RICKETTSIAL DISEASES
Dr. BHUWAN SHARMAAsst. Professor (Grant Govt. Medical College)
RICKETTSIAE
Rickettsiae are obligate intracellular gram negative parasites.
Most are zoonoses spread to humans by arthropods (except Q fever).
Rickettsiae replicate within the cytoplasm of endothelial cells and smooth muscle cells of capillaries, arterioles and small arteries causing necrotizing vasculitis.
Most are febrile infections with a characteristic rash.
An ESCHAR, a black ulcerated lesion may develop at the site of inoculation
MORPHOLOGY
In smears from infected tissues, rickettsiae appear as pleomorphic gram negative coccobacilli
Non motile, Non capsulated They stain bluish purple with Giemsa
and Castaneda stains Unable to grow in cell free media Growth generally occurs in the
cytoplasm of infected cells
DISEASES RICKETTSIAL AGENT
INSECT VECTOR
MAMMALIAN RESERVOIR
TYPHUS GROUP
a) Epidemic typhus
R. prowazekii Louse Human
b) Murine typhus (Endemic typhus)
R. typhi Flea Rodents
c) Scrub typhus
R. tsutsugamushi
Mite Rodents
DISEASES RICKETTSIAL AGENT
INSECT VECTOR
MAMMALIAN RESERVOIR
SPOTTED FEVER GROUP
a) Indian tick typhus
R. conorii Tick Rodent, Dog
b) Rocky mountain spotted fever
R. rickettsii Tick Rodents, Dogs
c) Rickettsial pox
R. akari Mite Mice
DISEASES RICKETTSIAL AGENT
INSECT VECTOR
MAMMALIAN RESERVOIR
OTHERS
a) Q fever C. burnetti Nil Cattle, sheep,goats
b) Trench fever
Rochalimaea quintana
Louse Human
Rickettsial diseases
Epidemic Typhus
•Fever/chills•Myalgia•Headache•Rash (No eschar) – all over body except palm sole & face.
Endemic Typhus
•Fever•Myalgia•Headache•Rash (No eschar)Trunk> extremities•Milder form of illness.
Scrub Typhus
•Fever•Headache•Rash with eschar•Lymphadeno-pathy
Indian Tick
Typhus
•Fever•Headache•Rash with eschar, first appear on wrist and ankle.
Q-fever
•Fever•Headache•Fatigue•Pneumonia• No Rash
Rickettsial diseases
Rocky Mountain Spotted Fever
•Fever•Headache•Rash (No eschar) – first appear on wrist & ankle•Palms & soles involved•Systemic Complications – R/S, CVS, CNS, Renal, Hepatic
Rickettsial Pox
•Mild Illness•Fever•Headache•Vesicular Rash with eschar•Lymphadenopathy•Resemblance to chicken pox
Among the major group of rickettsioses, the commonly reported diseases in India are
Scrub typhus Murine (Endemic) typhus Indian tick typhus Q fever
SCRUB TYPHUS IS CONSIDERED IN SOME DETAIL … WHY?
To be aware of this condition during the outbreaks of many fevers like DF,CKG Fever, Leptospirosis & other viral fevers with secondary infections.
Suspicion of the condition & initiation of specific therapy cures the condition rapidly otherwise may lead to serious complications.
SCRUB TYPHUS
Causative agent is Rickettsiae
tsutsugamushi.
Found in areas where they harbour the
infected chiggers particularly areas of
heavy scrub vegetations.
I.P. – 10-12 days
RESERVOIR: Trombiculid mite which feeds on small mammals. MODE OF TRANSMISSION: By bite of infected larval mites.Infection occurs during rainy season when the mites lay their eggs. It is the larva (chigger) that feeds on vertebrate hosts.
TRANSMISSION CYCLE
MITE------ RATS AND MICE----- MITE---- RATS AND MICE
MAN
CLINICAL FEATURES:
FeverChillsGen. Lymphadenopathy
ESCHAR – A punched out ulcer covered with a blackened scab which indicates the location of the mite bite.
Eschar is found only in around 50% of patients.
Eschar is painless and patient wont complain of it.
Often the patient wont notice it because of its presence in concealed sites.
ENDEMIC TYPHUSMURINE OR FLEABORNE TYPHUS
Natural infection in rats R.typhi (R.mooseri)-causative agent Vector –Xenopsylla cheopis (rat flea) Rickettsia multiplies in the gut of the
flea shed in faeces. Flea is unaffected but remain
infectious for the rest of life
Mode of transmission 1. Through the bite of infected fleas, when
their saliva /faeces inoculated in skin through bite wound.
2. Through aerosols of dried faeces .3. Ingestion of food contaminated with rat
urine /flea faeces
Human infection is a dead end Man to man transmission does not
occur .
CLINICAL FEATURES
• Low grade Fever• Myalgia• Headache• Rash (No eschar) Trunk> extremities• Milder form of illness than
epidemic typhus.
‘Q’ FEVER
Causative agent- Coxiella burnetti Zoonosis Vector –Ixodid ticks Coxiella abundant in tick faeces , survive in
dried faeces for long periods Shed in the milk of infected animals Particularly abundant in products of
conception contaminate environment at parturition
No arthopod vector involved in transmisson to humans.
Human infection occupational hazard Veterinary surgeons Person handling wool or hides Meat animal products contaminated with Coxiella
burnetti Drinking infected milk
Routes of entry Through skin mucosa Inhalation Ingestion
Person to person transmission is rare Ticks are not important in human infection
Human disease 1. Acute systemic infection –interstitial
pneumonia 2. Chronic infection – hepatitis ,meningitis ,
endocarditis 3. Spontaneous recovery is usual
Coxiella burnetti is an obligate intracellular pathogen primarily affect monocytes –macrophage cells Remain dormant after recovery in the tissue of the patient for 2-3 years latent infection
In dried faeces or wool it survives for a year
It cannot be destroyed with pasteurisation by the holder method but flash method is effective
Lab 1. Culture - yolk sac of chicken embryo cell
cultures2. Serology – CFT,IFA3. Isolation of Coxiella from blood, sputum and
other clinical specimens possible. But not recommended due to laboratory infection
Vaccines Formalin killed whole cells trichloro acetic
acid extracts live attenuated vaccine
Treatment : Doxycycline Endocardits : combination therapy
Tetracycline +Co- trimoxazole Tetracycline+ Rifampicin
INDIAN TICK TYPHUS
An infectious disease that is caused by Rickettsia conorii which is transmitted by the brown dog tick (Rhipicephalus sanguineus).
The disease occurs predominantly in Mediterranean areas such as India and Africa.
The onset of symptoms is usually sudden and the incubation period is usually between 6 and 10 days
• Symptoms include fever, headache, rash with eschar which first appear on wrist and ankle.
Treatment – Doxycyclin/ Tetracyclin.
RICKETTSIAL POX
Mildest Rickettsial disease of humans Self limited , non fatal , vasicular exanthem
first observed in New york 1946 Resembles chicken pox Also called vesicular /varicelliform Ricketsiosis R. akari- Causative agent Reservoir of infection –Domestic mice Vector – mite R. akari has also been isolated from wild
rodent in Korea The disease has also been reported from
Eastern Europe and Korea .
ROCKY MOUNTAIN SPOTTED FEVER
Causative agent –R. rickettsii Vector – Tick Reservoir – Rodents and dog Symptoms – Initial signs and symptoms of the
disease include sudden onset of fever, headache, and muscle pain, followed by development of rash on wrist and ankle (Palms and soles involved). The disease can be difficult to diagnose in the early stages, and without prompt and appropriate treatment it can be fatal.
• Systemic Complications – R/S, CVS, CNS, Renal, Hepatic.
Rocky Mountain spotted fever remains a serious and potentially life-threatening infectious disease. Despite the availability of effective treatment and advances in medical care, approximately three to five percent of patients die from the infection.
Abnormal laboratory findings seen in patients with Rocky Mountain Spotted Fever may include thrombocytopenia, hyponatremia, or elevated liver enzyme levels.
INVESTIGATIONS IN RICKETTSIAL DISEASE
PCR SEROLOGICAL TESTS• Indirect Flourescent antibody test (IFA) test ( Titer ≥ 1: 200 ), • the Complement Fixation Test. • The Weil Felix Test• IgM ELISA Test: Highly specific test
WEIL-FELIX TEST
Agglutination test in which sera are tested for agglutinins to the O antigens of certain non motile Proteus strains OX19, OX2 and OXK. The basis of the test is the sharing of an Alkali stable carbohydrate antigen by rickettsiae and by certain strains of Proteus.
WEIL-FELIX TEST (CONTD)
Sera from Epidemic and Endemic typhus agglutinate OX19 and sometimes OX2.
In tick borne spotted fever, both OX19 and Ox2 are agglutinated.
OXK agglutinins are found only in scrub typhus. The test is negative in Rickettsial pox and Q fever.
WEIL-FELIX TEST (CONTD)
False positive reaction may occur in some cases of urinary or other infections by Proteus and at times in liver diseases and Typhoid fever.
Hence it is desirable to demonstrate a rise in titer of antibodies for the diagnosis of rickettsial infections. A 4 fold rise in agglutinin titres in paired titres is diagnostic.
WEIL-FELIX TEST (CONTD)
However, with a single serum sample
available, the test is suggestive of infection only at a high cut off titer
(≥ 1: 320) at which the positive
predictive value and the specificity is
reliable.
WEIL –FELIX REACTION HETEROPHYLE AGGLUTINATION
OX 19 OX 2 OX K
Epidemic typhus +++ + -
Endemic typhus +++ ± -
Tick born spotted fever
++ ++ -
Scrub typhus - - ++
The other serological tests for Rickettsial diseases including the specific IgM antibody tests become positive only in the second week and a second sample is often required.
Serological tests cannot provide early diagnosis and a specific diagnosis may not be available until after the patient has died or recovered.
TREATMENT
Tetracycline is the DOC.
Doxycycline 100mg Bid PO ×7-15 days.
Chloramphenicol 500mg qid PO×7-15
days.
IV Chloramphenicol 150 mg/ kg per day
for 5 days.
CONTROL
Vector control.
Clearing the vegetation
where rats and mice live.
Rodent control
Q1. VECTOR FOR SCRUB TYPHUS ?
• R. Prowazekii• R. Typhi• R. tsutsugamushi• R. conorii
Q.2 INCUBATION PERIOD OF SCRUB TYPHUS
8-10 days 10-12 days 3-5 weeks None
Q.3 CAUSATIVE AGENT FOR RICKETTSIAL POX
Mite Tick Louse None
Q4. CAUSATIVE AGENT FOR Q- FEVER
Mite Flea Louse None
Q5. ESCHAR IS THE CHARACTERISTIC FEATURE OF WHICH OF THE GIVEN DISEASE ?
Rocky Mountain Spotted Fever Epidemic Typhus Q- Fever Scrub Typhus
Q6. SPECIFIC ANTIGEN FOR DIAGNOSIS OF SCRUB TYPHUS IN WEIL-FELIX TEST ?
OX 19 OX 2 Ox K None
THANKS
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