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