''Rickettsia felis'' is a species of

bacterium Bacteria (; : bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were among the ...

, the

pathogen In biology, a pathogen (, "suffering", "passion" and , "producer of"), in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a Germ theory of d ...

that causes cat-flea typhus in humans, also known as flea-borne spotted fever. '' Rickettsia felis'' also is regarded as the causative organism of many cases of illnesses generally classed as fevers of unknown origin in humans in Africa.

Transmission and concerns

Fleas are the main vectors of ''Rickettsia felis'' and it is present in cat fleas worldwide. Human infection usually results from flea feces coming into contact with scratched or broken skin. Human infection is known as ''cat flea rickettsiosis'', ''flea-borne spotted fever'', and ''cat flea typhus''. An

eschar Eschar (; ; ; or ''an'' eschar) is a slough or piece of necrosis, dead tissue that is cast off from the surface of the skin, particularly after a Burn, burn injury, but also seen in gangrene, Ulcer (dermatology), ulcer, mycosis, fungal infection ...

develops at the site of the flea bite.

Doxycycline Doxycycline is a Broad-spectrum antibiotic, broad-spectrum antibiotic of the Tetracycline antibiotics, tetracycline class used in the treatment of infections caused by bacteria and certain parasites. It is used to treat pneumonia, bacterial p ...

is used for treatment of clinical patients. Fleas are believed to be the likely reservoir of ''R. felis''. ''R. felis'' is transmitted transovarially between fleas. More recently, some authorities have published increasing concerns about the role of more and more species of

arthropod Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...

vectors of this organism; ''Rickettsia felis'' has by now been detected in many arthropods in the wild, including various species of

mite Mites are small arachnids (eight-legged arthropods) of two large orders, the Acariformes and the Parasitiformes, which were historically grouped together in the subclass Acari. However, most recent genetic analyses do not recover the two as eac ...

s, ticks, blood-sucking bugs in the genus ''Cimex'', sucking lice, flea species of various types, both free-living and " sticktight fleas", and various other biting insects.Brown, Lisa D. Macaluso, Kevin R. Rickettsia felis, an Emerging Flea-Borne Rickettsiosis. Curr Trop Med Rep (2016) 3: 27. doi:10.1007/s40475-016-0070-6 In particular there is concern about the prevalence of ''Rickettsia felis'' in regions such as parts of sub-Saharan Africa, in mosquito genera such as '' Anopheles'', ''

Aedes ''Aedes'' (also known as the tiger mosquito) is a genus of mosquitoes originally found in tropical and subtropical zones, but now found on all continents except Antarctica. Some species have been spread by human activity: ''Aedes albopictus'', ...

'', '' Mansonia'', and '' Culex''; all of these genera include species that are challenging to control and have long been recognised as effective vectors of various important human and animal diseases. The mosquito species '' Anopheles gambiae'', which is notorious mainly as a malaria vector, has been demonstrated to be a competent vector for ''Rickettsia felis''. More unexpectedly, cells of some important disease vector species of mosquitoes in the genus ''Aedes'', which is most commonly seen as a vector for

arbovirus Arbovirus is an informal name for any virus that is Transmission (medicine), transmitted by arthropod Vector (epidemiology), vectors. The term ''arbovirus'' is a portmanteau word (''ar''thropod-''bo''rne ''virus''). ''Tibovirus'' (''ti''ck-''bo ...

es, support growth of ''Rickettsia felis''.Parola, Philippe. Musso, Didier. Raoult, Didier. Rickettsia felis: the next mosquito-borne outbreak? The Lancet Infectious Diseases, Volume 16, Issue 10, 1112 - 1113 In addition, in tropical regions where ''Aedes albopictus'' and ''Aedes aegypti'' are established disease vectors and ectoparasites of humans, patients have tested positive for ''Rickettsia felis''. To some authorities this suggests that ''Aedes'' species might be able to infect their hosts with ''Rickettsia felis'', and that patients in, or returning from, the tropics with fevers of unknown origin, should be tested for ''Rickettsia felis'' infection. They see as very real, the possibility that ''Rickettsia felis'' might be the next mosquito-borne pathogen to emerge as a multi-continental disease outbreak.

Australia

Human cases of ''Rickettsia felis'' were diagnosed in Australia in 2009, these were the first reported human infections in Australia.

Diagnosis

Diagnosis of ''R. felis'' infection requires specific

polymerase chain reaction The polymerase chain reaction (PCR) is a method widely used to make millions to billions of copies of a specific DNA sample rapidly, allowing scientists to amplify a very small sample of DNA (or a part of it) sufficiently to enable detailed st ...

(PCR) testing to distinguish serological results from ''R. typhi'' infection.

References

External links

* {{Taxonbar, from=Q7331931 Rickettsiaceae Cat diseases Bacteria described in 2001