Featured Research

from universities, journals, and other organizations

Parasites with greater infectivity associated with treatment failure

Date:
October 8, 2013
Source:
American Society for Microbiology
Summary:
Relapses after treatment for Leishmania infection may be due to a greater infectivity of the parasite rather than drug resistance, as has been previously thought.

Relapses after treatment for Leishmania infection may be due to a greater infectivity of the parasite rather than drug resistance, as has been previously thought, according to a study published in mBio, the online open-access journal of the American Society for Microbiology.

Visceral leishmaniasis, also called kala-azar, is a parasitic disease that strikes 400,000 people every year and kills around 1 in 10 of its victims. The disease has proven difficult to treat, in part because a large percentage of patients who take the drug of choice, miltefosine, relapse after treatment, coming down with the same disease all over again. Doctors and scientists have long suspected that drug resistance was behind the failure of miltefosine, but that's not so, according to the researchers. The study reveals that parasites in patients who relapse after leishmaniasis treatment have a greater infectivity than parasites from patients who were treated successfully. They are essentially a worse, more dangerous form of the parasite.

"Parasites from relapsed patients show an increased capacity to infect host cells," says co-author Manu Vanaerschot of the Institute of Tropical Medicine in Antwerp,Belgium. The authors write that it remains to be seen whether miltefosine treatment causes the increased infectivity of the parasite, or if parasites with greater infectivity are capable of escaping treatment.

Miltefosine is at the heart of a vast program aimed at ending visceral leishmaniasis on the Indian subcontinent (India, Bangladesh and Nepal), but 6.8% of Indian patients redevelop symptoms of the disease within 6 months after treatment and 20% of Nepalese patients relapse within 12 months after miltefosine treatment. Parasites collected from patients before and after treatment have been fingerprinted and are very close genetic matches, indicating that these patients are not simply re-infected with new parasites once their treatment ends, they are still carrying the same strain that sickened them before treatment. Other work revealed another surprising fact: parasites from relapsed patients were sensitive to miltefosine, so the failure of treatment was not due to drug resistance, a common suspect in cases where infectious disease treatment fails.

With re-infection and drug resistance now crossed off the list of possible reasons for the high relapse rate, the researchers set out to see what factors might really be at work. They examined the morphology of parasites taken from visceral leishmaniasis patients who were treated successfully and patients who relapsed. They found a significant association between the number of parasites in the metacyclic stage of their life cycle and patient treatment outcome. In other words, patients who relapsed were infected with parasites that have a greater infectivity, meaning they were more capable of infecting human cells.

The precise link between infectivity and treatment failure is not known, write the authors, but they propose that parasites with greater infectivity might cause a greater parasite load in the patient, making the case moredifficult to treat, or perhaps they are able to evade the drug by hiding in parts of the body it doesn't easily penetrate, like the skin.

Vanaerschot says he and his colleagues saw a similar correlation between infectivity and treatment failure in patients who had been treated with the types of drugs that used to be favored in the region, pentavalent animonials. "At the time we thought that it was a very special case. But now that we've also seen this in parasites treated with other drugs, this indicates that it might be a more common problem than we originally thought."

Co-author Jean-Claude Dujardin, of the Institute of Tropical Medicine and the University of Antwerp, in Belgium, says regardless of the underlying cause-and-effect relationship, the findings are a wake-up call about the possible effects a therapy might have on pathogens it's supposed to kill.

"When we develop a drug to fight against a pathogen, we need to think about possible collateral damage. Of course we have to use these drugs, but we need surveillance to see if more aggressive parasites start to spread," says Dujardin.


Story Source:

The above story is based on materials provided by American Society for Microbiology. Note: Materials may be edited for content and length.


Journal Reference:

  1. Keshav Raia,b, Bart Cuypersa, Narayan Raj Bhattaraib, Surendra Uranwb, Maya Berga, Bart Ostync, Jean-Claude Dujardina,d, Suman Rijale, Manu Vanaerschota. Relapse after Treatment with Miltefosine for Visceral Leishmaniasis Is Associated with Increased Infectivity of the Infecting Leishmania donovani Strain. mBio, October 2013

Cite This Page:

American Society for Microbiology. "Parasites with greater infectivity associated with treatment failure." ScienceDaily. ScienceDaily, 8 October 2013. <www.sciencedaily.com/releases/2013/10/131008091711.htm>.
American Society for Microbiology. (2013, October 8). Parasites with greater infectivity associated with treatment failure. ScienceDaily. Retrieved September 19, 2014 from www.sciencedaily.com/releases/2013/10/131008091711.htm
American Society for Microbiology. "Parasites with greater infectivity associated with treatment failure." ScienceDaily. www.sciencedaily.com/releases/2013/10/131008091711.htm (accessed September 19, 2014).

Share This



More Health & Medicine News

Friday, September 19, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

The Cost of Ebola

The Cost of Ebola

Reuters - Business Video Online (Sep. 18, 2014) As Sierra Leone prepares for a three-day "lockdown" in its latest bid to stem the spread of Ebola, Ciara Lee looks at the financial implications of fighting the largest ever outbreak of the disease. Video provided by Reuters
Powered by NewsLook.com
What HealthKit Bug Means For Your iOS Fitness Apps

What HealthKit Bug Means For Your iOS Fitness Apps

Newsy (Sep. 18, 2014) Apple has delayed the launch of the HealthKit app platform, citing a bug. Video provided by Newsy
Powered by NewsLook.com
U.S. Food Makers Surpass Calorie-Cutting Pledge

U.S. Food Makers Surpass Calorie-Cutting Pledge

Newsy (Sep. 18, 2014) Sixteen large food and beverage companies in the United States that committed to cut calories in their products far surpassed their target. Video provided by Newsy
Powered by NewsLook.com
Residents Vaccinated as Haiti Fights Cholera Epidemic

Residents Vaccinated as Haiti Fights Cholera Epidemic

AFP (Sep. 18, 2014) Haitians receive the second dose of the vaccine against cholera as part of the UN's vaccination campaign. Duration: 00:34 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:
from the past week

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