental datasets also allows researchers to incorporate standardized geographical information into predictive modelling approaches.

4. Predictive Species Range Mapping Using Boosted Regression Trees

These three sets of data were then combined to produce predictive species range maps using the Boosted Regression Tree method.

The three datasets consisted of:

Contemporary mosquito occurrence records.
Published expert opinion range maps refined by a technical advisory group.
Environmental and climate variables associated with anopheline ecology.

The Boosted Regression Tree (BRT) method is a statistical modelling approach that combines decision trees through an iterative boosting process.

It can identify complex relationships between environmental variables and species occurrence, including interactions and nonlinear associations that may be difficult to capture using simpler statistical models.

In ecological research, this approach can be used to estimate the potential geographical distribution of species based on observed occurrence data and environmental characteristics.

For malaria vector research, predictive species range maps can help identify areas with environmental conditions associated with the presence of particular mosquito species.

These maps can also provide useful information for planning entomological surveys, prioritizing surveillance activities and improving the geographical targeting of vector-control interventions.

5. Predicted Geographic Distribution of the Nine Dominant Vector Species

The predicted geographic extent for each of the following species (or species complex*) are provided:

5.1. Anopheles (Nyssorhynchus) albimanus Wiedemann, 1820

Anopheles albimanus is one of the recognized malaria vector species in the Americas. Its geographical distribution and ecological characteristics are important for understanding malaria transmission potential in areas where it occurs.

Investigating its occurrence patterns can help researchers identify suitable habitats and determine which environmental conditions are associated with its distribution.

5.2. Anopheles (Nyssorhynchus) albitarsis species complex

Anopheles albitarsis is included as a species complex, reflecting the importance of distinguishing closely related mosquito taxa in vector research.

Species complexes can present challenges for identification and geographical mapping because different members may have distinct ecological characteristics and distributions.

Accurate characterization is therefore important for understanding the contribution of individual taxa to malaria transmission.

5.3. Anopheles (Nyssorhynchus) aquasalis Curry, 1932

Anopheles aquasalis is another dominant malaria vector included in the geographical analysis.

Understanding its distribution requires consideration of the environmental characteristics of its habitats and the ecological conditions that influence mosquito population persistence.

Mapping its occurrence can support investigations into the geographical variation of malaria vector populations.

5.4. Anopheles (Nyssorhynchus) darlingi Root, 1926

Anopheles darlingi is an important malaria vector in the Americas and is particularly relevant to malaria transmission research in tropical environments.

Its geographical distribution is an important element in identifying areas where vector surveillance and control activities may be necessary.

Understanding its ecological preferences can also contribute to the development of more targeted mosquito-control strategies.

5.5. Anopheles (Anopheles) freeborni Aitken, 1939

Anopheles freeborni is included among the dominant vector species considered in the study.

Its distribution provides additional information about the geographical diversity of malaria vectors in the Americas.

The investigation of its environmental associations can contribute to a more comprehensive understanding of the ecological factors influencing malaria vector occurrence.

5.6. Anopheles (Nyssorhynchus) marajoara Galvão & Damasceno, 1942

Anopheles marajoara is another species included in the predictive distribution analysis.

Its geographical occurrence and ecological characteristics are relevant to understanding the distribution of malaria vectors in the region.

The integration of occurrence records and environmental variables provides a framework for examining its potential geographical range.

5.7. Anopheles (Nyssorhynchus) nuneztovari species complex

The Anopheles nuneztovari species complex represents another important taxonomic group included in the analysis.

The study of species complexes is particularly relevant to malaria vector research because closely related taxa may differ in their geographical distribution, ecological preferences and epidemiological importance.

Reliable identification and distribution mapping can therefore help improve the understanding of vector populations.

5.8. Anopheles (Anopheles) pseudopunctipennis species complex

Anopheles pseudopunctipennis is included as a species complex in the geographical assessment.

Its distribution contributes to the broader understanding of malaria vector diversity in the Americas.

Examining the environmental conditions associated with its occurrence may help identify geographical areas where suitable habitats are present.

5.9. Anopheles (Anopheles) quadrimaculatus Say, 1824

Anopheles quadrimaculatus is the final species included in the list of nine dominant malaria vectors considered in the study.

Its geographical distribution provides additional information about the composition of malaria vector populations across the Americas.

As with the other species, the combination of occurrence records, expert knowledge and environmental variables supports the development of predictive distribution maps.

6. The Importance of Species-Specific Bionomics Reviews

A bionomics review summarising ecology and behaviour relevant to the control of each of these species was also compiled.

Bionomics refers to the biological and ecological characteristics of an organism, including its habitat preferences, feeding behaviour, reproduction, population dynamics and interactions with the environment.

For malaria vectors, understanding these characteristics is essential because different mosquito species may respond differently to vector-control interventions.

Important ecological and behavioural characteristics include:

Breeding habitat preferences: The types of aquatic environments used for egg laying and larval development.
Feeding behaviour: Host preferences and patterns of blood-feeding activity.
Resting behaviour: Whether mosquitoes tend to rest indoors or outdoors after feeding.
Biting activity: The periods during which mosquitoes are most active and likely to feed.
Habitat distribution: The environmental conditions associated with mosquito population occurrence.
Population dynamics: Seasonal and geographical variations in mosquito abundance.

These characteristics can influence the effectiveness of different malaria prevention strategies.

For example, mosquito species that predominantly feed or rest indoors may be more accessible to certain indoor vector-control interventions, whereas outdoor-feeding or outdoor-resting species may require complementary approaches.

Species-specific bionomics information therefore helps researchers and public health professionals understand why vector-control interventions may have different outcomes depending on the mosquito species present in a particular area.

7. Applications for Integrated Malaria Vector Control

The combination of contemporary occurrence data, expert distribution maps and environmental variables provides a valuable framework for supporting integrated malaria vector control.

Accurate geographical information can help identify areas where dominant malaria vectors are likely to occur and guide the allocation of surveillance resources.

Predictive maps may also help identify locations where additional field investigations are required, particularly in areas with limited entomological data.

When combined with species-specific ecological and behavioural information, these maps can contribute to more targeted control strategies.

Such an approach is particularly important in the Americas, where maintaining progress in malaria prevention requires continuous monitoring of vector populations and adaptation to changing environmental conditions.

Integrating geographical modelling with field-based entomological research can therefore improve the understanding of malaria vector distribution and support more informed public health decisions.

Conclusion

Understanding the contemporary distribution of dominant malaria vector species is essential for maintaining and improving malaria control efforts in the Americas.

The compilation of nearly 6000 occurrence records from 25 countries, together with expert opinion range maps and environmental and climate variables, provided a comprehensive dataset for predictive geographical modelling.

Using the Boosted Regression Tree method, researchers produced predicted distribution maps for nine dominant malaria vector species or species complexes.

The inclusion of a bionomics review for each species also provides important information about ecological characteristics and behaviours relevant to mosquito control.

Overall, combining geographical occurrence data, environmental modelling and species-specific ecological knowledge offers an important framework for improving malaria vector surveillance and supporting integrated vector-control strategies throughout the Americas.