Bartonella Henselae

Bartonella Henselae

Introduction

The genus Bartonella consists of small, Gram-negative, facultatively intracellular bacteria that are mainly transmitted by arthropod vectors (Mosbacher et al., 2010). Less than 20 years ago only a few species of Bartonella were known. However, in the early 1990's Bartonella henselae was discovered to be the etiologic agent of cat-scratch disease (CSD) creating worldwide interest in this genus (Mogollon-Pasapera et al., 2009). Since then, at least 24 separate Bartonella species have been identified, including bacterial species originally included in the genera Rochalimaea and Grahamella (Guptill, 2010). The members of the Bartonella genus have been found within a growing number of mammal reservoirs and arthropod vectors (Table 1), and at least 13 Bartonella species are known or suspected to be human pathogens (Chomel and Kasten, 2010). Bartonella infections can result in a wide range of clinical symptoms in humans, ranging from asymptomatic or self-limiting diseases to life-threatening illnesses such as Trench fever and Carrion's disease (Mogollon-Pasapera et al., 2009). B. bacilliformis, B. quintana, and B. henselae are the most clinically important members of the Bartonella genus and have the unique capacity to cause vasoproliferative tumor lesions (Kaiser et al., 2011). However, while all three species rely on arthropod vectors, B. bacilliformis and B. quintana are human-specific and have no other known mammalian reservoirs. B. henselae is considered to be a zoonotic Bartonella species and is found primarily in feline reservoirs, although it has been identified in numerous mammals (Table 2) (Kaiser et al., 2011).

Transmission and Prevalence

Currently, B. henselae is the most studied member of the zoonotic Bartonella species (Guptill, 2010). Cats are the main reservoirs of this organism, with approximately 25-45% of healthy cats seropositive for B. henselae throughout the world (Breitschwerdt, 2008). However, the prevalence of B. henselae infection in cats varies considerably. Levels of infection appear to be affected by latitude, with lower levels at northern latitudes and increasing levels of infection in warmer, humid climates (Chomel and Kasten, 2010). The highest levels of infection are found in areas where conditions most favor survival of arthropod vectors, as the bacterial parasite is naturally transmitted between cat reservoirs by the cat flea Ctenocephalides felis (Kaiser et al., 2011). Upon infection with B. henselae, cat reservoirs commonly enter a healthy, asymptomatic state with chronic recurring bacteremia. High levels of the bacteria within the feline bloodstream facilitate acquisition by the arthropod vector when it takes blood meals from infected carriers (Guptill, 2010). It has been shown that the transfer of carrier-fed fleas to uninfected cats allows transmission of B. henselae. While transmission by flea saliva has not been documented, B. henselae infection of the cat flea gut is common and the exposure to infected flea feces appears to be the route of infection for cats (Telford and Wormser, 2010). It has been shown that intradermal inoculation of excrement from carrier-fed fleas can result in infection (Guptill, 2010). Additionally, experimental data indicates that B. henselae transmission does not occur when infected cats interact with uninfected cats in flea-free environments, indicating that ...