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Rickettsia prowazekii

Rickettsia prowazekii

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Encyclopedia
Rickettsia prowazekii is a species of gram negative, Alpha Proteobacteria, obligate intracellular parasitic
Obligate intracellular parasite
Intracellular parasites are parasitic microorganisms - microparasites that are capable of growing and reproducing inside the cells of a host.-Facultative:...

, aerobic
Aerobic organism
An aerobic organism or aerobe is an organism that can survive and grow in an oxygenated environment.Faculitative anaerobes grow and survive in an oxygenated environment and so do aerotolerant anaerobes.-Glucose:...

 bacteria
Bacteria
Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

 that is the etiologic agent of epidemic typhus, transmitted in the feces of lice. In North America, the main reservoir for R. prowazekii is the flying squirrel
Flying squirrel
Flying squirrels, scientifically known as Pteromyini or Petauristini, are a tribe of 44 species of squirrels .- Description :...

. R. prowazekii is often surrounded by a protein microcapsular layer and slime
Mucus
In vertebrates, mucus is a slippery secretion produced by, and covering, mucous membranes. Mucous fluid is typically produced from mucous cells found in mucous glands. Mucous cells secrete products that are rich in glycoproteins and water. Mucous fluid may also originate from mixed glands, which...

 layer; the natural life cycle of the bacterium generally involves a vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...

 and an invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...

 host, usually an arthropod
Arthropod
An arthropod is an invertebrate animal having an exoskeleton , a segmented body, and jointed appendages. Arthropods are members of the phylum Arthropoda , and include the insects, arachnids, crustaceans, and others...

, typically the human body louse. A form of R.. prowazekii that exists in the feces of arthropods remains stably infective for months. R. prowazekii also appears to be the closest free-living relative of mitochondria, based on genome sequencing.

Discovery


Henrique da Rocha Lima
Henrique da Rocha Lima
Henrique da Rocha Lima was a Brazilian physician, pathologist and infectologist. He discovered Rickettsia prowazekii, the pathogen of epidemic typhus. Rickettsia prowazekii was named after German zoologist Stanislaus von Prowazek.Henrique da Rocha Lima received his M.D. degree from the Medical...

, a Brazilian doctor, discovered this bacterium in 1916. He named it after his colleague Stanislaus von Prowazek
Stanislaus von Prowazek
Stanislaus Josef Mathias von Prowazek, Edler von Lanow , born Stanislav Provázek, was a Czech zoologist and parasitologist, who along with pathologist Henrique da Rocha Lima discovered the pathogen of epidemic typhus.Prowazek had studied epidemic typhus in Serbia and Istanbul...

, who had died from typhus in 1915. Both Prowazek and Rocha Lima had been infected with typhus while studying its causative agent in a prison hospital in Hamburg
Hamburg
-History:The first historic name for the city was, according to Claudius Ptolemy's reports, Treva.But the city takes its modern name, Hamburg, from the first permanent building on the site, a castle whose construction was ordered by the Emperor Charlemagne in AD 808...

, Germany
Germany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

.

Evolutionary History


The genome of R. prowazekii provides great insight, especially to the origin of modern-day mitochondria. The R. prowazekii is not only the closest known relative to mitochondria through genome sequencing, as it also has a highly derived genome like that of mitochondria. Since the two are so similar, they likely have a very similar evolutionary history. It is commonly believed that mitochondria evolved through endosymbiosis, and R. prowazekii could have evolved in a similar way. It is even possible for a bacterium similar to R. prowazekii to have been the initiator of endosymbiosis.

Treatment


Vaccines against R. prowazekii were developed in the 1940s, and were highly effective in reducing typhus deaths among U.S. soldiers during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

. Immunity
Immunity (medical)
Immunity is a biological term that describes a state of having sufficient biological defenses to avoid infection, disease, or other unwanted biological invasion. Immunity involves both specific and non-specific components. The non-specific components act either as barriers or as eliminators of wide...

 following recovery from infection with, or by immunization against, R. prowazekii is lifelong in most cases. However, R. prowazekii can establish a latent
Virus latency
Virus latency is the ability of a pathogenic virus to lie dormant within a cell, denoted as the lysogenic part of the viral life cycle. A latent viral infection is a type of persistent viral infection which is distinguished from a chronic viral infection...

infection, which can reactivate after years or decades (referred to as Brill-Zinsser disease). Treatment with tetracycline antibiotics is usually successful.