Asymptomatic protozoa community infections in humans from southwestern China

Abstract

Background: Giardia.lamblia (G.lamblia), Entamoeba histolytica (E.histolytica), Blastocyistis hominis (B. hominis ) and Cryptosporidium spp. infections have been frequently reported as etiological agents for gastroenteritis but also as common gut inhabitants in healthy individuals. Co-infections with protozoa pathogens were previously described but little is known about whether these assemblages are purely random or structured in communities. Methods From 1st July 2016 to 31st March 2017, fresh stool samples were collected from randomly selected individuals in sentinel hospitals in Tengchong City, Yunnan Province, China. molecular biology method was used to detect G.lamblia, E.histolytica, Cryptosporidium spp and B. hominis. Sequencing was applied to confirm the these protozoon genotypes. The data analysis method was involved chi-square test, multivariable logistic regression, null models and Partial least square regression (PLSR) methods with R 3.2 software. Results: The prevalence of the four enteric protozoa in all subjects were (in order of frequency of detection) : B.hominis 9.5% [95%Confidence Interval (CI) 7.1-12.4%], G.lamblia 2.2% (95%CI 1.1-3.8%); E.hystolitica 2.0% (95%CI 0.9-3.6%) whereas Cryptosporidium spp. was not detected at all. The prevalence of, at least, one enteric protozoa was 12.4% (95%CI 9.7-15.6), and the prevalence of 2 different enteric protozoa species was 1.2% (95%CI 0.4-2.6). The most common co-infection found was E.histolytica and B.hominis, (1.0%; 95%CI 0.3-2.2). Regarding genetic profiles, 10 out of 11 G.lamblia strains were classified in assemblage A, sub-assemblage I, and 1 sample was classified in assemblage B, sub-assemblage IV. B.hominis was detected in 48 samples, 25 were classified as genotype III, 13 as genotype I, 8 samples as genotype VII and the 2 remaining isolates as genotype IV. Our null modelling confirmed the random protozoa co-occurrence and our PLSR analysis the lack of association between these enteric pathogens and clinical symptomatology. Conclusions: The occurrence of these enteric protozoa was purely random. Not specific interactions were detected between the four protozoa studied and neither their presence, jointly or separately, nor the patient’s age were predictors for developing clinical symptoms associated with these pathogens. Further research including a broader range of pathogen species is needed to address remaining knowledge gaps in co-infections and diarrhoeal disease.