Spotted fever group rickettsioses present a threat to human health worldwide. These bacteria are the cause of potentially fatal febrile illnesses in humans. They are transmitted by arthropod vectors such as ticks, mites, fleas and lice, which are associated with vertebrate host animals including rodents and companion animals.
Background
Rickettsia are obligate intracellular bacteria that are widely distributed throughout the world, causing both emerging and re-emerging infectious diseases (Parola et al., 2005). They are small (approx. 0.7–1.0 μm in length, 0.3–0.5 μm in width), highly pleomorphic cocco-bacillary Gram-negative rods belonging to the class Alphaproteobacteria (Maina et al 2012). They are associated with arthropod vectors: ticks, …show more content…
They mainly invade endothelial cells, induce the formation of vasculitis and causes acute flu-like symptoms, including chills, high fever, head-ache, skin rash and photophobia (Renvoisé et al. 2009). Their pathogenesis is dependent upon several stages, including its arthropod interactions and those with the host endothelial cells such as entry, phagosomal escape, subsequent actin-based motility, and consequent spread to adjacent cells, cumulating in injury of the host (Maina et al 2012). Over the last two decades, the development of molecular diagnostic assays and cell culture systems has enhanced the detection of new rickettsial species, of varying degrees of virulence or unknown pathogenicity, from various arthropod vectors and humans (Raoult et al., 2005). Also the availability of complete genome sequences has allowed new approaches to phylogenetic inference and provided new perspectives on rickettsial evolution. In recent years, the taxonomy of rickettsiae has been reorganized and continues to be modified as new data become available (Parola et al., 2013; Parola and Raoult 2006). For the past years, serology was the main criterion used to classify rickettsiae in only two groups (Philip et …show more content…
prowazekii and R. typhi, the agents responsible for epidemic and murine typhus, the spotted fever group (SFG), consisting of approximately 20 species, including the best known species, Rickettsia rickettsii, the agent responsible for Rocky Mountain spotted fever; the ancestral group (AG), consisting of R. canadensis and R. bellii and the transitional group (TRG), consisting of R. akari, R. felis and R. australis ( Wood and Artsob 2011). The classification of Rickettsia into separate groups was initially based on serology but these groupings have been confirmed by molecular and phylogenetic analyses (Gillespie et al., 2007, 2008). A more recent analysis proposes to split the ancestral group in two with one Rickettsia in each group (i.e., R. bellii and R. canadensis) and to include the transitional group within the spotted fever group (SFG) (Merhej and Raoult
Background
Rickettsia are obligate intracellular bacteria that are widely distributed throughout the world, causing both emerging and re-emerging infectious diseases (Parola et al., 2005). They are small (approx. 0.7–1.0 μm in length, 0.3–0.5 μm in width), highly pleomorphic cocco-bacillary Gram-negative rods belonging to the class Alphaproteobacteria (Maina et al 2012). They are associated with arthropod vectors: ticks, …show more content…
They mainly invade endothelial cells, induce the formation of vasculitis and causes acute flu-like symptoms, including chills, high fever, head-ache, skin rash and photophobia (Renvoisé et al. 2009). Their pathogenesis is dependent upon several stages, including its arthropod interactions and those with the host endothelial cells such as entry, phagosomal escape, subsequent actin-based motility, and consequent spread to adjacent cells, cumulating in injury of the host (Maina et al 2012). Over the last two decades, the development of molecular diagnostic assays and cell culture systems has enhanced the detection of new rickettsial species, of varying degrees of virulence or unknown pathogenicity, from various arthropod vectors and humans (Raoult et al., 2005). Also the availability of complete genome sequences has allowed new approaches to phylogenetic inference and provided new perspectives on rickettsial evolution. In recent years, the taxonomy of rickettsiae has been reorganized and continues to be modified as new data become available (Parola et al., 2013; Parola and Raoult 2006). For the past years, serology was the main criterion used to classify rickettsiae in only two groups (Philip et …show more content…
prowazekii and R. typhi, the agents responsible for epidemic and murine typhus, the spotted fever group (SFG), consisting of approximately 20 species, including the best known species, Rickettsia rickettsii, the agent responsible for Rocky Mountain spotted fever; the ancestral group (AG), consisting of R. canadensis and R. bellii and the transitional group (TRG), consisting of R. akari, R. felis and R. australis ( Wood and Artsob 2011). The classification of Rickettsia into separate groups was initially based on serology but these groupings have been confirmed by molecular and phylogenetic analyses (Gillespie et al., 2007, 2008). A more recent analysis proposes to split the ancestral group in two with one Rickettsia in each group (i.e., R. bellii and R. canadensis) and to include the transitional group within the spotted fever group (SFG) (Merhej and Raoult