The opportunistic protist, Giardia intestinalis , occurs in gut-healthy humans in a high-income country

Abstract

Giardia intestinalis , a cosmopolitan gastrointestinal protist, is detected mainly in patients with clinical giardiasis in high-income countries. In contrast, there is very little information on the presence of Giardia in asymptomatic individuals. Therefore, the aim of this study was to determine the presence and prevalence of Giardia in gut-healthy volunteers in the Czech Republic and to perform a comparative evaluation of different diagnostic methods, since Giardia diagnostics is complicated. Our results confirmed that the qPCR method is the most sensitive method for detecting Giardia and revealed a prevalence of 7% (22/296) in asymptomatic individuals. In most cases, the colonization intensity ranged from 10 −1 –10 1 . A conventional PCR protocol targeting the TPI gene was used to identify the assemblages. However, this protocol had limited sensitivity for Giardia amplification, effectively detecting colonization above an intensity of 10 4 . In addition, Giardia was detected in 19% of the animals, which were closely associated with the study participants. However, due to methodological limitations, zoonotic transmission could not be clearly confirmed. Notably, contact with animals proved to be the only factor that had a significant impact on the incidence of Giardia in gut-healthy humans.

Protozoan Infections Acquired from Food or Drinking Water: An Update

“…Metabarcoding at the glutamate dehydrogenase gdh locus showed that assemblage B comprises multiple variants [176]. Currently, the possibility that Giardia assemblages could represent distinct species is under consideration [15].…”

“…intestinalis is ranked 11th In the FAO/WHO risk management list of intestinal parasites [19], is responsible for approximately 180 million symptomatic infections annually and several studies indicated that its prevalence in the stool of asymptomatic children was between 17% and 18% in Spain and between 18% and 64% in subtropical countries such as Brazil, Ethiopia, Argentina, and Mozambique. Asymptomatic colonization occurs also in animals and a higher prevalence was observed in individuals with animal contact regardless of the type of animal [15].…”

“…In 1987, the World Health Organization (WHO) declared that protozoan parasites commonly transmitted by contaminated food and water, mainly Entamoeba histolytica, Cryptosporidium spp., and Giardia intestinalis (also denominated G. lamblia or G. duodenalis [15]), represent a heavy public health concern and cause malapsorption in children especially in developing countries [16]. These…”

Food and Drinking Water as Sources of Pathogenic Protozoans: An Update

“…These organisms colonize the small intestine of mammals [138]. G. intestinalis is divided into assemblages, or subtypes, A-H, and sub-assemblages are distinguished based on different conventional PCR or qPCR assays on genes encoding the small subunit ribosomal RNA (SSU rRNA), glutamate dehydrogenase (gdh), triosephosphate isomerase (tpi) or β-giardin (bg) [15,139]. Assemblages A and B have a wide host range and cause most infections in humans with the latter responsible for most cases.…”

“…In 1987, the World Health Organization (WHO) designated some of the protozoan parasites commonly transmitted through contaminated food and water-namely Cryptosporidium spp., Entamoeba histolytica, and Giardia intestinalis (basonyms G. lamblia and G. duodenalis [15])-as a heavy public health concern since they cause malabsorption in children mainly in developing countries [16]. These microorganisms cause intestinal parasitic infections (IPIs) with prolonged diarrhea that impairs children's growth [17].…”