''Rickettsia felis'' is a species of

bacterium Bacteria (; singular: 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

pathogen In biology, a pathogen ( el, πάθος, "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 ...

that causes cat-flea typhus in humans, also known as

flea-borne spotted fever Flea-borne spotted fever or California pseudotyphus is a condition characterized by a rash of maculopapules or furuncle A boil, also called a furuncle, is a deep folliculitis, which is an infection of the hair follicle. It is most commonly caus ...

. ''

Rickettsia ''Rickettsia'' is a genus of nonmotile, gram-negative, nonspore-forming, highly pleomorphic bacteria that may occur in the forms of cocci (0.1 μm in diameter), bacilli (1–4 μm long), or threads (up to about 10 μm long). The term "rickett ...

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

Until recently, fleas have been the recognised vectors of ''Rickettsia felis'' and it is present in cat flea populations of North and South America, Southern Europe, Africa, Thailand and Australia. Human infection usually results from flea feces coming into contact with scratched or broken skin. More recently, some authorities have published increasing concerns about the role of more and more species of

arthropod Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and Arth ...

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). Mites span two large orders of arachnids, the Acariformes and the Parasitiformes, which were historically grouped together in the subclass Acari, but genetic analysis does not show clear evid ...

tick Ticks (order Ixodida) are parasitic arachnids that are part of the mite superorder Parasitiformes. Adult ticks are approximately 3 to 5 mm in length depending on age, sex, species, and "fullness". Ticks are external parasites, living by ...

s, blood-sucking bugs in the genus ''Cimex'', sucking lice, flea species of various types, both free-living and "

sticktight flea ''Echidnophaga gallinacea'', also known as the hen flea or sticktight flea, is part of the 2,500 known flea types in the Siphonaptera order. ''Echidnophaga gallinacea'' appear dark brown in colour and is a small flea measuring approximately 2 m ...

s", 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 ''Anopheles'' () is a genus of mosquito first described and named by J. W. Meigen in 1818. About 460 species are recognised; while over 100 can transmit human malaria, only 30–40 commonly transmit parasites of the genus ''Plasmodium'', which c ...

'', ''

Aedes ''Aedes'' is a genus of mosquitoes originally found in tropical and subtropical zones, but now found on all continents except perhaps Antarctica. Some species have been spread by human activity: ''Aedes albopictus'', a particularly invasive spe ...

'', '' Mansonia'', and ''

Culex ''Culex'' is a genus of mosquitoes, several species of which serve as vectors of one or more important diseases of birds, humans, and other animals. The diseases they vector include arbovirus infections such as West Nile virus, Japanese encep ...

''; 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 The ''Anopheles gambiae'' complex consists of at least seven morphologically indistinguishable species of mosquitoes in the genus ''Anopheles''. The complex was recognised in the 1960s and includes the most important vectors of malaria in sub- ...

'', 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 transmitted by arthropod vectors. The term ''arbovirus'' is a portmanteau word (''ar''thropod-''bo''rne ''virus''). ''Tibovirus'' (''ti''ck-''bo''rne ''virus'') is sometimes used to more spe ...

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. The infected individuals were family members who had been exposed to flea bites from infested kittens. In this cluster an otherwise healthy nine-year-old girl was admitted to hospital with fever and a rash. This later worsened three days later when her lungs filled with fluid and she was admitted to intensive care.

References

External links

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