An appraisal of current and new techniques intended to protect bulls against Culicoides and other haematophagous nematocera: the case of Schmergow, Brandenburg, Germany

Abstract

The outbreak of bluetongue (BTV-8) in many parts of north-western Europe led to efforts to curb the spread of the disease, particularly in farms with valuable livestock, as on a stud bull farm in Schmergow, Brandenburg, Germany. In the abundance of the putative BT vectors, Palaearctic Culicoides species, several vector control methods were applied in the hope for a reduction of the target insect populations. Insecticide-impregnated ear tags and regular treatments at 6-week intervals of all bulls with deltamethrin pour on were expected to achieve the desired control of the biting midges. Additionally, insecticide-treated mosquito fences circumventing much of the pens were tried for the first time against Culicoides. Two suction black-light traps (BioGents(R) sentinel traps) helped to monitor the densities of Culicoides and other haematophagous nematocera during the trial period from July to December 2007. Despite all efforts, the densities of Culicoides were not distinctly reduced. Several thousand midges were repeatedly recorded during one-night catches. Examinations of midges and other haematophagous nematocera (Aedes and Anopheles species) revealed high percentages of successful feedings between 10% and 35% for Culicoides and more than 50% for Aedes and Anopheles species. Since all insects were caught inside the pens, the concept of endophily vs exophily or endophagy vs exophagy for some Culicoides species needs to be revised accordingly. Also, stabling of valuable livestock does not reduce the host-vector interface and, hence, the risk of transmission of BT.