Rickettsia

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Rickettsia

• The disease and Panbio product training

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Infectious Agent

• Rickettsia sp.
• Gram-negative coccoid or rod-shaped bacteria
• Obligate intracellular bacteria with an ability
  to grow in a variety of eukaryotic cells
• Do not survive well outside their host
  environment
• Different species cause different diseases

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Infectious Agent cont...

• The Rickettsia are subdivided into three groups
  of species according to the type of clinical
  disease they cause
• Typhus Group
• Spotted fever Group
• Scrub typhus Group
• They are further subdivided according to host and
  arthropod vector.

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Infectious Agent cont...

• Spotted Fever Group
• R. australis
• R. rickettsii (Rocky Mountain spotter fever)
• R. conorii (Mediterranean spotted fever)
• R. sibirica
• Typhus Group
• R. prowazekii (Louse-borne typhus)
• R. typhi (Murine typhus)
• Scrub Typhus Group
• Orientia tsutsugamushi

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Epidemiology

• Occurrence worldwide
• Epidemic and endemic regions
• Mode of Transmission
• Ticks, mites, and fleas

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Distribution Spotted fever group
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Distribution Typhus group
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Distribution Scrub typhus group
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Clinical Scrub Typhus

• Clinical manifestations
• fever
• headache
• raised ulcer (eschar)
• rash (later in illness)
• myalgia
• lymphadenopathy

Eschar
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Clinical Scrub Typhus

• Mortality rates 60 in untreated virulent strains
• 23 of all fever in endemic regions of Asia
• Antigenic diversity of strains exists within this
  group
• Vector - larval trombiculid mites (chiggers)
• Host - native rat species
• Incubation - 7 to 14 days

Chigger infected foot
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Clinical Spotted Fever

• Vector - predominantly tick borne
• Host - rats, bandicoots
• Incubation - 5 to 7 days
• Common protein antigens with Typhus
• Benign course of infection common, mortality rate
  of 35 for RMSF
• Reactivation may occur

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Clinical Typhus Group

• R. prowazekii
• Vector - body louse
• Incubation - 8 to 12 days
• Brill-Zinsser typhus (reactivation)

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Clinical Typhus Group

• R. typhi (Murine/endemic typhus)
• R. typhi also known as R. mooseri
• Vector - oriental rat flea
• Self-inoculation, flea faeces bites
• Non-specific clinical manifestations
• Low mortality rate

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Life cycle of Rocky Mountain spotted fever,
rickettsial pox and murine typhus.

• A. Life cycle of Rickettsia rickettsii in its
  tick and mammalian hosts.
• B. Rickettsia akari life cycle.
• C. Rickettsia typhi life cycle.

Azad A.F. C.B. Beard (1998) Rickettsial
Pathogens and Their Arthropod Vectors. Emerg.
Infect. Dis.4179-186
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Area where murine typhus is a risk
Areas in which murine typhus poses a risk
according to seroepidemiologic studies, case
series, or imported cases in traveller.
Parola, P. (1998) Murine typhus in travelers
returning from Indonesia. Emerg. Infect. Dis.
4677-680.
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Clinical notes

• Prevention
• Use of mite repellents to exposed skin surfaces
• Elimination of mites from populated areas
• Doxycycline has been found to be an effective
  preventative measure in a small Malaysian trial
• An effective vaccine is yet to be developed
• Treatment
• Doxycycline

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Antibody response

• Antibody levels may be low or absent during early
  infection.
• Antibody response may be delayed or eliminated in
  some patients being treated with antibiotics.
• Elevated or rising IgM and/or IgG antibodies
  indicate recent or active infection.
• Infection results in prolonged immunity to
  homologous strain.
• During a period of months after primary
  infection, infection with heterologous strain
  will result in mild disease.

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Diagnosis

• Weil Felix
• OX-19 (Typhus)
• OX-K strain Proteus mirabilis (Scrub Typhus)
• Dot blot EIA (Dip-S-Ticks from Panbio)
• IFA (Gold Standard)
• Agglutination based assays
• indirect haemagglutination (IHA)
• latex agglutination (LA)
• ELISA

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Weil Felix

• Non-specific test that uses various Proteus spp.
• Test based on presence of common antigens in both
  the Rickettsia and Proteus spp.
• Lacks both sensitivity and specificity should
  no longer be used as better methods available
• Leptospirosis and some other febrile illnesses
  may cause a positive Weil-Felix reaction
• Re-infection does not always lead to a rise in
  Weil-Felix agglutinins

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Agglutination-based assays

• Indirect haemagglutination (IHA) latex
  agglutination (LA)
• Detect antibodies to Spotted fever and Typhus
  group.
• Uses solubilised antigen from purified
  rickettsiae absorbed onto untreated red blood
  cells.
• Detects IgG and IgM

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Panbio Dip-S-TickTM

• Panbio Dipsticks (Dot EIA) for
• R. typhi (Murine typhus) Total IgG
• R. rickettsii (RMSF) Total IgG
• R. conorii Total IgG
• Principle-
• specific antibodies if present in patients serum
  bind to the antigen spotted on membrane
• reaction visualised by addition of alkaline
  phosphatase-conjugated anti-human antibodies
  which is then reacts with enzyme substrate
  reagent to form a spot.

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Panbio IFA

• Excellent sensitivity specificity
• Panbio has IFA slides for the following-
• Typhus group
• Murine Typhus (R. typhi)
• Louse-borne typhus (R. prowazekii)
• Scrub Typhus Group
• Scrub Typhus (O. tsutsugamushi)
• Spotted Fever Group
• Rocky Mountain Spotted Fever (R. rickettsii)
• Mediterranean Spotted Fever (R. conorii)

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Panbio IFA
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Panbio Rickettsial ELISA kits

• Scrub Typhus Group IgG Cat E-RST01G
• Scrub Typhus Group IgM Cat E-RST01M
• Fast - 1.5 hours total assay time
• Spotted Fever Group IgG Cat E-RSF01G
• Spotted Fever Group IgM Cat E-RSF01M
• Fast - 1.5 hours total assay time

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Ordering information
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