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Rickettsia Prowazekii

Rickettsia Prowazekii



NAME: Rickettsia prowazekii

SYNONYM OR CROSS REFERENCE: Louse-borne typhus fever, Louse-borne epidemic typhus, LBET, Epidemic typhus, exanthematic typhus, historical typhus, classic typhus, sylvatic typhus, red louse disease, jail fever, Brill Zinsser disease

CHARACTERISTICS: Rickettsia prowazekii is an obligate intracellular bacterium of the Rickettsiacae family(1,2). It is a small, gram-negative α-proteobacteria and is a coccobacillus(3).


PATHOGENICITY/TOXICITY: Epidemic typhus is usually characterized by 1-3 days of malaise before abrupt onset of severe headaches and fever (40 ºC)(1,4). Symptoms include myalgia, arthralgia, abdominal pain, anorexia, chills, trachypnea, diarrhoea, myocarditis and tachycardia(1,4). In 20-40% of cases, non-confluent erythematous rashes start in the axilla and then spread to the rest of the body with the exception of the face, palms of hands and soles of feet(1,5). Up to 80% of cases have CNS complications such as delirium, seizures, coma, meningeal irritation, confusion, drowsiness, and hearing loss(1). Cough has been reported in 38- 70% of cases and gangrene and necrosis of fingers and toes have occurred(1). The disease usually lasts for two weeks, although it may take months to fully recuperate(3). The mortality rate is estimated at 4% if the patient is treated with the appropriate antibiotics but the mortality rate is higher in individuals who are over the age of 60(1). A milder recurrent form of typhus called Brill Zinsser disease may occur in a patient that has previously had epidemic typhus and this form has a mortality rate of 1%(1,6).

EPIDEMIOLOGY: The disease is found in areas with cold weather, homelessness and poverty(1). It is a particular problem during famine, conflict and natural catastrophes as cramped conditions and lack of hygiene facilitate the spread of body lice(2). In the past 25 years, cases have been reported in Africa (Ethiopia, Nigeria and Burundi), Mexico, Central America, South America, Eastern Europe, Afghanistan, Northern India, China and the United States(2,6). Since 1976, 39 cases of epidemic typhus were reported in the United States and at least one third of the cases were related to contact with flying squirrels(6).

HOST RANGE: Humans, flying squirrels (Glaucomys volans ) and body and head lice have been shown to contain the infectious agent in their tissues(1). Livestock and donkeys have also been found to have Rickettsia prowazekii antibodies in their systems(1).

INFECTIOUS DOSE: The median infectious dose for epidemic typhus is < 10 rickettsial particles(7).

MODE OF TRANSMISSION: The infection is caused by the contamination of a louse bite site, superficial abrasion, conjunctivae or mucous membranes with louse feces or crushed louse tissues(1,8). The disease can also be transmitted by inhalation of infectious aerosols (like louse fecal dust), which poses a potential risk for healthcare workers and laboratory personnel(2,8). The body louse is infected when feeding on an infected human and the flying squirrel may be infected by fleas and lice(1).

INCUBATION PERIOD: The incubation period is usually 10-14 days(1,2).

COMMUNICABILITY: Although human-to-human transmission does not occur, proximity to an infected individual increases the chances of exposure to infected body lice(1). Humans remain infective for life and can pass the disease to lice(2). The lice tend to leave sick individuals and go towards healthier hosts(1). Lice become infective 5-7 days after exposure and remain so for life; however, they tend to die 1 week after contracting the bacteria(1,3,9). The lice feces remain infective for 100 days as aerosols and this is the proposed mode of transmission between flying squirrels and humans(1,3).


RESERVOIR: Humans are necessary to maintain the infection; however, flying squirrels may also be a potential reservoir for the disease(1).

ZOONOSIS: The flying squirrel may spread the disease to humans indirectly via infected lice or infective lice feces in aerosol form(1).

VECTORS: The body louse, Pediculus humanis corporis is the main vector for epidemic typhus although it has been proposed that head lice, Pediculus humanis capitis , could also be a vector(1,10).


DRUG SUSCEPTIBILITY: The infectious agent is susceptible to tetracyclines, chloramphenicol, or doxycycline. Therapy with doxycycline for 5-7 days, or 2-4 days after defervescence, is recommended to preclude relapses. In outbreak situations, a single oral dose of doxyxycline can be given(1,2,3).

SUSCEPTIBILITY TO DISINFECTANTS: Gram-negative bacteria are susceptible to 1% sodium hypochlorite, 4% formaldehyde, 2% glutaraldehyde, 70% ethanol, 2% peracetic acid, 3- 6% hydrogen peroxide and 0.16% iodine(8).

PHYSICAL INACTIVATION: Rickettsia prowazekii is susceptible to moist heat (121 ºC for at least 15 minutes) and dry heat (170 ºC for at least 1 hour)(11).

SURVIVAL OUTSIDE HOST: Rickettsia prowazekii is stable in lice feces for up to 100 days and can be viable in a blood sample for several years if kept at -70 ºC(1,3).


SURVEILLANCE: Monitor for symptoms(12). The infection can be identified by PCR, latex agglutination test, or immunological tests (i.e. enzyme-linked immunoabsorbent, immunoperoxidase, dot blot, Western blotting, and IFA assays, CF and latex agglutination tests)(1,3,4,13). Microbiological diagnosis is usually based on serology, where a four-fold rise in titre in paired samples is considered diagnostic. The organism can be isolated following culture of clinical samples (blood or skin biopsy) and visualized using microscopy following Gimenez staining or immunofluorescence(1).

Note: All diagnostic methods are not necessarily available in all countries.

FIRST AID/TREATMENT: If typhus is suspected, the appropriate antibiotic treatment should be given without waiting for laboratory confirmation(12).

IMMUNIZATION: No vaccine is currently commercially available; however, some experimental vaccines are being developed for high-risk individuals (such as healthcare workers and scientists)(1,3,4,8).

PROPHYLAXIS: If louse infestation is present, clothes should be removed, washed and not worn for 7 days. Insecticides (i.e. malathion or permethrine) should be used on body and hair to kill louse eggs but can also be used on clothes(1).


LABORATORY-ACQUIRED INFECTIONS: 56 laboratory-acquired infections with 3 deaths caused by epidemic typhus have been reported although all of these are prior to 1968(8,12). There were 57 cases additional of unidentified typhus within that same period of time(12).

SOURCES/SPECIMENS: Infective lice, their tissues and their feces may contain the infective agent(12). Flying squirrels may also be a direct source of infection.

PRIMARY HAZARDS: The primary hazards are accidental parenteral inoculation and exposure to infectious aerosols or animals(12).




CONTAINMENT REQUIREMENTS: Containment Level 3 facilities, equipment, and operational practices for work involving infected or potentially infected materials, animals, or cultures.

PROTECTIVE CLOTHING: Personnel entering the laboratory should remove street clothing and jewellery, and change into dedicated laboratory clothing and shoes, or don full coverage protective clothing (i.e., completely covering all street clothing). Additional protection may be worn over laboratory clothing when infectious materials are directly handled, such as solid-front gowns with tight fitting wrists, gloves, and respiratory protection. Eye protection must be used where there is a known or potential risk of exposure to splashes(15).

OTHER PRECAUTIONS: All activities with infectious material should be conducted in a biological safety cabinet (BSC) or other appropriate primary containment device in combination with personal protective equipment. Centrifugation of infected materials must be carried out in closed containers placed in sealed safety cups, or in rotors that are loaded or unloaded in a biological safety cabinet. The use of needles, syringes, and other sharp objects should be strictly limited. Open wounds, cuts, scratches, and grazes should be covered with waterproof dressings. Additional precautions should be considered with work involving animals or large scale activities(15).


SPILLS: Allow aerosols to settle and, wearing protective clothing, gently cover spill with paper towels and apply appropriate disinfectant, starting at the perimeter and working towards the centre. Allow sufficient contact time before clean up (30 min)(15).

DISPOSAL: Decontaminate all materials before disposal by steam sterilization or incineration(15).

STORAGE: The infectious agent should be stored in a sealed and identified container in a level 3 containment laboratory(15).


REGULATORY INFORMATION: The import, transport, and use of pathogens in Canada is regulated under many regulatory bodies, including the Public Health Agency of Canada, Health Canada, Canadian Food Inspection Agency, Environment Canada, and Transport Canada. Users are responsible for ensuring they are compliant with all relevant acts, regulations, guidelines, and standards.

UPDATED: July 2010

PREPARED BY: Pathogen Regulation Directorate, Public Health Agency of Canada.

Although the information, opinions and recommendations contained in this Pathogen Safety Data Sheet are compiled from sources believed to be reliable, we accept no responsibility for the accuracy, sufficiency, or reliability or for any loss or injury resulting from the use of the information. Newly discovered hazards are frequent and this information may not be completely up to date.

Copyright © Public Health Agency of Canada, 2010 Canada

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