SC Connecticut News

For the tick-borne infection babesiosis, adding the antimalarial drug tafenoquine may be a lifesaver for vulnerable patients who relapse after standard treatment, according to a new study by researchers at the Yale School of Public Health (YSPH).

“Tafenoquine is going to make a huge difference, I think, in people who are severely immunocompromised,” said Dr. Peter J. Krause, MD, a senior research scientist in the YSPH Department of Epidemiology of Microbial Diseases and first author of the study, which was conducted in collaboration with researchers at Brown University and Tufts Medical Center.

Alongside Lyme disease and anaplasmosis, babesiosis is one of the most common tick-borne diseases globally. It is endemic in the Northeast, upper Midwest, and northeastern China. The infection typically results in fevers as well as soaking sweats, chills, headache, malaise, joint and muscle pain, and/or weakness.

The disease is caused by parasitic microorganisms of the genus Babesia and has long been known to infect cattle, mice, and other animals. It was first reported in humans in 1957. As with malaria, the parasite invades red blood cells. That similarity intrigued researchers who first considered using tafenoquine in babesiosis.

In most people, babesiosis treatment is straightforward. Weakened immunity due to age (over 50 years), certain cancers, HIV/AIDS use of immunosuppressant drugs or lack of a spleen can render a patient vulnerable to relapse after apparent cure. Among those who relapse as many as one-fifth die.

The new study describes five New England residents with immune deficiencies whose Babesia microti infections were not permanently eliminated by the usual standard of care — a two-drug combination treatment that was established in an earlier study by Krause and collaborating investigators published in the New England Journal of Medicine in 2000.

Instead these five patients experienced dangerous relapses.

Krause and colleagues considered treating these patients with tafenoquine normally used to prevent or treat malaria. A study of tafenoquine in hamsters inspired this idea though it had failed in a previously reported human case of relapsing babesiosis.

This time it worked repeatedly. Providers added tafenoquine to the drug regimens of four highly immunocompromised patients with relapsing babesiosis all were cured (A fifth received tafenoquine on its own which did not clear the infection).

A higher dose was used than in the previously reported case that failed.

Tafenoquine overcame antimicrobial resistance in the Babesia microti parasite whose genome had mutated researchers found.

By demonstrating treatment success these results are helping shape a new standard for treating babesiosis among such patients.

“This is the first case series I think it confirms that tafenoquine can be very useful adjunct” Krause said.

The study appears Clinical Infectious Diseases.

The standard two-drug combination of atovaquone azithromycin “works virtually every patient mild disease” said co-author Edouard Vannier assistant professor Division Geographic Medicine Infectious Diseases Tufts Medical Center Boston Massachusetts.

Vannier’s role was test organism genetic mutations could explain drug resistance.

“In patients severely ill severely immunocompromised because resolution does not happen fast enough parasite chance mutate,” Vannier explained “Very often atovaquone resistance noted.”

“Testing mutations future treating these patients opens door personalized medicine,” Vannier said Detecting mutation may allow providers course-correct more effective treatment

“The whole idea tailor therapy patient” he said

Several limitations noted study Tafenoquine treatment unsafe patients inherited condition G6PD deficiency study too small determine best duration treatment clinical trial planned

Study funding provided Llura A Gund Laboratory Vector-borne Disease Research Gordon Llura Gund Foundation National Institutes Health funds Dammin Windsor families

Krause Vannier Ralph Rogers Division Infectious Diseases Warren Alpert Medical School Brown University Providence Rhode Island contributed equally project Other co-authors include Monika K Shah Infectious Diseases Service Department Medicine Memorial Sloan Kettering Cancer Center MSKCC New York New York Department Medicine Weill Cornell Medical College Cornell University New York Rich Kodama also Infectious Diseases Service MSKCC HeeEun Kang Jeffrey Parsonnet both Section Infectious Diseases International Health Dartmouth-Hitchcock Medical Center Lebanon New Hampshire