Volume 358:428-431 January 24, 2008 Number An Appraisal of "Chronic Lyme Disease" To the Editor: Feder et al., Oct. 4 issue,1 review the great controversy surrounding "chronic Lyme disease."v For most patients with this diagnosis, the authors advocate against the use of antibiotics. But before the decision is made not to use antibiotics for patients with post–tick-bite symptoms, anaplasma, babesia, bartonella, 2 and ehrlichia must be ruled out. These tick-borne 2 intracellular pathogens are difficult to diagnose and can establish long-term, persistent infection. 3,4,5 Anaplasma, babesia, and bartonella are underdiagnosed: the nonspecific symptoms of infections with these organisms tend to be ascribed to the more easily identifiable Lyme disease, which often accompanies them.2,3,4,5,6 Indeed, when studied prospectively, 65 of 161 patients with Lyme disease, 40%, were coinfected with babesia, and 11 of 161, 7%, with anaplasma.6 Accurate diagnosis of these infections helps steer successful treatment: babesia 3 and bartonella 5 are especially difficult to eradicate. Accurate diagnosis is also important, since babesia 3 and anaplasma 4 can spread through blood transfusion. As Feder et al. note, "chronic Lyme disease" is often unrelated to borrelia. If symptoms occur after a tick bite in the absence of evidence of active borrelia infection or if they persist despite anti-borrelia treatment, another tick-borne infection should be suspected. If such an infection is found, the patient may indeed benefit from appropriate antibiotics