MONDAY, Sept. 5 (HealthDay News) -- An uncommon, but potentially fatal, tick-borne illness may be creeping into the U.S. blood supply and doctors need to develop a way to spot it, researchers report.

Babesiosis is a parasitic infection that is transmitted through a tick bite or during a blood transfusion. Symptoms range from mild flu-like symptoms to severe difficulty with breathing, organ damage and death. People with compromised immune systems are most at risk for fatal babesiosis infection.

The first tick-borne case of babesiosis was documented in Massachusetts in 1969, and the first known transfusion-related infection occurred in 1979. Since then, there have been 159 transfusion-associated babesiosis cases reported in the United States, according to a study published in the Sept. 6 issue of the Annals of Internal Medicine.

There is no approved screening test for blood donors, and many people have no symptoms so they don't even realize they are infected when they donate blood.

Study author Dr. Barbara Herwaldt, a medical epidemiologist at U.S. Centers for Disease Control and Prevention, called the threat "uncommon, but important."

Transfusion-related cases know no boundaries. "Most tick-borne cases of babesiosis occur during the warm months and have only been seen within seven states in Northeast and Midwest," she said. "Transfusion-related infection can occur in all four seasons and, in theory, could occur anywhere," she said. "Blood donors travel and blood components are shipped across state lines."

The U.S. Food and Drug Administration is currently working on ways to keep babesia out of the blood supply, but until that occurs doctors must put babesiosis on their radar screen, particularly if someone has unexplained fever or a certain type of anemia known as hemolytic anemia (low red blood cell count). These are the blood cells where the parasite takes up residence during babesiosis infection.

"Consider the diagnosis and then order the appropriate test," Herwaldt said. Diagnosis involves looking at droplets of blood under a microscope. "Babesiosis is treatable with antibiotics that are commonly and readily available."

"Babesia infection is on the rise and is potentially fatal, especially for immune-compromised and older people," said Philip Tierno, director of clinical microbiology and immunology at New York University Langone Medical Center in New York City. "This is an important consideration in terms of testing on blood supply."

Time is of the essence, he said. The best option right now is for blood banks to look at a droplet of a donor's blood under a microscope. They may not be able to tell what is tainting the blood, but they will know it is tainted, he explained.

"They would be able to tell that the red cells may be parasitized by something, and that the blood needs to be further checked in microbiology lab," he said. "This is the best option right now in light of increase in numbers of cases."

Babesiosis in the U.S. blood supply "is something to be reckoned with, and by the time that anyone develops a test that is simple enough to be used by blood banks, it will be too late," he said. Excluding people with a history of babesiosis infection from the blood donor pool won't work because most people don't know they have it.

People who are receiving blood transfusions may be especially vulnerable to babesiosis, he said.

Prevention also has a role in keeping infection out of the blood supply in the first place, he said. "Keep away from ticks," Tierno said. "The same ticks that can give you Lyme disease and other types of tick-borne illness can give you babesiosis."

When you go outdoors during tick season, wear protective clothing and use an insect repellent, he added.

The CDC also recommends doing full-body checks and showering within a few hours of being in the woods, as well as tossing used clothes in the dryer to kill any ticks that may be hiding on them.

More information

Learn more about babesiosis at the U.S. Centers for Disease Control and Prevention.