CDC-Supplied Drug Helps Save Kids From Brain-Eating Ameba

August 22, 2013

Two children appear to be recovering from a usually deadly infection caused by the "brain-eating ameba" with the help of an experimental antibiotic supplied by the Centers for Disease Control and Prevention (CDC).

The CDC announced today that it is making the antibiotic miltefosine available to treat cases of primary amebic meningoencephalitis (PAM) just a day after news broke that 12-year-old Zachary Reyna of LaBelle, Florida, had beaten his PAM infection after receiving the experimental antibiotic along with other drugs. His clinicians had borrowed a medication strategy that appears to have saved the life of Kali Hardig, a 12-year-old girl in Benton, Arkansas, who contracted PAM in July.

The CDC provided the miltefosine used to treat both children, said Jennifer Cope, MD, an epidemiologist in the Division of Foodborne, Waterborne, and Environmental Diseases in the CDC's National Center for Emerging and Zoonotic Infectious Diseases.

The brain infection stems from the free-living ameba (FLA) Naegleria fowleri, which thrives in warm freshwater and hot springs. Reyna caught the bug after knee-boarding in a water-filled ditch, and Hardig fell sick after swimming in a spring-fed water park, according to news accounts.

PAM is almost always fatal. Of 128 known cases in the United States from 1962 through 2012, there was only a single survivor, in 1978.

Reyna's recovery has just started, and his condition is still perilous. His father posted on Facebook yesterday that although tests show "negative activity from the amoeba," the infection has extensively damaged the boy's brain. Hardig's rebound is cause for more hope, Dr. Cope told Medscape Medical News. "We're more and more confident that we can call this 12-year-old a survivor." According to news reports, she is beginning to walk and talk again.

"We're definitely excited," Dr. Cope said about the effect of miltefosine on the Arkansas girl. "We're talking about 30-plus years since we've seen anyone survive."

Importing the Drug in the Past Could Take Up to a Week

Miltefosine, made in Germany, is marketed in other countries to treat leishmaniasis, a potentially fatal infection transmitted by sandflies. A Canadian pharmaceutical company has asked the US Food and Drug Administration (FDA) to approve the drug for this indication. When combined with other antibiotics and antifungals, miltefosine has increased the odds of survival for patients with another FLA infection called granulomatous amebic encephalitis, which is caused by Balamuthia mandrillaris and Acanthamoeba.

The FDA, in conjunction with the CDC, has permitted the emergency importation and use of miltefosine on a patient-by-patient basis to treat FLA infections since 2009. Importing the drug each time from Germany, which might take up to a week, has worked well enough for slower-growing FLA infections, but not for PAM, which develops much faster, said Dr. Cope. This barrier to timely treatment, she said, explains why patients with PAM treated with miltefosine and other antibiotics in the past have not survived, although the drug has killed N fowleri in vitro.

To speed up miltefosine therapy, the CDC worked with the FDA to expand the drug's investigational status so that it is directly available from a CDC stockpile whenever it is needed to treat PAM and other FLA infections. Dr. Cope said the CDC was able to ship the drug from its headquarters in Atlanta, Georgia, to Hardig's physicians in Arkansas in 12 hours on request.

Miltefosine is not a "magic bullet" for PAM, noted Dr. Cope, because it is prescribed along with a clutch of other antibiotics. In the cases of Hardig and Reyna, miltefosine was administered along with amphotericin B, rifampin, fluconazole, and azithromycin. Clinicians also cooled Hardig below her body temperature to reduce brain swelling, said Dr. Cope, who did not know whether Reyna received this treatment.

Miltefosine is well tolerated, according to the CDC. The most commonly reported adverse events are gastrointestinal symptoms such nausea and vomiting.

Physicians who suspect a patient is infected by N fowleri or some other FLA can contact an FLA expert at the CDC about diagnostic assistance, specimen collection guidance, shipping instructions, and treatment recommendations. The telephone number to call is 1-770-488-7100.

More information on PAM is available on the CDC Web site.

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