NAME: Rickettsia akari
SYNONYM OR CROSS REFERENCE: Rickettsialpox, vesicular rickettsiosis.
CHARACTERISTICS: R. akari is a member of the family Rickettsiaceae. It is an obligate intracellular gram-negative coccobacillus and has a pleomorphic life cycle Footnote 1. The bacterium is approximately 0.3 – 0.5 μm by 9 μm, has a transverse septum between two bacilli, and reproduces by binary fission Footnote 2, Footnote 3.
PATHOGENICITY/TOXICITY: R. akari is the agent of rickettsialpox, which is a mild self-limited zoonotic febrile illness of the spotted fever group Footnote 4. Infection is characterized by, in 80% of cases, the appearance of a 0.5 – 1.5 cm eschar or painful lymph nodes associated with lymphadenopathy at the site of the infectious mite bite Footnote 5, Footnote 6. About 3-7 days after the skin lesion develops, the patient develops fever, headache and other systemic symptoms. Approximately 2-3 days later, a papulovesicular rash erupts on the trunk and extremities, which may be confused with chickenpox. Symptoms may later develop into organ-specific afflictions such as nausea, vomiting, and abdominal pain Footnote 7. No deaths have been reported from R. akari infections Footnote 8.
EPIDEMIOLOGY: Worldwide distribution – the bacteria have been found most commonly in urban areas of eastern United States, Turkey, Croatia, Ukraine, Russia, Mexico, Africa, and areas of Europe and Asia Footnote 5, Footnote 9, Footnote 10. The first and only large epidemic occurred in 1946 in the Queens borough of New York City, and a causal agent was delineated shortly thereafter Footnote 9. In total, approximately 800 cases of rickettsialpox have been reported; most of them having occurred between 1940–1950, and none has resulted in death Footnote 8. Very few cases have been reported in the past 30 years.
INFECTIOUS DOSE: Unknown.
INCUBATION PERIOD: The typical incubation period is 12-15 days, but can be up to 28 days Footnote 1.
COMMUNICABILITY: Cannot be directly transmitted between humans.
RESERVOIR: R. akari is maintained in nature by mites carried by the house-mouse (Mus musculus) and domestic rats. Humans and other mammals can be accidental reservoirs Footnote 4.
ZOONOSIS: Yes. The bacteria can be transferred from animals to humans by mites Footnote 5.
DRUG SUSCEPTIBILITY: Susceptible to tetracycline, and oral doxycycline for mild cases. Chloramphenicol can also be used as an alternative Footnote 1.
DRUG RESISTANCE: R. akari has not been found to be drug-resistant Footnote 11. The most effective antibiotic used to treat rickettsial infections is doxycycline.
SUSCEPTIBILITY TO DISINFECTANTS: Susceptible to 1% sodium hypochlorite, formaldehyde, ethanol, 2% glutaraldehyde Footnote 12.
PHYSICAL INACTIVATION: R. akari cells can be quickly inactivated at 56°C Footnote 13.
SURVIVAL OUTSIDE HOST: Rickettsia species can only grow in living host cells (cell cultures or embryonated eggs) and do not survive well in the environment. The bacteria are unstable outside of the host and quickly lose their infectivity, as the bacteria are metabolically inactive outside of a host cell Footnote 2.
SURVEILLANCE: Monitor for characteristic symptoms of infection, and for formation of an eschar at site of bite. Serological techniques such as indirect immunofluorescence antibody test (IFA) and enzyme-linked immunosorbent assays (ELISAs), and polymerase chain reaction techniques can also be used to diagnose R. akari infection Footnote 1, Footnote 8, Footnote 9.
Note: All diagnostic methods are not necessarily available in all countries.
FIRST AID/TREATMENT: Administer appropriate antibiotic treatment. Doxycycline is the treatment of choice for all rickettsial infections Footnote 14. Supportive therapy for the patient is important, with attention to fluid and electrolyte balance and maintenance of proper renal function.
IMMUNIZATION: No vaccines are currently available for R. akari (or any rickettsial species) Footnote 1.
PROPHYLAXIS: None. Measures in commercial rodent-control can be effective Footnote 8.
LABORATORY-ACQUIRED INFECTIONS: 4 cases of rickettsialpox occurred in laboratory workers shortly after an outbreak in 1946 Footnote 15. Other cases include infections in a rickettsiologist who worked with the pathogen, and in a technician who was believed to have been exposed through the respiratory or conjunctival mucous membranes during work with chicken yolk sacs infected with R. akari Footnote 10.
SOURCES/SPECIMENS: Blood and serum samples of infected mammals Footnote 4.
SPECIAL HAZARDS: None.
RISK GROUP CLASSIFICATION: Risk Group 3 Footnote 16.
CONTAINMENT REQUIREMENTS: Containment Level 3 facilities, equipment, and operational practices for work involving infectious or potentially infectious materials, animals, or cultures Footnote 17.
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.
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.
SPILLS: Allow aerosols to settle and, wearing protective clothing, gently cover spill with paper towels and apply an appropriate disinfectant, starting at the perimeter and working towards the centre. Allow sufficient contact time before clean up.
DISPOSAL: Decontaminate, either by steam sterilization, incineration, or chemical disinfection, before disposal.
STORAGE: The infectious agent should be stored in sealed containers that are appropriately labelled and locked in a Containment Level 3. R. akari cells are best preserved by rapid freezing and storage below –50˚C Footnote 13.
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: December, 2011
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.
Public Health Agency of Canada, 2011