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. 2022 Jun 14;12(1):9849.
doi: 10.1038/s41598-022-14051-x.

Towards environmental detection of Chagas disease vectors and pathogen

Grace Gysin  1 , Plutarco Urbano  2   3 , Luke Brandner-Garrod  1 , Shahida Begum  1 , Mojca Kristan  1 , Thomas Walker  1 , Carolina Hernández  2   4 , Juan David Ramírez  2   5 , Louisa A Messenger  6
Affiliations

Towards environmental detection of Chagas disease vectors and pathogen

Grace Gysin et al. Sci Rep. .

Abstract

Chagas disease vector control relies on prompt, accurate identification of houses infested with triatomine bugs for targeted insecticide spraying. However, most current detection methods are laborious, lack standardization, have substantial operational costs and limited sensitivity, especially when triatomine bug densities are low or highly focal. We evaluated the use of FTA cards or cotton-tipped swabs to develop a low-technology, non-invasive method of detecting environmental DNA (eDNA) from both triatomine bugs and Trypanosoma cruzi for use in household surveillance in eastern Colombia, an endemic region for Chagas disease. Study findings demonstrated that Rhodnius prolixus eDNA, collected on FTA cards, can be detected at temperatures between 21 and 32 °C, when deposited by individual, recently blood-fed nymphs. Additionally, cotton-tipped swabs are a feasible tool for field sampling of both T. cruzi and R. prolixus eDNA in infested households and may be preferable due to their lower cost. eDNA detection should not yet replace current surveillance tools, but instead be evaluated in parallel as a more sensitive, higher-throughput, lower cost alternative. eDNA collection requires virtually no skills or resources in situ and therefore has the potential to be implemented in endemic communities as part of citizen science initiatives to control Chagas disease transmission.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
Standard curves for individual detection of R. prolixus 12S rRNA (A), T. cruzi satellite DNA (B) and simultaneous detection of R. prolixus 12S rRNA and T. cruzi satellite DNA (C), across serial gDNA dilution series.
Figure 2
Figure 2
Design of experiments to investigate the impact of different environmental conditions on R. prolixus eDNA detection, including variables altered, number of jars and number of triatomines used. Figure created with BioRender.com.
Figure 3
Figure 3
Detection of R. prolixus eDNA from FTA cards under different environmental conditions. (A) Time; (B) darkness; (C) degradation at ambient temperature; (D) temperature; (E) R. prolixus number; (F) feeding status. N = number of separate DNA extractions performed. qPCR detection for all extractions were run in technical triplicate. Conditions sharing a superscript do not differ significantly (Dunn’s multiple comparisons test, p > 0.05). Error bars indicate 95% confidence intervals (CIs).
Figure 4
Figure 4
Detection of R. prolixus and T. cruzi eDNA from cotton swabs taken from 33 house with confirmed triatomine infestations in Casanare, Colombia. Red arrows indicate houses with reported human T. cruzi infection.
Figure 5
Figure 5
Photos of experimental set-ups. (A) QIAcard FTA classic card, stapled to plain A4 paper, to be secured over a glass jar opening with an elastic band; (B) bug number experiment with 25 blood-fed 3rd/4th instar R. prolixus; (C) process to invert glass jars; (D) aggregating behaviour of 3rd/4th instar R. prolixus; (E) time point assay experiment; (F) temperature experiment with incubator set to 32 °C for 24 h; (G) darkness experiment with blackout blanket over inverted jars; (H) blood-feeding the triatomines with Hemotek feeder using equine blood; (I) appearance of fed (left) vs. unfed bugs (right) in feeding status experiment.
Figure 6
Figure 6
Houses and peri-domestic sites where eDNA was collected in Casanare Department, Colombia.
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