Evaluation of 16S, map1 and pCS20 probes for detection of Cowdria and Ehrlichia species

A panel of 16S ribosomal RNA gene probes has been developed for the study o f the epidemiology of heartwater; five of these detect different cowdria ge notypes, one detects five distinct genotypes; one detects any Group III Ehr lichia species other than Cowdria and one detects any Group II Ehrlichia sp ecies. These probes have been used on PCR-amplified rickettsial 16S rRNA ge nes from over 200 Amblyomma hebraeum ticks. Control ticks were laboratory-r eared and either uninfected or fed on sheep experimentally infected with di fferent cowdria isolates, field ticks were collected from animals in heartw ater-endemic areas. All tick-derived DNA samples were also examined by PCR amplification and probing for two other cowdria genes (map1 and pCS20) whic h have previously been used for heartwater epidemiology. This paper describ es the first direct comparison of all currently available DNA probes for he artwater-associated organisms.