Bartonella melophagi in blood of domestic sheep (Ovis aries) and sheep keds (Melophagus ovinus) from the southwestern US: Cultures, genetic characterization, and ecological connections.

Bartonella melophagi sp. nov. was isolated from domestic sheep blood and from sheep keds (Melophagus ovinus) from the southwestern United States. The sequence analyses of the reference strain performed by six molecular markers consistently demonstrated that B. melophagi relates to but differ from other Bartonella species isolated from domestic and wild ruminants. Presence of 183 genes specific for B. melophagi, being absent in genomes of other Bartonella species associated with ruminants also supports the separation of this bacterial species from species of other ruminants. Bartonella DNA was detected in all investigated sheep keds; however, culturing of these bacteria from sheep blood rejects a speculation that B. melophagi is an obligatory endosymbiont. Instead, the results support the hypothesis that the domestic sheep is a natural host reservoir for B. melophagi and the sheep ked its main vector. This bacterium was not isolated from the blood of bighorn sheep and domestic goats belonging to the same subfamily Caprinae. B. melophagi has also been shown to be zoonotic and needs to be investigated further.