Rickettsia rickettsii
It is group of microorganisms that can cause infection in humans when transmitted through bites of fleas, ticks, lice or mites.
Morphology
Rickettsia are non motile, non capsulated gram negative.
Rickettsia are Pleomorphic.
Size; 0.3-0.6 micrometer X 0.8-2.0 micrometre
Characteristics
Optimum temperature for growth is 32-35 degree celcius.
They can been seen under light microscope.
Multiplication is by binary fission.
Sensitive to antibiotics and lysoenzymes.
Sources and Modes of Transmission
Transmitted bite of anthropods (insects).
Major source of infection to human are anthropods and rodents.
They also serve as reservoir host of Rickettsia.
Pathogenesis
Pathogens enter via skin
Skin swollen and necrotic
Spread through blood stream
Infected vascular, organs covered by blood vessels.
Produce disease; Rocky mountain spotted fever (when infected wood ticks or dog tick bites), typhus fever (pathogen is excrated in louse feces).
Laboratory Diagnosis
Specimen collection
It cannot be cultured in artificial medium in laboratory.
Indirect immunofluorescence (serological test)
Treatment
Doxycycline is effective for Rocky mountain spotted fever.
But drug pregnancy, chloramphenicol is the drug of choice.
Prevention
Infected can be prevented by vector control such as;
Rodents
Removal of mites by using ticks
Mites repellent
Frequent inspection of host body
Removal of attached ticks.
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