Investigation of potential zooanthroponotic transmission of cryptosporidiosis and giardiasis through agricultural use of reclaimed wastewater∗

∗Note: Nucleotide sequence data reported in this paper are available in the GenBank under the Accession numbers DQ114992 to DQ115005 and DQ116604 to DQ116625.

Abstract

A field study in the Juarez Valley of Mexico was performed to investigate the potential transmission of Cryptosporidium and Giardia to sheep livestock grazing on forage irrigated with reclaimed wastewater, and the potential for disease transmission back to humans. United States Environmental Protection Agency Method 1623 immunofluorescent assay (IFA) revealed high levels of pathogens in reclaimed wastewater, with 183 to >7000 Giardia cysts and 9 – 762 Cryptosporidium oocysts detected per litre. Infectious Cryptosporidium were detected in the reclaimed wastewater using the cell culture focus detection method (FDM). Polymerase chain reaction (PCR) analyses revealed reclaimed wastewater contained the C. parvum bovine (zoonotic) genotype, human-specific C. hominis subgenotypes, and G. lamblia (syn. G. duodenalis, G. intestinalis) Assemblage A genotypes (A2 and A3). Despite high levels of Cryptosporidium and Giardia in the reclaimed wastewater, these pathogens were rarely found on the forage plants, possibly due to environmental attenuation. Sheep fecal specimens were positive for only livestock-associated G. lamblia Assemblage E genotypes. Therefore, in this field study, there was no evidence of zooanthroponotic transmission of Cryptosporidium or Giardia.

Keywords:

• Giardia lamblia (syn. G. duodenalis, G. intestinalis)
• Cryptosporidium parvum
• Cryptosporidium hominis
• zoonoses
• cell culture
• reclaimed wastewater

Acknowledgements

We thank Anthony Sisk and Adriana Galindo for their technical assistance. We are grateful to Greg Sturbaum for his critical review of the manuscript. We thank Carlos Mendez for his comments on border region water quality issues. This study was funded by the Paso del Norte Health Foundation – Center for Border Health Research; Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture under Agreement No. 2003-34461-13278; and the Texas Agricultural Experiment Station, Texas A&M University System.

Notes

∗Note: Nucleotide sequence data reported in this paper are available in the GenBank under the Accession numbers DQ114992 to DQ115005 and DQ116604 to DQ116625.