My friend just told me that she has been diagnosed with babesiosis, in combination with Lyme disease. She has been treated for Lyme disease for seven years now (with limited success), but this is the first time any doctor ever mentioned babesiosis. Can you tell me what the disease is and how it affects humans? Also, what is its connection with Lyme disease?

S.

Babesiosis is an infection by a group of protozoa called Babesia. The disease is similar in many ways to malaria. However, it is most commonly seen in the United States, where malaria is quite rare. Babesiosis is an important disease of cattle, and livestock infections have resulted in substantial economic losses in the past. In the United States, the disease is most commonly seen in the northeast, particularly parts of Massachusetts. Cases have also been reported in the Midwest and along the West Coast.

As you may know, the northeastern United States is the region where Lyme disease is also most prevalent. That is because both diseases are spread by the same creature, the deer tick (species name Ixodes scapularis). In fact, there are numerous reports of the same patient being infected with Babesia and Borrelia burgdorferi (which causes Lyme disease) simultaneously.

Babesiosis is a highly variable disease. In many patients, the disease is mild, causing fatigue, fever, chills and headache. Conjunctivitis (red eyes), sore throat, cough, vomiting and abdominal pain may also occur. Two groups of patients are at higher risk of severe disease. First are patients who have no spleen. The spleen is an organ in the upper left part of the abdomen that aids in the body's immune defense against various types of organisms. Babesiosis patients who have had their spleens removed due to trauma or disease can develop hemolytic anemia (the breakdown of red blood cells), liver disease, lung disease and even death. For some reason, in Europe, most cases of babesiosis involve patients who have no spleen, and severe disease has frequently resulted in death. The other patients at increased risk of severe disease are the elderly. Such patients can develop many of the symptoms of patients without a spleen.

Babesiosis is diagnosed quite easily. A smear of blood will show microscopic organisms. The infection is sometimes confused with malaria, but an experienced laboratory and a physician's knowledge of the two diseases will usually lead to an accurate diagnosis. Given the fact that the same tick can transmit both babesia and Lyme disease, some experts recommend that all patients diagnosed with babesiosis be tested for Lyme disease as well.

Treatment for babesiosis is relatively straightforward. In mild cases, patients generally recover without treatment. In more severe cases, treatment with quinine (trade name Quinamm) and clindamycin (Cleocin) is usually successful. If anemia is severe, a blood transfusion may be necessary.