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Kroeber, Thomas
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Kroeber, Thomas
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Voici les éléments 1 - 3 sur 3
- PublicationMétadonnées seulementAn in vitro feeding assay to test acaricides for control of hard ticks(2007)
; Animal husbandry could not be practised over large areas of the planet without acaricides. The prevention of tick bite and the transmission of diseases requires the use of pesticides, but this contributes to the development of tick resistance against acaricides. This drives the quest for new molecules that target physiological processes crucial to tick survival. In vivo trials involve multiple repetitions because of inherent variations between host animals, requiring large amounts of test products and ticks. An in vitro alternative should permit the testing of the ability of a product to restrict attachment and feeding by ticks at precise doses. In this paper an in vitro feeding system is described where the European tick Ixodes ricinus L. feeds on blood through a cellulose rayon-reinforced silicone membrane. The membrane Shore hardness is modified to imitate the elastic retraction forces of skin that ensure the closing of tick penetration sites on the membrane to prevent bleeding. Tick attachment (75-100%) is achieved by adding chemical and mechanical stimuli to the membrane. Survival curves for different doses of fipronil and ivermectin tested with the method showed highly reproducible acaricide effects within 5 - 7 days. Significant effects are recorded down to ppb levels in blood. Standardised tests can be made with blood from the same donor animal or culture medium under the membrane. (c) 2006 Society of Chemical Industry. - PublicationMétadonnées seulementIn vitro assays for repellents and deterrents for ticks: differing effects of products when tested with attractant or arrestment stimuli(2003)
; Most in vivo and in vitro tests with repellents or deterrents against ticks have not considered which sensory channel is being targeted. We have recorded the responses of two hard tick species (Acari: Ixodidae) in vitro to determine if such products can disrupt the perception of an attractant in a repellent assay or the perception of an arrestment stimulus in a deterrent assay. Ethyl butylacetylaminopropionate (EBAAP), N,N-diethyl-methyl-benzamide (deet), permethrin and indalone were chosen to test their capacity to inhibit the attraction of Amblyomma variegatum Fabricius to its aggregation-attachment pheromone. Vapours of each test product plus those from a synthetic blend of the pheromone were delivered to the walking tick in an air stream on a locomotion compensator. Neither EBAAP, deet, permethrin nor indalone could inhibit attraction of A. variegatum even when each of the test products was delivered at 10(6) times the pheromone. Indalone did decrease the attraction of A. variegatum to the pheromone and induced repulsion of A. variegatum when presented on its own in the air stream. The effect of permethrin, a sodium channel blocker, was also tested in a deterrent assay measuring the arrestment of Ixodes ricinus (L.) adults on its own faeces and faecal constituents. Permethrin deterred arrestment at doses of 670 fg/cm(2) to 67 ng/cm(2), i.e. at levels five times lower than the dose of chemostimuli present in the arrestment stimulus. This sensitivity to permethrin suggests that it acts via the contact chemoreception channel. - PublicationMétadonnées seulementThe dynamics of an avoidance behavior by ixodid ticks to liquid water(2000)
; Life stages of different tick species avoid walking on a wet surface surrounding a dry patch by systematically returning to the dry each time they contact the wet surface beyond the border with the tip of a first leg tarsus. Sequential analysis of the border behaviors shows that repetitive contact with the water increases the probability of walks astride the border. Ticks accept this unilateral contact with the water for longer intervals and eventually walk on to the wet surface after a combination of a short patch walk followed by a border walk which is longer than the foregoing ones. Staying time on a small circular patch is shorter than on a large one, arising probably from faster adaptation of peripheral receptors following a higher frequency of border contacts. However, an equal number of border reactions on patches of different sires and shapes suggests that a 'counter' in the CNS may also influence dry patch departure.