The prevalence of E. ruminantium in adult male and un-engorged female Amblyomma hebraeum ticks derived from cattle in the area of Mnisi (Mpumalanga), South Africa

Abstract

Heartwater, a tick-borne disease that affects domestic and wild ruminants, is caused by the intracellular gram-negative bacterium Ehrlichia ruminantium and is transmitted by Amblyomma hebraeum ticks in South Africa. As part of this study, during the period of May and June 2015, ticks were derived from clinically healthy cattle from 11 different villages in the Mnisi area and DNA extraction, PCR and gel electrophoresis of amplified DNA was performed on the collected ticks. This way the prevalence of E.ruminantium in adult male and un-engorged female A. hebraeum ticks could be determined. Over a period of four weeks, no typical signs of heartwater were noticed in the cattle in any of the villages. Adult A. hebraeum ticks were mostly found on the udder and in the armpits of the animals, causing purulent ulcers and abcesses in those regions. Twenty percent (22 out of 110) of the adult A. hebraeum ticks tested positive for E. ruminantium. The overall prevalence of E. ruminantium infection in ticks was 21.8% (12 out of 55) in male A. hebraeum ticks and 18.2% (10 out of 55) in female A. hebraeum ticks. The infection of E. ruminantium in ticks has to be taken in consideration in tick control policies. Complete eradication of ticks from cattle could ultimately lead to a disruption of the endemic stability in this area. On the other hand, it is important to reduce the physical damage on cattle caused by Amblyomma ticks. It can be concluded that the current tick control policy of dipping needs to be reinforced in the Mnisi area.