We tested serum samples collected in 1997 and 1998 from a cohort of 204 injection drug users (IDUs) recruited from Central and East Harlem, New York City, New York, for
antibodies reactive with seven rickettsial or Bartonella spp.
antigens. Rodent-associated Bartonella elizabethae and Rickettsia akari were the primary etiologic agents of interest. The testing panel also included Bartonella henselae, Bartonella quintana, Rickettsia prowazekii, Rickettsia rickettsii, and Rickettsia typhi. The highest prevalence of seroreactive serum samples (46%) was found with B. elizabethae
antigens; 10% of the samples reacted with B. henselae
antigens, while 2% reacted with B. quintana
antigens. Reactivity to the latter two
antigens was likely due to cross-reactivity with B. elizabethae
antigens in most instances. Among the
spotted fever group rickettsiae, 18 (9%) samples reacted with R. akari, including 10 samples (5%) that also reacted with R. rickettsii. Cross-adsorption studies demonstrated that most of the
spotted fever group rickettsiae
antibodies were due to R. akari
infections. Among the
typhus group rickettsiae, 5 samples reacted weakly to R. prowazekii
antigens, and no samples reacted with R. typhi
antigens. These findings suggest that Harlem IDUs are commonly exposed to two rodent-associated zoonotic agents. Further study of IDU populations may help elucidate transmission cycles of these agents in inner cities where higher levels of transmission occur.