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Rickettsia typhi
Rickettsia typhi is a small, aerobic, obligate intracellular, rod shaped gram negative bacterium. It belongs to the typhus group of the Rickettsia genus, along with R. prowazekii. R. typhi has an uncertain history, as it may have long gone shadowed by epidemic typhus (R. prowazekii). This bacterium is recognized as a biocontainment level 2/3 organism. R. typhi is a flea-borne disease that is best known to be the causative agent for the disease murine typhus, which is an endemic typhus in humans that is distributed worldwide. As with all rickettsial organisms, R. typhi is a zoonotic agent that causes the disease murine typhus, displaying non-specific mild symptoms of fevers, headaches, pains and rashes. There are two cycles of R. typhi transmission from animal reservoirs containing R. typhi to humans: a classic rat-flea-rat cycle that is most well studied and common, and a secondary periodomestic cycle that could involve cats, dogs, opossums, sheep, and their fleas.
R. typhi was once one of the most prevalent causes of rickettsial diseases worldwide, but has since experienced a drop in case reports with the implementation of pest control programs. The microorganism is concentrated in warmer climate and coastal ports where there is an abundance of rats and their fleas, which are the preferred hosts for the pathogen. R. typhi is transmitted between competent flea and mammalian hosts through flea bites and contact with infected feces and tissues.
There are several laboratory tests available for the diagnosis of Rickettsial species, with the traditional diagnosis based on serology. However, newer laboratory techniques such as real-time PCR and microimmunofluorescence can be used to identify Rickettsia faster and down to the Rickettsia typhi species level.
In the early 20th century epidemic typhus (R. prowazekii) ran rampant throughout many parts of the world. It was associated with high mortality, high virulence, and thought to be transmitted via louse. During this period, less severe and untraceable cases began appearing. These cases were characterized by fever, rash, headache, as well as musculoskeletal and gastro intestinal signs. Epidemiologist Kenneth F Maxy recognized this and began questioning and isolating the presence of another typhus within the United States aside from R. prowazekii, he detailed this in an article released in 1926. Maxy speculated the presence of another arthropod vector transmitting this new form of typhus, which would later be discovered as R. typhi. It is thought that R. typhi has historically been under diagnosed compared to its typhus group member R. prowazekii. The discovery of R. typhi lead to the creation of the typhus group Rickettsia, which contains R. typhi and R. prowazekii. Rickettsia species are generally broken into 3 groups, the spotted fever group, typhus group and scrub typhus group.
Rickettsia typhi is a small, aerobic, obligate intracellular, rod shaped, gram negative bacterium. R. typhi is a zoonotic bacterium that is recognized as a biocontainment level 2/3 organism (dependent upon the tissue being worked with). As obligate intracellular pathogens, R. typhi can be difficult to isolate, and are not able to be cultured using standard plating methods seen with most other organisms. R. typhi are motile, creating movement through actin based motility, with little control over directionality and speed, and are often seen moving in a circular pattern.
Rickettsia typhi is a flea-borne disease organism and is widely distributed throughout the world. There are two cycles in R. typhi transmission from animal reservoirs to human: a classic rat-flea-rat cycle, and a peridomestic cycle involving cats, dogs, opossums, sheep, and their fleas.
R. typhi circulates amongst rats (Rattus rattus or Rattus norvegicus) and rat fleas (Xenopyslla cheopis), but other rodents and their ectoparasites also play a role in maintaining R. typhi in nature. While the rat flea is the main vector of R. typhi, P. h. humanus, Polypax lice and bloodsucking mites of rats have been reported to be capable of acquiring R. typhi, either naturally or experimentally.
Transmission of R. typhi from the rat flea is affected by contact with rickettsia-containing flea feces during or after blood feeding, as well as via flea bite. The rickettsiae have no harmful effects on the fitness of either the vector or the rat, showing a true mutual relationship. Infected fleas can maintain R. typhi for life, giving them potential for infecting large number of susceptible hosts.
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Rickettsia typhi
Rickettsia typhi is a small, aerobic, obligate intracellular, rod shaped gram negative bacterium. It belongs to the typhus group of the Rickettsia genus, along with R. prowazekii. R. typhi has an uncertain history, as it may have long gone shadowed by epidemic typhus (R. prowazekii). This bacterium is recognized as a biocontainment level 2/3 organism. R. typhi is a flea-borne disease that is best known to be the causative agent for the disease murine typhus, which is an endemic typhus in humans that is distributed worldwide. As with all rickettsial organisms, R. typhi is a zoonotic agent that causes the disease murine typhus, displaying non-specific mild symptoms of fevers, headaches, pains and rashes. There are two cycles of R. typhi transmission from animal reservoirs containing R. typhi to humans: a classic rat-flea-rat cycle that is most well studied and common, and a secondary periodomestic cycle that could involve cats, dogs, opossums, sheep, and their fleas.
R. typhi was once one of the most prevalent causes of rickettsial diseases worldwide, but has since experienced a drop in case reports with the implementation of pest control programs. The microorganism is concentrated in warmer climate and coastal ports where there is an abundance of rats and their fleas, which are the preferred hosts for the pathogen. R. typhi is transmitted between competent flea and mammalian hosts through flea bites and contact with infected feces and tissues.
There are several laboratory tests available for the diagnosis of Rickettsial species, with the traditional diagnosis based on serology. However, newer laboratory techniques such as real-time PCR and microimmunofluorescence can be used to identify Rickettsia faster and down to the Rickettsia typhi species level.
In the early 20th century epidemic typhus (R. prowazekii) ran rampant throughout many parts of the world. It was associated with high mortality, high virulence, and thought to be transmitted via louse. During this period, less severe and untraceable cases began appearing. These cases were characterized by fever, rash, headache, as well as musculoskeletal and gastro intestinal signs. Epidemiologist Kenneth F Maxy recognized this and began questioning and isolating the presence of another typhus within the United States aside from R. prowazekii, he detailed this in an article released in 1926. Maxy speculated the presence of another arthropod vector transmitting this new form of typhus, which would later be discovered as R. typhi. It is thought that R. typhi has historically been under diagnosed compared to its typhus group member R. prowazekii. The discovery of R. typhi lead to the creation of the typhus group Rickettsia, which contains R. typhi and R. prowazekii. Rickettsia species are generally broken into 3 groups, the spotted fever group, typhus group and scrub typhus group.
Rickettsia typhi is a small, aerobic, obligate intracellular, rod shaped, gram negative bacterium. R. typhi is a zoonotic bacterium that is recognized as a biocontainment level 2/3 organism (dependent upon the tissue being worked with). As obligate intracellular pathogens, R. typhi can be difficult to isolate, and are not able to be cultured using standard plating methods seen with most other organisms. R. typhi are motile, creating movement through actin based motility, with little control over directionality and speed, and are often seen moving in a circular pattern.
Rickettsia typhi is a flea-borne disease organism and is widely distributed throughout the world. There are two cycles in R. typhi transmission from animal reservoirs to human: a classic rat-flea-rat cycle, and a peridomestic cycle involving cats, dogs, opossums, sheep, and their fleas.
R. typhi circulates amongst rats (Rattus rattus or Rattus norvegicus) and rat fleas (Xenopyslla cheopis), but other rodents and their ectoparasites also play a role in maintaining R. typhi in nature. While the rat flea is the main vector of R. typhi, P. h. humanus, Polypax lice and bloodsucking mites of rats have been reported to be capable of acquiring R. typhi, either naturally or experimentally.
Transmission of R. typhi from the rat flea is affected by contact with rickettsia-containing flea feces during or after blood feeding, as well as via flea bite. The rickettsiae have no harmful effects on the fitness of either the vector or the rat, showing a true mutual relationship. Infected fleas can maintain R. typhi for life, giving them potential for infecting large number of susceptible hosts.