Variety is the spice: The role of morphological variation of Triatoma infestans (Hemiptera, Reduviidae) at a macro-scale.

Chagas disease is caused by the protozoan parasite Trypanosoma cruzi (Chagas, 1909). One of the primary vectors of T. cruzi in South America is Triatoma infestans (Klug, 1834). This triatomine species is distributed across a huge latitudinal gradient, inhabiting domiciliary , peridomiciliary , and wild environments. Its wide geographic distribution provides an excellent opportunity to study the relationships between environmental gradients and intraspecific morphological variation. In this study, we investigated variations in wing size and shape in T. infestans across six ecoregions. We aimed to address the following questions: How do wing size and shape vary on a regional scale, does morphological variation follow specific patterns along an environmental or latitudinal gradient, and what environmental factors might contribute to wing variation? Geometric morphometric methods were applied to the wings of 162 females belonging to 21 T. infestans populations, 13 from Argentina (n = 105), 5 from Bolivia (n = 42), and 3 from Paraguay (n = 15). A comparison of wing centroid size across the 21 populations showed significant differences. Canonical Variate Analysis (CVA) revealed significant differences in wing shape between the populations from Argentina, Bolivia, and Paraguay, although there was a considerable overlap, especially among the Argentinian populations. Well-structured populations were observed for the Bolivian and Paraguayan groups. Two analyses were performed to assess the association between wing size and shape, geographic and climatic variables: multiple linear regression analysis (MRA) for size and Partial Least Squares (PLS) regression for shape. The MRA showed a significant general model fit. Six temperature-related variables, one precipitation-related variable, and the latitude showed significant associations with wing size. The PLS analysis revealed a significant correlation between wing shape with latitude, longitude, temperature-related, and rainfall-related variables. Wing size and shape in T. infestans populations varied across geographic distribution. Our findings demonstrate that geographic and climatic variables significantly influence T. infestans wing morphology.

First winter record of Latrodectus mirabilis (Araneae: Theridiidae) in arid Patagonia: A consequence of climate change and urbanization?

Cases of araneism reported in the province of Chubut (Argentina) have tripled in the last two decades, and almost 80 % of them involve Latrodectus mirabilis (Holmberg) (Araneae: Theridiidae). According to descriptions of the life cycle of this species in Argentina, the low temperatures typical of autumn-winter cause the death of all adult spiders, so that no adult specimens of L. mirabilis are observed in winter. Field samplings, observations by the Grupo de Entomología Patagónica (GENTPAT, IPEEC CCT CENPAT CONICET), and citizen reports for more than 15 years suggested a similar cycle in northeastern Patagonia. However, for the last three consecutive years, we have recorded adult females in the field throughout the Patagonian winter. Some of these individuals even survived the winter and were alive the following spring. The purpose of this note is to report the field presence of adult female specimens of L. mirabilis in the outskirts of the city of Puerto Madryn (Chubut, Argentina) during the last three consecutive winters corresponding to the years 2021, 2022 and 2023; and to note that at least two of them survived the winter, arriving alive (and in good condition) the following spring. Given the medical importance of this spider, the publication of this information, the context of the findings, and their ecological implications will help to prevent its spread and reduce the likelihood of accidents.

Categorization by Score of Mosquito Species (Diptera: Culicidae) Related to Yellow Fever Epizootics in Argentina.

The mosquito-borne yellow fever virus (YFV) is the cause of a zoonotic disease, with both sylvatic and urban cycles. Some mosquito species have been associated directly with transmission of the virus in South America, although the importance given to each species varies depending on the bibliography, geographical location, or year of publication. For Argentina, few publications have assessed the involvement of mosquito species, especially those included in the sylvatic cycle. Therefore, the goal of our paper was to gather all the information available in South America and categorize all mosquito species potentially involved in the YFV transmission cycle in Argentina according to incriminating vector criteria. Based on three main characteristics ('Hosts', 'Mosquito vector', and 'YF outbreak'), we generated scales of importance by species, one exclusively for Argentina and another for all of South America, Sabethes albiprivus Theobald, 1903 was the most important species in Argentina; whereas the most important species in South America were Haemagogus janthinomys Dyar 1921, Hg. leucocelaenus Dyar and Shannon, 1924, and Sa. chloropterus Von Humboldt, 1819. Our review highlights the lack of research that evaluates the importance of these species for YFV transmission in Argentina, while serving as a starting point to establish priorities for research on the bionomics and vector status of these species.

Database of Sabethes and Haemagogus (Diptera: Culicidae) in Argentina: Sylvatic Vectors of the Yellow Fever Virus.

Yellow fever is an endemic disease in America caused by an arbovirus that circulates in the sylvatic cycle between nonhuman primates and mosquitoes of the genera Sabethes Robineau-Desvoidy and Haemagogus Williston. The main goal of this work is to report the distribution patterns of these genera in Argentina through an updated database built from published records as well as from own sample collections. These genera are represented in Argentina by a total of 18 species distributed in 14 provinces and 10 ecoregions. The ecoregions with greatest biodiversity were Paranense Forest, Yungas, Campos and Malezales. This database will also allow generating distribution maps for these mosquito genera, and their respective species in Argentina, to establish areas with high probability of viral circulation that are an essential input for vector surveillance, as a tool for public health decision-makers.

Analysis of Chagas disease vectors occurrence data: the Argentinean triatomine species database.

BACKGROUND: Chagas disease is a neglected tropical disease and Trypanosoma cruzi (its etiological agent) is mainly transmitted by triatomines (Hemiptera: Reduviidae). All triatomine species are considered as potential vectors; thus, their geographic distribution and habitat information should be a fundamental guide for the surveillance and control of Chagas disease. Currently, of the 137 species distributed in the Americas (Justi and Galvão 2017), 17 species are cited for Argentina: Panstrongylus geniculatus, P. guentheri, P. megistus, P. rufotuberculatus, Psammolestes coreodes, Triatoma breyeri, T. delpontei, T. eratyrusiformis, T. garciabesi, T. guasayana, T. infestans, T. limai, T. patagonica, T. platensis, T. rubrofasciata, T. rubrovaria and T. sordida. Almost 20 years have passed since the publication of the "Atlas of the Triatominae" by Carcavallo et al. (1998) and no work has been done to provide an updated complete integration and analysis of the existing information for Argentinean triatomine species. Here we provide a detailed temporal, spatial and ecological analysis of updated occurrence data for triatomines present in Argentina. NEW INFORMATION: This is the first database of the 17 triatomine species present in Argentina (15917 records), with a critical analysis of the temporal, spatial and ecological characteristics of 9788 records. The information spans the last 100 years (1918-2019) and it was mostly obtained from the DataTri database and from the Argentinean Vector Reference Center. As 70% of the occurrences corresponded to the last 20 years, the information was split into two broad periods (pre-2000 and post-2000). Occurrence data for most species show distribution range contractions, which, from the pre-2000 to post-2000 period, became restricted mainly to the dry and humid Chaco ecoregions. Concurrently, the highest species richness foci occurred within those ecoregions. The species T. infestans, T. sordida, T. garciabesi and T. guasayana mostly colonise human dwelling habitats. This study provides the most comprehensive picture available for Argentinean triatomine species and we hope that any knowledge gaps will encourage others to keep this information updated to assist health policy-makers to make decisions based on the best evidence.

Host range of Triatoma virus does not extend to Aedes aegypti and Apis mellifera.

Vector control is the most effective method to prevent transmission of Chagas disease. Control is mostly made through chemical insecticides although they have negative impact on wild pollinators, such as bees. Reducing pesticide use through biological alternatives could minimize the damage to these beneficial insects. Triatoma virus (TrV) is a pathogen able to kill triatomines and thus a valid candidate to be used as biological control agent. In this study we evaluate the capacity of TrV to infect an important beneficial insect (Apis mellifera) as well as a plague insect (Aedes aegypti). Results indicate that TrV does not infect the bees or mosquitoes tested in this study. The possible specificity of TrV for kissing bugs reinforces the possible use of TrV as a biological control agent for triatomines.

Evaluación de insecticida en terreno para el control del vector del dengue / Evaluation of an insecticide in the field for the control of the dengue vector

INTRODUCCIÓN Las enfermedades transmitidas por insectos vectores, como el dengue y la enfermedad de Chagas, registran cada año miles de defunciones. El control de las poblaciones de los vectores es la principal herramienta para prevenir estas enfermedades. En este marco, existen protocolos para la evaluación de insecticidas en terreno que no se adaptan a las diversas realidades sociales, climáticas y ambientales que presenta nuestro país. OBJETIVO Se proponen dos objetivos; 1) Diseñar protocolos de evaluación de insecticidas en terreno para el control de los vectores del dengue y la enfermedad de Chagas con adaptaciones a la heterogeneidad de la región; y 2) evaluar la eficacia en terreno de un insecticida con efecto larvicida y adulticida para el control de las poblaciones de Ae. aegypti. METODOS Se diseñaron protocolos para la evaluación de insecticidas contra las poblaciones de Ae. aegypti y T. infestans. Además, se evaluó el efecto larvicida y adulticida de un producto contra Ae. aegypti en Santo Tomé (Corrientes). Para ello se estimó la supervivencia de adultos, mortalidad de estadios preimaginales, porcentaje de emergencia e indicadores entomológicos de la población local de forma semanal en viviendas de dos áreas de la ciudad. En una se aplicó el producto mediante máquina UBV y la otra fue considerada como control. RESULTADOS Se generaron dos protocolos para la evaluación de insecticidas en terreno; uno para Ae. aegypti y otro para T. infestans. En la evaluación sobre Ae. aegypti, se observó un incremento del 24,06% de mortalidad total de los estados preimaginales y una disminución del 29,32% de la emergencia de los adultos. Solo la cantidad de adultos y el índice de Breteau de los índices entomológicos presentaron una merma en las semanas posteriores al tratamiento. DISCUSIÓN El producto evaluado mostró una elevada eficacia. Sin embargo un incremento de los índices en la semanas subsiguientes al tratamiento sugieren la implementación de técnicas de control adicionales en el tiempo

Can Triatoma virus inhibit infection of Trypanosoma cruzi (Chagas, 1909) in Triatoma infestans (Klug)? A cross infection and co-infection study.

Triatoma virus occurs infecting Triatominae in the wild (Argentina) and in insectaries (Brazil). Pathogenicity of Triatoma virus has been demonstrated in laboratory; accidental infections in insectaries produce high insect mortality. When more than one microorganism enters the same host, the biological interaction among them differs greatly depending on the nature and the infection order of the co-existing species of microorganisms. We studied the possible interactions between Triatoma virus (TrV) and Trypanosoma cruzi (the etiological agent of Chagas disease) in three different situations: (i) when Triatoma virus is inoculated into an insect host (Triatoma infestans) previously infected with T. cruzi, (ii) when T. cruzi is inoculated into T. infestans previously infected with TrV, and (iii) when TrV and T. cruzi are inoculated simultaneously into the same T. infestans individual. Trypanosoma cruzi infection was found in 57% of insects in the control group for T. cruzi, whereas 85% of insects with previous TrV infection were infected with T. cruzi. TrV infection was found in 78.7% of insects in the control group for TrV, whereas insects previously infected with T. cruzi showed 90% infection with TrV. A total of 67.9% of insects presented simultaneous infection with both types of microorganism. Our results suggest that TrV infection could increase adhesion of T. cruzi to the intestinal cells of triatomines, but presence of T. cruzi in intestinal cells would not increase the possibility of entry of TrV into cells. Although this study cannot explain the mechanism through which TrV facilitates the infection of triatomines with T. cruzi, we conclude that after TrV replication, changes at cellular level should occur that increase the adhesion of T. cruzi.

Modelling the potential geographic distribution of triatomines infected by Triatoma virus in the southern cone of South America.

BACKGROUND: Triatoma virus (TrV) is the only entomopathogenous virus identified in triatomines. We estimated the potential geographic distribution of triatomine species naturally infected by TrV, using remotely sensed and meteorological environmental variables, to predict new potential areas where triatomines infected with TrV may be found. METHODS: Detection of TrV infection in samples was performed with RT-PCR. Ecological niche models (ENM) were constructed using the MaxEnt software. We used 42 environmental variables derived from remotely sensed imagery (AVHRR) and 19 bioclimatic variables (Bioclim). The MaxEnt Jackknife procedure was used to minimize the number of environmental variables that showed an influence on final models. The goodness of fit of the model predictions was evaluated by the mean area under the curve (AUC). RESULTS: We obtained 37 samples of 7 species of triatomines naturally infected with TrV. Of the TrV positive samples, 32% were from sylvatic habitat, 46% came from peridomicile habitats and 22% from domicile habitats. Five of the seven infected species were found only in the sylvatic habitat, one species only in the domicile and only Triatoma infestans was found in the three habitats. The MaxEnt model estimated with the Bioclim dataset identified five environmental variables as best predictors: temperature annual range, mean diurnal range, mean temperature of coldest quarter, temperature seasonality and annual mean temperature. The model using the AVHRR dataset identified six environmental variables: minimum Land Surface Temperature (LST), minimum Middle Infrared Radiation (MIR), LST annual amplitude, MIR annual amplitude annual, LST variance and MIR variance. The potential geographic distribution of triatomine species infected by TrV coincides with the Chaco and the Monte ecoregions either modelled by AVHRR or Bioclim environmental datasets. CONCLUSIONS: Our results show that the conditions of the Dry Chaco ecoregion in Argentina are favourable for the infection of triatomine species with TrV, and open the possibility of its use as a potential agent for the biological control of peridomestic and/or sylvatic triatomine species. Results identify areas of potential occurrence that should be verified in the field.

Phylogenetics based on partial ORF2 of triatoma virus in triatomines collected over a decade from domiciliary habitats.

The only virus sequenced and studied in triatomines is the Triatoma virus, from the Dicistroviridae family, which causes delayed development, reduced oviposition, and premature death of infected insects. With the goal of expanding the sequences already obtained in previous years and verifying if any changes occurred in their genomic sequences, 68 samples of triatomines from several provinces of Argentina were analyzed. Sixteen positive samples were obtained by Reverse Transcription (RT)-polymerase chain reaction using the VP3-VP1 subregion of open reading frame-2 as a diagnostic method; after sequencing, 11 samples were obtained from Triatoma infestans. These new sequences showed no significant differences in the analyzed regions, which were not grouped by species or habitat or geographical distribution. There were no differences when compared with the sequences found during 2002-2012, all obtained from the wild. We conclude that despite being an RNA virus, the different sequences show high homology.

Detection of triatomine infection by Triatoma virus and horizontal transmission: protecting insectaries and prospects for biological control.

Triatoma virus (TrV) is the only triatomine entomopathogenic virus identified so far. Propagation of TrV in insectaries depends on handling procedures and triatomine population dynamics. The effects of propagation can be devastating and entire colonies must often be sacrificed to prevent spread of the virus throughout the insectary. This study found that after 41.3 days from TrV ingestion of human blood with 0.04 mg of viral protein by 5th instar Triatomainfestans, viral particles could be detected by RT-PCR; in a second horizontal transmission experiment time to detection resulted in a mean of 42.5 days. These results should rise awareness of TrV dynamics in nature, help estimate the spread of this virus when TrV-infected field-collected insects are incorporated into an insectary, and provide a base for the consideration of TrV as an agent of biological control of some species of triatomines.

First study of different insect cells to triatoma virus infection.

The use of viruses for biological control is a new option to be considered. The family Dicistroviridae, which affects only invertebrates, is one of the families that have been proposed for this purpose. The Triatoma virus (TrV), a member of this family, affects triatomine transmitters of Chagas disease, which is endemic in Latin America but also expanding its worldwide distribution. To this end, we attempted virus replication in Diptera, Aedes albopictus (clone C6/36) and Lepidoptera Spodoptera frugiperda (SF9, SF21) and High Five (H5) cell lines. The methodologies used were transfection process, direct inoculation (purified virus), and inoculation of purified virus with trypsin. Results were confirmed by SDS-PAGE, Western blotting, RT-PCR, electron microscopy, and immunofluorescence. According to the results obtained, further analysis of susceptibility/infection of H5 cells to TrV required to be studied.

First description of hemagglutination by a virus belonging to the family Dicistroviridae.

Triatoma virus is the only virus whose genome has been sequenced and studied in triatomines. It belongs to the family Dicistroviridae. In order to detect whether TrV has the ability to agglutinate erythrocytes of domestic and laboratory animals, we performed a hemagglutination assay. Positive hemagglutination was found for red blood cells of guinea pigs. The HA assay could be used as a titration method, at least for purified viral particles obtained from triatomine stool. This is the first record of hemagglutinating properties for Dicistroviridae.

New Triatoma virus hosts in wild habitats of Argentina.

Triatoma virus (TrV), a member of the Dicistroviridae family, replicates in intestinal epithelial cells, causing delayed development and death of infected individuals. The aims of this study were to find naturally infected species of Triatominae in the wild in the region endemic for Chagas disease and analyze and compare the sequence diversity of TrV obtained from different Triatominae. A total of 253 Triatominae belonging to 10 species were captured by active or passive collection. Three new sequences were obtained from Triatoma infestans, Triatoma delpontei and Psammolestes coreodes and the analysis revealed that these sequences were very similar. Ps. coreodes is a new host for TrV.