Infection intensity and infectivity of the tick‐borne pathogen Borrelia afzelii

2015

Phil. Trans. R. Soc. B

Infections frequently consist of more than one strain of a given pathogen. Experiments have shown that co-infecting strains often compete, so that the infection intensity of each strain in mixed infections is lower than in single strain infections. Such within-host competition can have important epidemiological and evolutionary consequences. However, the extent of competition has rarely been investigated in wild, naturally infected hosts, where there is noise in the form of varying inoculation doses, asynchronous infections and host heterogeneity, which can potentially alleviate or eliminate competition. Here, we investigated the extent of competition between Borrelia afzelii strains (as determined by ospC genotype) in three host species sampled in the wild. For this purpose, we developed a protocol for 454 amplicon sequencing of ospC , which allows both detection and quantification of each individual strain in an infection. Each host individual was infected with one to six ospC strains. The infection intensity of each strain was lower in mixed infections than in single ones, showing that there was competition. Rank-abundance plots revealed that there was typically one dominant strain, but that the evenness of the relative infection intensity of the different strains in an infection increased with the multiplicity of infection. We conclude that within-host competition can play an important role under natural conditions despite many potential sources of noise, and that quantification by next-generation amplicon sequencing offers new possibilities to dissect within-host interactions in naturally infected hosts.

Section: Discussionsupporting

confidence: 66%

Section: Discussionmentioning

confidence: 85%

Section: (D) 454 Sequence Annotation and Quantification Of Borrelia Amentioning

confidence: 99%

“…The overall B. afzelii infection intensity in each of the 124 samples was measured by qPCR targeting flaB as described in [20]. All samples were run in duplicate on separate plates.…”

Section: (B) Optimization Of Amplificationmentioning

confidence: 99%

See 2 more Smart Citations

Within-host competition betweenBorrelia afzelii ospCstrains in wild hosts as revealed by massively parallel amplicon sequencing

Strandh

2015

Phil. Trans. R. Soc. B

“…afzelii was detected and quantified with a qPCR assay targeting the flaB gene as previously described (21). To check for contamination, eight negative controls were included on each plate.…”

Section: Methodsmentioning

confidence: 99%

Infection Dynamics of the Tick-Borne Pathogen “Candidatus Neoehrlichia mikurensis” and Coinfections with Borrelia afzelii in Bank Voles in Southern Sweden

Andersson

Scherman

2014

Appl Environ Microbiol

The tick-borne bacterium "Candidatus Neoehrlichia mikurensis" has recently been recognized as a human pathogen. Together with Borrelia afzelii, it is one of the most common pathogens found in the tick Ixodes ricinus. Here, we compared the epidemiologies of "Ca. Neoehrlichia mikurensis" and B. afzelii by longitudinal sampling from May to September in one of their most abundant vertebrate hosts, the bank vole (Myodes glareolus), using real-time PCR for detection and quantification. The prevalences of "Ca. Neoehrlichia mikurensis" and B. afzelii were determined to be 19% (50/261) and 22% (56/261), respectively. The prevalence of "Ca. Neoehrlichia mikurensis" increased significantly during the sampling season. The clearance rate of "Ca. Neoehrlichia mikurensis" was significantly higher than that of B. afzelii. We found a high frequency of double infections; 46% of all samples infected with "Ca. Neoehrlichia mikurensis" also had a coinfection with B. afzelii. The frequency of coinfections was significantly higher than expected from the prevalence of each pathogen. The high level of coinfections can be caused by interactions between the pathogens or might reflect variation in general susceptibility among voles.

Comparison of spleen transcriptomes of two wild rodent species reveals differences in the immune response against Borrelia afzelii

Zhong

Lundberg

2020

Ecology and Evolution

Different host species often differ considerably in susceptibility to a given pathogen, but the causes of such differences are rarely known. The natural hosts of the tick‐transmitted bacterium Borrelia afzelii, which is one of causative agents of Lyme borreliosis in humans, include a variety of small mammals like voles and mice. Previous studies have shown that B. afzelii‐infected bank voles (Myodes glareolus) have about ten times higher bacterial load than infected yellow‐necked mice (Apodemus flavicollis), indicating that these two species differ in resistance. In this study, we compared the immune response to B. afzelii infection in these host species by using RNA sequencing to quantify gene expression in spleen. Gene set enrichment analysis (GSEA) showed that several immune pathways were down‐regulated in infected animals in both bank voles and yellow‐necked mice. Moreover, IFNα response was up‐regulated in B. afzelii‐infected yellow‐necked mice, while IL6 signaling and the complement pathway were down‐regulated in infected bank voles; differences in regulation of these three pathways between bank voles and yellow‐necked mice could thus contribute to the difference in resistance to B. afzelii between the species. This study provides knowledge of gene expression induced by a zoonotic pathogen in its natural host, and possible species‐specific regulation of immune responses associated with resistance.