The compiled information for Argentina spans the period from 1918 to 2019, with 70% of the occurrences corresponding to the last 20 years (Fig. 1, Table 1). Considering that most of the records belong to the latter time interval and to describe better the information, the dataset was split into two periods, (a) a pre-2000 period (up to and including 2000) and (b) a post-2000 period (2001 to the present).

Figure 1.  

Temporal distribution of Argentinean triatomine occurrence data. Frequency distribution of the number of occurrence data per 7-year intervals. Records with temporal information expressed as a time range that spanned both sides of the pre- and post-2000 time boundary (e.g. 1998-2006) were assigned to the time interval with the largest number of years of collection.

There are 2930 occurrence records in the pre-2000 period corresponding to information on 17 triatomine species, compared to 6858 records corresponding to 13 triatomine species in the post-2000 period. The species missing from the post-2000 period are P. megistus, P. rufotuberculatus, T. limai and T. rubrofasciata (Table 1). In the pre-2000 period, the largest contribution of occurrence data corresponds to T. infestans (43.36%), T. guasayana (10.34%), P. guentheri (6.38%), Ps. coreodes (6.11%) and T. garciabesi (4.09%), while, in the post-2000 period, the records of T. infestans by themselves represent 82.72% of all occurrences (Table 1).

Most of the records (62.79%) were obtained from DataTri and 37.21% from the other three datasets (AMH-CeNDIE/ANLIS, AMH-CeReVe and GeoVin). The main data sources contributing to the pre-2000 records were public repositories (96.66%), while in the post-2000 period, AMH-CeReVe and data provided by colleagues were the data sources with the greatest contribution (51.82% and 33.68%, respectively) (Table 2).

According to the type of habitat where collected, 29.96% of the species are found inside human dwellings, 65.02% in the vicinity of human dwellings and 5.01% in natural environments (Table 3). A classification, based on the range of habitat types, includes seven categories (Table 3): (1) Domestic species, characterised by adults, nymphs, eggs and exuviae present within the house (i.e. the entire life cycle of the insect occurs within human dwellings); (2) Domiciliary species, characterised by having their complete cycle inside human dwellings, but maintaining small populations, i.e. showing recent (and relatively poor) adaptation to houses; these populations may disappear from human domiciles without any control intervention; (3) Domiciliary intrusive species, characterised by the presence of adult individuals in human dwellings, probably attracted by light or introduced by passive transport, but without evidence of colonisation (i.e. without the presence of nymphs, eggs or exuviae within the domicile); (4) Peridomestic species, similar to the Domestic species, but completing their entire life cycle around human dwellings; (5) Peridomiciliary species, characterised by species that complete their entire life cycle in the vicinity of human dwellings; (6) Peridomiciliary intrusive species, characterised by adult individuals reported around human dwellings, but without evidence of colonisation; and (7) Sylvatic species, characterised by having their complete life cycle in natural environments.

Triatoma infestans is the only species categorised as Domestic and Peridomestic, while T. garciabesi, T. guasayana and T. sordida are mainly Domiciliary and Peridomiciliary species. In the case of T. eratyrusiformis, T. patagonica and T. platensis, they are mainly Peridomiciliary species, whereas P. geniculatus and P. guentheri are mainly Peridomiciliary intrusive species. Additionally, even though the relative frequency of records for each species in natural environments are heterogeneous, Ps. coreodes, T. breyeri and T. delpontei are Sylvatic species, with the maximum percentage of nymphal stages recorded in this habitat type (Table 3).

The occurrence data for triatomine species are distributed over 15 ecoregions, amongst which those with highest number of species occurrences in both periods are Dry Chaco, Humid Chaco, Espinal, Plains and Plateaus Monte and Hills and Bossoms Monte (Suppl. material 1).

The species with widest geographic distribution is T. infestans (Fig. 2), with the highest number of records in both periods (Table 1). For the pre-2000 period, records of T. infestans are distributed in all continental ecoregions, while in the post-2000 period, there are no records for this species in the ecoregions High Andes, Patagonian Forest, Paraná Flooded Savannahs and Campos and Malezales ecoregions (Fig. 2). Despite this absence in some ecoregions in the post-2000 records and that the geographic distribution of the species is mainly restricted to one ecoregion (Dry Chaco), for this time period, T. infestans has four times the number of records of the pre-2000 period (Table 1).

Figure 2.  

Distribution of occurrence data for T. infestans. (a) pre-2000 records (b) post-2000 records. Species occurrence data are shown as black dots. Coloured areas represent the ecoregions. Red star is a questionable occurrence (Piccinali et al. 2010).

Triatoma guasayana is the species with the second highest number of occurrence data (6.29%), followed by T. garciabesi and T. sordida (7.65%, including the T. garciabesi-T. sordida records) (Table 1). The occurrence data for post-2000 for T. guasayana records are concentrated in central and north Argentina and mainly restricted to the Dry Chaco ecoregion (Fig. 3). In the case of T. garciabesi, the distribution of occurrence data for both periods included north-western Argentina (mainly Dry Chaco), whereas those of T. sordida included north-eastern Argentina (mainly Humid Chaco). The geographic distribution of T. garciabesi -T. sordida is similar for the pre-2000 and post-2000 periods and shows partial overlap between the distributions of both species (Fig. 3).

Figure 3.  

Distribution of occurrence data for T. garciabesi, T. garciabesi-T. sordida, T. sordida and T. guasayana (a) pre-2000 records (b) post-2000 records. Species occurrence data are shown as black dots (T. garciabesi and T. guasayana), white circles with black dots (T. sordida) and white triangle (T. garciabesi-T. sordida). Coloured areas indicate the ecoregions. Red stars are questionable records for T. sordida (Abalos and Wygodzinsky 1951, Manso Soto and Martinez 1948).

Triatoma eratyrusiformis presented similar distribution patterns of occurrence between the pre-2000 and post-2000 periods. For T. patagonica, occurrences in the post-2000 period were restricted to the southern Dry Chaco, Plains and Plateaus Monte and the Espinal ecoregion in southern Buenos Aires Province (Fig. 4). Similarly, occurrence data for T. platensis for the post-2000 period were restricted mainly to the ecoregions Dry Chaco and Plains and Plateaus Monte (Fig. 4).

Figure 4.  

Distribution of occurrence data for T. eratyrusiformis, T. patagonica and T. platensis. (a) pre-2000 records (b) post-2000 records. Species occurrence data are shown as black dots. Coloured areas represent the ecoregions. Red star is a questionable record for T. eratyrusiformis (Bachmann 1999).

There are fewer records of P. geniculatus and P. guentheri in the post-2000 than in the pre-2000 period, with occurrences restricted to the Humid and Dry Chaco ecoregions, respectively (Fig. 5). Meanwhile, P. guentheri is the species that shows greatest reduction of its distribution between the pre-2000 and the post-2000 periods (Fig. 5).

Figure 5.  

Distribution of occurrence data for P. geniculatus and P. guentheri (a) pre-2000 records (b) post-2000 records. Species occurrence data are shown as black dots. Coloured areas represent the ecoregions. Red star is a questionable record for P. guentheri (Carcavallo et al. 1994).

The species Ps. coreodes, T. breyeri, T. delpontei and T. rubrovaria show reduction of their geographic ranges from pre-2000 to post-2000 periods, with scarce post-2000 records (Fig. 6).

Figure 6.  

Distribution of occurrence data for Ps. coreodes, T. breyeri, T. delpontei and T. rubrovaria (a) pre-2000 records (b) post-2000 records. Species occurrence data are shown as black dots. Coloured areas represent the ecoregions. Red stars are questionable records for T. breyeri (Moreno et al. 2006) and for T. rubrovaria (Carcavallo and Martinez 1968).

No reports of occurrence were found for P. megistus, P. rufotuberculatus, T. limai and T. rubrofasciata in the post-2000 period; thus, Fig. 7 shows only the geographic information corresponding to the pre-2000 period for these species. Panstrongylus megistus has 27 records; P. rufotuberculatus, one record; T. limai, nine records; and T. rubrofasciata, one record (Table 1).

Figure 7.  

Distribution of occurrence data for triatomine species with only pre-2000 information available. Species occurrence data are shown as black triangles (P. megistus), black squares (P. rufotuberculatus), black stars (T. limai) and black dots (T. rubrofasciata). Coloured areas represent the ecoregions.

These data show a trend of reduction in species richness of triatomines over the last 20 years in central-western Argentina (an area corresponding mainly to the southern and central Dry Chaco ecoregion) (Fig. 8). The maximum number of species sharing a cell in the pre-2000 period is eight species, while this maximum decreased to seven in the post-2000 period. Furthermore, for the pre-2000 period, high species richness values were found in several ecoregions of Argentina, whereas in the post-2000 period, they occurred mainly in only four areas within the Dry Chaco (Fig. 8b). The species with greatest contribution to overall richness in both periods and in decreasing order are T. infestans, T. platensis, T. guasayana and T. garciabesi (details in Table 1).

Figure 8.  

Spatial pattern of Argentinean triatomine species richness. (a) pre-2000 occurrence data and (b) post-2000 occurrence data. The colour gradient corresponds to the number of species present in each cell. Dashed lines indicate limits between ecoregions.

We compiled a large amount of occurrence data and associated information and integrated it into a single database to better understand the geographic distribution of triatomine species present in Argentina over the last 100 years, as well as the temporal variation of these distributions.

One of our key findings was that the number of records in the post-2000 period almost tripled the number of those from the pre-2000 period. While for the pre-2000 period, public repositories (mainly records from researcher’s fieldwork published in scientific journals) were the major data sources providing spatial information, in the last two decades, the balance shifted towards records provided by the CeReVe, as well as focused field campaigns carried out by several research groups, which were the major data sources for the post-2000 period. However, these sources have become increasingly focused on the species with major epidemiological importance, mainly T. infestans and few records provide information about other species. We propose the following hypotheses that may account for this difference: (a) the results of chemical control and vector eradication campaigns that were carried out through the creation of the INCOSUR initiative in 1992 (http://www.paho.org) became evident only in the post-2000 period; (b) in the 1997-2007 period, Argentinean researchers received the highest number of grants from WHO Special Programme for Research and Training in Tropical Diseases (TDR) and the Pan American Health Organization (PAHO), which resulted also in the highest number of related publications in peer-reviewed scientific journals (Carbajal de la Fuente and Yadón 2013); and (c) in the last 20 years, the CeReVe began to play a major role as one of the most important institutions for the compilation of triatomine records of Argentina, becoming the main source of records for this country in the post-2000 period.

Another of the key findings concerns the number of triatomine species present in Argentina. According to Carcavallo et al. (1998) and Ceccarelli et al. (2018), there are 17 triatomine species mentioned for Argentina. However, in this analysis, we found that this number of species is valid only for the pre-2000 period, given that, for at least in the last 20 years, there are no records for P. megistus, P. rufotuberculatus, T. limai or T. rubrofasciata. In the case of P. megistus, the last record found for Argentina corresponds to 1995 (Damborsky et al. 2001); however, the records mentioned for Brazil (Ceccarelli et al. 2018) and Bolivia (Rojas-Cortez 2007) in the post-2000 period, suggest that this species might still be present in Argentina. Although only one record was found for P. rufotuberculatus in the Yungas ecoregion (Salomón et al. 1999) for the pre-2000 period, the species has been detected in Tarija (Bolivia) several times (Rojas-Cortez 2007), leading us to consider that the scarcity of data may be due to a lack of sampling in that ecoregion. Similarly, T. limai was mentioned in only two publications for Argentina (Abalos and Wygodzinsky 1951, Carcavallo and Martinez 1968), while Del Ponte (1929) mentioned that it is distributed in Brazil, but without specifying a locality. Finally, given that T. rubrofasciata is a cosmopolitan species suspected of having been transported on ships to some countries, we concluded that it is possible that this species arrived accidentally to Argentina at some point. The only record of T. rubrofasciata is considered as doubtful because Neiva (1914), Larrousse (1924) and Del Ponte (1930) do not agree on the location of the record. Abalos and Wygodzinsky (1951) do not mention T. rubrofasciata in Argentina and Carcavallo et al. (1965) proposed to remove it from the list of Argentinean triatomines, since apparently it was found occasionally and was never able to colonise any environment in Argentina. Therefore, we consider that the specimens of T. limai, allegedly found in Argentina, do not belong to the species described by del Ponte in 1930 and as there has been no record of T. rubrofasciata in Argentina for more than 100 years, we chose to remove both species from the current list of Argentinean triatomines. On the other hand, we decided to keep P. megistus and P. rufotuberculatus, judging that the small number of occurrences in the last 20 years can be attributed to poor sampling.

In the case of insect vectors, it is common for those species with greater public health importance (e.g. domiciliated species) to receive more attention, as in the case of T. infestans that makes up 70.98% of all the occurrence data and has the largest geographic distribution in Argentina. The occurrence records for some species are also biased towards certain regions and habitats: occurrence data of most species show distributions restricted mainly to the Dry and Humid Chaco ecoregions in the post-2000 period, with P. guentheri showing the greatest reduction of occurrence distribution, from 10 ecoregions in the pre-2000 period to only one in the post-2000 period. Undoubtedly, this phenomenon involves not only the usual tendency of researchers to survey specific or more accessible places (Sastre and Lobo 2009), but also the fact that some areas receive more attention from vector control programmes (Carbajal de la Fuente and Yadón 2013). Thus, this uneven distribution of missing data, influenced by various factors, results in a less accurate representation of the actual occurrence patterns. Thus, the known distribution of a species provides a view of its distribution that is at best incomplete, if not actually misleading. A critical step towards improving this picture is to reinforce the efforts in unsampled and under-sampled areas, considering not only the domiciliary and peridomiciliary species, but also the sylvatic ones. When compiling the distribution data from public sources, we often found it useful to allocate attention to species and regions depending on data availability, because databasing sylvatic species from an under-sampled region provides more novel information than duplicating records for well-known species (domiciliary species) and regions (endemic areas). Applications based on citizen-science projects, such as GeoVin, aim to promote an increase in reports of sylvatic species, as well as an update of records of species more commonly known for their major vector importance (such as T. infestans) from locations outside those areas where reports are commonly made. We also found that unpublished data, such as the records provided by CeReVe and CeNDIE/ANLIS, from colleagues or from studies that are not focused on geography (e.g. molecular, morphometric etc.) are highly-valuable sources of geographic records and we recommend and encourage them to publish their data with geographic coordinates. We also advise them to publish those data in public databases (instead of as part of scientific articles only) because online databases of observations from field studies not only facilitate data gathering, but also contribute to guarantee the persistence and availability of those data.

Finally, on the basis of the information about habitat and the categorisation presented here, we show that, although the greatest proportion of records in all habitat types corresponds to T. infestans, there are also other species, namely T. sordida, T. garciabesi and T. guasayana, that occur as both adults and nymphs inside and around human dwellings. In the case of T. eratyrusiformis, T. patagonica and T. platensis, the records of occurrence within human dwellings include adult individuals only, but these species also occur as nymphs in the vicinity of human dwellings. The categorisation used in this work could contribute to the development of vector risk indices and, combined with the maps of species distributions, could be extremely useful for decision-makers in health organisations, since the risk of these insects acting as vectors of T. cruzi to result in Chagas disease is not only due to the presence of the triatomines themselves, but also depends on their proximity to and colonisation of human dwellings.

In summary, we used an approach, based on occurrence data analysis, to assess temporal, spatial and ecological patterns of the triatomines present in Argentina. Our results provide updated information regarding various aspects of Argentinean triatomines that will improve the ways in which these species are identified, controlled and managed in Argentina. Two major outcomes of this work are, on one hand, the inclusion of 15 species in the updated list of Argentinean triatomines: P. geniculatus, P. guentheri, P. megistus, P. rufotuberculatus, Ps. coreodes, Triatoma breyeri, T. delpontei, T. eratyrusiformis, T. garciabesi, T. guasayana, T. infestans, T. patagonica, T. platensis, T. rubrovaria and T. sordida. On the other hand, the database analysed will add records to those of DataTri, thus becoming the largest open access database of American triatomines with around 30000 records so far, which not only represents a fundamental resource for Chagas disease decision-making, but also contributes to the initiatives related to open access data. Ongoing investment in national records for vector control is crucial for the continuous growth of the datasets upon which our analyses are based. The methods that we developed and implemented can be easily transferred to and applied in other countries where these types of data are available, thus improving our understanding of existing triatomine information.