The term "rickettsia" has nothing to do with rickets (which is a
deficiency disease resulting from lack of vitamin D); the bacterial
genus Rickettsia was named after Howard Taylor Ricketts, in honor of
his pioneering work on tick-borne spotted fever.
Rickettsia species are transmitted by numerous types of arthropod,
including chigger, ticks, fleas, and lice, and are associated with human
animal and plant diseases.
Most notably, Rickettsia species are the pathogens responsible
for typhus, rickettsialpox, boutonneuse fever, African tick-bite
fever, Rocky Mountain spotted fever, Flinders Island spotted fever,
and Queensland tick typhus (Australian tick typhus).
The majority of Rickettsia bacteria are susceptible to antibiotics of
the tetracycline group.
3. 1.Obligate intracellular parasite
2.Gram negative pleomorphic rods
3.Parasite of arthropods – fleas, lice, ticks and mites.
4.No Human to human transmission.
5.Rickettsia inside the host cell TICK ,FLEA, LICE ,MITE
Rickettsial species and its disease
Epidemic typhus, Brill-Zinsser disease – Human body louse
R. typhi – Endemic typhus – Rat flea
4. Rocky-Mountain spotted fever - Ticks
R. conori – Boutonneuse fever - Ticks
R. australis – Australian tick typhus - Ticks
R. siberica – Siberian tick typhus - Ticks
R. akari – Rickettsial pox - Mites
5. Pathogenesis and Clinical manifestations of Rickettsia rickettsii.
Human gets infected when infected adult tick inoculates Rickettsia
rickettsii into the skin while taking a blood meal. Rocky Mountain
spotted fever is a potentially lethal, but usually curable tick borne
disease, and common rickettsial infection.
High fever ( 39-41 0 C)
Macular rash after 4-7 days – first on trunk and spreads to limb. Lacks
7. LABORATORY DIAGNOSIS
Isolation from experimental animals
Blood – collected in febrile illness
ISOLATION Blood is inoculated in guinea pigs/mice.
Observed on 3 rd – 4 th week. Animal responds to different rickettsial species
Rise in temperature – all species.
swelling,necrosis – R.typhi, R.conori, R.akari ( except R.prowazekii) serology
Reliable test to confirm rickettsial diseases.
Antibody detection by Weil-felix test Antigen detection by IFA
Heterophile agglutination test using