New Contributions to the Elimination of Chagas Disease as a Public Health Problem: Towards the Sustainable Development Goals by 2030

Triatoma venosa and Panstrongylus geniculatus challenge the certification of interruption of vectorial Trypanosoma cruzi transmission by Rhodnius prolixus in eastern Colombia

Reactivation of Trypanosoma cruzi transmission by native vectors with different domiciliation capabilities is a major concern for Chagas disease control programs. T. cruzi transmission via intra-domestic Rhodnius prolixus was certified as interrupted by the Pan American Health Organization in Miraflores municipality (Boyacá, Colombia) in 2019. However, Triatoma venosa, a native vector infected with T. cruzi has been increasingly found inside human dwellings across rural areas. In this study, the aim was to describe the eco-epidemiological aspects of T. cruzi transmission in the rural area of Miraflores. For this, we designed a comprehensive, multi-faceted study in 6 rural villages and performed: (i) A cross-sectional serological and molecular study enrolling 155 people and 58 domestic dogs living within 80 households, (ii) a domestic entomological survey, (iii) a determination of the natural infection and blood meal source in collected triatomine bugs, and (iv) an evaluation of synanthropic mammal infection by parasitological and molecular tools. The T. cruzi seroprevalence rates in humans and dogs were 9.03% (14/155) and 22.4% (13/58), respectively. Most infected humans were adults between the ages of 55 and 85 years old. No evidence of T. cruzi DNA was found using qPCR in human blood samples, but we found high parasitemia levels in the infected dogs. In total, 38 triatomine bugs were collected inside dwellings and peridomestic areas: 68.4% (26/38) Triatoma venosa, 29% (11/38) Panstrongylus geniculatus, and 2.6% (1/38) P. rufotuberculatus. Natural infection prevalence was 88% (22/25) for T. venosa, 100% (12/12) for P. geniculatus, and 100% (1/1) P. rufotuberculatus: only TcI was found. No evidence of R. prolixus was found in the area. Two feeding sources were identified in T. venosa (humans and cats), while P. geniculatus fed on cows and bats. Lastly, seven D. marsupialis were captured in peridomestic areas, three were infected with T. cruzi (TcI). The results suggest the existence of T. cruzi transmission cycle between triatomines, dogs, and opossums representing a risk of infection for the human population in rural areas of Miraflores. Despite PAHO declaring Miraflores municipality, Colombia an area of T. cruzi transmission interruption in 2019, this study documents evidence of a secondary vector establishing in domestic settings. T. venosa entomological surveillance is warranted to evaluate prospective human transmission risk in an otherwise 'no-risk' perceived Chagas disease region.

Anti-Trypanosoma cruzi antibody profiling in patients with Chagas disease treated with benznidazole assessed by genome phage display

BACKGROUND

There have been significant improvements in Chagas disease therapy and it is now widely accepted that most patients with chronic disease might benefit from therapy. However, there are challenges to monitor drug efficacy and cure for these patients, which are important impediments for current and future therapies. Trypanosoma cruzi-PCR is highly variable while IgG seroconversion takes decades yielding variable results depending on the antigen(s) used for the assay.

METHODS AND RESULTS

We used the genomic phage display (gPhage) platform to perform a pairwise comparison of antigens and epitopes recognized by twenty individual patients with chronic Chagas disease before and after treatment with benznidazole. In total, we mapped 54,473 T. cruzi epitopes recognized by IgG from individual patients (N = 20) before benznidazole treatment. After treatment, the number of epitopes recognized by all patients was significantly smaller (21,254), a reduction consistent with a decrease in anti-T. cruzi antibodies. Most of these epitopes represent distinct fragments from the same protein and could, therefore, be grouped into 80 clusters of antigens. After three years of treatment with benznidazole, we observed a 64% reduction in the number of clusters of antigens recognized by patients (59 clusters before versus 21 clusters after treatment). The most abundant antigenic clusters recognized by patients correspond to the surface antigen CA-2 (B13) followed by the microtubule associated antigen, which highlights the value of these epitopes in Chagas disease diagnosis. Most importantly, quantitative pairwise comparison of gPhage data allowed for the prediction of patient response to treatment based on PCR status.

PRINCIPAL FINDING

Here, we compiled a list of antigens and epitopes preferentially recognized by Chagas disease patients before and after benznidazole treatment. Next, we observed that gPhage data correlated with patient PCR-status and could, therefore, predict patient response to treatment. Moreover, gPhage results suggest that overall, independent of PCR status, treatment led to a reduction in the presence of T. cruzi-specific antibody levels and the number of antigens and epitopes recognized by these patients.

CONCLUSION

The gPhage platform use of unbiased library of antigens, which is different from conventional serological assays that rely on predetermined antigens, is a contribution for the development of novel diagnostic tools for Chagas disease.