Rickettsia africae in Amblyomma variegatum and Domestic Ruminants on Eight Caribbean Islands

Abstract

We used PCRs with omp A primers to determine if spotted fever group rickettsiae occurred in Amblyomma variegatum from 6 Caribbean islands. Positive amplicons were obtained from ticks from the U.S. Virgin Islands (9/18; 50%), Dominica (39/171; 30%), Montserrat (2/5; 40%), Nevis (17/34; 50%), St. Kitts (46/227; 20%), and St. Lucia (1/14; 7%). Sequences for a convenience sample of reaction products obtained from A. variegatum on St. Kitts (7), American Virgin Islands (4), Montserrat (2), and St. Lucia (1) were 100% homologous with that of Rickettsia africae , the agent of African tick-bite fever. To determine if transmission of R. africae occurred, we used Rickettsia rickettsii antigen in IFA tests and found positive titers (≥ 1/80) with sera from cattle, goats, and sheep from Dominica (24/95 [25%], 2/136 [2%], 0/58 [0%]), Nevis (12/45 [27%], 5/157 [3%], 0/90 [0%]), St. Kitts (2/43 [5%], 1/25 [4%), 1/35 [3%]), and St. Lucia (6/184 [3%] cattle), respectively. No seropositive animals were found in Grenada (0/4, 0/98/, 0/86), Montserrat (0/12, 0/26, 0/52), or Puerto Rico (0/80 cattle). Our study indicates that R. africae and African tick-bite fever are widespread in the Caribbean.