Snake Fungal Disease culprit found

From a co-worker:


SNAKE FUNGAL DISEASE - USA (03): ETIOLOGY, EXPERIMENTAL EVIDENCE
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A ProMED-mail post

ProMED-mail is a program of the
International Society for Infectious Diseases


Date: Tue 17 Nov 2015
Source: Eurekalert! [edited]



Researchers working for the U.S. Geological Survey have identified the
fungal culprit behind an often deadly skin infection in snakes in the
eastern U.S.

Published this week in mBio, an online open-access journal of the
American Society for Microbiology, the research shows that
_Ophidiomyces ophiodiicola_ is the definitive cause of snake fungal
disease (SFD), which will help researchers pinpoint why it is emerging
as a threat to snake populations and how its impacts can be
mitigated.

SFD joins a list of fungal diseases causing decimation to animal
populations, including white-nose syndrome in bats and
chytridiomycosis in frogs and amphibians. Different fungi cause the 3
conditions, but their potential for destruction raises concerns.

"Unlike many bacterial and viral pathogens, fungal spores can live in
the environment without a host," explains Jeffrey Lorch, a
microbiologist at the USGS National Wildlife Health Center in Madison,
Wisconsin. "And that means that as the host population declines, the
fungus can persist in the environment, which could potentially mean it
could drive hosts to extinction."

Since 2009, Lorch and his colleagues at the center have diagnosed SFD
in 7 species of snakes from 9 different states, all in the eastern
half of the U.S. In some species, such as massasauga rattlesnakes
found in Illinois, the infection appears to have a mortality rate of
100 percent. For other species, the infection is not as deadly. "There
is a fear that _Ophidiomyces_ could drive at least some populations of
snakes to extinction," says Lorch.

Although skin lesions on infected snakes often contained _Ophidiomyces
ophiodiicola_, no one had shown the definitive laboratory proof that
it was causing the disease. The USGS-led team ran those experiments by
culturing _O. ophiodiicola_ from an infected wild water snake and then
using it to inoculate 5 different skin sites on 8 corn snakes in the
laboratory. All 8 snakes developed swelling and scale lesions
characteristic of SFD. In contrast, none of the 7 control group
snakes, which were sham inoculated with saline solution, developed
lesions.

The lesions appeared within 4-8 days and were more likely to form at
sites that had 1st been rubbed with sandpaper to cause an abrasion.
After about 2 weeks, the infected snakes had rough, brown crusty
lesions and proceeded to molt. Infected snakes molted more frequently,
possibly as an immune response that helps snakes shed the fungus. Two
infected snakes refused food when they were experiencing severe head
swelling. Infected snakes were also observed out in the open and
exposed area of their enclosures twice as often as uninfected snakes.

It's not known how the skin disease causes death in wild animals, but
Lorch suspects it is multifactorial. "It could be due to predation or
exposure if snakes are out and about when they shouldn't be. They
could be getting secondary skin infections if bacteria get in." He
notes that dehydration or starvation could also pose problems for
infected snakes. There is also concern that environmental factors such
as climate change could be compromising the ability of wild snakes to
avoid, fight off, and recover from the infections.

"We can't move forward with management of a disease in the wild if we
don't know what's causing it," says Lorch. The identification of _O.
ophiodiicola_ will allow researchers and wildlife biologists to build
a management plan, especially for at-risk snake populations.

--
Communicated by:
ProMED-mail from HealthMap Alerts


[Snake fungal disease (SFD) is an emerging disease of wild snakes in
the eastern and midwestern USA. This experimental study reproduced the
skin lesions observed in the field and confirmed that the etiologic
agent is the fungus _Ophidiomyces ophiodiicola_. This fungus had been
consistently associated with the often-fatal skin, face, and eye
lesions characteristic of the disease. In recent years, cases of this
fungal infection have been increasing. Further studies should explore
whether _O. ophiodiicola_ is a sufficient cause of mortality.

The scientific paper referred to can be accessed at
.

A picture of the lesions observed in snakes with SFD can be seen at
. - Mod.PMB

A HealthMap/ProMED-mail map can be accessed at:
.]

[See Also:
Snake fungal disease - USA (02): spread
http://promedmail.org/post/20150619.3451334
Snake fungal disease - USA: (MI) rattlesnake
http://promedmail.org/post/20150304.3207195
2014
----
Snake fungal disease - USA: (GA) free-ranging snake 1st report
http://promedmail.org/post/20140829.2734218
2013
----
Snake fungal disease - USA (04): (SC) 1st report
http://promedmail.org/post/20131018.2008729
Snake fungal disease - USA (03)
http://promedmail.org/post/20130913.1942160
Snake fungal disease - USA (02): (TN)
http://promedmail.org/post/20130617.1777532
Snake fungal disease - USA
http://promedmail.org/post/20130501.1683967]