Abstract
A 12-month study was conducted in 4 communal grazing areas in the Bushbuckridge region, Limpopo Province, South Africa. The main objective was to investigate the impact of reduced acaricide application on endemic stability to bovine babesiosis (Babesia bigemina and Babesia bovis) and anaplasmosis (Anaplasma marginale) in the local cattle population. To this end 60 cattle in each communal grazing area were bled at the beginning and the conclusion of the experimental period and their sera were assayed for B. bovis, B. bigemina and Anaplasma antibodies. Cattle in the intensively dipped group were dipped 26 times and maintained on a 14-day dipping interval throughout the study, whereas cattle in the strategically dipped group were dipped only 13 times. Three cattle, from which adult ticks were collected, were selected from each village, while immature ticks were collected by drag-sampling the surrounding vegetation. During the dipping process, a questionnaire aimed at assessing the prevalence of clinical cases of tick-borne disease, abscesses and mortalities was completed by an Animal Health Technician at each diptank. An increase in seroprevalence to B. bovis and B. bigemina and a decrease in seroprevalence to Anaplasma was detected in the strategically dipped group while in the intensively dipped group the converse was true. Amblyomma hebraeum was the most numerous tick species on the cattle, and Rhipicephalus (Boophilus) microplus was more plentiful than Rhipicephalus (Boophilus) decoloratus. Drag samples yielded more immature stages of A. hebraeum than of Rhipicephalus (Boophilus) spp. The incidence of clinical cases of tick-borne disease and of abscesses increased in the strategically dipped group at the start of the survey.
Highlights
Tick infestation and the diseases transmitted by ticks are a major problem for farmers in the tropical and subtropical regions of the world and are widespread in Africa[12,26]
Occur in the region, namely bovine babesiosis, caused by Babesia bovis and Babesia bigemina, bovine anaplasmosis caused by Anaplasma marginale, and heartwater or cowdriosis, caused by Erhlichia (Cowdria) ruminatium
It is generally accepted that endemic stability to tick-borne diseases (TBD) exists when the number of seropositive animals in a herd reaches 75 % by 9 months[25,30]
Summary
Tick infestation and the diseases transmitted by ticks are a major problem for farmers in the tropical and subtropical regions of the world and are widespread in Africa[12,26]. Ticks and tick-borne diseases (TBD) cause considerable economic losses to owners in those areas of southern Africa in which cattle are communally grazed, and the occurrence of tick worry, abaDepartment of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort, 0110 South Africa. Three economically important TBD occur in the region, namely bovine babesiosis, caused by Babesia bovis and Babesia bigemina, bovine anaplasmosis caused by Anaplasma marginale, and heartwater or cowdriosis, caused by Erhlichia (Cowdria) ruminatium. Babesia bovis is transmitted by Rhipicephalus (Boophilus) microplus, the only known vector in southern Africa[38], B. bigemina by Rhipicephalus (Boophilus) decoloratus and R. Livestock production in southern Africa is heavily dependent on improved animal health and this entails good tick and TBD control. There has been a shift towards strategic and threshold tick control with acaricides applied less frequently during periods of low tick abundance and more frequently during the critical times of the year to avoid the damaging effects of adult ticks[15,29]
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