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Sea Life Is Accumulating Pathogens A wide range of marine animals also contains microbes that are resistant to antibiotics |
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| Enlarge ImageAfter white-sided dolphins became stranded in Wellfleet on Cape Cod, a team of researchers worked together to perform necropsies on eight of the animals in the necropsy facility in the Marine Research Facility at Woods Hole Oceanographic Institution. Andrea Bogolmoni, center (facing camera), took samples from the dolphins to analyze for the presence of disease-causing and zoonotic organisms, part of a large-scale survey of seabirds, marine mammals, and sharks on the East coast.
(Photo by Tom Kleindinst, WHOI) |
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| Enlarge ImageCarefully positioning a dead white-sided dolphin on the stainless steel table, WHOI biologist Michael Moore, one of the zoonosis study's leads, and Colby Moore, a guest student visiting WHOI from the College of the Atlantic, prepare to begin the necropsy. The dolphin, one of eight that became stranded and brought to WHOI's necropsy facility, was sampled to look for disease-causing microbes.
(Photo by Tom Kleindinst, WHOI) |
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| Enlarge ImageThe bodies of northern eider ducks litter a Cape Cod beach. Repeated large die-offs of these seabirds prompted a coalition of researchers from several organizations to investigate the causes of death, and whether the birds' diseases could be transferrable to other animals, or to people.
(Photo by Jim Canavan, WHOI) |
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| Enlarge ImageThis male eider duck, part of a large die-off on Massachusetts beaches, was likely infected with a parasitic worm. WHOI researcher Andrea Bogolmoni had previously found the same phyla of worm in harbor and harp seals. Seeing parallel disease organisms in different species led to an unprecedented study involving several organizations and initiated by WHOI biologists Michael Moore, Rebecca Gast, and Bogolmoni to survey 370 marine animals for zoonotic diseases, whiich means they can be transferred between animals and people.
(Courtesy of Michael Moore, WHOI) |
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| Enlarge ImageWHOI researcher Andrea Bogolmoni and WHOI biologist Michael Moore tend to a dying eider duck, hoping to learn about its illness and whether it carries zoonotic microbes—those that could infect other species as well.
(Photo by Jim Canavan, WHOI) |
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| Enlarge ImageGrey seals congregate and relax on Billingsgate
Shoal, Cape Cod. Fecal samples from live seals and birds revealed that
even apparently healthy marine animals such as these seals can harbor
pathogens, including antibiotic-resistant microbes and Giardia, an intestinal parasite that can cause fever, vomiting, and diarrhea that is well known to hikers.
(Photo by Jim Canavan, WHOI. NOAA Permit 775-1875-00) |
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| Enlarge ImageWHOI microbiologist Rebecca Gast, one of the survey's lead scientists, is now finding the disease-causing freshwater intestinal parasitic microbes Cryptosporidium and Giardia in seawater, as well as in many of the surveyed marine animals. Gast speculated that these organisms might indicate pollution levels in the ocean, since they can be carried to the sea in sewage.
(Photo by Tom Kleindinst, WHOI) |
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An unprecedented survey of seabirds, marine mammals, and sharks on the
U.S. East Coast has revealed that marine wildlife contains a wide
variety of disease-causing microbes—including many that have developed
resistance to antibiotics and several that can be transmitted to
humans.
The newly published study provides no evidence that the widespread
presence of these disease agents in marine animals is affecting the
health of people. But it raises several provocative questions:
- Are more marine animals acquiring disease-causing microbes
in coastal waters contaminated by human, agricultural, and medical
waste?
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Can marine life act as carriers for infectious diseases, spreading pathogens through the oceans?
-
Can marine animals ingesting antibiotics in medical waste, serve as
incubators to maintain, multiply, and spread antibiotic-resistance
genes through marine and coastal ecosystems?
Over the past three years, a research team led by Woods Hole
Oceanographic Institution (WHOI), collected and analyzed samples from
370 marine animals, encompassing 33 species of whales, dolphins, seals,
porpoises, sharks, and seabirds, ranging from Kent Island, Canada, to
Virginia. WHOI biologists Andrea Bogomolni, Michael Moore, and Rebecca
Gast spearheaded the study and led efforts to collect fecal samples
from live seals and seabirds, as well as specimens of dead animals
found in the wild. The research team necropsied animals in the newly
built Marine Research Facility at WHOI, in search of infectious agents.
To collect more specimens, Bogomolni also forged links with stranding
networks and fisheries managers, who sent samples of stranded marine
mammals and bycaught animals (animals unintentionally caught in fishing
gear) to the WHOI necropsy facility. She accompanied fishermen to gain
access to seals on the beaches of local islands. She even took
advantage of a unique opportunity to collect samples from mako and
thresher sharks caught during a local shark-fishing tournament.
The study, published online Aug. 20 in the journal Diseases of Aquatic Organisms,
also included Julie Ellis of the Tufts University Cummings School of
Veterinary Medicine; Katie Pugliares of the Cape Cod Stranding Network
and International Fund for Animal Welfare; and Betty Lentell of the
National Marine Fisheries Service. (See the published study on the Inter-Research Diseases of Aquatic Organisms Web site.)
Giardia, Brucella, and Crytosporidium
The researchers focused on testing their specimens for four relatively
common microbes known to be zoonotic, or transferable from animals to
humans: Brucella, Leptospira, Crytopsporidium, and Giardia—which
cause symptoms that include high fever, severe headaches, chills,
muscle aches, vomiting, and diarrhea. Thirty-five percent of the
animals they examined contained Brucella; 17 percent contained Giardia; 13 percent had Crytopsporidium. To date, the initial results indicating the presence of Leptospira in 10 percent of the tested animals has not been confirmed. All together they found nearly 100 types of disease-causing
agents in their specimens.
The number of zoonotic agents in the animals surprised the researchers,
but they strongly cautioned against interpreting their results as a
reason to avoid the beach. Zoonotic microbes are not new, infection
usually requires a bite or other direct exposure, and people have
developed immunities to many such organisms, explained Moore, a
biologist at WHOI. But it is one of the many reasons to leave beached
seals well alone, he said.
Gast, a microbiologist at WHOI, also noted that the presence of Cryptosporidium and Giardia
cysts in fecal material does not necessarily mean that the animals were
infected; they might be carriers that spread or shed only small amounts
of pathogens.
Nevertheless, the presence of Cryptosporidium and Giardia
may be an indicator of pollution levels in the ocean, Gast said. The
parasites live in the intestines of their warm-blooded hosts and are
released to the environment in feces that ends up in the ocean.
Marine animals can become infected with zoonotic microbes when they
ingest contaminated water while filtering the water for food, or by
eating infected prey, such as plankton, shellfish or fish. Some
animals—gulls, for example—may become infected by foraging from sewage
collection ponds.
Although Cryptosporidium and Giardia are freshwater
inhabitants well known to wary hikers, these microbes are now popping
up in the marine environment, Gast said. People don’t drink seawater,
but they do consume many of the animals that live in it. Armored with a
hard outer shell, the microbes can survive harsh environmental
conditions for weeks—more than enough time to be ingested and find a
cozy new home inside the gut of an animal or human host.
Reservoirs for antibiotic resistance?
Even more surprising to the researchers was the high degree of
antibiotic-resistant bacteria in the ocean harbored in the animals they
tested: 73 percent of the animals they tested had at least one
antibiotic-resistant bacterium; more than 50 percent of the animals
sampled had bacteria resistant to two or more antibiotics.
"One porpoise showed resistance to 15 out of 20 antibiotics we tested
for,” Bogomolni said. “One of the antibiotics we screened for was
gentamicin, which is an agricultural antibiotic. It was ridiculous just
looking down the list (of antibiotics) and seeing, ‘Resistant,
resistant, and resistant.’ Porpoise are coastal animals, so maybe they
are picking (antibiotics or resistant bacteria) up along their
migration.”
The finding also questions the degree of contamination in coastal
waters from treated and untreated sewage discharges or rainwater and
river runoff. And it raises concerns that marine animals can act as
reservoirs for bacteria—acquiring and maintaining antibiotic-resistant
genes and then multiplying and spreading them to other marine life.
“Most of the marine animals sampled have extensive migratory and
foraging ranges, and it is likely that they could serve as vectors in
the spread of antibiotic resistance in the marine environment,” the
study’s authors wrote.
“Marine animals interact with each other as predators, scavengers, and
through the shared use of marine and beach environments,” they wrote.
“Our results indicate that marine mammals, fish, and seabirds may not
only suffer as victims of disease from zoonotic pathogens, but also act
as vectors, moving these human pathogens to different geographic
locations in the ocean and terrestrial environments.”
Fresh off the boat
The seeds of the study germinated at a Cape Cod Natural History
Conference in 2005, when Bogomolni heard a presentation by Becky
Harris, Ellis’s predecessor as coordinator of SEANET at Tufts
University, a program that investigates threats to marine birds
throughout the Atlantic coast. Harris described a parasite detected in
eider ducks that had died in large numbers recently on Massachusetts
beaches. Bogomolni had found the same phyla of parasite in stranded
harp and harbor seals.
About the same time, the National Oceanic and Atmospheric
Administration advertised a grant program for research focusing on
links between the ocean and human health. Moore, Gast, and Bogomolni
applied for funding to begin to investigate zoonotic agents in the
marine environment off the U.S. East Coast.
“We wanted to see what was out there and find out what is happening in
different populations of animals and what is happening between them,”
she said.
Seeking samples of animals to analyze, Bogomolni wrote a letter to
officials at the NOAA Fisheries Northeast Observer Program, requesting
the delivery to her lab of fresh so-called “bycaught” animals that were
inadvertently caught by fishing boats. The letter resulted in a
valuable collaboration, which benefited both Bogomolni and the fishery
observer program.
“We received birds sent to us overnight from places like North Carolina
and Virginia—that has never happened before,” Bogomolni said. “Right
off the boat, they came in fresh directly to our door.”
“The timing was right,” explained study co-author Lentell, who is
incidental take team leader for NOAA Fisheries Northeast Observer
Program. “Transport wasn’t an issue, and we had sufficient staff. We
all coordinated and managed the effort to get the samples to the lab so
they were as fresh as possible.”
The timing was also right because WHOI had just completed building a
new Marine Mammal Facility, with a modern suite of necropsy facilities.
In a gesture of appreciation for delivering the samples, Bogomolni
offered NOAA fisheries observers the opportunity to participate in the
necropsies.
“The observers and commercial fishermen are now realizing what we can
learn from these animals and the importance of collecting data,”
Bogomolni said.
Sharks and seal poop
Bogomolni had wanted the bycaught animals as a representative sample of
“normal” or “healthy” animals, but she discovered that even the
bycaught animals were not in good health. The examinations revealed
that, similar to the live and stranded animals, bycaught animals
harbored pathogens, such as Giardia,
and antibiotic-resistant microbes. Whether the bycaught animals are, or
are not, representative of the normal population requires further
research, Moore said.
Bogomolni also received support from the Cape Cod Hook Fishermen
Association—a consortium of commercial hook and line fishermen and
concerned coastal residents in favor of conserving marine resources
through sustainable fishing.
“They arranged to take me out with local fishermen to Chatham Harbor
and wait for me while I collected samples with my seal poop collection
kit,” Bogomolni said. Fecal samples are important in revealing bacteria
and parasites.
Greg Skomal, shark research program director at the Massachusetts
Division of Marine Fisheries, also assisted in the effort by providing
Bogomolni with the opportunity to collect tissue samples from sharks
during a shark tournament off Martha’s Vineyard.
“It was a bonus opportunity to see what we could learn from these
animals that were within the area of our study,” Bogomolni
explained.
“It’s really amazing what you find once you start looking,” Bogomolni
said. “We’ve learned that it’s not just marine mammals, it’s not
just birds, and it’s not just one geographic area that’s affected. You
cannot look at a system and just look at one species or one group.
Everything is connected.”
—Kristin Thoms
Samples from bycaught animals were collected under a permit from the NOAA Office of Protected Species.
Posted: August 21, 2008 [top] |
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