Research Grants 22/16262-3 - Babesiose, Carrapatos - BV FAPESP
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Indicators of resistance to the Rhipicephalus microplus tick and babesiosis in Canchim cattle: new strategies.

Abstract

Infestations by Rhipicephalus microplus tick and infections by Babesia protozoa represent a significant obstacle to the use of taurine cattle and their crosses due to their greater sensitivity to these parasites. Zebu animals are recognized for their excellent resistance to parasites and ability to adapt to tropical breeding conditions. Canchim is a synthetic cattle breed composed of 3/8 Zebu and 5/8 Charolais developed to combine the greater productivity and precocity of taurus with desirable adaptive characteristics of Zebu. Therefore, this project will evaluate 50 Canchim females for 18 months, regarding tick infestations and Babesia infections. The data will be used to identify indicators of resistance to develop new strategies to control these parasites in Canchim breed. All proposed assessments will be evaluated in each season annually. Ticks will be counted using three methods: (1) counts by visual assessment of all adult females greater than 4.5 mm in size present on the left side of each animal, which is the standard technique; (2) capture of images from the rear and front of the animals using conventional (RGB) and (3) thermographic cameras. The qPCR technique will verify B. bovis and B. bigemina infection levels. The animals' productive performance (live weight and body score) and reactivity in the containment trunk will be evaluated. Complete blood count (CBC) analysis will be used as indicator of animal health. Histamine levels will be assessed through immunoenzymatic tests (Elisa). Finally, the levels of CD4+ lymphocytes in animals' blood samples will be evaluated using flow cytometry. The animals will also be genotyped for mutations in the bovine CD4+, pointed out as causative by altered phenotypic profiles related to anti-CD4. Data of different tick counts, quantification of hemoparasite levels, productive performance, reactivity, histamine levels, and CD4+ phenotyping and genotyping will be analyzed and associated with resistance traits. The data obtained could be used in genetic breeding programs in Canchim and serve as a model for similar studies in other breeds. The results will enrich the discussion on natural defense mechanisms to control hemo and ectoparasites in cattle. (AU)

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