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 e