During this class, we’ve mainly focused on viruses of humans
and other primates (hence the name “Humans and Viruses”). However even viruses that don't infect people (like the papaya virus I looked at in a previous post) can still affect us indirectly.
One such virus
that affects a completely different group of animals has been on many marine biologists’ minds recently: a sea star parvovirus has caused millions of
sea stars to, as one scientist so astutely pointed out, “fall apart into a pile
of goo on the bottom of the seafloor” (http://www.reuters.com/article/2014/11/17/us-science-starfish-idUSKCN0J129K20141117).
Obviously this is a much more pathogenic Parvovirus than Parvovirus B19, the pathogenic agent of 5th disease, a mild rash seen primarily in children (never too early to start reviewing: http://www.cdc.gov/parvovirusb19/fifth-disease.html).
They’re an important predator that acts as a keystone species in shallow water,
so it’s important to protect these animals for the health of these ecosystems,
which humans rely on. Additionally, they themselves provide food for Alaskan
king crabs (a commercially valuable species known for its legs and feature
show, Deadliest Catch) (http://www.adfg.alaska.gov/static/education/wns/alaska_king_crabs.pdf).
The virus, sea star associated Densovirus (SSaDV), causes sea star wasting
disease. The virus has been detected in museum specimens from as early as
1942. The particular strain responsible
for this epidemic was first spotted in August 2013 when divers noticed
massive die-offs of the sunflower star Pycnopodia
helianthoides near Vancouver, Canada. It doesn’t show any signs of slowing.
Many species of sea star have been affected, including sun stars, (Orthasterias koehleri), giant pink stars, (Pisaster
brevispinus), leather stars (Dermasterias imbricata),
and bat stars (Patiria miniata).
It is possible that the virus mutated, or that increasing
population density combined with changing water temperature and chemistry
allowed the virus to cause an epidemic. This is the largest recorded natural
die off of marine invertebrates, even larger than similar die-offs that
occurred in 1970’s, 1980’s and 1990’s.
SSaDV is a parvovirus of the genus Densovirus. The team who discovered
that SSaDV was the cause of sea star wasting disease used a similar process as
the people who discovered tobacco mosaic virus (TMV); they could infect health
sea stars with tissue biopsies of infected ones, and found that the viral load
in recently deceased sea stars was much higher than it was in healthy ones.
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| Healthy sunflower star Pycnopodia helianthoides |
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| An unidentified species of diseased sunflower star... yuck! |
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