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Tick-host interaction: development of resistance to Boophilus microplus and Amblyomma cajennense (Acari: Ixodidae) in wooless sheep


Adults of the lone star tick Amblyomma cajennense infests selectively equids. However, due to its low specificity, immature stages (larvae and nymphs) parasite cattle, deers, domestic and wild dogs, birds, rodents and men also. This tick species is broadly distributed through the American continent and in Brazil is the main vector of Rickettsia rickettsii, the Spotted Fever pathogen, re-emergent disease of Public Health interest. On the other hand, the cattle tick Boophilus microplus infests cattle, but may parasitize other domestic and wild hosts like deers. Moreover, it is the vector of Texas Fever pathogens.Because of the low international prices of wool associated to a better quality and greater supply of synthetic fibers, wooless sheeps have been bred for milk and beef production, as well as leather industry and manufactories. Furthermore, the productivity of beef lamb in Brazil is still low partialy due to the bad and primitive management. Actually, breeders use to feed sheeps sharing the same pasture with horses and/or cattle, exposing them to ectoparasites as A. cajennense and/or Boophilus microplus. The aim of this project is to evaluate the acquisition of resistance in wooless sheep to nymphs of the lone star tick A. cajennense after repeated and controlled infestations. Twenty wooless lambs aged 3-6 month, males and females, supplied by private breeders, will be used throughout the experiments. Larvae of B. microplus and nymphs of A. cajennense will be supplied by the tick colony of the Animal Pathology Department of University campus of Jaboticabal, kept in controlled conditions of temperature (28ºC), relative umidity (85%) and photoperiod (12:12) in BOD ovens. Lambs will be infested thrice with 100 larvae or nymphs/animal/infestation, at 30 days interval. The following biological parameters will be determined: weight and % yielding, engorgement and molting periods, % molting. Lamb sera will be collected before every infestation for use in immunohistochemistry and immunoblotting. Lamb skin biopsies will be used to study the tick bite lesion, including inflammatory cell counts at several times after nymph attachment in every infestation. (AU)

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