Rickettsial Family - Mymensingh Medical College file/Rickettsia, akram.pdf · Rickettsial Family Prof. Md. Akram Hossain Prof. Muhammad Akram Hossain, Ricketssia 1. Howard Taylor

Rickettsial Family

Prof. Md. Akram Hossain

1Prof. Muhammad Akram Hossain, Ricketssia

� Howard Taylor Ricketts (1871-1910)was an American pathologist afterwhom the Rickettsiaceae family andthe Rickettsiales are named.

� In the earlier part of his career,Ricketts undertook research at

Prof. Muhammad Akram Hossain, Ricketssia

Ricketts undertook research atNorthwestern University onblastomycosis and later at theUniversity of Chicago on and RockyMountain spotted fever

� In 1909, Ricketts became interested intyphus due to an outbreak in MexicoCity and the apparent similarity of thedisease to spotted fever. Somewhatironically, days after isolating theorganism that he believed causedtyphus, he himself died of thedisease.

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Charles Jules Henry Nicolle(September 21, 1866 Rouen -February 28, 1936) was a Frenchbacteriologist who received theNobel Prize in Medicine for his


Nobel Prize in Medicine for hisidentification of lice as thetransmitter of epidemic typhus in1903.

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� Henrique da Rocha Lima(1879–1956) was a Brazilianphysician, pathologist andinfectologist.

� Working in Germany, he discoveredRickettsia prowazekii, thepathogen of epidemic typhus.


pathogen of epidemic typhus.� He named it Rickettsia prowazeki,

after Howard Taylor Ricketts(1871)-1910) and German zoologistProwazek, who both died of this

disease.

� In 2007, a new strain of Gram-negative bacteria was named afterRocha Lima, Bartonellarochalimae

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Frank Macfarlane Burnet, Australianbiologist.

He was a pioneer in the application ofecological principles to viral diseases.

He proposed two concepts in immunology –acquired immunological tolerance and the


acquired immunological tolerance and theclonal selection theory of antibodyproduction

In the later stages of his life he lectured andwrote extensively about problems of humanbiology and human affairs, ageing and cancer.He was a Foundation Fellow and, from 1965 to1969, President of the Australian Academy ofScience.

Coxiella burnetti is named after him.Frank Macfarlane Burnet5

� 3 genera - obligate intracellular parasites:� Rickettsia


� Rickettsia� Coxiella� Ehrlichia

� Not an intracellular parasite� Rochalimaea (transferred to Bartonella)

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General Characteristics

� Resemble bacteria/grow only in living cells (NOT viruses)

� Parasites of arthropods = lice, fleas,


� Parasites of arthropods = lice, fleas, ticks, mites - infect humans via bite

� Similar in size and shape - nonmotile coccobacillary forms

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Pathogenesis: Rickettsia� Arthropod bite � Invade endothelial cells/vascular� Destroy endothelial cells


� Destroy endothelial cells� Inflammatory cells

accumulate/blood leakage: rash� Released organisms reinfect

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Signs of Infection

� Fever, chills� Severe headache

4th-6th day later = skin rash =


� 4th-6th day later = skin rash = lasts throughout course of disease

� EXCEPTION: Q-fever = no rash

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Rash

Prof. Muhammad Akram Hossain, Ricketssia 10

Important Clinical Diseases

� Typhus Group

�Rickettsia prowazekii = Epidemic typhus


Epidemic typhus–body louse = bite/feces–fever/severe headache–skin rash = trunk to extremities

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� Spotted Fever Group� Rickettsia rickettsii = Rocky Mountain

spotted fever


spotted fever

–tick bite–fever/severe headache–skin rash = wrists and ankles to

trunk/palms of hands, soles of feet

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Compliments of the CDC







� Scrub Typhus Group�Rickettsia tsutsugamushi =

Scrub typhus


Scrub typhus–mite bite–fever/severe headache–skin rash = covers body/eschar

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� Q-Fever Group

�Coxiella burnetii - Q fever–inhale contaminated aerosol;


–inhale contaminated aerosol; resist dessication = up to 3 years outside host

–intermittent fever/pneumonia–NO skin rash

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� Scrub Typhus Group�Rickettsia tsutsugamushi =

Scrub typhus


Scrub typhus–mite bite–fever/severe headache–skin rash = covers body/eschar

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� Q-Fever Group

�Coxiella burnetii - Q fever–inhale contaminated aerosol;


–inhale contaminated aerosol; resist dessication = up to 3 years outside host

–intermittent fever/pneumonia–NO skin rash

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� Trench Fever Group - transferred to Bartonella

�Rochalimaea quintana - Trench


�Rochalimaea quintana - Trench fever–body louse bite/feces–fever/headache/mild symptoms–skin rash - global

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Diagnosis of Rickettsial Diseases

� Rise in serum antibody/often do not develop in early stages


Treatment, Prevention, and Control

� tetracycline/chloramphenicol�vaccines under study/one=


Q fever�control =

insecticides/cleanliness

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Pathogenesis: Ehrlichia

� Tick bite (deer or dog)� Invasion of white cells: lymphocytes,

neutrophils, monocytes


neutrophils, monocytes� 20% of patients show rash� Lymph nodes up, high fever, headache,

malaise, myalgia� Treat with doxycycline

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Rickettsial Family - Mymensingh Medical College file/Rickettsia, akram.pdf · Rickettsial Family Prof. Md. Akram Hossain Prof. Muhammad Akram Hossain, Ricketssia 1. Howard Taylor

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