Featured Research

from universities, journals, and other organizations

Sea Grant Study Finds Chinese Mitten Crabs Appear Free Of Human Parasite Lung Flukes

Date:
November 15, 2001
Source:
National Sea Grant College Program
Summary:
A study funded by California Sea Grant suggests that Chinese mitten crabs (Eriocheir sinensis) in the San Francisco Bay estuary are not infected with a dangerous human parasite that has caused deaths in Asia.

Santa Barbara, CA -- A study funded by California Sea Grant suggests that Chinese mitten crabs (Eriocheir sinensis) in the San Francisco Bay estuary are not infected with a dangerous human parasite that has caused deaths in Asia.

Related Articles


Jenifer Dugan, Mark Walter and Carrie Culver of the Marine Science Institute at the University of California at Santa Barbara analyzed tissue samples from more than 800 mitten crabs collected in the bay -- not a single crab was shown to be infected with either Asian or North American lung flukes. The crabs were collected at 15 to 20 sites over a two-year period beginning in 1999.

Dugan said, "We have not found any evidence of lung flukes. There have been a few other parasites found, but only in a couple of specimens. The crabs seem to be healthy and thriving. Nonnative species may flourish in a new habitat because they have escaped many of their native predators and parasites."

Lung flukes are parasites with a complex lifecycle that requires them to infect two intermediate hosts before they mature into adults inside a warm-blooded animal or person. Flukes in their "larval" form infect snails, then crustaceans, such as mitten crabs and crayfish. In mammals, they attack the respiratory system as they breed.

In Asia, where mitten crabs are a delicacy, people regularly suffer lung damage from eating infected seafood. The flukes can also spread to the brain.

State health officials have been concerned that mitten crabs in the San Francisco Bay area might also be carrying lung flukes and putting recreational fishers at a health risk. Although commercial fishing for the crabs is prohibited, sport fishing is allowed, and people do eat the crabs. Live females with eggs can sell for more than $20 per crab in Asian markets, although the sale and transport of live mitten crabs is illegal in California, an effort to curb their spread.

Chinese mitten crabs are native to China and Korea but are a highly invasive nuisance species elsewhere. The crabs were first identified in California in 1992, after a shrimp trawler working the South San Francisco Bay hauled up a strange looking crab with fuzzy claws.

However, the crab most likely was introduced to San Francisco South Bay much earlier, in the late 1980s. A hearty and fecund invader, the crab has multiplied to such numbers that it now overruns parts of the bay. In 1998, state workers hauled away about 50 tons worth of mitten crabs that had clogged fish screens at state water pumps near Tracy. Besides clogging fish salvage tanks, mitten crab burrows undermine banks and levees, accelerating erosion and unwanted slumping.

To date, there are no strategies in place for controlling the crab's numbers. Fishers are suggesting that the crab population be culled by opening the mitten crab to commercial fishing, but this is problematic, too.

Dugan said, "The idea is to figure out a way to get rid of the crabs. If you open a fishery, suddenly, they have a value."

Another concern is that parasites could spread like fire in a hayloft through the bay at some later date, because of the sheer number of crabs. Not just people but also raccoons and other animals that feed on mitten crabs could be infected.

Because crayfish are a potential intermediate host for the flukes, the scientists also dissected more than 400 crayfish from the estuary. Like the crabs, all the crayfish appear free of lung flukes.

Despite their findings, the scientists are cautious about concluding that eating the crabs is safe now or in the future.

"Until we finish our survey of the region's snails," Walter said, "we can't assess the risk of future introductions of lung flukes."

The scientists are in the process of analyzing hundreds of freshwater snails from the area to look for evidence of lung flukes. Even if the snails turn up clean, Culver said, there are other major health concerns - such as bioaccumulation of contaminants like mercury, selenium, arsenic and DDE (a byproduct of DDT) within the crabs.

The nation's Aquatic Nuisance Species Task Force has federal jurisdiction over the problem. Culver sits on the Task Force's Mitten Crab Control Committee, which has been asked to develop and oversee the implementation of a management plan. She said the committee is addressing four main issues: preventing the crab's spread; detecting new populations; reducing its negative effects; and, controlling its numbers.

###

The National Sea Grant College Program is a university-based program that promotes the wise use and stewardship of coastal and marine resources through research, outreach and education.

Websites:

http://www.delta.dfg.ca.gov/mittencrab/

http://www.mp.usbr.gov/mittencrabs/


Story Source:

The above story is based on materials provided by National Sea Grant College Program. Note: Materials may be edited for content and length.


Cite This Page:

National Sea Grant College Program. "Sea Grant Study Finds Chinese Mitten Crabs Appear Free Of Human Parasite Lung Flukes." ScienceDaily. ScienceDaily, 15 November 2001. <www.sciencedaily.com/releases/2001/11/011115072138.htm>.
National Sea Grant College Program. (2001, November 15). Sea Grant Study Finds Chinese Mitten Crabs Appear Free Of Human Parasite Lung Flukes. ScienceDaily. Retrieved December 19, 2014 from www.sciencedaily.com/releases/2001/11/011115072138.htm
National Sea Grant College Program. "Sea Grant Study Finds Chinese Mitten Crabs Appear Free Of Human Parasite Lung Flukes." ScienceDaily. www.sciencedaily.com/releases/2001/11/011115072138.htm (accessed December 19, 2014).

Share This


More From ScienceDaily



More Plants & Animals News

Friday, December 19, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Researchers Test Colombian Village With High Alzheimer's Rates

Researchers Test Colombian Village With High Alzheimer's Rates

AFP (Dec. 19, 2014) In Yarumal, a village in N. Colombia, Alzheimer's has ravaged a disproportionately large number of families. A genetic "curse" that may pave the way for research on how to treat the disease that claims a new victim every four seconds. Duration: 02:42 Video provided by AFP
Powered by NewsLook.com
Navy Unveils Robot Fish

Navy Unveils Robot Fish

Reuters - Light News Video Online (Dec. 18, 2014) The U.S. Navy unveils an underwater device that mimics the movement of a fish. Tara Cleary reports. Video provided by Reuters
Powered by NewsLook.com
Kids Die While Under Protective Services

Kids Die While Under Protective Services

AP (Dec. 18, 2014) As part of a six-month investigation of child maltreatment deaths, the AP found that hundreds of deaths from horrific abuse and neglect could have been prevented. AP's Haven Daley reports. (Dec. 18) Video provided by AP
Powered by NewsLook.com
Dads-To-Be Also Experience Hormone Changes During Pregnancy

Dads-To-Be Also Experience Hormone Changes During Pregnancy

Newsy (Dec. 18, 2014) A study from University of Michigan researchers found that expectant fathers see a decrease in testosterone as the baby's birth draws near. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins