Natural levels of Rhipicephalus microplus infestation and Anaplasma marginale infection in Angus and Ultrablack calves

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Frabetti, Acucena Fragnan ; Katiki, Luciana Morita ; Caetano, Laura ; Sarti, Mayne Barboza ; Falasca, Thamires Marocci ; Polli, Hiago ; Verissimo, Cecilia Jose ; Vercesi Filho, Anibal Eugenio ; de Oliveira, Henrique Nunes ; Oliveira, Marcia Cristina de Sena ; Giglioti, Rodrigo

• Document type: Journal article
• Source: Experimental and Applied Acarology; v. 89, n. 1, p. 10-pg., 2023-01-05.

Abstract

Infections by Anaplasma marginale and infestations by Rhipicephalus microplus occur en-demically in Brazil, representing an obstacle to expanding the use of taurine breeds, which are more susceptible. In this study, the levels of infection by A. marginale and infestation by R. microplus were monitored in 31 calves that were either purebred or had a high degree of taurine blood: 17 Angus (100% taurine) and 14 Ultrablack (ca. 82% taurine and 18% Zebu). The animals were evaluated on 13 occasions at 12-day intervals. The levels of A. marginale infection were determined by quantification of DNA copy number (CN) by qPCR, and ticks were monitored by two methods: counting adult females (>= 4.5 mm) and scoring the level of tick infestation considering all visible instars in the animals' bod-ies. No significant effects were observed between the means of CN of A. marginale, tick counts and scores among Angus and Ultrablack animals. The repeatability estimates for CN of A. marginale, tick counts and tick scores were 0.53, 0.12 and 0.16, respectively. The correlations between CN and tick counts and scores were close to zero, whereas the correlations between tick assessment methods were 0.57. The absence of differences between the two genetic groups indicates, under the conditions of the present study, that the low degree of Zebu blood did not influence the levels of infection by A. marginale or infestation by R. microplus. The results also suggest that the evaluation of the levels of infestation by ticks using scores can provide information closer to the real infestation rate considering that it uses all the visible instars of the parasites. (AU)

• FAPESP's process: 19/22675-6 - Transcriptome analysis of resistance and/or susceptibility in beef cattle of different genetic groups to Babesia bovis infections
• Grantee: Rodrigo Giglioti
• Support Opportunities: Regular Research Grants
• FAPESP's process: 18/19452-2 - Multi user equipment approved in grant 2017/50.339-5: nanoespectrofotômetro BioDrop
• Grantee: Renata Helena Branco Arnandes
• Support Opportunities: Multi-user Equipment Program