Clinical and immunological responses in sheep after inoculation with Himar1-transformed Anaplasma phagocytophilum and subsequent challenge with a virulent strain of the bacterium

In Norway, the tick-transmitted bacterium Anaplasma phagocytophilum is estimated to cause tick-borne fever (TBF) in 300 000 lambs on pastures each year, resulting economic and animal welfare consequences. Today, prophylactic measures mainly involve use of acaricides, but a vaccine has been requested by farmers veterinarians for decades. Several attempts have made produce against A. including antigenic surface proteins, inactivated whole cell vaccines challenge followed treatment. current study, virulent wild type strain named Ap.Norvar1 (16S rRNA sequence partial identical GenBank acc.no M73220) was subject genetic transformation with Himar1-transposon, which resulted three bacterial mutants, capable propagation tick line (ISE6). order test immunogenicity pathogenicity live, mutated bacteria, these were clinically tested an inoculation- study sheep. One group inoculated as infection control. After inoculation, sheep bacteria developed typical clinical signs humoral immune response. Ap.Norvar1, 28 days later all groups showed bacteremia while initially protection disease. The shows weak, animals that received both inoculation challenge, responded homologues protection.