VECTOR-BORNE DISEASES, SURVEILLANCE, PREVENTION New Approaches to Detection and Identification of Rickettsia africae and Ehrlichia ruminantium in Amblyomma variegatum (Acari: Ixodidae) Ticks From the Caribbean

Imported from Africa in the 1700s and despite frequent modern eradication efforts, Amblyomma variegatum (F.) spread through the Caribbean by cattle transport, small ruminants, and migrating birds. A. variegatum is a vector for Rickettsia africae, the causative agent of African tick bite fever, and Ehrlichia ruminantium, the causative agent of heartwater. We examined 95 A. variegatum and six Rhipicephalus (Boophilus) microplus (Canestrini) collected from cattle at an abattoir in Antigua. Engorged tick extracts adsorbed on Nobotu Þlter paper strips and new nested polymerase chain reaction (PCR) assays for E. ruminantium andDermatophilus congolensiswere used to evaluate these ticks for the presence of these pathogenic bacteria. Amblyomma ticks (62.4%) contained R. africaeDNA by PCR/restriction fragment length polymorphism analysis and DNA sequencing of the OmpA and 17-kDa antigen genes. Twenty Amblyomma and two Rh. microplus contained E. ruminantiumDNA.NoE. chaffeensis,Anaplasma phagocytophilum,Coxiella burnetii, orD. congolensisDNA was detected in these ticks. The continued presence of Am. variegatum in the Caribbean poses a signiÞcant risk of infection in cattle with E. ruminantium and in humans by R. africae. Eradication efforts are essential to prevent the further spread of Am. variegatum.