Seasonal fluctuations of Babesia bigemina and Rhipicephalus microplus in Brangus and Nellore cattle reared in the Cerrado biome, Brazil

Background In 2022, fluralaner was launched on the market for use in the control of the cattle tick Rhipicephalus microplus after showing 100% efficacy in registration trials against the causative agents of cattle tick fever (TFAs). The aim of the present study was to determine whether a strategic control regimen against R. microplus using fluralaner (FLU) in Holstein calves grazing in a tropical region would alter the enzootic stability status of cattle tick fever, triggering outbreaks in these animals up to 22 months age. Methods In this study, a group of calves treated with FLU was compared with a control group treated with the regimen currently being used on the farm, which consisted of the fipronil + fluazuron formulation (FIFLUA). In the first experiment, the efficacy of the FIFLUA pour-on formulation was evaluated in a field study. In the second experiment, which lasted 550 days, two experimental groups (n = 30/group) of Holstein calves naturally infested with R. microplus were analyzed. Calves aged 4 to 10 months received either a specific treatment regimen with FLU (experimental group) or FIFLUA (control group). During this period, tick counts, animal weight measurement, feces collection (to determine eggs and oocysts per gram of feces), tick fever monitoring, blood smears (to ascertain enzootic stability of the herd), PCR testing for TFAs and serology (indirect enzyme-linked immunosorbent assay [iELISA]) were performed. All calves were evaluated for signs of tick fever between ages 11 and 22 months. Results FIFLUA showed an acaricidal efficacy of > 90% from post-treatment days 14 to 35. Regarding treatments against the TFAs, the average number of treatments was similar between groups, but animals treated with FLU had a smaller reduction in packed cell volume on some of the evaluation dates of the second and third treatment against TFAs. In calves aged 10 months in the FLU group, B. bovis was not detected by PCR (0/15 samples), 40% of the samples had antibody titers and 33% (10/30) of the samples had positive blood smears. Regarding B. bigemina, > 86% of the samples in both groups tested positive for B. bigemina DNA and antibodies; there was no difference in the antibody titers between the groups. There were no clinical cases of cattle tick fever in calves aged 11 to 22 months. Conclusions In comparison with the control treatment, the strategic control regimen against R. microplus with FLU that was implemented in the present study did not negatively affect the enzootic stability status of A. marginale and B. bigemina in the herd up to 22 months of age. The enzootic stability status of B. bovis was not reached by either group. These results likely represent a characteristic of the local tick population, so further studies should be performed. Graphical Abstract

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Reappraisal on the Diversity of Ticks and Their Endosymbiont Prevalent in Indo-myanmar Border

Lalawmpuii,

Biakzuala,

Jacob

et al. 2024

Preprint

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In this study, we explored the genetic diversity of ixodid ticks for the first time from Myanmar border of India, Mizoram and investigate their genetic affinities with other Indian isolates as well as with different populations from other countries. For genetic analyses, we employed phylogenetic inferences, genetic divergence, and haplotype networks based on the mitochondrial 16S rRNA, nuclear ITS-2, and 18S rRNA markers. We also implement multivariate principal coordinate analysis to visualize the genetic differentiation across ixodid ticks. Our genetic analyses affirm the identity of the ticks infesting bovine livestock in Mizoram as Rhipicephalus microplus, Haemaphysalis bispinosa, and Amblyomma habraeum. The phylogenetic inferences drawn in this study reveal instances of polytomies within Rhipicephalus species complex which could potentially arise from incomplete lineage sorting as a consequence of rapid diversification. Moreover, the genetic analysis also dictated R. microplus s.l. populations in India, China, and Pakistan constitute a closely related matrilineal lineage and form a distinct cluster of haplotypes with respect to R. microplus s.s. Despite the study, population of R. microplus from Mizoram nested within a single haplotype, our study signified a noticeable intraspecies divergence within R. microplus s.l. across India revealing the recovery of seven distinct matrilineal haplotypes based on the mitochondrial 16S rRNA marker, while a single and three distinct haplotypes are seen in the nuclear 18S rRNA and ITS-2 markers, respectively. This study also unveiled an infection rate of 5% for bovine haemoparasites and 97% for Coxiella-like-endosymbionts among the studied tick population. In conclusion, this study addresses a significant knowledge gap by providing the first documentation report on tick diversity within Myanmar border of India, Mizoram state.

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Seasonal fluctuations of Babesia bigemina and Rhipicephalus microplus in Brangus and Nellore cattle reared in the Cerrado biome, Brazil

Cited by 3 publications

References 48 publications

Vector-borne Apicomplexa

Vector-borne Apicomplexa

Enzootic stability of tick fever in Holstein calves grazing in a tropical region, subjected to strategic cattle tick control with fluralaner

Reappraisal on the Diversity of Ticks and Their Endosymbiont Prevalent in Indo-myanmar Border

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