Bacteria Genomes - RICKETTSIA FELIS

Rickettsia are small Gram-negative, aerobic, coccobacilli that are obligate intracellular parasites of eukaryotic cells and are responsible for a variety of human diseases. Members of the genus are commonly associated with hematophagous arthropods such as ticks, fleas, or lice. Formerly called ELB agent, Rickettsia felis is a bacterium transmitted by the cat flea ( Ctenocephalides felis), which also acts as a reservoir for transmission.

Rickettsia typhi is the type of Rickettsia that is most notably the cause of murine typhus however R. felis being an endosymbiont of the cat flea is capable of transmitting by vector, plague and murine typhus to humans, though such reports are rare. There are also varied allergic responses to their bites, depending upon the sensitivity of the host. People get murine typhus from an infected flea. Most fleas defecate while biting, the faeces of infected fleas contain the rickettsial organism. The Rickettsiae enter the body through the bite wound or from a person scratching the bite area.

R. felis is phylogenetically more closely related to the spotted fever group of rickettsiae than the typhus group, it shares antigens with R. typhi and produces a murine typhus-like illness. Rickettsia felis has been detected in cat fleas and opossums.

R. felis was first identified as a human pathogen in 1994, and cases of "flea-borne spotted fever," which have signs and symptoms of febrile exanthema, have now been reported in the United States. Among eight reported cases of human infection with R. felis, all had fever and constitutional symptoms. The majority manifested rash, headache, and central nervous system (CNS) involvement, and variable proportions suffered nausea, vomiting, diarrhea, abdominal pain, myalgia and conjunctivitis.

The distribution of R. felis is potentially as wide as that of its insect host, and to date, its presence has been confirmed in cat flea populations in North and South America and southern Europe.However despite the widespread geographic distribution and prevalence of R. felis in cat fleas, there have been only a handful of clinical investigations undertaken to diagnose cat flea typhus.

Rickettsia felis can be maintained in cat fleas by vertical transmission for up to 12 generations without the benefit of an infected host.

References:

http://www.cdc.gov/ncidod/eid/vol8no1/01-0193.htm
http://www.sbmt.org.br/revista/2004/3/238-240.pdf
http://textbookofbacteriology.net/Rickettsia.html
http://www.cfsresearch.org/rickettsia/research/8.htm
http://edis.ifas.ufl.edu/IN137