Date Published: January 25, 2019
Publisher: Public Library of Science
Author(s): Carolina Valença-Barbosa, Teresa Cristina Bergamo do Bomfim, Bernardo Rodrigues Teixeira, Rosana Gentile, Sócrates Fraga da Costa Neto, Bárbara Souza Neil Magalhães, Daniel de Almeida Balthazar, Fabio Alves da Silva, Renata Biot, Claudia Masini d’Avila Levy, Helena Lúcia Carneiro Santos, Abdallah M. Samy.
The enteric protist Blastocystis is one of the most frequently reported parasites infecting both humans and many other animal hosts worldwide. A remarkable genetic diversity has been observed in the species, with 17 different subtypes (STs) on a molecular phylogeny based on small subunit RNA genes (SSU rDNA). Nonetheless, information regarding its distribution, diversity and zoonotic potential remains still scarce, especially in groups other than primates. In Brazil, only a few surveys limited to human isolates have so far been conducted on Blastocystis STs. The aim of this study is to determine the occurrence of Blastocystis subtypes in non-human vertebrate and invertebrate animal groups in different areas of the state of Rio de Janeiro, Brazil. A total of 334 stool samples were collected from animals representing 28 different genera. Blastocystis cultivated samples were subtyped using nuclear small subunit ribosomal DNA (SSU rDNA) sequencing. Phylogenetic analyses and BLAST searches revealed six subtypes: ST5 (28.8%), ST2 (21.1%), ST1 and ST8 (19.2%), ST3 (7.7%) and ST4 (3.8%). Our findings indicate a considerable overlap between STs in humans and other animals. This highlights the importance of investigating a range of hosts for Blastocystis to understand the eco-epidemiological aspects of the parasite and its host specificity.
Blastocystis is a genus of unicellular anaerobic eukaryotic organisms in the diverse Stramenopiles group that includes brown algae, diatoms, slime nets and water molds [1–3]. It is a cosmopolitan enteric parasite and one of the most common protist parasites worldwide. The ability of Blastocystis to cause gastrointestinal and other diseases has been questioned, but the parasite undoubtedly possesses pathogenic potential although its virulence mechanisms are not well understood [4, 5].
We analyzed 334 stool samples from 28 different animal genera. Overall occurrence of Blastocystis in fecal cultures was 34.4% (115/334) or 1/1 (100%) in the case of the armadillo, 21/26 (81%) in marsupials, 30/39 (77%) in pigs, 9/13 (69%) in reptiles, 7/11(64%) in rodents, 33/89 (37%) in NHPs, 12/57 (21%) in birds, and 2/96 (2%) in cockroaches (Table 1).
This is the first study of Blastocystis subtypes in a variety of non-human animal hosts in Brazil. Blastocystis has a wide host range, with subtypes overlapping in several animal genera. Our study highlights the large genetic diversity between Blastocystis isolates from animals, provides the first molecular evidence from armadillo and Nectomys squamipes, and of the presence of different Blastocystis subtypes in cockroaches (ST4), rodents (ST8), pigs (ST4 and ST8).
Our results indicate a considerable overlap between Blastocystis subtypes across in different hosts. Future studies should extend our findings need and investigate a larger number of samples and animal orders, so as to better understand the ecology, epidemiology and host specificity of Blastocystis. Our findings also further contribute to defining the genetic characteristics of Blastocystis in different hosts in Brazil and other countries.