Cahill et al discuss on anaplasmosis and ehrlichisis as rickettisial tickbone diseases that have had at least a twofold increase in prevalence in the US since 2000. Surveillance efforts are complicated by ambiguous terminology and serologic testing with antibody cross-reactivity. During 2007-2008, the number of physician-reported anaplasmosis cases nearly doubled in Maine, and ehrlichiosis cases increased more than fourfold. To examine this increase, the Maine Department of Health and Human Services analyzed available data on tick burden and physician-reported cases of anaplasmosis and ehrlichiosis during 2000-2008. This report describes the results of that analysis, which indicated that Ixodes scapularis was broadly distributed in Maine, whereas Amblyomma americanum was scarce. A CDC editorial note is also presented.
Vol. 58 / No. 37 MMWR 1033 Anaplasmosis and Ehrlichiosis — Tick Surveillance Data Maine, 2008 During 2000–2008, the Vector Borne Disease Laboratory of the Maine Medical Center Research Institute conducted active Anaplasmosis and ehrlichiosis are rickettsial tickborne dis- surveillance of ticks in Maine (through flagging and trapping) eases that have had at least a twofold increase in prevalence and passive surveillance (through receipt of ticks submitted in the United States since 2000 (1,2). Despite similar clinical by state residents through the mail) (4). A total of 5,089 presentations, the causative organisms are carried by different I. scapularis were collected, but only 15 A. americanum ticks ticks with distinct geographic and ecologic associations (3). were detected. All life stages of I. scapularis (larvae, nymphs, Surveillance efforts are complicated by ambiguous terminology and adults) were identified; the tick distribution increased and serologic testing with antibody cross-reactivity. Although and expanded along the southern coastline and up the river anaplasmosis historically has been reported in Maine, ehrli- valleys, corresponding to areas of increasing settlement of chiosis has been reported infrequently. During 2007–2008, human populations in this geographic distribution. During the number of physician-reported anaplasmosis cases nearly 2007–2008, Maine residents submitted 1,968 I. scapularis and doubled in Maine, and ehrlichiosis cases increased more than only six A. americanum. The surveillance results suggested that fourfold. To examine this increase, the Maine Department of A. americanum, the ehrlichiosis vector, had only a sparse and Health and Human Services (MDHHS) analyzed available data sporadic distribution in Maine. on tick burden and physician-reported cases of anaplasmosis and ehrlichiosis during 2000–2008. This report describes the Human Anaplasmosis Surveillance Data results of that analysis, which indicated that Ixodes scapularis (the tick vector for Anaplasma phagocytophilum) was broadly During 2000–2008, a total of 45 cases of anaplasmosis cases distributed in Maine, whereas Amblyomma americanum (the were reported in Maine. Fifteen (33%) cases were confirmed, tick vector for Erhlichia chaffeenisis) was scarce. Moreover, 95% 30 (67%) were probable, and no suspect cases were reported of physician-reported ehrlichiosis cases lacked a concurrent (Tables 1 and 2). Among the 15 confirmed cases, three (20%) serologic assessment to exclude anaplasmosis, suggesting that patients were diagnosed by demonstration in paired sera of a antibody cross-reactivity might have resulted in misclassifica- fourfold or greater increase in antibodies to A. phagocytophi- tion. In 2008, Maine modified case classification to enhance lum in acute versus convalescent samples; 12 (80%) patients specificity; ehrlichiosis cases that lack a concurrent test for were diagnosed by polmerase chain reaction (PCR) detection anaplasmosis are now classified as suspect rather than probable of A. phagocytophilum DNA, including two patients who also and therefore are not included in national surveillance summa- had positive single A. phagocytophilum serologic test. Among ries. The accuracy of case classification and surveillance can be the 30 probable cases, 23 (77%) patients were diagnosed only improved by educating health-care providers regarding 1) the by a single test for antibodies to A. phagocytophilum, includ- expected geographic distribution of tick vectors and 2) recom- ing one (3%) patient who also had detection of morulae mendations for confirmatory testing to distinguish between the consistent with A. phagocytophilum on a blood smear. Seven causative organisms of anaplasmosis and ehrlichiosis. (23%) patients were tested for antibodies to both A. phago- In Maine, laboratories electronically report positive anaplas- cytophilum and E. chaffeensis, and all showed higher antibody mosis and ehrlichiosis results to the health department (referred titers to A. phagocytophilum. The median patient age among to as physician reported). Field epidemiology personnel follow all confirmed and probable cases was 57 years (range: 21–89 up positive results by interviewing physicians and patients and years); 28 patients (62%) were males. Seventeen (38%) by obtaining clinical, laboratory, and epidemiologic informa- patients were hospitalized, and one (2%) patient died from tion required to complete the CDC tickborne rickettsial disease renal failure relating to infection. Two (4%) patients were case report form.* MDHHS conducted a review of available diagnosed with concurrent Lyme disease, and two (4%) with data on tick burden in the state and reviewed the clinical and concurrent babesiosis. Reported anaplasmosis cases
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