De?nition systems (Ricciardi& Rasmussen, 1999). Emerging diseases have interrelate

De?nition of
emerging disease

an infectious
disease that has newly appeared in a population or that has been known for some
time but is rapidly increasing in incidence or geographic range

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Multiple environmental stressors in
freshwater ecosystems

Freshwater
ecosystems are the most severely tainted and distorted ecosystems on the earth because
humans have always need water for the survival that’s why the live near
freshwater bodies for millennia. Their comparatively small volumes and the fact
that fresh waters receive terrestrial run-off have contributed to their
degradation whilst dam construction, canalisation and water abstraction have
extensively altered freshwater habitats (for review see Davis, Sim& Chambers,
2010; Tockner et al., 2010

. In marine ecosystems
introductions for sports ?sheries are unfeasible because of the huge and open environment
of the marine habitation although introductions via aquaculture may have
implicated for emerging disease.

certainly, the
number of deaths rate in freshwater environment are greater than in most earthly
environments (Dudgeon et al., 2006), and also freshwater ecosystem have more
risks of endangered and endangered species than in marine or terrestrial
systems (Ricciardi& Rasmussen, 1999). Emerging diseases have interrelate
with these high environmental losses in fresh waters in various ways.

Finally,
fresh waters are challenged by outstanding habitation loss via water build as
competing human stakeholders effect an increasing shortage of clean freshwater
as a result of climate change (Johnson et al., 2009; Grantham,
Merelender, 2010).

Unique environmental attributes of
fresh waters may contribute to

Disease

Parasites
caused many diseases which have complicated life cycles that include both marine
and terrestrial stages (e.g. Lv et al., 2011), and freshwater systems present
differentiate and inherent facial appearance agreeable to such life histories.  experience possibility between transferable
agents and vulnerable hosts is increased by the small volumes and the linear
nature of rivers

Freshwater
ecosystems also linked with the other ecosystems like terrestrial and marine
ecosystems. This has inference for disease emergence if anadromous species act
as vectors to move pathogens between marine, estuarine and freshwater
environments. For example, the fungal-like parasite of marine ?sh,
IchthyophonushoferiPlehn, can rapidly establish in freshwater
aquaculture situations following feeding with infected material. Thus, at least
some marine pathogens are capable of invading freshwater systems if the
opportunity arises (Ono et al., 1966

Baseline data and understanding
long-term trends

First and leading
is the common lack of baseline data need to assess whether the rate of diseases
are increasing in frequently or strictly

The data is
very useful for the establishment of international guidence of aquatic ?sh
diseases due to the increasing occurrence arising from pollutant contact

Trophic loss and ecosystem function

The related
structural and functional transformations of ecosystems caused by over?shing
raise the thorny question of whether longterm overexploitation of resources may
act as an underlying driver of subsequent change and argue for caution when
identifying causes of disease emergence and disease management strategies.

Alternatively,
disease outbreaks may occur if trophic changes result in habitat degradation
that in turn cause stress and greater susceptibility to disease. For instance,
loss of higher trophic levels via over?shing may precondition for species
introductions or eutrophication (e.g. via the harvesting of suspension-feeding
oysters in Chesapeake Bay; Jackson, 20 An unresolved issue is whether the
longer period of over?shing and ecosystem transformation in freshwater systems
is signi?cant for disease emergence. Did the effects of over?shing in
freshwater systems occur so long ago that the loss of trophic structure may no
longer underlie and contribute to disease emergence01) both of which in turn have
been linked with disease emergence.. At present, it is not clear whether
disease emergence might facilitate such shifts, although links with
eutrophication suggest that diseases may play a role in driving communities
from one state to another. There is evidence that marine diseases may
contribute to ecosystem change, with diseases of corals facilitating phase
shifts from a coraldominated state to an algal-dominated state.

Some environments are improving

Although the
emerging diseases are always depend on the environment, the change in the
environment is causing disease emergence in a number of situations, it is also
the case that some freshwater bodies are improving in quality. For example, the
environmental recovery of the River Thames demonstrates the dramatic turnaround
possible in environmental quality and ?sh biodiversity following remediation
actions such as improved sewage ef?uent treatment and reductions in industrial
waste inputs.