Description:
<jats:title>ABSTRACT</jats:title>
<jats:p>
Knowledge of host specificity, combined with genomic sequencing of
<jats:named-content content-type="genus-species">Giardia</jats:named-content>
and
<jats:named-content content-type="genus-species">Cryptosporidium</jats:named-content>
spp., has demonstrated a microbial source tracking (MST) utility for these common waterborne microbes. To explore the source attribution potential of these pathogens, water samples were collected in a mixed rural-urban watershed in the Township of Langley, in southwestern British Columbia (BC), Canada, over a 2-year period.
<jats:named-content content-type="genus-species">Cryptosporidium</jats:named-content>
was detected in 63% of surface water samples at concentrations ranging from no positive detection (NPD) to 20,600 oocysts per 100 liters.
<jats:named-content content-type="genus-species">Giardia</jats:named-content>
was detected in 86% of surface water samples at concentrations ranging from NPD to 3,800 cysts per 100 liters of water. Sequencing at the 18S rRNA locus revealed that 50% of
<jats:named-content content-type="genus-species">Cryptosporidium</jats:named-content>
samples and 98% of
<jats:named-content content-type="genus-species">Giardia</jats:named-content>
samples contained species/genotypes (
<jats:named-content content-type="genus-species">Cryptosporidium</jats:named-content>
) or assemblages (
<jats:named-content content-type="genus-species">Giardia</jats:named-content>
) that are capable of infecting humans, based on current knowledge of host specificity and taxonomy.
<jats:named-content content-type="genus-species">Cryptosporidium</jats:named-content>
genotyping data were more promising for source tracking potential, due to the greater number of host-adapted (i.e., narrow-host-range) species/genotypes compared to
<jats:named-content content-type="genus-species">Giardia</jats:named-content>
, since 98% of
<jats:named-content content-type="genus-species">Giardia</jats:named-content>
isolates were zoonotic and the potential host could not be predicted. This report highlights the benefits of parasite genomic sequencing to complement Method 1623 (U.S. Environmental Protection Agency) and shows that
<jats:named-content content-type="genus-species">Cryptosporidium</jats:named-content>
subtyping for MST purposes is superior to the use of
<jats:named-content content-type="genus-species">Giardia</jats:named-content>
subtyping, based on better detection limits for
<jats:named-content content-type="genus-species">Cryptosporidium</jats:named-content>
-positive samples than for
<jats:named-content content-type="genus-species">Giardia</jats:named-content>
-positive samples and on greater host specificity among
<jats:named-content content-type="genus-species">Cryptosporidium</jats:named-content>
species. These additional tools could be used for risk assessment in public health and watershed management decisions.
</jats:p>