Avian Reservoirs of the Agent of Human Granulocytic Ehrlichiosis?

To the Editor: Human granulocytic ehrlichiosis (HGE), first described in 1994 (1), is the second-most common tick-borne disease in the United States; Lyme disease is the most prevalent.Both diseases are transmitted by blacklegged ticks (Ixodes scapularis Say) that are abundant in southern New York state (2).Factors that influence the risk for infection, particularly the role of wildlife in transmitting the etiologic agent, Anaplasma (formerly Ehrlichia) phagocytophilum (3,4), to vector ticks are not well understood.In the absence of transovarial transmission (5,6), acquisition of A. phagocytophilum by its vector must result either from feeding on the blood of reservoircompetent hosts or by cofeeding of uninfected ticks in close proximity to infected ticks (7).The role that birds may play in HGE ecology is potentially very important.Birds in the northeastern United States routinely host immature I. scapularis (8), and several species are competent reservoirs of Borrelia burgdorferi (9), the causative agent of Lyme disease, thus providing an opportunity to transport infected ticks to new areas.While data for HGE are lacking, A. phagocytophilum-infected I. ricinus nymphs have been collected from migrating birds in Sweden (10); reservoir competence was not established, however.Our goal was to determine if several common bird species might serve as reservoirs of A. phagocytophilum and, as such, transmit the pathogen to feeding I. scapularis larvae.Birds were sampled at a deciduous woodland preserve in Tarrytown, Westchester County, New York, an area where Lyme disease and HGE are endemic.Birds were captured with Japanese mist nets (#3, EBBA Net Committee, Bryn Athyn, PA), and all