Unique strains of Anaplasma phagocytophilum segregate among diverse questing and non-questing Ixodes tick species in the western United States


The emerging tick-borne pathogen Anaplasma phagocytophilum infects humans, domestic animals, and wildlife throughout the Holarctic. In the western US, the ecology of A. phagocytophilum is particularly complex, with multiple pathogen strains, tick vectors, and reservoir hosts. A recent phylogenetic analysis of A. phagocytophilum strains isolated from various small mammal hosts in California documented distinct clustering of woodrat strains separate from sciurid (chipmunk and squirrel) strains. Here, we identified strains of A. phagocytophilum in various Ixodes tick species in California and related these genotypes to those found among reservoir and clinical hosts from the same areas. The sequences from all of the nidicolous (nest-dwelling) Ixodes ticks grouped within a clade that also contained all of the woodrat-origin A. phagocytophilum strains. Two of the I. pacificus sequences were also grouped within this woodrat clade, while the remaining five belonged to a less genetically diverse clade that included several sciurid-origin strains as well as a dog, a horse, and a human strain. By comparing A. phagocytophilum strains from multiple sources concurrently, we were able to gain a clearer picture of how A. phagocytophilum strains in the western US are partitioned, which hosts and vectors are most likely to be infected with a particular strain, and which tick species and reservoir hosts pose the greatest health risk to humans and domestic animals.

1 Comment

  • sue meub says:

    please post some sources for reference that are recent in peer reviewed journals to support your current reccomendations for treatement of Lyme and Co INfection..The guidlines from Germany are based on research done , for the most part, more than 5 years aga and many references are from the 1990’s or before..It looks there hasent been haven’t had much peer reviewed,quality research since the 1990’s .. come on… if we are to discuss current treatment lets publish some stuff that is not just reliant on heresay and annecdotal evidence…..lets find evidenec to support long term antibiotics , vitamon and mineral regimens that work …lets find out why they work and support those findings with acceptable research so that we can be taken seriously..