Assessment of Amblyomma Hebraeum for Acaricide resistance in the heartwater-endemic Southern district of Botswana

Abstract

Cattle tick Amblyomma hebraeum has become a common problem for cattle herders in Botswana for many years, despite the availability of many different acaricides products. The aim of this research was to assess the resistance status of A. hebraeum to deltamethrin and amitraz at recommended doses using AIT. A cross sectional questionnaire survey was conducted on the 18th-23rd of November 2019 on four farms where farmers had reported acaricides failure before. Engorged adult female Amblyomma hebraeum ticks were collected and sent to Botswana international university of Science and technology laboratory in Palapye. The Adult immersion test was used to assess the resistance-susceptibility level of the Amblyomma tick population collected to amitraz and deltamethrin. The results showed slight resistance to deltamethrin I Lotlhakane and Pitseng and 100% susceptibility for Good hope. Ticks from all villages were susceptible to amitraz. DNA was extracted from ticks amplified and sequenced to confirm that there was no underlying genetic basis for deltamethrin resistance. No polymorphisms were identified in the loci associated with resistance to deltamethrin.The mechanism for deltamethrin tolerance used by Amblyomma hebraeum in the Southern District of Botswana remains unknown and needs further investigation. This study provides baseline information on the effectiveness of acaricides against Amblyomma hebraeum, infection level of the tick species with ehrlichia ruminantum and possible polymorphisms responsible for resistance to occur in the Southern District of Botswana, where heartwater continues to be a tick-borne livestock disease of concern.