Prevalence of intestinal parasites, with emphasis on the molecular epidemiology of Giardia duodenalis and Blastocystis sp., in the Paranaguá Bay, Brazil: a community survey

Parasit Vectors. 2018 Aug 30;11(1):490. doi: 10.1186/s13071-018-3054-7.


Background: Intestinal protozoan parasites are major contributors to the global burden of gastrointestinal disease causing significant socioeconomic consequences. Children living in resource-poor settings with restricted access to water and sanitary services are particularly at risk of these infections.

Methods: A prospective, community-based, cross-sectional survey was conducted in Paraná (southern Brazil) between May 2015 and May 2016. A total of 766 stool samples were individually collected from volunteers (male/female ratio: 0.99; age range: 0-76 years) and used for investigating the presence of intestinal helminth and protozoan species by routine microscopic procedures including the Kato-Katz and modified Ritchie concentration methods and the Ziehl-Neelsen stain technique. Quantitative real-time PCR confirmed microscopy-positive samples for Giardia duodenalis and the assemblages and sub-assemblages determined by multilocus sequence-based genotyping of the glutamate dehydrogenase (gdh) and β-giardin (bg) genes of the parasite. Identification of Blastocystis subtypes was carried out by amplification and sequencing of a partial fragment of the small-subunit ribosomal RNA gene (SSU rDNA) of this heterokont microorganism.

Results: Overall, 46.1% (353/766) of the participants were infected/colonised by at least one intestinal parasite/commensal species. Protozoan and helminth species were detected in 42.7% and 10.1% of the surveyed population, respectively. Blastocystis sp. (28.2%), Endolimax nana (14.9%), and Giardia duodenalis (11.0%) were the most prevalent species found among protozoans and Ascaris lumbricoides (5.0%), Trichuris trichiura (4.6%) and hookworms (1.0%) among helminths. A total of 38 G. duodenalis-positive samples were genotyped at gdh and bg markers, revealing the presence of the sub-assemblages AII (47.4%), AII/AIII (2.6%), BIII (5.3%), BIV (26.3%) and BIII/BIV (13.1%). Two samples (5.3%) were only identified as assemblage B. AII was predominantly found in females aged 5-9 years and was associated with a higher likelihood of reporting gastrointestinal symptoms. A total of 102 Blastocystis-positive samples were successfully subtyped at the SSU rRNA gene revealing the presence of ST1 (36.3%), ST2 (15.7%), ST3 (41.2%), ST4 (2.9%), ST6 (1.0%) and ST8 (2.9%).

Conclusions: Data presented here indicate that enteric parasites still represent a pressing health concern in Paraná, Brazil, probably due to sub-optimal water, sanitation and hygiene conditions. A mostly anthroponotic origin is suspected for G. duodenalis and Blastocystis sp. infections.

Keywords: Brazil; Community; Genotyping; Helminth; Human; Intestinal parasites; Microscopy; Nematode; Protozoa; Soil-transmitted helminths.

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Blastocystis / genetics*
  • Blastocystis Infections / epidemiology*
  • Blastocystis Infections / parasitology
  • Brazil / epidemiology
  • Child
  • Child, Preschool
  • Cross-Sectional Studies
  • DNA, Ribosomal
  • Feces / parasitology
  • Female
  • Genetic Variation
  • Giardia lamblia / genetics*
  • Giardiasis / epidemiology*
  • Giardiasis / parasitology
  • Humans
  • Infant
  • Infant, Newborn
  • Intestinal Diseases, Parasitic / epidemiology*
  • Intestinal Diseases, Parasitic / parasitology
  • Male
  • Middle Aged
  • Prevalence
  • Prospective Studies
  • Residence Characteristics / statistics & numerical data
  • Surveys and Questionnaires
  • Young Adult


  • DNA, Ribosomal