Arbobacteria – Pathogens Transmittable by Arthropods

Anaplasma phagocytophilum, marginatum; Bartonella henselae; Borrelia burgdorferi, afzelii, garinii; Coxiella burnetii; Ehrlichia chaffeensis; Francisella tularensis; Rickettsia prowAZekii, akari, rickettsii and Yersinia pestis are also known as arbobacteria. Diseases caused by these bacteria are basically zoonoses, i.e. diseases transmittable from animals to humans, and have been known as such for about 100 years (table (table1).1). A part of the individual pathogens have not been described until the past few decades. Based on molecular biology analyses, R. prowazekii, Ehrlichia and Anaplasma are categorised as Rick-ettsiales, while Bartonella is categorised as alpha-2-proteobacteria, Coxiella, Rickettsia grylli and F. tularensis as gamma proteobacteria, and Y. pestis as enterobacteria [1]. Table 1 Vectors for arbobacteria Most arbobacteria grow predominantly intracellularly. However, Borrelia bacteria grow intracellularly and extracellularly, and Yersinia mainly extracellularly. The above described arbobacteria, when transmitted by ticks, show seasonal occurrence and a partly changed antigen repertoire in vector and mammal. R. prowazekii is transmitted by lice world-wide throughout the year. The major clinical symptoms such infections have in common include fever, exanthema, headache, and lymph node swelling, partly a pronounced erythema at the site of the sting, and en-cephalitic disorders. Neutropenia and thrombocytopenia can occur later. Treatment: Doxycycline is the treatment of choice against most of these bacteria, followed by chloramphenicol and cephalosporins. Quinolones are ineffective against R. prowazekii. The treatment of choice against Y. pestis and F. tularensis is streptomycin or gentamycin, and in addition doxycycline or ciprofloxacine. C. burnetii has been dealt with separately [2]. Therefore, this pathogen is not included in the present review, neither are rare tropical and/or pure tropical diseases. The oriental flea (Xenopsylla cheopsis) is considered as the most effective transmitter for Y. pestis. More than 30 other flea species are known which can transmit Y. pestis as intermediary hosts, including Pulex irritans (human flea), which can play a role in human-to-human transmission. The human louse can also be a vector for transmission of Y. pestis [3]. The following section provides for each pathogen information on the general state of knowledge, characteristics of the pathogen, infectious disease, epidemiology, methods of detection and occurrence of the pathogen in the donor population. This is followed by information concerning all pathogens on epidemiology, defence situation, treatment and prevention in recipient populations as well as a summary evaluation.