HEMOCYTIC RICKETTSIA-LIKE ORGANISMS IN IXODES-SCAPULARIS - TRANSOVARIAL AND TRANSOVARIAL TRANSMISSION

Unengorged, host-seeking female Ixodes scapularis were collected from the northeastern United States (Rhode Island and Massachusetts) in Apr il 1992. Hemolymph preparations from F-1 males and females were tested to determine if hemocytic rickettsia-like organisms, having shared an tigens with ehrlichiae, are passed transovarially and transstadially. Fluorescein-labeled dog anti-Ehrlichia canis antiserum was used to det ect infected hemocytes by means of direct fluorescent antibody stainin g methods. In duplicate tests of F-1 ticks, hemocytes from 25 males an d 25 females were tested by indirect fluorescent antibody staining met hods with antisera from two persons who had Rocky Mountain spotted fev er. These hemolymph preparations were nonreactive, but those from coho rts of ticks oared from five infected females and tested with anti-E. canis antiserum contained rickettsia-like organisms in the cytoplasm o f hemocytes. Thirty-four (54.8%) of 62 males and 71 (63.4%) of 112 fem ales were positive. Prevalence of positive males among the five cohort s ranged from 18.8 to 80%, while results for females varied between 21 .2 and 91.7%. The unidentified rickettsia-like hemocytic organisms, wh ich have shared antigens with Ehrlichia species, are transmitted trans ovarially and transstadially in I. scapularis.