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A ProMED-mail post
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International Society for Infectious Diseases
Date: 5 Nov 2010
Source: Gazette Times [edited]
A sharp increase in the number of sick and dead California sea lions
has been reported along the Oregon coast in recent weeks, and
necropsies conducted on dozens of the animals suggest that many may
have died from leptospirosis.
Leptospirosis is a bacterial disease found in a variety of animal
species and can be transmitted to humans, according to Jim Rice, an
Oregon State University scientist who coordinates the statewide
Oregon Marine Mammal Stranding Network.
"We are now getting calls for multiple sick or dead sea lions daily,
which is higher than normal," said Rice, an OSU Marine Mammal
Institute researcher who works at the university's Hatfield Marine
Science Center in Newport.
"The overall number of sea lions also has risen, so it's difficult to
compare mortality rates from year to year, but certainly we're seeing
an increase in animals that test positive for leptospirosis."
Rice and his colleagues at the stranding network have sent dozens of
dead animals to the Veterinary Diagnostic Laboratory in OSU's College
of Veterinary Medicine. And though not all of the animals have tested
positive, many showed clear signs of leptospirosis, which raises
concern about human health.
Kathy O'Reilly, who heads the bacterial section of the Veterinary
Diagnostic Lab, said leptospirosis can be virulent.
"There have been 50 to 100 cases per year in the United States
reported to the Centers for Disease Control," O'Reilly said, "and in
31 percent of the human cases, it is traced back to contact with
infected rats, and in 30 percent of the cases, it is tracked to infected dogs."
Dogs can be infected with leptospirosis through contact with stricken
sea lions. Rice said coastal visitors should always avoid sea lions
on the beach and during outbreaks of leptospirosis should keep their
dogs on a leash. The disease can be transmitted by direct contact, or
even through contact with damp sand, soil or vegetation contaminated
by the urine of infected animals. Rice said that in 2009, the network
had 350 reports of California sea lions stranded on Oregon beaches,
either dead or severely ill and presumed to have died. And Oregon is
on pace to surpass that total this year [2010], he pointed out.
"Typically, sea lions with leptospirosis are quite emaciated and
lethargic," Rice said. "Those that don't die on the beach may get
washed out to sea and die, or they may move elsewhere. It's possible
that some recover, but these are very sick animals."
The Oregon Marine Mammal Stranding Network is a collaborative
volunteer effort to respond to reports of sick or dead marine mammals
-- including whales, seals and sea lions -- and report data about the
strandings to the National Marine Fisheries Service. It is
headquartered at OSU's Marine Mammal Institute at the Hatfield Marine
Science Center and coordinated by Rice.
Partners in the Oregon Marine Mammal Stranding Network include OSU,
Portland State University, the University of Oregon's Institute for
Marine Biology, the Oregon Department of Fish and Wildlife, the
Oregon State Police, the Oregon Department of Parks and Recreation and others.
Persons seeing dead or sick marine mammals on Oregon beaches are
encouraged to call the Oregon State Police at 1-800-452-7888.
[Byline: Mark Floyd]
--
Communicated by:
HealthMap Alerts via
ProMED-mail
[Leptospirosis is a bacterial disease caused by the spirochete
_Leptospira_ sp. There are over 17 species and various serovars. The
taxonomy can become confusing. Regardless of the taxonomy, this
bacteria infects both human beings and a variety of animals. It is
generally thought of as an infection within the kidneys, because it
can be transmitted by contact with infected urine, or through water
having urine from infected wild animals, rats, etc. There are some
serovars that may affect the liver as well.
The California sea lion (_Zalophus californianus_) is thought to be
infected with _L. interrrogans_.
When sea lions are infected, they demonstrate the unusual behavior of
drinking water. Most sea lions acquire the water they need through
the food they consume. When ill sea lions demonstrate the behavior of
drinking water, they are tested for leptospirosis if they are in a
marine habitat facility.
Animals who are sick and brought to a marine mammal facility where
they can be treated can recover from the disease. However, many
animals in the wild, not recognized as being ill, die and wash up on
shore and are then found.
California sea lions (_Zalophus californianus_) breed in rookeries
along the southern California coast during May and June (Zuerner et
al., 2009). The female sea lions typically stay close to the
rookeries to nurse their pups, but they may move as far north as
Monterey Bay; however, the males travel north and spend the winter
anywhere from California to south Alaska (Melin, 2002). Even though
they stay close to the coast, occasionally they leave to look for
food, and males can cover 644 km on a single trip (Weise et al.,
2006). Their ability to travel great distances gives the disease the
opportunity to spread geographically (Zuerner et al., 2009).
Terrestrial animals may get leptospirosis because sick or injured sea
lions either die at sea or are stranded on beaches where other
animals can come into contact with them. Leptospirosis has a latency
period of about 10-14 days between contact and developing signs,
leading researchers to believe that the animals are able to travel
during this latency period spreading the disease. Since some of the
population is continuously in a latency state of infection, the
distribution of infected animals spreads as animals disperse across
different geographical areas. Infected animals are often found near
fresh water estuaries, which potentially increases the chance of
transmitting the disease to humans, domesticated animals, and
terrestrial wildlife (Zuerner et al., 2009).
References:
Melin, S.R., (2002). The Foraging Ecology and Reproduction of the
California sea lion (_Zalophus californianus californianus_).
University of Minnesota, Minneapolis.
Zuerner, Richard L., Cameron, Caroline E., Raverty, Stephen,
Robinson, John, Colegrove, Kathleen M., Norman, Stephanie A.,
Lambourn, Dyanna, Jeffries, Steven, Alt, David P., & Gulland,
Frances. (2009). Geographical dissemination of Leptospirosa
interrogans serovar Pomona during seasonal migration of California
sea lions. Veterinary Microbiology 137 105-110.
Photos of the California sea lion may be seen at:
The state of Oregon can be seen on the HealthMap/ProMED-mail
interactive map at:
[see also:
2004
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Leptospirosis, sea lions - USA (CA) 20040926.2659]
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