MLST scheme of< i> Ehrlichia ruminantium: Genomic stasis and recombination in strains from Burkina-Faso (original) (raw)
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Genetic diversity of Ehrlichia ruminantium strains in Cameroon
Onderstepoort J Vet Res, 2014
In order to investigate the extent of genetic diversity among Ehrlichia ruminantium strains in Cameroon, a partial fragment (800 bp) of the E. ruminantium map1 gene was amplified by nested polymerase chain reaction in 121 of 156 E. ruminantium pCS20-positive DNA samples extracted from ticks and cattle collected from two ranches. Deoxyribonucleic acid sequencing of the map1 gene products indicated the presence of at least 21 genotypes at the nucleotide level and 16 genotypes at the amino acid level circulating within the study sites. Some of the genotypes were identical to Antigua (U50830), Blaaukrans (AF368000) or UmBanein (U50835), whilst the others were new genotypes. Twenty-four representative sequences were deposited in GenBank and given accession numbers JX477663 – JX477674 (for sequences of tick origin) and JX486788 – JX486799 (for sequences of cattle origin). Knowledge of E. ruminantium strain diversity could be important in understanding the epidemiology of heartwater
Genetic diversity of Ehrlichia ruminantium strains in Cameroon
Onderstepoort J Vet Res, 2014
In order to investigate the extent of genetic diversity among Ehrlichia ruminantium strains in Cameroon, a partial fragment (800 bp) of the E. ruminantium map1 gene was amplified by nested polymerase chain reaction in 121 of 156 E. ruminantium pCS20-positive DNA samples extracted from ticks and cattle collected from two ranches. Deoxyribonucleic acid sequencing of the map1 gene products indicated the presence of at least 21 genotypes at the nucleotide level and 16 genotypes at the amino acid level circulating within the study sites. Some of the genotypes were identical to Antigua (U50830), Blaaukrans (AF368000) or UmBanein (U50835), whilst the others were new genotypes. Twenty-four representative sequences were deposited in GenBank and given accession numbers JX477663 – JX477674 (for sequences of tick origin) and JX486788 – JX486799 (for sequences of cattle origin). Knowledge of E. ruminantium strain diversity could be important in understanding the epidemiology of heartwater
2017
Ehrlichia ruminantium is the causal agent of heartwater, a ruminant tropical fatal disease transmitted by Amblyomma ticks. Up to now, no effective vaccine is available due to a limited cross protection of vaccinal strains on field isolates mainly associated to a high genetic diversity of E. ruminantium within geographical locations. Thus, both characterization of E. ruminantium genetic population structure at worldwide and regional scale and estimation of E. ruminantium tick prevalence are important to delimitate better control strategies and improve heartwater monitoring strategies. In Section I, we developed two new qPCR s, pCS20 Sol1 T q M and Sol1 SG, to scree n E. ruminantium in Amblyomma ticks, which are powerful tools for: 1) heartwater epidemiological studies, 2) diagnosis in the context of heartwater clinical cases and 3) follow - up of experimental infections, both in ticks and hosts. The pCS20 Sol1 T q M qPCR was found as sensitive (up to 30 copies/ reaction ) and specifi...
Differential strain-specific diagnosis of the heartwater agent: Ehrlichia ruminantium
Infection, Genetics and …, 2008
Ehrlichia ruminantium is the causative agent of heartwater, a major tick-borne disease of livestock in Africa introduced in the Caribbean and threatening to emerge and spread in the American mainland. Complete genome sequencing was done for two isolates of E. ruminantium of differing phenotype, isolates Gardel (Erga) from Guadeloupe Island and Welgevonden (Erwe) originating from South Africa and maintained in Guadeloupe. The type strain of E. ruminantium (Erwo), previously isolated and sequenced in South Africa; is identical to Erwe with respect to target genes. They make the Erwe/Erwo complex. Comparative analysis of the genomes shows the presence of 49 unique CDS and 28 truncated CDS differentiating Erga from Erwe/Erwo. Three regions of accumulated differences (RAD) acting as mutational hot spots were identified in E. ruminantium. Ten CDS, six unique CDS and four truncated CDS corresponding to major genomic changes (deletions or extensive mutations) were considered as targets for differential diagnosis on four isolates of E. ruminantium: Erga, Erwe/Erwo, Senegal and Umpala. Pairs of PCR primers were developed for each target gene. PCR analysis of the target genes generated strain-specific patterns on Erga and Erwe/Erwo as predicted by comparative genomics, but also for isolates Senegal and Umpala. The target genes identified by bacterial comparative genomics are shown to be highly efficient for strain-specific PCR diagnosis of E. ruminantium and further vaccine management tools.
Phylogenetic Relationships among Ehrlichia ruminantium Isolates
Annals of the New York Academy of Sciences, 2003
Ehrlichia ruminantium, the causative agent of heartwater, is a tickborne pathogen infecting ruminants throughout sub-Saharan Africa and on some Caribbean islands. The most reliable test for E. ruminantium is PCRbased, but this gives positive results in some areas free of clinical heartwater and of the known Amblyomma spp. tick vectors. To investigate the molecular basis for this finding we have sequenced and carried out phylogenetic analysis of a range of genes from a number of E. ruminantiurn isolates. The genes include ribonuclease 111 and cytochrome c oxidase assembly protein genes (the pCS20 region), groESL, citrate synthase (gltA), and 16s ribosomal RNA. Relationships among major antigenic protein (mapl) genes have been exhaustively investigated in a previous study that showed that the genes are variable in length, have non-synonymous mutations, and show no geographical specificity among isolates. The 16s sequences are highly conserved, except in the V1 loop region. The pCS20, groESL, and gltA genes show only single nucleotide polymorphisms (SNPs) dispersed throughout the sequenced regions. Phylogenetic analysis using pCS20 data differentiates the western African isolates into a single clade, which also includes a southern African isolate. All other southern African isolates and a Caribbean isolate fall into a further clade, which is subdivided into two groups. Sequence variation within this clade is greater than that within the western African clade, suggesting that E. ruminantiurn originated in southern Africa.
Parasites & Vectors, 2011
Background: The rickettsial bacterium Ehrlichia ruminantium is the causative agent of heartwater in ruminants. A better understanding of the population genetics of its different strains is, however, needed for the development of novel diagnostic tools, therapeutics and prevention strategies. Specifically, the development of effective vaccination policies relies on the proper genotyping and characterisation of field isolates. Although multi-locus sequence typing (MLST) has been recently developed, only strains from geographically restricted collections have been analysed so far. The expansion of the MLST database to include global strains with different geographic origins is therefore essential. In this study, we used a panel of reference strains from geographically diverse origins and field samples of E. ruminantium detected from its vector, Amblyomma variegatum, in heartwater-endemic areas in Uganda. Results: A total of 31 novel alleles (six, four, six, three, two, five, three, and two for gltA, groEL, lepA, lipA, lipB, secY, sodB, and sucA loci, respectively) and 19 novel sequence types (STs) were identified. Both neighbour-joining and minimum spanning tree analyses indicated a high degree of genetic heterogeneity among these strains. No association was observed between genotypes and geographic origins, except for four STs from West African countries. When we performed six different tests for recombination (GeneConv, Bootscan, MaxChi, Chimaera, SiScan, and 3Seq) on concatenated sequences, four possible recombination events were identified in six different STs. All the recombination breakpoints were located near gene borders, indicating the occurrence of intergenic recombination. All four STs that localized to a distinct group in clustering analysis showed evidence of identical recombination events, suggesting that recombination may play a significant role in the diversification of E. ruminantium. Conclusions: The compilation of MLST data set across the African continent will be particularly valuable for the understanding of the existing genetic diversity of field isolates in African countries. Comprehensive information on the degree of cross-protection between strains and further understanding of possible relationships between genotypes and phenotypes such as vaccine efficacy are expected to lead to the development of region-specific vaccination strategies.
Veterinary Microbiology, 2008
Understanding genetic diversity of Ehrlichia ruminantium in host and vector populations is an important prerequisite to controlling heartwater by vaccination in traditional livestock systems in sub-Saharan Africa. We carried out a study in two phases: i) evaluating the usefulness of the PCR-RFLP assay based on the map1 coding sequence of E. ruminantium as a discriminatory tool to characterise genetic diversity, ii) applying the technique to field samples from A. variegatum ticks and small ruminants to characterise genotypic diversity of the organism in 3 main agroecological zones of The Gambia, Sudano-Guinean (SG), Western Sudano-Sahelian (WSS) and Eastern Sudano-Sahelian (ESS). Restriction fragment length polymorphisms were observed among different strains of E. ruminantium supporting the usefulness of the PCR-RFLP technique for studying genetic diversity of the organism. Restriction enzyme map1 profile analysis indicated the presence in The Gambia of multiple genotypes (at least 11) of E. ruminantium with sites in the WSS and SG zones showing comparatively high number of diverse genotypes. Profiles similar to the Kerr Seringe genotype (DQ333230) showed the highest distribution frequency, being present at sites in all 3 agroecological zones, thereby making the strain a suitable candidate for further characterisation in cross-protection studies. An additional 3 genotypes showed relatively high distribution frequency and were present in all 3 zones making them equally important for isolation and subsequent characterisation. The study demonstrated the occurrence of mixed infections with E. ruminantium genotypes in ruminants and ticks.
Comparative Genomics of Three Strains of Ehrlichia ruminantium
Annals of the New York Academy of Sciences, 2006
The tick-borne Rickettsiale Ehrlichia ruminantium (E. ruminantium) is the causative agent of heartwater in Africa and the Caribbean. Heartwater, responsible for major losses on livestock in Africa represents also a threat for the American mainland. Three complete genomes corresponding to two different groups of differing phenotypes, Gardel and Welgevonden, have been recently described. One genome (Erga) represents the Gardel group from Guadeloupe Island and two genomes (Erwo and Erwe) belong to the Welgevonden group. Erwo, isolated in South Africa, is the parental strain of Erwe, which was maintained for 18 years in Guadeloupe under different culture conditions than Erwo. The three strains display genomes of differing sizes with 1,499,920 bp, 1,512,977 bp, and 1,516,355 bp for Erga, Erwe, and Erwo, respectively. Gene sequences and order are highly conserved between the three strains, although several gene truncations could be pinpointed, most of them occurring within three regions of accumulated differences (RAD). E. ruminantium displays a strong leading/lagging compositional bias inducing a strand-specific codon usage. Finally, a striking feature of E. ruminantium is the presence of long intergenic regions containing 417 418 ANNALS NEW YORK ACADEMY OF SCIENCES tandem repeats. These repeats are at the origin of an active process, specific to E. ruminantium, of genome expansion/contraction based on the addition or removal of tandem units.
Detection of Ehrlichia ruminantium infection in cattle in Cameroon
BMC Research Notes, 2018
Objectives: Ehrlichia ruminantium infection (heartwater) is a major constraint that impacts negatively on the cattle industry development in sub-Saharan Africa and so far, little is known of the presence of heartwater in cattle in Cameroon. This study sought to investigate the prevalence of E. ruminantium infection in cattle in Cameroon and to determine the predictors of infection. Results: A species-specific semi-nested pCS20 polymerase chain reaction was used to screen the buffy coats from 182 cattle (comprising 82 cattle that received intensive tick control regimen and 100 cattle on strategic tick control) from two study sites in Cameroon for E. ruminantium DNA in a cross-sectional study. E. ruminantium infection was confirmed in 12 (6.6%) of the 182 cattle comprising 11 that received intensive tick control and one on strategic tick control. Of the 12 cattle detected, 11 were apparently healthy and one was clinically diagnosed of heartwater. All DNA sequences of pCS20 amplicons were identical to each other (a representative sequence deposited in GenBank under accession number JQ039939). These findings which have veterinary and epidemiological significance, suggest the need for further investigation to determine the extent and role of heartwater in cattle in Cameroon.