Detection of Cryptosporidium spp. oocysts and Giardia spp. cysts in surface water destined for public supply in the state of Goiás, Brazil

Abstract

The protozoa Cryptosporidium spp. and Giardia spp. are etiological agents responsible for the transmission of gastroenteritis, mainly due to the consumption of contaminated water. Their (oo)cysts are resistant to adverse environmental conditions, as well as to most conventional water treatment processes. Thus, the objective of this work was to evaluate the occurrence of (oo)cysts of these protozoans in surface water collected for human consumption in the state of Goiás, Brazil. Fifteen samples of raw water were collected to assess the occurrence of (oo)cysts of the protozoa using the Membrane Filtration method, in addition to turbidity and pH analyses. Recovery rates in tests with ultrapure water reached the USEPA (2012) criteria for Giardia (78.1% ± 0%) and for Cryptosporidium (60.6% ± 32.6%); however, recovery in raw water was lower due to turbidity. All samples (n = 15) were positive for Cryptosporidium spp. oocysts, with a maximum concentration of 250 oocysts/L, demonstrating that these protozoa are disseminated in the aquatic environment of the state of Goiás and pose a risk to public health. Due to the use of water sources for public consumption, it is recommended that public authorities and sanitation companies act to preserve and maintain water courses, carry out periodic monitoring of treatment plants that supply the Cerrado, Santana and São Manoel streams and improve existing treatment technologies. The results did not allow to infer whether animal load and grazing area promote an increase in contamination of the lotic aquatic systems.

Risk to human health from protozoan (oo)cysts in water treatment plants

“…The ease of implementation, the possibility of preserving (oo)cysts for future infectivity tests (MACIEL & SABOGAL-PAZ, 2016), and the use in research involving water supply sources in different regions in the world (ALMEIDA et al, 2015;BAUTISTA et al, 2018;SILVA & SCALIZE, 2020) were other criteria for choosing the aforementioned technique.…”

“…and Cryptosporidium spp. have been detected in surface water in different Brazilian cities (SATO et al, 2013;OLIVEIRA, 2017;SILVA;SCALIZE, 2020) and regions worldwide (NISHI et al, 2009;NAKADA et al, 2019). Outbreaks caused by the (oo)cysts of these pathogens occur due to their high infectivity in addition to resistance to environmental conditions and the treatment of conventional chlorination (THOMPSON, 2004;KARANIS, 2011).…”