Abstract
Because dogs are such loved companion animals, their health and wellbeing is of great importance to their human companions. Moreover, controlling ticks and fleas on dogs is also important in respect of the zoonotic risk that some of these parasites pose to their human companions. Numerous products are available to
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veterinarians and dog owners for controlling ticks and fleas. By comparing the efficacy of these products, important information can be collected that will help the end-user to decide on the most appropriate product. It was hypothesized that the combination of different active substances and alternative routes of administration using improved delivery systems, could enhance the speed of kill as well as duration of efficacy of various compounds. Moreover, if the speed of kill was rapid enough, these products could potentially prevent infections with tick-borne and flea-borne pathogens. Therefore the aim of the studies described in this thesis was to evaluate and compare the efficacy of various classes of compounds, with different modes of action, used for the control of tick and flea infestation on dogs. The efficacy of these compounds was evaluated either separately, or administered in combination, using different application modes, such as topical application, impregnated collars or oral formulations. Moreover, the ability of several compounds to prevent transmission of selected tick- and flea-borne pathogens was also assessed. In Chapter 2 the efficacy of various compounds against Haemaphysalis elliptica, Dermacentor reticulatus and Rhipicephalus sanguineus as well as Ctenocephalides felis was evaluated on dogs in controlled laboratory studies. In order to protect a dog from the detrimental effects of tick infestation pharmaceutical products must not only be able to control ticks, but the onset of action must be fast enough to prevent transmission of harmful tick-borne pathogens. In Chapter 3 the ability of different compounds to prevent the transmission of the tick-borne pathogen Babesia canis by Dermacentor reticulatus is evaluated in controlled laboratory studies. In Chapter 4 the ability of different compounds to prevent the transmission of the tick-borne pathogen Ehrlichia canis by Rhipicephalus sanguineus is evaluated in controlled laboratory studies. Moreover, the speed of transmission of E. canis by infected R. sanguineus was evaluated and compared in vivo on dogs and in vitro on artificial feeding membranes. Finally, in addition to the immediate irritation that flea infestations cause to dogs, fleas are also intermediate hosts of the metacestode stages of the cestode Dipylidium caninum. In Chapter 5 the prophylactic effectiveness of a collar formulation against infected fleas is evaluated and consequently also its ability to prevent D. caninum infection in dogs.
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