Detection and significance of inapparent infection in Chagas disease in western Venezuela

Update on Chagas disease in Venezuela during the period 2003-2018. A review

The present article reviews the status of Chagas disease in Venezuela during the period 2003-2018, based on the detection of Trypanosoma cruzi-infection in 3,343 blood samples of individuals from rural localities and 182 patients referred from health centers to confirm presumptive clinical diagnostic. The study involved samples from 81 rural localities of 17 states located at different regions and ecological life zones of the country. Analysis by parasitological (fresh microscopic observation, hemoculture and Giemsa stained blood smears), serological (DAT, IFAT-polyvalent, IgM, IgG tests) and molecular (PCR) tests, revealed 10.7% seroprevalence and 42.8% T. cruzi-infection, in individuals from rural localities and referred patients, respectively. In both groups T. cruzi-infection was detected at any age, revealing active transmission in children under 10-years-old. Clinical profile detected in referred patients, showed significantly major number of symptoms in orally infected patients than in infected by vectorial route (P<0.01). Genetic characterization of T. cruzi isolates obtained from orally and vectorial transmitted acute Chagas disease in western Venezuela, revealed the circulation of DTUI and DTUIII in the former, and DTUI, DTUII and DTUIII in patients infected by vectorial route. DTUI predominated in both cases, and haplotype Ib was the most frequently found in this genotype. Statistical analysis of clinical profile - T. cruzi DTUs - transmission route relationships did not show association among these variables and, consequently, chagasic patient's clinical condition did not depend of T. cruzi genotype or its route of transmission. In addition, differences in clinical severity may be associated with host susceptibility and/or parasite load received by the human receptor in spite of the T. cruzi genotype itself. The epidemiological implications of the present findings are discussed, and the need for developing efficient tools as well as implementation of urgent and radical changes in the public health policy to control Chagas disease transmission in the Venezuelan territory are suggested.

Rapid immunochromatographic tests for the diagnosis of chronic Chagas disease in at-risk populations: A systematic review and meta-analysis

BACKGROUND

Despite of a high disease burden, mainly in Latin America, Chagas disease (CD) is underdiagnosed and undertreated. Rapid diagnostic tests (RDTs) might improve the access to diagnosis. The aim of this study is to review the accuracy of commercially available RDTs used in field conditions for the diagnosis of chronic CD in populations at risk, in endemic and non-endemic countries.

METHODS/PRINCIPAL FINDINGS

We undertook a comprehensive search of the following databases: PubMed, SCOPUS, LILACS (last up-date on the 01st July, 2017), without language or date limits. Non-electronic sources have been also searched. This review included clinical studies with cohort recruitment of individuals at risk of T. cruzi exposure, without age limits; adequate reference standards for the diagnosis of CD. We excluded case-control studies and those testing RDTs during acute CD. Data on test accuracies were pooled through a bivariate random-effects model. Only one index test was evaluated separately. Geographical area, commercial brand, disease prevalence, study size, and risk of bias were explored as possible source of heterogeneity. Values of sensitivity and specificity were computed to obtain summary positive/negative likelihood ratios, and summary diagnostic odds ratio. Ten studies were included on six different immunochromatographic RDTs. The pooled sensitivity and specificity of the RDTs resulted 96.6% (95% CI 91.3-98.7%) and 99.3% (95% CI 98.4-99.7%), respectively. Test accuracy was particularly good in endemic areas (98.07%/99.03% of sensitivity/specificity, respectively). One test (Stat-Pak) showed an overall sensitivity of 97% (95% CI 87.6-99.3) and specificity of 99.4% (95% CI 98.6-99.8).

CONCLUSIONS/SIGNIFICANCE

RDTs demonstrated to be sufficiently accurate to recommend their use for screening in endemic areas, even as stand-alone tests. This approach might increase the accessibility to the diagnosis. However, an additional confirmatory test in case of positive result remains a prudent approach.

Trypanosoma cruzi Infection in an Indigenous Kariña Community in Eastern Venezuela

We investigated the seroprevalence of Trypanosoma cruzi infection in an indigenous Kariña population in eastern Venezuela. A total of 175 serum samples were collected in the community of Piñantal during February 2009. Interviews targeting socioeconomic and environmental factors associated with the T. cruzi transmission were also conducted. Samples were evaluated using trypomastigote excreted/secreted antigens (TESAs) in an ELISA format. TESA-ELISA positive samples were confirmed by indirect haemagglutination (HAI) (Wiener). A nonsystematic collection of vectors was also undertaken. T. cruzi seroprevalence was 7.43% according to both assays, and the mean age of infected patients was 48.61±10.40 years (range 34 to 73 years). The vector infection rate was 20.00% (2/10). T. cruzi seropositivity was associated with a history of triatomine bites, the ability to recognize the vector and poor knowledge about Chagas disease, but no associations were found with gender, house type, knowledge of how the disease is transmitted, or the presence of vectors or animals inside dwellings. To our knowledge, this is the first study of the seroprevalence of T. cruzi in an indigenous population in eastern Venezuela. All of the epidemiological variables required for the establishment of active vectorial transmission of T. cruzi were present in this community.

Characterization of Trypanosoma cruzi telomerase

High telomerase activity is always associated with actively dividing cells, however the detection of this activity in dividing Leishmania and Trypanosoma cruzi cells has always been disappointingly low. Recently, we have found that Leishmania major telomerase activity can be activated by heat, which combined with dilutions of the nuclear extracts produced an increase in activity comparable to cancer cells. Here we examined whether T. cruzi telomerase shares the same physicochemical properties of primer specificity and overall features of the L. major. Our studies revealed that no telomerase inhibitory factors were present in the nuclear lysates of T. cruzi however the enzyme was activated by heat and was very resilient to heat denaturation. We also showed the extension primer specificity, susceptibility to RNase-A and RNase-H digestion, and the effect of telomerase inhibitors.

Trypanosoma cruzi persistence at oral inflammatory foci in chronic chagasic patients

The persistence of Trypanosoma cruzi in seropositive individuals, previously diagnosed as chronic chagasic patients (CCP), was detected for the first time in biopsies taken from gingival inflammatory foci processed by polymerase chain reaction (PCR). Seven out of 31 (22.5%) gum samples from selected unquestionably CCP showing different degrees of gingival inflammation revealed T. cruzi-DNA using 3 specific PCR assays. All the included CCP had been diagnosed in previous studies carried out over the last 19 years. Samples of inflamed gums were recently taken from the indicated patients at: an outpatient hospital cardiac unit; a village where Chagas disease is endemic; and a specialized diagnostic research center, showing molecular evidence of parasite persistence in 17.6%, 42.8% and 14.3% of them, respectively. The relatively frequent parasite persistence, demonstrated here in oral inflammatory processes of treated and/or untreated patients bearing long term T. cruzi-infection, suggests the establishment of secondary small foci for the maintenance of hidden or inapparent chagasic infection. The easy and low-risk, non-invasive method to get the sample may add the use of gingival biopsy as a potential alternative diagnostic tool to confirm T. cruzi-infection in CCP. The significance of T. cruzi persistence as a primary cause of chronic Chagas disease and the proposal of this mechanism to explain the pathogenesis in CCP are considered.

Infected dogs as a risk factor in the transmission of human Trypanosoma cruzi infection in western Venezuela

A total of 565 mongrel dogs from rural localities of Venezuela were examined by serological (DAT, IFAT and ELISA) and parasitological tests to address the status of Trypanosoma cruzi infection and to evaluate their role in the transmission of the infection to human population. The overall percentage of sero-positive infected dogs shown to be 67.6% (382/565):253 (61.7%) from 47 villages belonging to 8 states located at 4 different geographical regions of western Venezuela and 129 (33.5%) dogs from 48 households located in areas where Chagas disease is endemic. From 101 sampled dogs living in close proximity to 30 acute chagasic patients, 84% expressed specific anti-T. cruzi antibodies (Ab) with 12 of them (14%) showing blood circulating parasites (BCP). In these houses a high proportion of sero-positive people (20%) and frequent indoor infestation by triatomine-bugs (70%) was also recorded. The analysis revealed that from the 47 rural villages sampled during the study, 91.5% had the presence of T. cruzi sero-positive dogs, ranging from 62% positive localities at the states of Falcon and Cojedes to 100% in the other six studied Venezuelan states. This demonstrates that T. cruzi-infected dogs are found throughout all the geographical regions of western Venezuela irrespective of their ecological differences. Molecular typing of T. cruzi isolates from infected dogs using ribosomal and mini-exon gene markers, revealed the presence of both T. cruzi I and T. cruzi II lineages. The coincidence in the circulation of T. cruzi II in dog and human populations at the same locality and at the same time is reported and its significance is discussed. The combined serological, parasitological, epidemiological and molecular data is gathered here to call the attention on the presence of infected dogs as a risk factor in the maintenance of T. cruzi as a source for infection to humans.

Predominance of lineage I among Trypanosoma cruzi isolates from Venezuelan patients with different clinical profiles of acute Chagas' disease

Trypanosoma cruzi isolates from 23 acute chagasic patients from localities of Western Venezuela (state of Barinas) where Chagas' disease is endemic were typed using ribosomal and mini-exon gene markers. Results showed that isolates of the two major phylogenetic lineages, T. cruzi I and T. cruzi II, were isolated from these patients. Six isolates (26%) were typed as T. cruzi II and 17 (74%) as belonging to T. cruzi lineage I. Analysis of random amplified polymorphic DNA (RAPD) patterns confirmed these two groups of isolates, but did not disclose significant genetic intra-lineage polymorphism. Patients infected by both T. cruzi I or T. cruzi II showed different clinical profiles presenting highly variable signs and symptoms of acute phase of Chagas' disease ranging from totally asymptomatic to severe heart failure. The predominance of T. cruzi I human isolates in Venezuela allied to the higher prevalence of severe symptoms of Chagas' disease (heart failure) in patients infected by this lineage do not corroborate an innocuousness of T. cruzi I infection to humans. To our knowledge, this is the first study describing predominance of T. cruzi lineage I in a large number of acute chagasic patients with distinct and well-characterized clinical profiles.

Update on Chagas disease in Venezuela: a review

The present article reviews the status of Chagas disease in Venezuela based on the detection of Trypanosoma cruzi infections both in referred patients with clinical presumptive diagnosis (1988-2002) and in individuals sampled from rural localities representative of the different geographical regions of the country (1995-2002). In the former group from 306 individuals examined, 174 (56.8%) were seropositive to T. cruzi; 73 (42%) in the acute phase with 52 (71%) showing blood circulating parasites, and from these 38% were children under 10 years old. The other 101 (58%) showed chronic infection at different degrees of cardiac complication. In addition, serologic examination of 3835 individuals from rural areas revealed 11.7% seroprevalence. From these, 8.5% (38/448) were children aged from 0 to 10 years old. These figures suggest that Chagas disease may be re-emerging in Venezuela judging for the active transmission detected during the last decade. The success of the Venezuelan anti-chagasic campaign during the last 40 years is evaluated in the frame of the present results. The epidemiological situation is discussed and recommendation to consider Chagas disease as a national priority is given.

Detection of Trypanosoma cruzi and Trypanosoma rangeli infection by duplex PCR assay based on telomeric sequences

We used the species specificity and repetitious nature of subtelomeric kinetoplastida sequences to generate a duplex PCR assay for the simultaneous detection of Trypanosoma cruzi and Trypanosoma rangeli in experimentally and naturally infected triatomine (Reduviid) bugs and in infected human subjects. The assay was species specific and was capable of detecting 1/20th of T. cruzi and 1/4th of T. rangeli cell equivalents without complementary hybridization. In addition, the PCR-based assay was robust enough for direct application to difficult biological samples such as Reduviid feces or guts and was capable of recognizing all T. cruzi and T. rangeli strains and lineages. Because the assay primers amplify entirely different target sequences, no reaction interference was observed, facilitating future adaptation of this assay to an automated format.