Enteric pathogens, which are frequently food- and waterborne transmitted, are highly abundant in Indigenous people living in remote rural areas of Colombia. As the frequency of gastroenteritis in the tropics shows seasonal differences, we analyzed variations of pathogen patterns in the stool samples of a Colombian Indigenous tribe called Wiwa during the dry (n = 105) and the rainy (n = 227) season, applying real-time PCR from stool samples and statistical analysis based on a multi-variable model. Focusing on bacterial pathogens, increased detection rates could be confirmed for enteropathogenic, enterotoxigenic and enteroaggregative Escherichia coli with a tendency for an increase in Campylobacter jejuni detections during the rainy season, while there was no seasonal effect on the carriage of Tropheryma whipplei. Salmonellae were recorded during the rainy season only. A differentiated pattern was seen for the assessed parasites. Entamoeba histolytica, Necator americanus and Trichuris trichiura were increasingly detected during the rainy season, but not Ascaris lumbricoides, Giardia duodenalis, Hymenolepis nana, Strongyloides stercoralis, and Taenia solium, respectively. Increased detection rates during the dry season were not recorded. Negative associations were found for Campylobacter jejuni and Giardia duodenalis with age and for Tropheryma whipplei with the body mass index, respectively. Positive associations of enteropathogenic Escherichia coli and Taenia solium detections were observed with age. In conclusion, facilitating effects of the tropical rainy season were more pronounced on bacterial enteric pathogens compared to enteropathogenic parasites.

Fecal-orally transmitted cyclosporiasis is frequent in remote resource-limited settings in Central and South America with poor hygiene conditions. In this study, we aimed at assessing seasonal effects on the epidemiology of colonization or infection with C. cayetanensis in Colombian indigenous people living under very restricted conditions. In the rainy season between July and November and in the dry season between January and April, stool samples from indigenous people with and without gastrointestinal symptoms were collected and screened for C. cayetanensis applying in-house real-time polymerase chain reaction (PCR). In the rainy season and in the dry season, positive PCR results were observed for 11.8% (16/136) and 5.1% (15/292), respectively, with cycle threshold (Ct) values of 30.6 (±3.4) and 34.4 (±1.6), respectively. Despite higher parasite loads in the rainy season, fewer individuals (2/16, 12.5%) reported gastrointestinal symptoms compared to the dry season (6/15, 40%). In conclusion, considerable prevalence of C. cayetanensis in Colombian indigenous people persists in the dry season. Low proportions of gastrointestinal symptoms along with higher parasite loads make colonization likely rather than infection.

The Kogui tribe is an indigenous population living in Colombia. The prevalence values of some enteric bacteria, parasites and microsporidia in Kogui stool samples (n = 192) were assessed by real-time polymerase chain reaction (PCR). Thus, genus- or species-specifically recorded positivity rates among the Kogui community were assessed. Protozoa were the leading microorganisms in the stool samples of the Kogui, with an average of 1.5 pathogens per sample, followed by bacteria, with 0.6 pathogens per samples and helminths, with 0.3 pathogens per sample. Microsporidia were not detected. Thereby, the majority of detected protozoa comprised species with questionable etiological relevance such as Blastocystis hominis (n = 173) and Dientamoeba fragilis (n = 44), but also a considerable proportion of Giardia duodenalis (n = 71). Cryptosporidium spp., in contrast, was found in a single instance only. The majority of recorded bacteria were Campylobacter spp., with a strikingly high proportion of 50% (n = 96), followed by Shigella spp./enteroinvasive E. coli (EIEC) (n = 14) and Aeromonas spp. (n = 4). The quantitatively most important detected helminths were Ascaris spp. (n = 15), Hymenolepis spp. (n = 14) and Trichuris trichiura (n = 12), followed by Necator americanus (n = 6), Taenia spp. (n = 3) and Strongyloides stercoralis (n = 3) in descending order of abundance. As expected, the Kogui people’s living conditions comprising poverty, lack of access to clean water and simple housing favor a high number of gastrointestinal infections. Preventive approaches are needed to reduce their risk of infection.

For the molecular diagnosis of Chagas disease by real-time PCR (polymerase chain reaction), optimization of diagnostic accuracy is desirable. The detection limit of real-time PCR assays for the diagnosis of Trypanosoma cruzi in human serum is affected by various influences including the choice of the nucleic acid extraction assay. In this study, three nucleic acid extraction assays were compared regarding their influence on the sensitivity of a T. cruzi-specific real-time PCR with 62 reference sera containing T. cruzi target DNA (deoxyribonucleotide acid). More than 95% of the positive sera were correctly identified after all three nucleic acid extraction strategies with a detection rate ranging from 96.8% (60/62) for the worst assay to 100% (62/62) for the best one. A matched pairs analysis for the comparison of the cycle threshold (Ct) values obtained with the 59 reference samples with positive real-time PCR results after all three nucleic acid extraction schemes indicated differences in a range of about 3 Ct steps. Summarized, all three compared nucleic acid extraction schemes were basically suitable for T. cruzi-specific PCR from serum with some minor differences. However, in the case of low quantities of circulating parasite DNA in the serum of a patient with Chagas disease, even minor effects can make a difference in the individual diagnosis.

This study was performed to comparably assess two commercial real-time PCR assays for the identification of Trypanosoma cruzi DNA in serum. A total of 518 Colombian serum samples with high pre-test probability for infections with either T. cruzi or apathogenic Trypanosoma rangeli were assessed. The assessment comprised the NDO real-time PCR (TIB MOLBIOL, ref. no. 53-0755-96, referred to as the TibMolBiol assay in the following) with specificity for T. cruzi and the RealStar Chagas PCR Kit 1.0 (altona DIAGNOSTICS, order no. 611013, referred to as the RealStar assay in the following) targeting a kinetoplast sequence of both T. cruzi and T. rangeli without further discrimination. To discriminate between T. cruzi- and T. rangeli-specific real-time PCR amplicons, Sanger sequencing results were available for a minority of cases with discordant real-time PCR results, while the amplicons of the remaining discordant samples were subjected to nanopore sequencing. The study assessment indicated a proportion of 18.1% (n = 94) T. cruzi-positive samples next to 24 samples (4.6%) containing DNA of the phylogenetically related but apathogenic parasite T. rangeli. The observed diagnostic accuracy as expressed by sensitivity and specificity was 97.9% (92/94) and 99.3% (421/424) with the TibMolBiol assay and 96.8% (91/94) and 95.0% (403/424) with the RealStar assay, respectively. Reduced specificity resulted from cross-reaction with T. rangeli in all instances (3 cross-reactions with the TibMolBiol assay and 21 cross-reactions with the RealStar assay). DNA from the six discrete typing units (DTUs) of T. cruzi was successfully amplified by both real-time PCR assays. In summary, both assays showed a comparable diagnostic accuracy for the diagnosis of T. cruzi from human serum, with a slightly higher specificity seen for the TibMolBiol assay. The pronounced co-amplification of DNA from apathogenic T. rangeli according to the RealStar assay may be a disadvantage in areas of co-circulation with T. cruzi, while the test performance of the two compared assays will be quite similar in geographic settings where T. rangeli infections are unlikely.