The distribution of Amblyomma variegatum and A. hebraeum in Zimbabwe and their infection with Ehrlichia ruminantium and Rickettsia africae

Abstract

The aim of this study was to give an update on the spatial distribution of the Amblyomma tick species in Zimbabwe and their infection rates with Ehrlichia ruminantium and Rickettsia africae pathogens. A total of 183 ticks were collected at 10 sites across Zimbabwe based on previous records of absence or presence of Amblyomma ticks. Morphological keys were used to identify the ticks using a stereo microscope. Infection of the ticks with Ehrlichia ruminantium was investigated using PCR targeting pCS20 (E. ruminantium), gltA(Rickettsia spp.) and ompA (R. africae) genes. Amblyomma ticks were found widespread in southern, central and north-western Zimbabwe. The species found were Amblyomma hebraeum, A. variegatum and A. gemma, which had previously not been reported in Zimbabwe. Amblyomma hebraeum was found in all the areas surveyed while A.variegatum and A. gemma were only found in some of the places. A limited spread in A.hebraeum and A.variegatum distribution in Zimbabwe was noted. It also showed that they are infected with rickettsial pathogens at relatively high rates (average 15.8% for E.ruminantium). The real-time PCR for R. africae gltA gene showed an average infection rate of 95% and for ompA it was 40%. DNA sequence analysis showed a high similarity (98-99%) with three other R. africae published sequences. The widespread distribution of Amblyomma ticks and their infection with rickettsial pathogens means heartwater and rickettsial infections will continue as problems for livestock and humans in Zimbabwe.