Trypanosoma cruzi infection in Triatoma infestans and high levels of human-vector contact across a rural-to-urban gradient in the Argentine Chaco

• Published in: Parasites & vectors Vol. 14; no. 1; p. 35
• Main Authors: Alvedro, Alejandra, Gaspe, María Sol, Milbourn, Hannah, Macchiaverna, Natalia Paula, Laiño, Mariano Alberto, Enriquez, Gustavo Fabián, Gürtler, Ricardo Esteban, Cardinal, Marta Victoria
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 09-01-2021; BioMed Central; BMC
• Subjects: Adult; Animals; Argentina - epidemiology; Blood; Blood-feeding sources; Cats; Chagas disease; Chagas Disease - epidemiology; Chagas Disease - transmission; Chickens; Confidence intervals; Deoxyribonucleic acid; Disease transmission; Distribution; DNA; Dogs; Enzyme-Linked Immunosorbent Assay; Feeding Behavior; Female; Goats; Health aspects; Health risks; Houses; Humans; Immunoassays; Infections; Infestation; Insect Vectors - parasitology; Insecticides; Insects; Male; Metropolitan areas; Mice; Nucleotide sequence; Parasitic diseases; PCR; Poultry; Protozoa; Protozoan diseases; Random sampling; Residential areas; Risk Factors; Rural areas; Rural environments; Rural Population; Sparsely populated areas; Statistical sampling; Surveying; Triatoma; Triatoma infestans; Tropical diseases; Trypanosoma cruzi; Urban areas; Urban environments; Urbanization; Vectors (Biology); Argentina; United States > US; Chaco region; Urbanization; Triatoma infestans; Blood-feeding sources; Trypanosoma cruzi
• ISSN: 1756-3305; 1756-3305
• DOI: 10.1186/s13071-020-04534-z

Peri-urban and urban settings have recently gained more prominence in studies on vector-borne transmission of Trypanosoma cruzi due to sustained rural-to-urban migrations and reports of urban infestations with triatomines. Prompted by the finding of Triatoma infestans across the rural-to-urban gradient in Avia Terai, an endemic municipality of the Argentine Chaco, we assessed selected components of domestic transmission risk in order to determine its variation across the gradient.
A baseline vector survey was conducted between October 2015 and March 2016, following which we used multistage random sampling to select a representative sample of T. infestans at the municipal level. We assessed T. cruzi infection and blood-feeding sources of 561 insects collected from 109 houses using kinetoplast DNA-PCR assays and direct enzyme-linked immunosorbent assays, respectively. We stratified triatomines according to their collection site (domestic or peridomestic), and we further categorized peridomestic sites in ecotopes of low- or high-risk for T. cruzi infection.
The overall adjusted prevalence of T. cruzi-infected T. infestans was 1.8% (95% confidence interval [CI] 1.3-2.3) and did not differ between peri-urban (1.7%) and rural (2.2%) environments. No infection was detected in bugs captured in the urban setting; rather, infected triatomines were mainly collected in rural and peri-urban domiciles, occurring in 8% of T. infestans-infested houses. The main blood-feeding sources of domestic and peridomestic triatomines across the gradient were humans and chickens, respectively. The proportion of triatomines that had fed on humans did not differ between peri-urban (62.5%) and rural (65.7%) domiciles, peaking in the few domestic triatomines collected in urban houses and decreasing significantly with an increasing proportion of chicken- and dog- or cat-fed bugs. The relative odds ratio (OR) of having a T. cruzi infection was nearly threefold higher in bugs having a blood meal on humans (OR 3.15), dogs (OR 2.80) or cats (OR: 4.02) in a Firth-penalized multiple logistic model.
Trypanosoma cruzi transmission was likely occurring both in peri-urban and rural houses of Avia Terai. Widespread infestation in a third of urban blocks combined with high levels of human-triatomine contact in the few infested domiciles implies a threat to urban inhabitants. Vector control strategies and surveillance originally conceived for rural areas should be tailored to peri-urban and urban settings in order to achieve sustainable interruption of domestic transmission in the Chaco region.