17.8.11
Mosquitoes 'developing resistance to bed nets'
Mosquitoes can rapidly develop resistance to bed nets treated with insecticide, a new study from Senegal suggests. In recent years the nets have become a leading method of preventing malaria, especially in Africa.
The researchers also suggest the nets reduced the immunity of older children and adults to malaria infection.
But other experts say the study was too small to draw conclusions about the long term effectiveness of nets.
In the war against malaria, the cheapest and most effective weapon to date has been the long-lasting insecticide-treated bed net.
Over the last few years the nets have been widely distributed in Africa and elsewhere - the World Health Organization says that when properly deployed they can cut malaria rates by half.
In Senegal, around six million nets have been distributed over the last five years. In this study researchers looked at one small village in the country and tracked the incidence of malaria both before and after the introduction of nets in 2008.
Within three weeks of their introduction the scientists found that the number of malaria attacks started to fall - incidence of the disease was found to be 13 times lower than before the nets were used.
The researchers also collected specimens of Anopheles gambiae, the mosquito species responsible for transmitting malaria to humans in Africa. Between 2007 and 2010 the proportion of the insects with a genetic resistance to one type of pesticide rose from 8% to 48%.
By 2010 the proportion of mosquitoes resistant to Deltamethrin, the chemical recommended by the World Health Organization for bed nets, was 37%.
In the last four months of the study the researchers found that the incidence of malaria attacks returned to high levels. Among older children and adults the rate was even higher than before the introduction of the nets.
The researchers argue that the initial effectiveness of the bed nets reduced the amount of immunity that people acquire through exposure to mosquito bites. Combined with a resurgence in resistant insects, there was a rapid rebound in infection rates.
The scientists were led by Dr Jean-Francois Trape from the Institut de Recherche pour le Developpement in Dakar. The authors are worried that their study has implications beyond Senegal.
"These findings are a great concern since they support the idea that insecticide resistance might not permit a substantial decrease in malaria morbidity in many parts of Africa," they write.
But other experts in this field say that it is impossible to draw wider conclusions.
True trend?In a commentary, Dr Joseph Keating from Tulane University, New Orleans, US, acknowledges the concerns the study raises.
"If indeed this is a real trend we are seeing in this part of Senegal then it has very important implications for future malaria prevention and control strategies."
But he says there are a number of important provisos.
"I would certainly advise extending the study a couple of more years which would be helpful in determining if this is a true trend or is it something specific to that particular area.
"We need to be very careful when generalising these data to the larger continent of Africa as a whole; there is plenty of variation between communities and within communities."
Dr Keating acknowledges there is a debate within the scientific community on the issue of acquired immunity, the level of resistance to the disease that people get through being bitten.
"There is a huge discussion around acquired immunity. And how long does it take for an individual to lose this immunity once they are no longer exposed to parasite?
"So if you give someone a net he would be less exposed to parasites and it is possible that their immunity would shift to become less - but I think over all the benefits of nets certainly outweigh this potential loss of acquired immunity." (
3.8.11
Scientists Find New Superbug Strain of Salmonella
Scientists have identified an emerging "superbug" strain of salmonella that is highly resistant to the antibiotic Ciprofloxacin, or Cipro, often used for severe salmonella infections, and say they fear it may spread around the world.
The strain, known as S. Kentucky, has spread internationally with almost 500 cases found in France, Denmark, England and Wales in the period between 2002 and 2008, according a study in the Journal of Infectious Diseases.
French researchers who led the study also looked at data from North America and said reports of infection in Canada and contamination of imported foods in the United States suggest the strain has also reached there.
The study was published Wednesday as U.S. health officials reported a multi-state outbreak of another strain of antibiotic-resistant salmonella — called S. Heidelberg — which has so far made at least 76 people sick and killed one.
Salmonella infection is a major public health problem worldwide. There are an estimated 1.7 million infections in North America each year and more than 1.6 million cases were reported between 1999 and 2008 in 27 European countries.
Although most salmonella infections produce only mild gastroenteritis with stomach cramps, fever and diarrhea, older people or those with weaker immune systems are particularly at risk of life-threatening infections.
These cases are typically treated with drugs in a class of antibiotics known as fluoroquinolones, which includes the commonly-used medicine ciprofloxacin. Cipro was originally developed by Bayer and is now available as a generic.
But as with many bacteria, multi-drug-resistant, or "superbug," strains of salmonella infection have developed as the bacteria has found new ways of outfoxing the drugs, and these can spread in food and from person to person.
In the French-led study, Francois-Xavier Weill and Simon Le Hello from the Institut Pasteur looked at surveillance data from the European countries and the United States and found 489 reported cases of the superbug S.Kentucky strain. Case numbers rose every year from 3 cases in 2002 to 174 cases in 2008.
They said the earliest infections seemed to have been picked up mainly in Egypt between 2002 and 2005, but since 2006 the infections have also been acquired in various parts of Africa and the Middle East.
"The absence of reported international travel in approximately 10 percent of the patients suggests that infections may have also occurred in Europe through consumption of contaminated imported foods or through secondary contaminations," they wrote.
As part of the study, multi drug-resistant S. Kentucky was also isolated from chickens and turkeys from Ethiopia, Morocco, and Nigeria, suggesting "poultry is an important agent for infection" the researchers said, adding the common use of fluoroquinolone antibiotics in chicken and turkey production in Nigeria and Morocco "may have contributed to this rapid spread."
They said the study highlights the importance of public health surveillance in a global food system.
"We hope that this publication might stir awareness among national and international health, food and agricultural authorities so that they take the necessary measures to control and stop the dissemination of this strain before it spreads globally," the researchers said. (Fox News)
HIV infection rates mostly stable, increasing among young, gay black men
The number of new HIV infections in the United States has remained steady, at around 50,000 cases a year over the past four years, according to the Center for Disease Control and Prevention. The new data, published online Wednesday in the scientific journal PLoS ONE, show the largest increases were among bisexual men and men who have sex with men (MSM). Of that group, young, black men had what the agency called "alarming increases."
"More than 30 years into the HIV epidemic, about 50,000 people in this country still become infected each year," said CDC Director Dr. Thomas Frieden. "Not only do men who have sex with men continue to account for most new infections, young gay and bisexual men are the only group in which infections are increasing, and this increase is particularly concerning among young African American MSM."
The data look at the period between 2006 and 2009. It's the first time HIV incidence numbers were calculated using a lab test that distinguishes recent infections from existing infections. The CDC estimates that MSM make up 2% of the U.S. population but 61% of 2009's new infections. Young men between the ages of 13 and 29 who had sex with men had the highest new infection rate/increase - more than a quarter of all new cases. The agency says while young MSM of all ethnic backgrounds have been hit hard, young blacks were the only group to see significant increases over the four-year period. Infection rates among this population jumped 48% during that time.
The reasons, according to the CDC, aren't clear. It says individual risk behaviors alone do not account for the increase. It says black MSM tend to have fewer sexual partners, are less likely to do IV drugs and are no more likely to have anal intercourse than other gay men. But the data suggests a number of possibilities for these trends - that young black MSM often don't know their HIV status, that the stigma of HIV and homosexuality in the black community can often impede the use of prevention services and that often there is limited access to health care services like testing and treatment in the black community.
"We are deeply concerned by the alarming rise in new HIV infections in young, black gay and bisexual men and the continued impact of HIV among young gay and bisexual men of all races," said Dr. Jonathan Mermin, director of CDC's Division of HIV/AIDS Prevention. "We cannot allow the health of a new generation of gay men to be lost to a preventable disease. It's time to renew the focus on HIV among gay men and confront the homophobia and stigma that all too often accompany this disease."
It's not just African Americans who are disproportionately affected. The data suggest that communities of color are shouldering a heavier burden. In 2009, blacks made up 14% of the population but accounted for 44% of all new infections. Their infection rate was almost 8 times that of whites. The rate among black men was the highest of any group - more than six times that of white men. The infection rate among black women was 15 times higher than white women. Hispanics make up about 16% of the population, and 20% of new HIV infections. Their rate of infection is about three times that of whites.
Dr. Kevin Fenton, director of CDC's National Center for HIV/AIDS, Viral Hepatitis, STD and TB Prevention, says the data are encouraging in that the number of new infections has significantly dropped from the peak seen in the mid-1980s, however there is still much work ahead. "We have plateaued at an unacceptably high level. Without intensified HIV prevention efforts, we are likely to face an era of rising infection rates and higher health care costs for a preventable condition that already affects more than 1 million people in this country."
Phill Wilson, founder & chief executive officer of the Black AIDS Institute, whose mission is to stop the pandemic in black communities says we have the tools to end the epidemic, but prevention efforts have been stalled for some time.
"What these numbers tell us is we are not going to be successful in driving down new infections until and unless we invest in those populations most at risk, and in America today those populations are black Americans, men who have sex with men of all races and especially young, black men who have sex with men," Wilson said. "It is outrageous that over the last three years reported in this data, since 2006-2009, we see a 48% increase in new cases among young black men who have sex with men age 13-29. We have to build the infrastructure and the capacity in these communities to respond to this epidemic in an appropriate manner."
The agency says it's working on a number of interventions for hardest hit populations. Officials hope some of the latest new prevention strategies like pre-exposure prophylaxis (PrEP) - exposing high risk populations to HIV drugs to prevent infection in both MSM, and heterosexual men and women - will have a strong impact on infection rates. In July, new data from several studies found PrEP was safe and effective in preventing infection in these populations. (Saundra Young/CNN News)
2.8.11
Tiny blood card offers easier tests for remote areas
A cheap and portable blood test could provide a breakthrough for diagnosing infections in remote areas of the world, a scientific study says.
The mChip is about the size of a credit card and can diagnose infections within minutes, according to a study in the journal Nature Medicine.
Prototype tests for diseases such as HIV and syphilis in Rwanda showed almost 100% accuracy, it said.
The US-developed device has a projected cost of $1 (60p).
This would make it much cheaper than the lab-based tests currently used.
The plastic chip contains 10 detection zones, and can test for multiple diseases with only a pinprick of blood.
Results can be seen with the naked eye or with a low-cost detector.
"The idea is to make a large class of diagnostic tests accessible to patients in any setting in the world, rather than forcing them to go to a clinic to draw blood and then wait days for their results," said Samuel Sia, a professor at New York's Columbia University who is a lead developer of the device.
Hundreds of tests using a prototype of the device were carried out in Kigali, Rwanda. They showed 95% accuracy for HIV and 76% accuracy for syphilis, the study says.
Researchers hope to use the mChip to help increase testing of sexually-transmitted diseases (STDs) in pregnant women, particularly in Africa.
A version of the device has also been designed to test for prostate cancer. (BBC News)
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