Researchers have reported the first local records of two triatomine species in Oaxaca's Teotitlán District, extending the known distribution of T. barberi to Teotitlán de Flores Magón and T. dimidiata to Mazatlán Villa de Flores. The study set out to document the insects in previously unreported areas and assess what their presence could mean for Chagas disease. The records mark a change in the map, not a finding that local transmission has been measured.
A bigger map, with a clear limit
To build that map, the researchers searched PubMed, SciELO and GBIF, limiting the GBIF search geographically to Oaxaca. Before the new records were added, eight triatomine species had been recorded in 150 of Oaxaca's 570 municipalities. The combined record now covers 151 municipalities, with T. barberi recorded in 80 and T. dimidiata in 55. Those municipality totals are occurrence records. They do not measure abundance or infection risk.
The insects came from homes and nearby spaces
The specimens came through voluntary community participation after educational outreach during a serological survey in the La Cañada region. Residents submitted insects found in domestic and peridomestic settings. In Teotitlán de Flores Magón, T. barberi were collected indoors and around homes. In Mazatlán Villa de Flores, homeowners submitted T. dimidiata captured inside houses. The collection was opportunistic, not a standardized entomological survey.
The report described four adult female T. barberi from a peridomestic habitat, plus one adult and four nymphs captured indoors. The T. dimidiata specimen from Mazatlán Villa de Flores was assigned to haplogroup 2 through an ImageJ-based comparison of its dorsal spot pattern. A haplogroup is a genetic grouping, although this assignment came from one reported specimen and a qualitative pattern comparison.
Morphology first, then DNA
Identification began with the insects' visible features: body size, coloration, head proportions, the width of the pronotum, a plate behind the head, and the abdomen, plus details of other head and leg structures. The team then extracted DNA and amplified, cloned and sequenced the ITS2 region, a stretch of genetic material used to check the species assignment. This two-part approach linked the physical description to a sequence-based identification.
The expected PCR products were 115 base pairs for T. barberi and 320 base pairs for T. dimidiata, and BLASTn comparison confirmed the species identities. In the sequence comparison, T. barberi matched both available sequences at 100% identity and 100% coverage, then clustered in the T. barberi clade, or genetic group. T. dimidiata matches ranged from 90% to 93.98% identity, with 98% of the submitted sequence and 91% of the comparison sequence covered.
What the findings do not answer
That evidence supports the species identifications and the presence of the insects at the reported sites. It does not show how many are present, whether they form reproducing populations, or whether the newly reported municipalities are endemic zones. Because collection was opportunistic and not standardized, the findings also cannot explain whether the records reflect passive human-mediated dispersal or displacement from nearby sylvatic habitats.
The study did not report testing the collected vectors for Trypanosoma cruzi infection, human serology or transmission events, so it cannot quantify local human risk. The authors instead recommend greater awareness, entomological surveillance and vector-control programmes to address future Chagas disease outbreak risk. Longer, standardized monitoring and direct infection testing would be needed to answer the questions left open by these records.
Paper data and sources
Original title: Range expansion of two Triatominae species in Oaxaca, Mexico: first report and molecular identification of Triatoma barberi and Triatoma dimidiata in the Cañada region
Authors: Carbajal-Olivier B, Cruz-López L, González-Guzmán S et al.
Journal/Repository: Memorias do Instituto Oswaldo Cruz
Status: Peer-reviewed
First online: 2026-10-19
DOI: Not available
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