Anaplasma (A.) phagocytophilum is the causative agent of anaplasmosis, a bacterial disease which is transmitted through bites from ticks of the genus Ixodes. A. phagocytophilum is a gram-negative, obligate intra-cellular bacterium which attacks mostly neutrophilic granulocytes, but also, in rare cases, eosinophilic granulocytes. Anaplasmosis occurs worldwide, its prevalence depending on the distribution area of the transmitting vectors.
Borrelia is the causative agent of Lyme borreliosis, a bacterial disease which is transmitted through bites from ticks of the genus Ixodes. The gram-negative bacteria are collectively referred to as Borrelia burgdorferi sensu lato. In this group, the genospecies Borrelia burgdorferi sensu stricto, Borrelia garinii and Borrelia afzelii are pathogenic for dogs and horses. Whereas in the U.S. only B. burgdorferi sensu stricto is relevant, more than 80 % of Borrelia in European ticks belong to the pathogenic genospecies B. garinii or B. afzelii. Dogs and horses have a significantly increased risk of infection because of their higher frequency of contact with ticks. Most of the infections, however, proceed asymptomatically. Infection does not confer strong immunity. Reinfection is therefore possible. Antibodies against B. burgdorferi can be found in the serum of specifically infected or vaccinated animals. An infection with B. burgdorferi is associated with a variety of clinical symptoms, which generally occur weeks or months after infection.
West Nile virus (WNV) is an enveloped single-stranded RNA virus of the Flaviviridae family. It is transmitted by a variety of mosquitoes and has so far been discovered in more than 40 different mosquito species and in several tick species. Birds represent the vertebrate reservoir. Acting as incidental hosts, mammals can also become infected when bitten by an infected mosquito.
The distribution area of ticks is continuously increasing due to global warming. Consequently, tick‑borne diseases such as anaplasmosis, borreliosis and tick‑borne encephalitis (TBE) occur more frequently in dogs and horses as well.