Natural <i>Ehrlichia phagocytophila</i> transmission coefficients from sheep ‘carriers’ to <i>Ixodes ricinus</i> ticks vary with the numbers of feeding ticks

Ogden, N. H.; Casey, A. N. J.; French, Nigel P.; Bown, Kevin; Adams, Jeff; Woldehiwet, Z.

doi:10.1017/s003118200100107x

Cited by 40 publications

(37 citation statements)

References 25 publications

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“…However, in none of the animals were obvious clinical signs apparent. The infection rate of 4% in German sheep was somewhat lower than those reported from other countries such as the United Kingdom (38%), Italy (18%), and Turkey (18%) (25,43,67). In contrast, 94% of the German roe deer investigated were positive for A. phagocytophilum, whereas the infection rate in neighboring European states was between 18 and 88% (18,36,44,46,53,56,77).…”

Section: Discussionmentioning

confidence: 53%

Distinct Host Species Correlate with Anaplasma phagocytophilum ankA Gene Clusters

et al. 2011

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Anaplasma phagocytophilum is a Gram-negative, tick-transmitted, obligate intracellular bacterium that elicits acute febrile diseases in humans and domestic animals. In contrast to the United States, human granulocytic anaplasmosis seems to be a rare disease in Europe despite the initial recognition of A. phagocytophilum as the causative agent of tick-borne fever in European sheep and cattle. Considerable strain variation has been suggested to occur within this species, because isolates from humans and animals differed in their pathogenicity for heterologous hosts. In order to explain host preference and epidemiological diversity, molecular characterization of A. phagocytophilum strains has been undertaken. Most often the 16S rRNA gene was used, but it might be not informative enough to delineate distinct genotypes of A. phagocytophilum. Previously, we have shown that A. phagocytophilum strains infecting Ixodes ricinus ticks are highly diverse in their ankA genes. Therefore, we sequenced the 16S rRNA and ankA genes of 194 A. phagocytophilum strains from humans and several animal species. Whereas the phylogenetic analysis using 16S rRNA gene sequences was not meaningful, we showed that distinct host species correlate with A. phagocytophilum ankA gene clusters.

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Section: Discussionmentioning

confidence: 53%

Distinct Host Species Correlate with Anaplasma phagocytophilum ankA Gene Clusters

et al. 2011

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“…One millilitre of diluted stabilate of each isolate was inoculated intravenously into one susceptible sheep bred and maintained in a tick-free environment. Blood samples were used to monitor infection by microscopy of Giemsa-stained smears and PCR (Ogden et al, 2002). DNA extracted from blood samples collected during the second day of bacteraemia was used for the amplification and sequencing of the 16S rRNA gene and the p44 gene as described below.…”

Section: Methodsmentioning

confidence: 99%

“…DNA was extracted from the engorged tick by alkaline digestion as previously described (Ogden et al, 2002). A nested PCR was used to amplify a 546 bp region of the 16S rRNA gene of A. phagocytophilum (Massung et al, 1998).…”

Section: Methodsmentioning

confidence: 99%

Groupings of highly similar major surface protein (p44)-encoding paralogues: a potential index of genetic diversity amongst isolates of Anaplasma phagocytophilum

et al. 2004

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Anaplasma phagocytophilum is a tick-borne bacterium that is zoonotic in the USA and southern Europe, but although the bacterium is endemic in the UK, no cases of clinical human disease have yet been detected in that country. Potential genomic differences amongst UK and USA isolates were investigated by comparing partial 16S rRNA gene and p44 paralogue sequences amplified by PCR from 10 UK ruminant or tick isolates, with published sequences from USA isolates. No significant clustering among the isolates was resolved by phylogenetic analysis of alignments containing 16S rRNA gene sequences. The structure of predicted proteins encoded by p44 paralogues, amplified from 81 clones obtained from the UK isolates, was similar to that described previously for paralogues from USA isolates. Paralogue sequences did not obviously cluster by country, host species or isolate, but most paralogues were 30-70 % similar, making meaningful alignments difficult. Some p44 paralogues from different isolates formed clusters of sequences that were more than 90 % similar to one another ('similarity groups'). The paralogues in each cluster were particularly similar in gene regions most likely to code for ligands. In the sample studied, 95 % of the similarity groups comprised paralogues from either USA or UK isolates only and occurred with greater frequency amongst paralogues from USA rather than UK isolates. These findings raise the hypothesis that sequences of paralogues in similarity groups may provide an index of adaptation of different 'strains' of A. phagocytophilum to specific reservoir hosts in different geographical locations, and any associations with infectivity for different species including humans.

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“…The role of sheep in the natural maintenance of A. phagocytophilum has been studied in some detail, and it is clear that in some settings they serve as its main reservoir. For instance, Ogden and colleagues (21,22) demonstrated the maintenance of A. phagocytophilum in "fell"-grazing sheep flocks in the absence of other important hosts such as rodents or deer. Early studies revealed that A. phagocytophilum infections can persist for several months or longer in sheep (15), and more recent experimental studies have further quantified their dynamics (11,31).…”

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Dynamic Transmission of NumerousAnaplasma phagocytophilumGenotypes among Lambs in an Infected Sheep Flock in an Area of Anaplasmosis Endemicity

et al. 2008

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The transmission dynamics of Anaplasma phagocytophilum strains circulating within juvenile members of a sheep flock grazing on an Ixodes ricinus-infested pasture in southern Norway were monitored. PCR-based detection of the bacterial p44 fragments in the blood of 16 lambs sampled weekly for 16 weeks following their release into pasture revealed rickettsemia in all animals, with an increasing proportion of infected animals as the survey progressed. Comparison of partial msp4 sequences obtained from infected blood samples revealed 24 distinct genotypes, some of which were repeatedly encountered, occurring in up to six sheep over a 14-week period, whereas others were observed only once. Individual sheep were infected by up to five distinct genotypes, with a specific genotype being encountered for between one and three consecutive weeks, and in some sheep, genotypes detected early in the study were also present in later samples. In general, detection of A. phagocytophilum by PCR correlated well with the observation of infected neutrophils in blood smears. Together these results reveal a previously unrecognized diversity of A. phagocytophilum strains simultaneously circulating within an infected population in an area of endemicity and are consistent with a remarkably dynamic transmission of strains among infected animals.

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Natural Ehrlichia phagocytophila transmission coefficients from sheep ‘carriers’ to Ixodes ricinus ticks vary with the numbers of feeding ticks

Cited by 40 publications

References 25 publications

Distinct Host Species Correlate with Anaplasma phagocytophilum ankA Gene Clusters

Distinct Host Species Correlate with Anaplasma phagocytophilum ankA Gene Clusters

Groupings of highly similar major surface protein (p44)-encoding paralogues: a potential index of genetic diversity amongst isolates of Anaplasma phagocytophilum

Dynamic Transmission of NumerousAnaplasma phagocytophilumGenotypes among Lambs in an Infected Sheep Flock in an Area of Anaplasmosis Endemicity

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