Abstract:
The aim of this study was to develop an improved strategy for the control of tick infestation on indigenous goats owned by emerging farmers in Limpopo Province, South Africa. The acaricidal efficacy was determined using a pour-on deltamethrin treatment on goats infested by ticks in Makhuduthamaga rural areas. The study was conducted between February and July 2018. In total, five livestock owners in three villages were involved in the study. Goats were divided into two groups: treated and untreated control groups, each consisting of five goats. Goats in the treatment group were treated with the pour-on acaricide deltamethrin Clout®, whereas the untreated goats from within the same household served as controls. Topical treatment with pour-on deltamethrin (Clout®) reduced tick numbers by 94.5% on indigenous goats in the treatment group compared to the control group. In total, 5,671 ticks were collected from the control group, with average of 9.44 ticks per goat, whereas a total of 296 ticks were collected from the treated group, with an average of 0.52 ticks per goat. Furthermore, it was observed that the number of ticks counted on the control goats slowly declined during the trial, which coincided with the approach of seasonal conditions that are less favourable for ticks. Reducing the acaricidal application interval to two weeks was recommended, since ticks were already re-infesting the goats toward the end of the application interval of three weeks. Lameness of goats was often observed due to massive infestation of ticks on the feet of control goats.
The study also contributed to the process of isolating current strains of heartwater to further our understanding of the disease dynamics and pathogenicity for small ruminants. Ehrlichia ruminantium, the causal agent of heartwater disease in ruminants, was detected in field collected Amblyomma hebraeum ticks and cryopreserved as ground-up-tick-supernatants (GUTS). One of the 8 GUTS (12.5%) was found to be positive for E. ruminantium by pCS20 PCR. Ground-up-tick-supernatants need to be tested for their infectivity to induce heartwater in experimental goats and adapted to in vitro growth in endothelial cell cultures to broaden the array of currently available heartwater strains. Including goats in strategic tick control programmes is recommended in order to reduce lameness due to A. hebraeum infestation and the risk of contracting heartwater disease.
