Molecular Diagnosis of Chagas Disease in Colombia: Parasitic Loads and Discrete Typing Units in Patients from Acute and Chronic Phases

Abstract

BackgroundThe diagnosis of Chagas disease is complex due to the dynamics of parasitemia in the clinical phases of the disease. The molecular tests have been considered promissory because they detect the parasite in all clinical phases. Trypanosoma cruzi presents significant genetic variability and is classified into six Discrete Typing Units TcI-TcVI (DTUs) with the emergence of foreseen genotypes within TcI as TcIDom and TcI Sylvatic. The objective of this study was to determine the operating characteristics of molecular tests (conventional and Real Time PCR) for the detection of T. cruzi DNA, parasitic loads and DTUs in a large cohort of Colombian patients from acute and chronic phases.Methodology/Principal FindingsSamples were obtained from 708 patients in all clinical phases. Standard diagnosis (direct and serological tests) and molecular tests (conventional PCR and quantitative PCR) targeting the nuclear satellite DNA region. The genotyping was performed by PCR using the intergenic region of the mini-exon gene, the 24Sa, 18S and A10 regions. The operating capabilities showed that performance of qPCR was higher compared to cPCR. Likewise, the performance of qPCR was significantly higher in acute phase compared with chronic phase. The median parasitic loads detected were 4.69 and 1.33 parasite equivalents/mL for acute and chronic phases. The main DTU identified was TcI (74.2%). TcIDom genotype was significantly more frequent in chronic phase compared to acute phase (82.1% vs 16.6%). The median parasitic load for TcIDom was significantly higher compared with TcI Sylvatic in chronic phase (2.58 vs.0.75 parasite equivalents/ml).Conclusions/SignificanceThe molecular tests are a precise tool to complement the standard diagnosis of Chagas disease, specifically in acute phase showing high discriminative power. However, it is necessary to improve the sensitivity of molecular tests in chronic phase. The frequency and parasitemia of TcIDom genotype in chronic patients highlight its possible relationship to the chronicity of the disease.

Untangling the transmission dynamics of primary and secondary vectors of Trypanosoma cruzi in Colombia: parasite infection, feeding sources and discrete typing units

“…This DTU has been reported in domestic cycles from southern Latin-American countries [7, 29]. However, insects infected with TcV have been reported in domestic habitats in Colombia including some reports of human infections [10, 30]. TcV associated with sylvatic cycles has been reported with a frequency of 3.5% [29].…”

Case Report: Orally Transmitted Acute Chagas’ Disease From a Case in a Public Hospital in Bucaramanga City, Colombia.

“…La forma infectiva es el tripomastigote metacíclico y tiene tropismo por el tejido muscular cardiaco, gastrointestinal, neuroglial y reticuloendotelial [1][2][3][4][5][6] . Este parásito tiene gran diversidad genética, con la descripción de siete grupos filogenéticos, según su genotipificación: Tc I-VI y Tcbat, siendo reportadas cinco subpoblaciones de los Tc I [6][7][8] . Estos difieren tanto en su distribución geográfica, el ciclo de transmisión, el vector y LAS formas clínicas, aún en estudio [6][7][8] .…”

“…Este parásito tiene gran diversidad genética, con la descripción de siete grupos filogenéticos, según su genotipificación: Tc I-VI y Tcbat, siendo reportadas cinco subpoblaciones de los Tc I [6][7][8] . Estos difieren tanto en su distribución geográfica, el ciclo de transmisión, el vector y LAS formas clínicas, aún en estudio [6][7][8] . La enfermedad ocurre luego del periodo de incubación de 1-2 semanas, produciendo la fase aguda caracterizada por la evidencia del sitio de inoculación, con linfadenopatías locales (chagoma -signo de Romaña), situación inusualmente observada en los casos de trasmisión oral; con posterior diseminación linfática a órganos diana; en niños generando en sistema nervioso: meningoencefalitis, encefalitis granulomatosa o neuropatía periférica; corazón: miocarditis difusa, alteración de la conducción cardíaca e incluso cardiopatía dilatada aguda severa y reticuloendotelial: como el caso de chagas congénito con hepatoesplenomegalia y compromiso medular, donde se observan los pseudoquistes de amastigotes en los tejidos [1][2][3][4][5][6] .…”

“…En todos los casos no se encuentra la presencia del triatomino en la vivienda, pero sí en el bosque o arboles aledaños o la convivencia con zarigüeyas (faras)5,6 . Respecto al genotipo de tripanosoma, en Colombia y particularmente en Santander, se han encontrado una mayor prevalencia de Tc I, relacionado a casos de transmisión oral y de co-infecciones de subgenotipos en un mismo paciente[6][7][8]11,12 .April 2019 Volume 6, Issue 4Los principales mecanismos de transmisión oral ocurren por ingesta directa del triatomino, alimentos contaminados con heces del mismo, sean frutas, verduras ó carne pobremente cocida y sangre de las zarigüeyas portadoras ó mamíferos reservorios, incluso se ha descrito mediante lactancia materna[1][2][3][4][5][6] . Los alimentos contaminados más frecuentemente asociados han sido el jugo de caña, jugo de açai, jugo de guayaba, jugo de naranja5,6,11 .…”

Increasing access to comprehensive care for Chagas disease: development of a patient-centered model in Colombia

“…However, CD can also spread via blood transfusion, organ transplant, or congenital transmission. Additionally, oral transmission through food contaminated by triatomine feces or contact with infected reservoir species is an emerging public health issue in Colombia and other Latin American countries (3)(4)(5)(6).…”