Pathogens co-transported with invasive non-native aquatic species:
implications for risk analysis and legislation
Abstract
Invasive Non-Native Species (INNS) can co-transport externally and
internally other organisms including viruses, bacteria and other
eukaryotes (including metazoan parasites), collectively referred to as
the symbiome. These symbiotic organisms include pathogens, a small
minority of which are subject to surveillance and regulatory control,
but most of which are currently unscrutinised and/or unknown. The
(putatively) pathogenic symbionts co-transported by an INNS host may be
latent or associated with asymptomatic infection and unable to cause
disease in the INNS, but may be opportunistic pathogens of other hosts,
causing impact to one or more hosts in their new range. These pathogens
potentially pose diverse risks to other species, with implications for
increased epidemiological risk to agriculture and aquaculture,
wildlife/ecosystems, and human health (zoonotic diseases). Aquatic INNS
and their symbionts have many introduction pathways, including commodity
and trade (releases, escapes, contaminant), transport (stowaway), and
dispersal (corridor, unaided). The risks and impacts arising from
co-transported pathogens, including other symbionts of unknown
pathogenic virulence, remain largely unexplored, unlegislated, and
difficult to identify and quantify. Here, we propose a workflow to
determine any known and potential pathogens of aquatic INNS. This
workflow acts as a prerequisite for assessing the nature and risk posed
by co-transported symbionts of INNS. A better understanding of
co-transported organisms, the risks they pose and their impact, is
necessary to inform policy and INNS risk assessments. This leap in
evidence will be instrumental to devise an appropriate set of statutory
responsibilities with respect to these symbionts, and to underpin new
and more effective legislative processes relating to the disease
screening and risk assessment of INNS.