Abstract
BackgroundTicks are a problem for cattle production mainly in tropical and subtropical regions, because they generate great economic losses. Acaricides and vaccines have been used to try to keep tick populations under control. This has been proven difficult given the resistance to acaricides and vaccines observed in ticks. Resistance to protein rBm86-based vaccines has been associated with the genetic diversity of Bm86 among the ectoparasite’s populations. So far, neither genetic diversity, nor spatial distribution of circulating Bm86 haplotypes, have been studied within the Mexican territory. Here, we explored the genetic diversity of 125 Bm86 cDNA gene sequences from R. microplus from 10 endemic areas of Mexico by analyzing haplotype distribution patterns to help in understanding the population genetic structure of Mexican ticks.ResultsOur results showed an average nucleotide identity among the Mexican isolates of 98.3%, ranging from 91.1 to 100%. Divergence between the Mexican and Yeerongpilly (the Bm86 reference vaccine antigen) sequences ranged from 3.1 to 7.4%. Based on the geographic distribution of Bm86 haplotypes in Mexico, our results suggest gene flow occurrence within different regions of the Mexican territory, and even the USA.ConclusionsThe polymorphism of Bm86 found in the populations included in this study, could account for the poor efficacy of the current Bm86 antigen based commercial vaccine in many regions of Mexico. Our data may contribute towards designing new, highly-specific, Bm86 antigen vaccine candidates against R. microplus circulating in Mexico.
Highlights
Ticks are a problem for cattle production mainly in tropical and subtropical regions, because they generate great economic losses
All sequences were analyzed for completeness and high quality with the following parameters: 1) extremes with low resolution were eliminated from the sequences, 2) where double peaks were observed for a single position in the chromatogram, only the tallest peak was considered, 3) amplicon sequences that did not have large overlapping fragments (> 100 bp) with the contiguous Bm86 cDNA sequence region, were not considered for any further analysis
From 150 Bm86 cDNA tick samples sequenced by Genscript, only 125 could be successfully assembled for the complete putative Bm86 cDNA sequence
Summary
Ticks are a problem for cattle production mainly in tropical and subtropical regions, because they generate great economic losses. Rhipicephalus microplus (Acari: Ixodidae) is a cattle one-host-tick, with a tropical and subtropical cosmopolitan distribution It is considered one of the most important ectoparasites of cattle in Mexico, negatively affecting weight gain and milk production which. Campaigns included strategies aiming to keep geographic regions free of ticks, as well as actions towards control and eradication of the ectoparasite from endemic areas (Mexican Official Standard NOM-019-ZOO-1994). Such actions are achieved mostly through application of acaricides which are currently presenting limited efficacy, as ticks have developed resistance, an issue that has been widely discussed in previous researches [4,5,6,7,8,9].
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