nuove malattie minacciano la biodiversita'

[alessandro gimona <ag0648@mluri.sari.ac.uk>]

Cari tutti,
la comaprsa di nuove malattie animali e' un nuovo problema per la
biodiversita'

Saluti,
Alessandro Gimona
------------------------------------------------------------
University of Georgia

Emerging infectious diseases of wild animals are a threat to
biodiversity
and human health, according to new report

ATHENS, Ga. - Newly discovered infectious diseases of free-living wild
animals may pose an increasing and significant threat to human health
and=
 to
global biodiversity, according to a just-published report.

While emerging human diseases such as Ebola have grabbed headlines in
rec=
ent
years, similar diseases in wildlife have been understudied, and few
regulations concerning exotic disease threats to wild animals or systems
=
for
surveillance are in place to prevent their spread.

"With a new wave of globalization on an unprecedented level, we don't
eve=
n
know what the greatest threats are in terms of emerging infectious
diseas=
es
of wildlife," said Dr. Peter Daszak of the University of Georgia's
Instit=
ute
of Ecology and department of botany. "The problem has largely been
ignore=
d
by policy makers and the threat that these wildlife pose to human,
direct=
ly
or indirectly, should be taken far more seriously."

A new report on the scope of the problem was published today in the
journ=
al
Science. Co-authors of the paper are Dr. Andrew Cunningham of the
Zoologi=
cal
Society of London and Dr. Alex Hyatt of the Australian Animal Health
Laboratory.

Human history is filled with the catastrophic consequences of emerging
infectious diseases. The introduction of smallpox, typhus and measles by
=
the
conquistadores in the 15th and 16th centuries resulted in a staggering
50
million deaths among native South Americans. Despite suspicious that
dise=
ase
may have caused similar effects on wildlife, systematic studies of
emergi=
ng
infectious diseases of wild animals and their effect on human
populations
have been few and far between.

That all changed with the discovery that wild animals can act as natural

reservoirs for diseases that can be extremely virulent among humans. The

influenza virus, for example, causes pandemics in humans following the
periodic exchange of genes between the viruses of wild and domestic
birds=
,
pigs and humans.

The report by Daszak and his colleagues points out that many emerging
infectious diseases of wildlife are associated with the "spill-over" of
pathogens from domestic animals to wildlife populations; with the
translocation of host or parasites by human intervention; and with
events
that have no human or domestic animal involvement, such as global
warming=
 or
floods. Whatever the reason, these diseases have spread just as human
diseases did.

"In the same way that Spanish conquistadores introduced smallpox and
meas=
les
to the Americas, the movement of domestic and other animals during
colonization introduced their own pathogens," said Daszak.

The first major method of animal disease transmission, "spill-over,"
refe=
rs
to the spread of infectious agents from reservoir animal species (often
domestic animals) to wildlife. Outbreaks of "spill-over" diseases
represe=
nt
a serious threat to wildlife and domestic animals, Daszak said. For
instance, a disease called brucellosis was probably co-introduced to
Amer=
ica
with cattle. The presence of the disease in bison of Yellowstone
National
Park is thus considered a potential threat to domesticated cattle
grazing=
 at
the park's boundaries. The problem has led to considerable tension
betwee=
n
conservationists and cattlemen and the shooting by farmers of bison that

graze near domesticated herds, even though thre is little evidence of
cat=
tle
becoming infected, according to Daszak.

The translocation of wildlife species - the second method of spreading
emerging infectious diseases - occurs often in conservation efforts or
fo=
r
agriculture or hunting.

"The introduction of animals to new geographic regions and the
co-introduction of their pathogens is a serious problem," said Daszak.
"F=
or
example, avian malaria on Hawaii is thought to have caused the
extinction=
 of
a number of native species and was originally introduced with exotic,
ali=
en
birds."

The emergence of infectious diseases without overt human involvement is
among the thornier issues facing conservationists. For instance, weather

patterns can cause changes in the prevalence of certain parasites that
ar=
e
deadly to some species of sheep. Researchers are finding new diseases
eve=
n
in sites considered pristine. A newly discovered fungal disease has
recen=
tly
been identified as the cause of amphibian mortality in the Central
Americ=
an
and Australian rain forests, areas scientists thought were beyond the
rea=
ch
of human environmental change.

Whatever the source of infectious wildlife diseases, both human health
an=
d
global biodiversity are being increasingly threatened, the authors
argue.

Recent analyses of nucleic acid sequences have shown that avian
influenza
can be transmitted directly from birds to humans. Potential non-human
primate reservoirs for HIV-1 and HIV-2 have also been found. Daszak said

that natural reservoir hosts for such feared disease as Ebola have been
m=
ore
elusive, though bats and some small forest-dwelling mammals have been
tentatively implicated.

Researchers involved with human health have begun to search for new
anima=
l
diseases as part of a strategy to control emerging disease threats to
humans, but far too little is known about potential threats at this
point=
,
the authors say.

While potential human disease outbreaks can be linked to animal disease,

just as troubling is the role of animal disease in the loss of global
biodiversity. While there are numerous examples of disease emergence
following the introduction of pathogens to a population, "there
undoubted=
ly
are many more that have not been identified as such."

The international movement of food crops, timber, agricultural materials
=
and
domesticated animals, as well as landfill wastes and ship ballast water,

combine to cause global threats. The authors say that even such areas as
=
the
Gal=E1pagos Islands and Antarctica are not exempt.

Just how science can offset the effects of emerging infectious diseases
i=
n
wildlife is yet unclear, but the scope of the problem is becoming
increasingly obvious, said Daszak. The problems involved have clear
econo=
mic
consequences. The authors point out that post-exposure treatment give to
=
655
people who had potential contact with a single rabid kitten in a New
Hampshire pet store in 1994 cost $1.1 million. The costs of Lyme disease

treatments of all kind in the U.S. may be as much as $500 million a
year.

"Current measures for the detection and control of emerging infectious
diseases in humans and livestock are inadequate for the identification
of
similar threats in wildlife," said Daszak. "The conservation community
ha=
s
drawn up guidelines to prevent the release of animals carrying exotic
pathogens to new areas, but these recommendations are now under-used. We

need an integrated approach, using traditional and cutting-edge
technique=
s,
to investigate outbreaks as they occur in wildlife."
###
Techniques now used to help control emerging diseases in humans and
domes=
tic
animals - including satellite imaging, Internet news groups, outbreak
investigations and large-scale vaccinations - may well work in certain
populations of wild animals. Until then, these diseases in wildlife will

likely continue to cause serious and growing problems for human health
an=
d
biodiversity.