3. HISTORY
• Derrick in 1935 investigating
outbreak of typhoid like
fever,transmitted the infection to
guinea pigs by inoculation
• Referred initially as Query or Q
fever
3
4. • Burnet identified the causative agent as a rickettsia – was named R
burnetii
• At same time same agent isolated by Cox and was named R diaporica
• Q fever agent differed from other rickettsiae in many features
• So it has been separated from rickettsiae into a special genus &
renamed Coxiella burnetti
4
5. DISTRIBUTION
• Highly infectious zoonotic disease
• Mainly in persons associated with
sheep,goats,cattle or other domestic
animals
5
7. MORPHOLOGY
• Gram negative
• Infect mainly the monocyte –macrophage
cells
• Occurs as rods or spheres
• Filterable
• Obligate intracellular pathogen
7
8. • Survives for an year or more at 4ºC in dried faeces or wool
• In meat – atleast a month
• In milk – may survive pasteurization by holding method
• Flash method is effect
• Grows well in yolk sac of chick embryos & various cell cultures
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10. 10
INFECTED ANIMALS
Shed disease agent
in faeces and urine
Soil
contamination
Placenta of infected
cows & sheeps
infectious aerosols
during parturition
11. MODE OF TRANSMISSION
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• Inhalation of infected dust
• Thru. aerosols
• Entry of organism through
abrasions,conjunctivae or
ingestion of contaminated foods
like meat,milk & milk products
Incubation period : 2-3 wks
13. CLINICAL FEATURES
• Acute in onset
• Fever,chills,generalised malaise & headache
• No rash or local lesion
• May lead to pnemonia,hepatitis,encephalitis
and endocarditis
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14. LABORATORY DIAGNOSIS
• By serology
• Complement fixation
• Indirect immunofluorescence
• Isolation from blood,sputum or other clinical
specimen possible but not recommended
due to hazard of laboratory infection
14
15. CONTROL MEASURES
TREATMENT:
• Prolonged treatment for 18 months or
longer
• Doxycycline – drug of choice
• In endocarditis-prolonged treatment
with tetracycline,cotrimoxazole or
rifampicin combinations
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16. PREVENTIVE MEASURES:
• Pasteurization or boiling of milk
• Sanitary cattle sheds
• Adequate disinfection & disposal
of waste
• Coxiella vaccines – for
occupationally exposed workers
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18. HISTORY
• First observed in japan where it was found to be transmitted by
mites
• Therefore called tsutsugamushi
• Tsutsuga meaning dangerous & mushi meaning insect or mite
• Found only in areas with suitable climate,plenty of moisture &
scrub vegetation
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19. DISTRIBUTION
• Zoonotic disease
• Endemic in Northern Japan,South East
Asia,Western Pacific Islands,Eastern
Australia,China,several parts of South Central
Russia,India & Sri Lanka
• Travel acquired cases occur during visits to
endemic countries for camping,hiking or
rafting
19
22. • RESERVOIR :
Trombiculid mite (Leptotrombidium delinese & L .akamushi)
Transovarian transmission from one generation to another
Nymph & adult-donot feed on vertebrate hosts
Larva (chigger) feed on vertebrate hosts-act as both
& vector
22
23. • Four factors are essential for the establishment of a microfocus of
infection
• Coexistence & intimate relationship among R
tsutsugamushi,chiggers,rats & secondary or transitional forms of
vegetation
• This is called zoonotic tetrad
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26. CLINICAL FEATURES
• Inucubation period – 10 to 12 days
• Acute in onset
• Chills and fever
• Headache,malaise, prostration
• Macular rash- 5th day of illness
• Generalised lymphadenopathy & lymphocytosis
26
27. • Typical feature – punched out ulcer
covered with a blackened scab (eschar)
• It indicates the location of mite bite
• Weil Felix reaction is strongly positive
with Proteus strain OXK
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28. LABORATORY DIAGNOSIS
• Isolation of rickettsiae
• Serology
• 3 major anigenic types-Karp,Gilliam &
Kato- complicates diagnosis
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