This document discusses Rickettsia, a genus of bacteria that are transmitted by arthropods like ticks, fleas, and mites. It causes diseases like typhus, Rocky Mountain spotted fever, and African tick-bite fever in humans and animals. Rickettsia species are obligate intracellular parasites that reside inside host cells. They are susceptible to tetracycline antibiotics. The document provides details on the pathogenesis and clinical manifestations of R. rickettsii which causes Rocky Mountain spotted fever, as well as methods for laboratory diagnosis and control of Rickettsia species.

1. Rickettsia
DR. SUDHA KUMARI
Assistant Proffecer
Department of Veterinary Microbiology
Bihar Veterinary College
Unit –II
VMC-602
06/11/2020

2. Rickettsia
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
R. rickettsii

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.
Severe headache
Chills
Generalised myalgia
High fever ( 39-41 0 C)
Vomiting
Macular rash after 4-7 days – first on trunk and spreads to limb. Lacks
consciousness.

7. LABORATORY DIAGNOSIS
Isolation from experimental animals
Serology: Specimens
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
can vary
Symptoms:
Rise in temperature – all species.
Scrotal inflammation,
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

8. Vector control
Live vaccine & killed vaccine are available but
not much effective
Ticks
Mites
lice
fleas