Estimates of repeatability and correlations of hemoparasites infection levels for cattle reared in endemic areas for Rhipicephalus microplus

Abstract

Rhipicephalus microplus is a vector of cattle tick fever, a disease caused by the protozoans Babesia bovisand B. bigemina, and also anaplasmosis, produced by the Rickettsiales Anaplasma marginale. These tick-borne pathogens cause considerable losses to Brazilian livestock breeders and represent an obstacle to the expanded use of taurine breeds due to their higher sensitivity to ticks and hemoparasites compared to zebu breeds. Differences in the susceptibility to hemoparasites were also verified within breeds, suggesting that may be possible to select a most resistant phenotype. Therefore, repeatability of R. microplus counts and copy number of hemoparasites DNA were estimated, along with correlations between themselves, aiming to verify if those measures can be used as parameters to classify animals according to their parasite resistance degrees. Forty-two Canchim females kept on pastures naturally infested by ticks were evaluated for the level of infestation by R. microplus and infection by B. bovis, B. bigemina, and A. marginale. Twenty-four evaluations were performed once a month, for adult female ticks counts and blood samplings. The experimental period was divided into four phases, according to the animals age range: Phase 1: 8 to 13 months (collections 1 to 6); phase 2: 14 to 19 months (collections 7 to 12); phase 3: 20 to 25 months (collections 13 to 18), and phase 4: 26 to 31 months (collections 19 to 24). Blood samples were submitted to absolute quantification of hemoparasites DNA sequences using qPCR. The hemoparasite and tick counts data were transformed for normalization and were analyzed using mixed models. Among three species of hemoparasites studied, A. marginale presented the highest level of infection. During phase 3, B. bigemina presented higher infection levels (p < 0.05) compared to B. bovis, whereas no differences were observed in other phases. Estimated repeatabilities for parasite infection levels varied from low to moderate during our experiment. There were low correlations between tick counts and parasite infection levels, and between parasite infection levels from different species by themselves. Based on these results, under conditions of the present study, we suggest that it is possible to identify animals presenting a most resistant phenotype against infection by both hemoparasites and ticks. Moreover, the animal age may be an important factor related to resistance against these pathogens. The data obtained shed more light on the resistance to hemoparasites studied.

Differential IL10 mRNA Profiles Associated to &lt;i&gt;Babesia bovis&lt;/i&gt; and &lt;i&gt;B. bigemina&lt;/i&gt; Infection Levels in Persistently Infected Animals

“…In the present study, although the selection of groups presenting high or low parasite levels intended to include tick counts, B. bovis and B. bigemina infection levels from monitoring period of a year before starting this experiment, no significant difference in tick counts was observed. Weak correlations between Babesia infec-Open Journal of Veterinary Medicine tion levels and ticks numbers were already demonstrated [13]. We observed significant differences between IL-10 mRNA levels in H and L group in our study.…”

“…Animals received water and mineral salt mixture ad libitum. This region was identified to be endemic for the occurrence of R. microplus, B. bovis and B. bigemina [12] [13]. Open Journal of Veterinary Medicine…”

“…The trial period was of 24 months (from August 2013 to July 2015) using 50 fe- tick counts from the whole experiment were compared to meteorological data (temperature and rainfall) and had already been previously published [13]. The present study was focused on the comparison of profiles of immune-related transcripts to Babesia infections levels.…”

qPCR estimates of Babesia bovis and Babesia bigemina infection levels in beef cattle and Rhipicephalus microplus larvae

“…The experiment was conducted at the research farm from Embrapa Livestock Southeast (Embrapa Pecuária Sudeste), located at São Carlos, São Paulo state (22°01′S and 47°53′W). This region is considered endemic for the occurrence of R. microplus and the hemoparasites transmitted by these ticks (Oliveira et al 2008;Giglioti et al 2018). Thirty six Canchim heifers (5/8 Charolais + 3/8 Zebu) with 10-13 months of age, naturally infested with ticks, were submitted to blood sampling (using EDTA vacutainer tubes) and collection of engorged female ticks (body lengths greater > 5 mm) during spring season (October 2013).…”

“…Endemic stability for B. bovis and B. bigemina is common in most of regions from Brazil (Kessler et al 1983;Vidotto et al 1997), wherein qPCR assays have been suscessfully applied for detection and quantification of these pathogens (Ramos et al 2011;Bilhassi et al 2014;Giglioti et al 2016Giglioti et al , 2017Giglioti et al , 2018. Recent studies have demonstrated no association between Babesia DNA levels in naturally infected cattle and tick counts (Giglioti et al 2016(Giglioti et al , 2017(Giglioti et al , 2018. However, studies regarding association between babesiosis infection levels in ticks and cattle host blood remain still scarce.…”