Urban Triatomines in Central México: Linking Ecological Niche Models with New Triatoma barberi (Reduviidae:Triatominae) Records

Simple Summary

Chagas disease is a parasitic infection transmitted by triatomine insects, which are commonly found in rural and urban environments. Triatoma barberi, one of these vectors, has been reported in central Mexico, but its distribution in Querétaro remains poorly understood. This study uses ecological niche modeling to predict its potential habitats, validate these predictions with statistical methods, and document new urban records. By identifying areas at risk, this research contributes to public health efforts aimed at controlling vector populations and mitigating disease transmission.

Abstract

Chagas disease, caused by Trypanosoma cruzi, is a significant health concern in Latin America, with triatomine insects serving as its primary vectors. Among them, Triatoma barberi is an important yet understudied species in Querétaro, Mexico. This study employs ecological niche modeling (ENM) to predict the potential distribution of T. barberi in the region, using occurrence records and environmental variables. The MaxEnt algorithm was used to generate the model, which was validated through AUC and TSS metrics. Results indicate that temperature seasonality and altitude are key drivers of T. barberi distribution, with high-suitability areas found in semi-urban and peri-urban zones. Additionally, six new occurrence records were documented, suggesting a growing urban presence of this species. These findings highlight the need for enhanced vector surveillance and targeted control measures to reduce the risk of Chagas disease transmission.

1. Introduction

Trypanosoma cruzi (Chagas, 1909) (Kinetoplastida: Trypanosomatidae) is a protozoan parasite responsible for Chagas disease, a neglected tropical disease affecting millions of people in Latin America [1]. Its transmission occurs primarily through triatomine bugs, which serve as vectors [2]. Over 150 species of triatomines are recognized, varying in their vectorial capacity depending on ecological and biological factors [3,4].

Some triatomine species adapt well to anthropogenic environments, increasing transmission risks in urban and peri-urban areas [5,6]. Among these, Triatoma barberi Usinger, 1939 has been identified as a relevant species in domestic and peridomestic habitats [7,8]. However, despite its known distribution in central Mexico, including Guanajuato, Querétaro, Michoacán, and Jalisco [9,10], the species remains underreported in Querétaro, potentially due to under-sampling or misclassification. Additionally, no significant biogeographical barriers exist between Querétaro and high-prevalence areas, raising the possibility of overlooked populations in urban and peri-urban habitats [11]. Given the increasing urban expansion of Querétaro and the persistence of suitable microhabitats, such as traditional adobe houses [12], it is crucial to reassess the distribution of T. barberi and its potential role in Chagas disease transmission in this region [13]. Furthermore, the association between environmental factors, particularly temperature seasonality and altitude, and the persistence of this species in human-modified landscapes, remains unclear. Triatoma barberi, traditionally considered a sylvatic vector, has been sporadically reported in domestic settings in central Mexico in recent years, particularly in rural areas of the Bajío region, suggesting a continued relevance to human Chagas disease transmission risk [14].

This study aims to (1) develop a robust ecological niche model (ENM) for T. barberi in the Metropolitan Area of Querétaro (ZMQ), (2) validate the model using multiple statistical approaches to ensure predictive reliability, and (3) report new records of this species to improve understanding of its potential distribution and epidemiological risks. The findings of this study will provide crucial insights into the potential adaptation of T. barberi to urban environments, and will aid in the development of targeted vector control strategies to mitigate the risk of Chagas disease transmission.

2. Materials and Methods

2.1. Study Area and Data Collection

The study was conducted in the Metropolitan Area of Querétaro (ZMQ), a rapidly urbanizing region historically characterized by agricultural activity. The selection of this area was based on its potential suitability for T. barberi, given its climatic conditions, topographic features, and the presence of older housing structures that may serve as refuges for triatomines.

Specimens of T. barberi were collected between 2018 and 2025 through a citizen science campaign in which residents were encouraged to report and submit captured insects. Additionally, targeted searches were conducted in areas with suitable environmental conditions. The specimens were identified using taxonomic keys from Lent and Wygodzinsky [10] and Carcavallo et al. [9,15], and their geographical coordinates were recorded using a GPS device. All specimens were deposited in the Entomological Collection of the Faculty of Natural Sciences at the Autonomous University of Querétaro (FCN-UAQE). Presence records were verified and supplemented with data from the Global Biodiversity Information Facility (GBIF) to ensure a comprehensive dataset [16].

2.2. Ecological Niche Model Construction

To predict the potential distribution of T. barberi in ZMQ, we used the MaxEnt algorithm (version 3.4.4) [17], a widely applied method for species distribution modeling based on presence-only data.

2.3. Data Preprocessing and Variable Selection

• Presence Data: A total of 451 verified occurrence records were used for model training. To minimize spatial autocorrelation, records were filtered to maintain a minimum separation distance of 1 km [16].
• Environmental Variables: Nineteen bioclimatic variables (bio01–bio19) from WorldClim v2.1 [18], along with altitude (MexDEM) [19], were considered as potential predictors. To reduce collinearity, a Pearson correlation analysis was performed, and highly correlated variables (r > 0.7) were excluded, retaining those with the highest ecological relevance.

2.4. Model Training and Validation

The dataset was split into 75% for training and 25% for testing. Model performance was evaluated using AUC (discriminatory power), TSS (predictive ability), and omission rate (capture of known presences at different thresholds). Jackknife and permutation importance tests identified key environmental variables influencing T. barberi distribution. Modeling was conducted in R using the dismo and maxnet packages for reproducibility.

3. Results

3.1. Model Performance and Validation

The ENM produced an AUC of 0.952 for the training set and 0.948 for the test set. The TSS score was 0.82. The omission rate at the minimum presence threshold was 0.007, and at the optimal threshold balancing sensitivity and specificity, it was 0.113.

3.2. Key Environmental Drivers

The variable with the highest contribution to the model was temperature seasonality (bio04), accounting for 41.2% of the total contribution and showing a permutation importance of 51.6%. Altitude contributed 25.3% to the model, with a permutation importance of 22.0%. Other variables, such as annual mean temperature (bio01) and precipitation of the driest quarter (bio17), had minor contributions.

3.3. Potential Distribution of T. barberi

The ENM predicted a probability of occurrence ranging from 45% to 60% in certain areas of the ZMQ (Figure 1). High-suitability zones were identified in semi-urban and peri-urban areas with historical agricultural land use.

3.4. New Records and Spatial Patterns

Six new T. barberi (Figure 2) occurrence records were documented in Querétaro (

Table 1. Collection sites for Triatomine specimens from Queretáro City.

Species	Collection Site	Coordinates	Date	Collection N°	STAGE
T. barberi	San Francisquito	20.589344, −100.383536	5 August 2020	UAQE-31364	Adult
			25 February 2021	UAQE-31365	Adult
			13 March 2022	UAQE-31366	Adult
			25 January 2025	UAQE-31369	Adult
	Menchaca	20.639362, −100.393677	28 February 2021	UAQE-31367	Adult
			28 October 2022	UAQE-31368	Nymph

), all collected intra domiciliary: four adult specimens from San Francisquito in 2020, 2021, 2022, and 2025 (Figure 3); one adult (2021) and one nymph (2022) from Menchaca.

4. Discussion

The presence of T. barberi in urban environments within the Bajío region has significant epidemiological implications, as this species is a known vector of T. cruzi, the causative agent of Chagas disease. While this study focused on Querétaro, the environmental conditions favoring T. barberi presence such as temperature seasonality and altitude are also found in other cities across the Bajío, including Celaya, León, Irapuato, and San Luis Potosí. This suggests a potential regional risk for Chagas disease transmission that extends beyond a single locality.

At both local and regional levels, future research should incorporate molecular diagnostics to determine T. cruzi prevalence in T. barberi populations. In Querétaro, this would provide a clearer assessment of the immediate risk to human populations, while at the regional scale, similar studies across the Bajío would help identify broader transmission patterns and epidemiological risk factors. The detection of infected vectors in multiple cities could indicate active transmission cycles, emphasizing the need for coordinated surveillance and intervention strategies across state borders.

The results underscore the importance of targeted vector surveillance programs, not only in Querétaro but throughout the Bajío region. Prioritizing areas predicted as high suitability zones by ecological niche models can enhance the efficiency of vector control strategies, enabling a more effective allocation of resources. Implementing similar predictive modeling approaches in other Bajío cities would strengthen regional preventive efforts against Chagas disease. Coordinated entomological monitoring programs, supported by local health authorities and research institutions, are essential for mitigating the public health impact of T. barberi and preventing the expansion of Chagas disease transmission in the region.

4.1. Urbanization and Triatomine Persistence

The rapid demographic expansion of Querétaro since the late 20th century has significantly altered land use and habitat availability. While urbanization often reduces suitable habitats for wildlife, certain conditions—such as older housing structures and proximity to green spaces—may create microhabitats that facilitate the persistence of triatomine populations. At the local level, the presence of T. barberi in urban environments raises concerns about human–vector interactions, particularly in neighborhoods where traditional housing is still prevalent.

The collection of a nymph in Menchaca suggests the possibility of local reproduction within the urban environment. This finding is particularly relevant for public health, as it indicates that T. barberi populations are not merely transient but may be establishing breeding populations in anthropogenic settings. Regionally, similar patterns could emerge in other cities with comparable urbanization dynamics, underscoring the importance of entomological surveillance to detect emerging colonization hotspots across the Bajío.

4.2. Public Health Implications

The presence of T. barberi in Querétaro’s urban landscape has significant epidemiological implications, particularly considering that a regional strain of Trypanosoma cruzi, previously isolated from this species, has demonstrated high virulence and immunogenicity in experimental models [20]. However, this study did not assess infection rates among the collected specimens. At the local level, future research should incorporate molecular diagnostics to determine T. cruzi prevalence in T. barberi populations within Querétaro, providing a clearer assessment of the risk to human populations. At the regional level, similar studies across the Bajío would help identify broader transmission patterns and epidemiological risk factors.

The results highlight the importance of targeted vector surveillance programs in Querétaro, particularly in areas predicted as high suitability zones by the ecological niche model. Integrating predictive modeling with active vector monitoring can improve the efficiency of control strategies, enabling a more effective allocation of resources to mitigate disease transmission risk. At the regional level, implementing similar strategies in other Bajío cities could strengthen preventive responses against Chagas disease.

4.3. Limitations and Future Research

Although this study provides valuable insights, several limitations must be considered. First, the reliance on presence-only data in MaxEnt modeling may introduce sampling biases. Despite efforts to minimize spatial autocorrelation and ensure data quality, additional field surveys in underrepresented areas would enhance model accuracy. At the regional level, expanding sampling efforts in other Bajío cities would allow for a broader evaluation of whether the conditions identified in Querétaro are applicable across a wider geographic context.

Second, the lack of infection data limits the epidemiological conclusions that can be drawn. Future research should prioritize testing for T. cruzi in collected specimens to determine the vector competence of T. barberi in Querétaro. Additionally, longitudinal studies are needed to assess how T. barberi populations fluctuate over time and how urbanization and climate change may further alter their distribution. At the regional scale, understanding these dynamics in the Bajío is essential for designing long-term vector control strategies and predicting future disease transmission risks.

5. Conclusions

This study presents a validated ecological niche model for T. barberi in the Central Mexico Area, identifying key environmental variables influencing its distribution and reporting new occurrence records in urban settings. Key findings include the following:

• High model performance (AUC = 0.95, TSS = 0.82) indicating strong predictive accuracy.
• Temperature seasonality (bio04) and altitude as primary drivers of species distribution.
• New records in urbanized areas, including evidence of nymph presence, suggesting potential establishment.

Given the potential risk of Chagas disease transmission, health authorities should prioritize vector surveillance in high-risk zones and implement community-based education programs to raise awareness about triatomine presence and control measures. Future studies should integrate molecular diagnostics to assess T. cruzi prevalence and evaluate the long-term stability of T. barberi populations under changing environmental conditions.

The integration of ecological modeling, field surveillance, and epidemiological assessments will be essential for improving Chagas disease prevention strategies in urban environments. By identifying high-suitability areas and understanding the factors driving T. barberi distribution, this research contributes to a proactive approach in vector-borne disease management.