Marine Mammals Suffer Human Diseases from Pollution

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Marine Mammals Suffer Human Diseases

 

By Bjorn Carey

LiveScience Staff Writer

posted: 23 February 2006

 

ST. LOUIS—Parasites from cat feces are causing deadly brain damage in

California sea otters. A combination of toxic chemicals and herpes virus is

killing off California sea lions.

 

And toxic algae blooms are contributing to record manatee deaths in Florida.

 

All of these animals live near coastlines, spending a majority of their

lives in the same waters people swim and surf in. Their daily cuisines

consist of the same foods we serve up in clam shacks and fine seafood

restaurants.

 

The difference between humans and these animals, says NOAA spokesperson Paul

Sandifer, is that the animals deal with the ocean conditions, good or bad,

full time. People can pick and choose when to go into the water and what to

eat.

 

As a result, marine animals, particularly mammals, play an important role as

sentinel species. When one of these species gets sick or dies from something

in the water, it is often a warning to humans of disease to come.

 

" Some of what we throw or flow into the water will return to bite us in the

gluteus maximus. You can bet on it, " said Sandifer, who organized a panel of

marine scientists to present their work here last week at the annual meeting

of the American Association for the Advancement of Science.

 

RED TIDE

The red tide algae blooms that turn waters off Florida's coast rust-colored

are becoming more frequent. Karenia brevis algae, responsible for red tide,

produce toxins called brevetoxins, which can kill fish, sea turtles, birds,

and marine mammals such as manatees.

 

The toxins seem to be sending more people to emergency rooms, too, said

Gregory Bossart of the Harbor Branch Oceanographic Institution.

 

In 2005, 151 manatees died from exposure to brevetoxin. Post-mortem

examinations revealed that the stuff was affecting their lungs.

 

" The animals are actually hemorrhaging into their lungs, " Bossart said.

" They're dying of acute toxic shock. "

Airborne brevetoxins, Bossart said, can affect human respiratory systems the

same way as a bad cold. A five-year study revealed that emergency room

admissions for respiratory illness, including pneumonia and asthma attacks,

increase by 54 percent during red tide blooms.

 

" While the toxin may not kill you, it will make you sick and

immuno-suppressed. It may make you susceptible to other infections, " Bossart

said. " What's disturbing is that humans appear to respond to prolonged

brevetoxin exposure in a way similar to manatees that die from it. "

 

Bossart recently published evidence that algae blooms may be of danger to

humans and marine animals even after they disappear.

 

Brevetoxins collect in filter-feeding shellfish. Within hours of ingesting

shellfish with high levels of the toxin, humans can experience temporary

neurotoxic shellfish poisoning (NSP). Symptoms of NSP include nausea and

diarrhea, dizziness, muscle aches, and tingling and numbness in the tongue,

lips, throat, and extremities.

 

Currently, scientists only monitor shellfish during a bloom. But Bossart

discovered that the concentration of brevetoxins in the water and in sea

grass continued to increase months after blooms faded.

 

" After the bloom, the toxins persist in some of the same food items that we

eat, " Bossart told LiveScience.

 

DEADLY CAT POOP

A deadly parasite that's the third most common cause of death due to

food-borne disease in the U.S. is also killing California sea otters at a

rapid rate.

 

Toxoplasma gondii, which causes the disease toxoplasmosis in humans, has

been found in 52 percent of dead otters and 37 percent of the living.

 

The parasites are tiny, mysterious, and tough, said Pat Conrad of the

University of California at Davis. They can invade an organism and stay

dormant for years. When the opportunity presents itself, they will emerge

from their dormant form and attack the animal's brain.

 

In otters, the parasite causes tremors, incoordination, and seizures. It is

the primary cause of death in some coastal otter populations.

 

" Some rescued otters need to be hand fed squid, their tremors are so bad, "

Conrad said.

 

Thanks, Kitty

But, Toxoplasma gondii can only reproduce in cats, which shed the parasites

in their feces. Although cats will only shed new parasites once in a

lifetime, millions come out at once.

 

This happens on land and in kitty litter boxes, though, so how are coastal

otter populations becoming infected?

Conrad says the major culprit is freshwater runoff, which washes feces from

backyards, streets, and illegally dumped kitty litter into streams, rivers,

and ultimately the ocean. Indeed, Conrad's studies have indicated that

infection risk potential for otters living near freshwater runoff increases

three times. For the otters of Morro Bay, the risk is more than nine times

increased.

 

Cat owners should try to keep their kitties indoors and to properly dispose

of kitty litter at a landfill to reduce the risk of spreading parasites,

Conrad said. She also notes that eco-friendly, flushable kitty litter may

contribute to the problem since sewage treatment systems do not effectively

eliminate the parasite from wastewater.

 

Scientists estimate that up to 25 percent of the U.S. population may be

infected with this same parasite, but people rarely show symptoms. If they

do, it might just appear as a flu-like illness.

 

Pregnant women infected with the parasite can pass it on to their developing

babies, increasing the chance of an abortion or miscarriage. If a baby

survives, it could have severe brain damage that may or may not be evident

at birth.

 

Of the infected otters, 72 percent harbor a parasite strain not seen often

in humans. Otters cannot pass the parasite to humans, but because of their

chronic exposure, they act as an early warning for people.

 

SEA LION CANCER

For California sea lions, a combination of persistent organic pollutants

(POPs) and herpes virus similar to the one that infects humans has led to an

increase in cancer.

 

Over the past 15 years, 17 percent of dead and stranded sea lions have been

diagnosed with urogenital cancer, striking females in the cervix and males

in the penis and prostate.

 

The cancer spreads to other organ systems in sea lions the same as in

humans. Eventually it erodes the spinal cord, paralyzing them and causing

them to wash up on the shore or strand in the open water, said Frances

Gulland of the Marine Mammal Center.

 

Many adult sea lions also have the herpes virus—up to 43 percent of males

and 23 percent of females. The higher rate for males is because it is a

sexually transmitted disease, Gulland said, and males have more sexual

partners.

But, since some herpes-infected animals are without cancer, Gulland suspects

that POPs, which can cause cancer on their own, are teaming up with the

virus to increase cancer rates.

 

While POPs are in the water, sea lions are exposed to them mainly through

the food they eat, in which the toxic chemicals accumulate.

 

" These are top level predators, " Gulland said. " Like us, they eat anchovies,

squid, salmon, and mussels—they are sentinels for human health because they

share our ecosystems and prey. We may see impacts in sea lions before

people—they could be an early warning. "