Officials say the brain-eating amoeba found in a west Ascension Parish water system this summer has been eradicated.
The announcement follows weeks of treatment involving pumping increased amounts of chlorine into water lines outside Donaldsonville.
State health officials say water with the amoeba has been safe to drink. However, water containing the amoeba poses a risk if it gets up someone’s nose and the amoeba has access to the brain.
Since 2011, three deaths in Louisiana have been attributed to the harmful strain of amoeba, prompting the Department of Health and Hospitals to order the state’s water systems to raise their chlorination levels.
Original Source: http://www.dddmag.com/news/2015/09/scientists-create-immunity-deadly-parasite-manipulating-hosts-genes
There are two common approaches to protecting humans from infectious disease: targeting pathogens and parasites with medicines such as antibiotics, or dealing with the conditions that allow transmission.
Now exciting new research from the University of Virginia School of Medicine and the University of Colorado demonstrates the effectiveness of a third strategy: adjusting the landscape of the human body to remove the mechanism that allows pathogens to cause disease.
The researchers have silenced genes within human cells to induce immunity to the parasite E. histolytica, which infects 50 million people and causes 40,000 to 110,000 deaths worldwide each year via severe diarrhea. “This amoeba is a cluster bomb – a voracious killer,” said U.Va.’s Chelsea Marie, a research scientist in infectious diseases and international health, noting the challenge the researchers faced in blocking the amoeba’s ability to kill human cells. “In the back of my mind, I was thinking the parasite was going to decimate the host cells no matter what we did with their genetics.”
The research group used a technique called RNAi to create a library of bladder cancer cells with thousands of independent, silenced genes. Then they challenged these cultures with E. histolytica. “We do this all the time in cancer research,” said Dr. Dan Theodorescu, formerly of U.Va. and now director of the University of Colorado Cancer Center. “Commonly, we’re looking for genes that, when silenced, will make cells more susceptible to chemotherapy.” In this case, the analogue of chemotherapy was the infectious, dangerous pathogen.
E. histolytica proved a stubborn foe, decimating many thousands of the manipulated cell cultures. However, a small number of cells seemed to resist the parasite. Was this the random chance of lucky survival, or had silenced genes somehow provided immunity?
To find out, Marie discarded the dead cells and retested the survivors; again she infected the cells with E. histolytica. “It wasn’t a fluke,” she said. “We did this over nine generations of cells, each time selecting the cells that survived and then re-applying the parasite. Over these generations of selection, we saw the cultures becoming more and more enriched for cells lacking specific genes.”
Using next-generation sequencing, Marie identified the genes that conferred resistance and found that many were involved in managing the flow of potassium into and out of human cells. A follow-up experiment showed that, left unimpeded, E. histolytica caused intestinal cells to pump out potassium directly before cell death.
“We started to see a pretty clear line of reasoning,” Theodorescu said. “The parasite was causing potassium efflux right before cell death, and cells that happened to be unable to transport potassium didn’t die.”
“There is a clear need for new drugs targeting E. histolytica,” said Marie’s mentor, Dr. William A. Petri Jr., chief of U.Va.’s Division of Infectious Diseases and International Health. “Right now there is a single antibiotic that works against this parasite. We know that eventually the parasite will develop resistance to the antibiotic, and at that point there’s no plan B. This could be the plan B – targeting the human genes that enable the parasite to cause disease.”
Marie is pushing forward, working to make the technique used in the study more efficient and move it toward use in humans. But just demonstrating it can work is a huge accomplishment.
“This is a major finding with translational implications for this infection that causes so many deaths worldwide, but also proof that this cancer-science approach can be used to explore genetic mechanisms of resistance in the field of infectious disease,” Theodorescu said.
People who become contract Naegleria fowleri may survive a little longer, or altogether, if doctors prevent their immune systems from responding to the infection. Centers for Disease Control and Prevention
Naegleria fowleri lives up to its nickname: the brain-eating amoeba. After a rush of contaminated fresh water, usually from lakes, rivers, and hot springs, enters the nose, the parasite moves up the nasal cavity toward the brain, where it feeds on cells and releases proteins that destroy brain tissue. This infection, called primary amebic meningoencephalitis (PAM), is almost always untreatable — in the U.S., only three of the 133 people who became infected since the parasite’s discovery in 1962 have survived. New approaches to treatment, however, may soon change that.
Doctors have treated the infection with the breast cancer drug miltefosine since at least 2013, when several cases of the infection emerged in Southern states. However, the parasite infects the brain so quickly — patients can die within five days of infection — that the drug is often not administered fast enough. Because of this, researchers have been looking for new treatment approaches, and a new study may have found one, suggesting that it’s the body’s own immune response that contributes to the parasite’s lethality.
Abdul Mannan Baig, of the Department of Biological and Biomedical Sciences at Aga Khan University in Pakistan, found that the brain reacts swiftly and intensely to the parasitic infection. As the parasite releases enzymes and toxins into the brain, destroying cells, the immune system mounts a counterattack, triggering an inflammatory response. This response backfires, however, causing pressure to build up and eventually break the blood-brain barrier. Thus, neuronal damage ensues not only from the ameba but also from inflammation.
Baig came to these conclusions after testing N. fowleri against brain cells in lab dishes. Brain cells paired with immune cells died about eight hours sooner than brain cells that didn’t get help from immune cells, New Scientist reported. Because of this, Baig suggested one of the first things doctors treat infected patients with is immunosuppressive drugs, and then drugs that combat PAM.
This approach could be especially beneficial to people living in Pakistan and the surrounding region, where Baig says about 20 people die each year from PAM. In the U.S., that number is far smaller. “It is worth testing, but it is very hard to test because the infection is so rare,” Jennifer Cope, of the Centers for Disease Control and Prevention, told New Scientist. Still, as climate change causes increases in temperatures across the U.S., infections may become more common.
Source: Baig AM. Pathogenesis of amoebic encephalitis: Are the amoebas being credited to an ‘inside job’ done by the host immune response? Acta Tropica. 2015.