title: Evaluation of a strategy for Toxoplasma gondii oocyst detection in water.
abstract: Several recent outbreaks of toxoplasmosis were related to drinking water. We propose a strategy for Toxoplasma oocyst detection as part of an approach to detecting multiple waterborne parasites, including Giardia and Cryptosporidium spp., by the U.S. Environmental Protection Agency method with the same sample. Water samples are filtered to recover Toxoplasma oocysts and purified on a sucrose density gradient. Detection is based on PCR and mouse inoculation (bioassay) to determine the presence and infectivity of recovered oocysts. In an experimental seeding assay with 100 liters of deionized water, a parasite density of 1 oocyst/liter was successfully detected by PCR in 60% of cases and a density of 10 oocysts/liter was detected in 100% of cases. The sensitivity of the PCR assay varied from less than 10 to more than 1000 oocysts/liter, depending on the sample source. PCR was always more sensitive than mouse inoculation. This detection strategy was then applied to 139 environmental water samples collected over a 20-month period. Fifty-three samples contained PCR inhibitors, which were overcome in 39 cases by bovine serum albumin addition. Among 125 interpretable samples, we detected Toxoplasma DNA in 10 cases (8%). None of the samples were positive by mouse inoculation. This strategy efficiently detects Toxoplasma oocysts in water and may be suitable as a public health sentinel method.
authors.affiliation: Laboratoire de Parasitologie-Mycologie, CHU Maison Blanche, 45 rue Cognacq-Jay, 51092 Reims, France. ivillena@chu-reims.fr
authors.forename: Isabelle
authors.initials: I
authors.lastname: Villena
authors.forename: Dominique
authors.initials: D
authors.lastname: Aubert
authors.forename: Philippe
authors.initials: P
authors.lastname: Gomis
authors.forename: Hubert
authors.initials: H
authors.lastname: Ferté
authors.forename: Jean-Christophe
authors.initials: JC
authors.lastname: Inglard
authors.forename: Hélène
authors.initials: H
authors.lastname: Denis-Bisiaux
authors.forename: Julie-Muriel
authors.initials: JM
authors.lastname: Dondon
authors.forename: Eric
authors.initials: E
authors.lastname: Pisano
authors.forename: Naïma
authors.initials: N
authors.lastname: Ortis
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Pinon
mesh_terms: D000818:Animals; D001681:Biological Assay; D016054:DNA, Protozoan / Q000032:analysis; D005260:Female; D005374:Filtration; D051379:Mice; D033661:Oocysts / Q000302:isolation & purification*; D016133:Polymerase Chain Reaction; D014122:Toxoplasma / Q000302:isolation & purification*; D014867:Water / Q000469:parasitology*; D014881:Water Supply
chemical_list: D016054:DNA, Protozoan; D014867:Water