Prevention of Tick-borne Fever outbreaks with deltamethrin in sheep introduced into nature reserves in the Netherlands

Abstract

It was investigated if treatment with deltamethrin can prevent Anaplasma phagocytophilum infection in sheep introduced into nature reserves in the Netherlands. A flock of sheep was divided into two groups, the Oosterbos group and the Bargerveen group. The groups were named after the fields where the sheep grazed on. Half of each group was treated with deltamethrin and the other half was not treated. This treatment was repeated every 5 weeks. After the initial blood collection, blood was drawn again in the Oosterbos group 3 and 5 weeks after introduction to the field. In the Bargerveen group blood was drawn each week after the start of the investigation. In the Oosterbos group, 56 percent of the treated sheep were infected with A. phagocytophilum 3 weeks after treatment, whereas 94 percent of the treated sheep were infected after 5 weeks. In the Oosterbos control group 81 percent was infected after 3 weeks, with no additional infections after 5 weeks. In the Bargerveen group all animals were infected after the first week. Overall, there was no significant difference between the treated and non-treated sheep. Therefore, deltamethrin is not an effective method of preventing A. phagocytophilum infection in sheep.