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| Author(s): |
Breno Cayeiro Cruz
Total Authors: 1
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| Document type: | Doctoral Thesis |
| Press: | Jaboticabal. 2017-12-13. |
| Institution: | Universidade Estadual Paulista (Unesp). Faculdade de Ciências Agrárias e Veterinárias. Jaboticabal |
| Defense date: | 2017-10-27 |
| Advisor: | Gilson Pereira de Oliveira; Alvimar José da Costa |
| Abstract | |
Rhipicephalus (Boophilus) microplus (Canestrini, 1888) is the main ectoparasite in Brazilian cattle industry, and its control demands behavioral knowledge of its biologic cycle, for increased success in actions over and out of the hosts, with treatments in periods of the year less favorable to this tick. Most of the information about its biology and ecology was originated in other countries or a long time ago. Based in recent climate changes and absence of ecologic and biologic data on this region, the present study, conducted in the Brazilian “Cerrado” biome and tropical savanna climate (Aw), obtained such data through the observation, during two consecutive years, of factors involved on parasitic and free living phases of its cycle, also evaluating the behavior of this strain regarding evolution of its resistance/susceptibility profile against acaricides. Observing the parasitic phase of the Southern Cattle Tick, it was possible to detect adaptations of this ixodid to climate changes, with five annual generations in two consecutive years being registered for the first time in literature, without significant correlations between its period parasitizing bovines and rain levels, environmental and soil level temperatures and relative air humidity. The free living period of its cycle was affected by climatic variables, with positive correlation between rainfall and the period before oviposition, and negative correlations between temperatures and the period before oviposition, egg incubation and period before hatching, and between relative air humidity and egg incubation and the period before larval hatching. Obtained data indicate that the dry season (autumn and winter) is more favorable for maintenance of the Southern Cattle Tick on the environment, as well as presenting highest parasitic burdens in hosts. Population dynamics calculated reinforces the adaptations of such ixodid to climate changes, leading to the existence of 5.212 yearly generations even in distinct climatic and environmental conditions, varying between 2.6 and 8.3 generations per year. Considering such data, a specific strategic control methodology was proposed, treating animals between the second half of spring and the first half of summer (October to February). Such treatments in rainy seasons would lead to smaller populations on the dry season, also reducing the “spring rise”. Analysis of efficacy of different chemical compounds using the Larval Packet Test generated contrasting results, with high efficacy indexes registered for pyrethroids and organophosphates, with variations in amitraz efficiency. Such values lead to a questioning of the applicability of such technique in monitoring resistance. Future studies must be proposed, analyzing the real efficacy of Larval Packet Tests, confronting different in vivo and in vitro methodologies; comparing population dynamics of such ixodid in different pastures, husbandry methods, stocking rates, altitudes and biomes; confirming the efficacy of the proposed strategic control method and, above all, confirming the possibility of observing more than eight R. microplus yearly generations in ideal climatic conditions. (AU) | |
| FAPESP's process: | 14/14820-2 - Ecological, biological and resistance aspects of Rhipicephalus (Boophilus) microplus (Acari: Ixodidae) at the region of Jaboticabal, State of São Paulo, Brazil |
| Grantee: | Breno Cayeiro Cruz |
| Support Opportunities: | Scholarships in Brazil - Doctorate |