Anaplasma phagocytophilum variants in sympatric red deer (Cervus elaphus) and sheep in southern Norway.

Infections by the ixodid tick-transmitted bacterial pathogen Anaplasma phagocytophilum are common in domestic ruminants and cervids in the coastal areas of southern Norway. Previous experimental work has shown that A. phagocytophilum strains recovered from red deer (Cervus elaphus) are infective in lambs, but epidemiological links between infections in red deer and sheep have yet to be established. To address this shortfall, the present study explores the genotypic relatedness between A. phagocytophilum strains infecting sympatric red deer and sheep. Blood from 32 lambs grazing on tick-infested pasture, and blood and tissues from 8 red deer shot in proximity to these pastures were collected during the summer and autumn of 2007. The presence of A. phagocytophilum in these samples was determined by PCR-based methods, and genotyping of detected strains was performed using comparative sequence analysis of 16S rDNA and msp4 fragments. A. phagocytophilum DNA was detected in 12 lambs and 7 red deer, 11 and 4 individuals of which 16S rDNA and msp4 sequence data were obtained from, respectively. A total of 9 genotypes were delineated, and only different individuals of the same host species were infected with indistinguishable A. phagocytophilum genotypes. Although 3 of the red deer-infecting genotypes belonged to a cluster of exclusively deer-associated strains phylogenetically remote from those commonly encountered in sheep, one red deer-infecting genotype, although unique, clustered tightly with genotypes associated with a wide range of hosts including sheep.