Featured Research

from universities, journals, and other organizations

River Blindness Caused By Bacteria, Not Worms, Suggesting Antibiotic Treatment For The Disease, Researchers Report

Date:
March 14, 2002
Source:
American Association For The Advancement Of Science
Summary:
River blindness, a devastating tropical disease that affects 18 million people in Africa, the Arabian peninsula, and Latin America, is caused by parasitic worms that burrow into the skin and release millions of tiny offspring that spread throughout the body. But, the worms themselves probably aren't the main culprits behind the disease, says an international team of scientists.

River blindness, a devastating tropical disease that affects 18 million people in Africa, the Arabian peninsula, and Latin America, is caused by parasitic worms that burrow into the skin and release millions of tiny offspring that spread throughout the body. But, the worms themselves probably aren't the main culprits behind the disease, says an international team of scientists.

Instead, it's the worms' cargo of Wolbachia bacteria that provokes the body's severe inflammatory response, leading to blindness and serious skin disorders, the researchers report in the 8 March issue of the journal Science, published by the American Association for the Advancement of Science.

Pinpointing bacteria as the direct factor behind the disease's virulence may suggest new therapies for combating river blindness, especially since recent studies in infected humans have shown that the bacteria can be killed by the common antibiotic doxycycline.

River blindness is the second leading infectious cause of blindness in the world. It is spread to humans by the bite of black flies infected with the parasitic worm Onchocerca volvulus. The battle against river blindness is taking place on two fronts at the moment, with programs to control the spread of the black fly and to freely distribute an anti-worm medicine called ivermectin.

Onchocerca larvae deposited by the fly's bite burrow into the skin, where they mature and eventually send out tiny offspring called microfilariae that can migrate through the skin to the eye. When the microfilariae die, they trigger a severe immune response, resulting in eye inflammation and eventual vision loss.

Onchocerca don't travel alone on this journey: At all stages of their life cycle, the worms contain Wolbachia bacteria that appear to be essential companions. Recent research by two of the Science authors, Achim Hoerauf and Lars Volkmann of the Bernhard Nocht Institute for Tropical Medicine in Hamburg, Germany, suggests that the worms need Wolbachia to reproduce successfully.

With the close connection between worm and bacteria in mind, the Science researchers devised experiments to uncover Wolbachia's exact role in the development of river blindness. Using a mouse model for the disease, the researchers infected mice with extracts taken from worms treated with doxycycline (which contain relatively few Wolbachia) and with extracts from nontreated worms (with a normal Wolbachia load).

Mice exposed to the treated extracts showed significantly less thickening and haze of the eye's cornea, and less signs of inflammation such as infiltration of white blood cells into the cornea, compared to mice infected with the untreated extracts.

"These data show that Wolbachia itself has a major role in the disease's pathology," says Pearlman.

The body's innate immune response also plays a large part in how the disease progresses, according to the researchers. Mice lacking a key immune cell receptor molecule called TLR4 showed fewer signs of eye inflammation when exposed to Wolbachia-laden worm extract.

These mice also produced smaller amounts of certain other immune molecules and proteins that are normally recruited to fight infection, suggesting that TLR4 might regulate Wolbachia-triggered inflammation by controlling the expression of these immune molecules.

Pearlman and colleagues conclude that antibiotic treatment of Wolbachia may help reduce the severity of the symptoms of river blindness in already-infected individuals. In addition, targeting Wolbachia could prevent the spread of Onchocerca parasites, say the authors.

Recent studies have shown that Wolbachia-killing doxycycline treatments in infected humans also sterilize their worm hosts, breaking the cycle of ever-spawning microfilariae. Current ivermectin treatments, by comparison, only deplete the number of skin microfilariae for a few months, requiring continued doses to keep the parasite under control.

The other members of the research team include Amιlie v. Saint Andrι, Nathan M. Blackwell, Laurie R. Hall, Amy G. Hise, Jonathan H. Lass, and Eugenia Diaconu of University Hospitals of Cleveland and Case Western Reserve University, Norbert W. Brattig of Bernhard Nocht Institute for Tropical Medicine, and Mark J. Taylor and Louise Ford of the Liverpool School of Tropical Medicine in Liverpool, UK. This research was supported in part by the National Institutes of Health, German National Merit Foundation, the European Union, the German Research Foundation, the Wellcome Trust, Fight For Sight, and Research to Prevent Blindness Foundation.


Story Source:

The above story is based on materials provided by American Association For The Advancement Of Science. Note: Materials may be edited for content and length.


Cite This Page:

American Association For The Advancement Of Science. "River Blindness Caused By Bacteria, Not Worms, Suggesting Antibiotic Treatment For The Disease, Researchers Report." ScienceDaily. ScienceDaily, 14 March 2002. <www.sciencedaily.com/releases/2002/03/020313080147.htm>.
American Association For The Advancement Of Science. (2002, March 14). River Blindness Caused By Bacteria, Not Worms, Suggesting Antibiotic Treatment For The Disease, Researchers Report. ScienceDaily. Retrieved September 22, 2014 from www.sciencedaily.com/releases/2002/03/020313080147.htm
American Association For The Advancement Of Science. "River Blindness Caused By Bacteria, Not Worms, Suggesting Antibiotic Treatment For The Disease, Researchers Report." ScienceDaily. www.sciencedaily.com/releases/2002/03/020313080147.htm (accessed September 22, 2014).

Share This



More Plants & Animals News

Monday, September 22, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Cat Lovers Flock to Los Angeles

Cat Lovers Flock to Los Angeles

AFP (Sep. 22, 2014) — The best funny internet cat videos are honoured at LA's Feline Film Festival. Duration: 00:56 Video provided by AFP
Powered by NewsLook.com
Washed-Up 'Alien Hairballs' Are Actually Algae

Washed-Up 'Alien Hairballs' Are Actually Algae

Newsy (Sep. 22, 2014) — Green balls of algae washed up on Sydney, Australia's Dee Why Beach. Video provided by Newsy
Powered by NewsLook.com
Raw: San Diego Zoo Welcomes Cheetah Cubs

Raw: San Diego Zoo Welcomes Cheetah Cubs

AP (Sep. 20, 2014) — The San Diego Zoo has welcomed two Cheetah cubs to its Safari Park. The nearly three-week-old female cubs are being hand fed and are receiving around the clock care. (Sept. 20) Video provided by AP
Powered by NewsLook.com
Chocolate Museum Opens in Brussels

Chocolate Museum Opens in Brussels

AFP (Sep. 19, 2014) — Considered a "national heritage" in Belgium, chocolate now has a new museum in Brussels. In a former chocolate factory, visitors to the permanent exhibition spaces, workshops and tastings can discover derivatives of the cocoa bean. Duration: 01:00 Video provided by AFP
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