![]() Blocking pathogen transmission during that period has been tried with success as seen with Ixodes scapularis and Borrelia burgdorferi ( Eisen and Dolan, 2016). This depends to a major part on environmental conditions like temperature and humidity, and on the ability of the vector to survive long enough to harbor the matured infectious stage to be transmitted at next bite. In the latter situation, pathogens need time to undergo development inside the vector and reach their infective stage. The arthropod can be either a mechanical vector, that is a simple carrier for dispersion, or a biological vector, within which the pathogen undergoes asexual and/or sexual multiplication before being transferred to a mammalian host. However, due to the diversity and specificity of vector parasite interactions, the blocking characteristics of those ectoparasiticides may not be sufficient to control other major pathogen transmitted by vectors to human, companion and farm animals. These promising results confirm that a rapid onset of action should be an essential component of a novel drug profile. These studies all report a complete prevention of pathogen transmission by fast elimination of the vector. In this scope, “speed of kill” has become an important commercial differentiator for recent marketed products ( Halos et al., 2014, Wengenmayer et al., 2014, Beugnet et al., 2016, Blair et al., 2016, Six et al., 2016) and many studies have been designed for testing the ability of those products to block transmission of some important pathogens of cats like Bartonella henselae ( Bradbury and Lappin, 2010), and of dogs like Dipilidium caninum ( Fourie et al., 2013a), Leishmania infantum ( Brianti et al., 2014), Ehrlichia canis ( Jongejan et al., 2015), Borrelia burgdorferi, Anaplasma phagocytophilum ( Honsberger et al., 2016), and Babesia canis ( Beugnet et al., 2014, Taenzler et al., 2016). Therefore, requirements for new ectoparasitic drugs should include not only the control of ectoparasites for a certain period of time, but also address their ability to block the transmission of the various vector-borne pathogens by a rapid onset of action. ![]() viruses, bacteria, protozoans, and worms, adding to their economic and emotional impact on human and animal health ( Mehlhorn, 2008). Besides causing discomfort, allergic reactions, skin damage and pain, many ectoparasites are also vectors of life-threatening or debilitating diseases caused by the transmission of a wide variety of pathogens, i.e. This complexity leads to important parameters to consider for ectoparasiticide research and when considering the ideal drug profile for preventing disease transmission.īlood-feeding ectoparasites are responsible for severe aggravation through their constant attempts to get blood from their hosts. Successful blocking depends on effective action in the context of the extremely diverse life-cycles of vectors and vector-borne pathogens of medical and veterinary importance which are summarized in this review. Chemical entities exhibiting repellent activity in addition to fast killing, like pyrethroids, could prevent pathogen transmission even in cases of immediate transfer. However, if the pathogen is transmitted immediately at bite as it is the case with most insects, blocking transmission becomes only possible if ectoparasiticides prevent the vector from landing on or, at least, from biting the host. ![]() The recently described systemic isoxazolines have been shown to successfully prevent disease transmission under conditions of delayed pathogen transfer. Blocking of transmission might work when transmission is delayed during blood meal, as often happens in ticks. Killing the vectors with ectoparasitic drugs before they have the opportunity to pass on their pathogens could be the ideal way to prevent vector borne diseases. ![]() Vector-borne diseases are responsible for significant health problems in humans, as well as in companion and farm animals.
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