Rickettsial Diseases

Rickettsial Pox

*Benign febrile illness with vesicular rashes resembling chickenpox* • Caused by *R. akari* • Vector: *Liponyssoides sanguineus (mite)*; Might also be carried on the brown dog tick, Rhipicephalus sanguineus • Reservoir: *Domestic mouse* (Mus musculus) • *Self-limiting*, non-fatal

Rickettsial Characteristics

*Obligate intracellular parasite* • *Gram negative pleomorphic bacteria* • *Most are zoonotically spread to humans by arthropods (except Q fever).* --> Flea, ticks, lice, mites • Cannot grow in culture media, only in living tissue. • No human to human transmission.

Treatment of Q fever

*tetracycline, prolong for 18 months* Preventive measures: - pasteurization/boiling of milk - providing sanitary cattle sheds - adequate disinfection & disposal of products. Personal prophylaxis: *Coxiella vaccination* to occupationally exposed workers.

Epidemic (Classic) Typhus

• 1812-1813: Napoleon suffers the greatest loss of troops to Epidemic typhus. • Typhus was particularly associated with siege warfare which had a high population density & poor hygiene. • *Still endemic in Africa (Burundi, Rwanda, Ethiopia) & South America (Peru, Bolivia, Ecuador)*

*Signs & Symptoms of Epidemic typhus*

• Acute febrile illness • Headache • Myalgia • Rash : 40-80% macular, centrifugal spread, spare palms & soles • Neurologic manifestations - stupor, delirium • *Vasculitis* • *Gangrene*

Signs & Symptoms of Scrub Typhus

• Acute onset with *chills & Fever, headache, myalgia, dry cough* • *Eschar* - ulcer covered with black scab; indicative of the site of the bite • *Macular rash appears around the 5th day of the bite* • Lymphadenopathy • Lymphocytosis • *Cardiac and cerebral involvement* necrotic ulcer that becomes covered by eschar --> if you see eschar --> scrub typhus typhus - refers to the confused state of the central nervous system

Q Fever (Query Fever)

• Etiology: *Coxiella burnetti* • Vector : None (DOES NOT NEED INSECT VECTOR for transmission) • Reservoir: *Sheep, Cattle, Goats* • Transmission: *ingestion of dust containing organisms or aerosols excreted in urine, feces, milk etc.* • Incubation period: 2-3 wks • Resembles *influenza or viral pneumonia* • Individuals at risk : food handlers, veterinarians, farmers • *Infective endocarditis occasionally in chronic Q fever*

History of Rickettsial Disease

• Hippocrates in 460 BC used the term Typhus, meaning *'smoke'* to describe a confused state of intellect i.e. stupor. • Rickettsia named after HOWARD TAYLOR RICKETTS died of Typhus fever contracted during his studies. Discovered Spotted fever Rickettsia (1906).

Trench Fever

• Rickettsial agent: *Bartonella quintana* • Insect vector: *Louse* • Mammalian Reservoir: *Human* • Transmission: louse feces • Disease mostly limited to central Europe.

Rocky Mountain Spotted Fever (RMSF)

• Rickettsial agent: *R. rickettsii* • Insect Vector: *Tick* • Mammalian Reservoir: *Rodents, dogs* • Incubation period: 3-7 days

Scrub Typhus

• Rickettsial agent: Orientia tsutugamushi • Insect Vector: Mite larvae (chiggers) • Transmission : chigger bite - chiggers found in areas of scrub vegetations. • Common in military and jungle warfare, farmers • Mammalian Reservoir: Rodents • Incubation period: 10-12 days

Diagnosis of Rickettsial Diseases

• Rise in serum antibody titers often do not develop in early stages. • Current rapid detection tests depend on detecting anti-Rickettsial antibody in the pt's serum • Therefore, no rapid laboratory tests are available to diagnose rickettsial diseases early in the course of illness.

Rickettsial diseases

• are considered some of the most covert emerging or reemerging diseases. • Rickettsial infections are difficult to diagnose clinically hence occurrence often goes unrecognized. • Failure of timely dx -Significant morbidity & mortality.

Worldwide Distribution of Rickettsial Diseases

1. *Q fever* outbreaks are most common in *slaughterhouses* & *research facilities*. Seen in *all parts of the U.S.* 2. *Endemic (Murine) typhus* prevalent in *South-East Asian region* & *Western Pacific* countries. In the U.S. it is seen in *Texas, southern California & Hawaii.* 3. *Epidemic typhus* was a most formidable disease in past. Found in *Asia, Africa, N. & S. America. (not in U.S.)* No case of this disease has been reported from South East Asia since 1978. 4. *Scrub typhus* is endemic in *Japan, Russia, SEA, Western Pacific Islands, China, India & Sri lanka* (not in U.S.) 5. *Trench fever* has been found on every continent except Australia & Antarctica. (not in U.S.)

Diagnosis, Treatment & Control of Endemic Typhus

Diagnosis: *liver enzyme elevated B* Treatment : *Doxycycline* Preventive measures : • residual insecticides - *BHC, Malathion* • rodent control measures in infested areas

Diagnostic Tests for Rickettsial Diseases

Immunological Assays: 1. Indirect Immune-Peroxidase/Immunoflouroscent assay 2. ELISA 3. PCR Rapid Detection Kits: 1. Dip-S-Ticks 2. Scrub typhus RCT 3. Scrub Typhus IgM / IgG Rapid Immuno-chromatographic Assay Multitest

Epidemic typhus (Classic typhus)

Rickettsial agent: *Rickettsia prowazekii* • Insect vector: *Louse* • Mammalian Reservoir: *Human, flying squirrels* • Transmission: Human to human via louse vector, directly in blood, or as the contaminated louse feces is scratched into the bite wound, or inhalation of infected louse feces or dust. • Incubation period: 5-21 days

Murine (Endemic) Typhus+

Rickettsial agent: *Rickettsia typhi* • Insect Vector: *Flea* • Mammalian Reservoir: *Rodents* • Transmission: inhalation of infected flee feces or dust; inoculation into skin with feces of infected fleas. • Incubation period: 1-2 weeks • Symptoms: Gradual onset of fever, HA, myalgia, cough • Rash: > 55% maculopapular rash on trunk

Signs & Symptoms of RMSF

Symptoms: *Abrupt onset fever, chills, headache, myalgia* • *Rash : first appears in extremities, moves centripetally (begins on extremities & moves towards the trunk) & involves palms. Spares face* • Mortality: *70% if left untreated in elderly* Complications: *HSM, jaundice, myocarditis, uremia, ARDS* Rash is opposite from rash in typhus Ebola rash also spares the face This is endemic in the US!

Treatment & Control of Scrub Typhus

Treatment: *tetracycline* • Vector control: Clearing the vegetation where rats & mice live • Application of insecticides: Lindane, Chlordane to the ground & vegetation • Personal prophylaxis : Impregnating clothes & blankets with miticial chemicals, i.e. benzyl benzoate. • Mite repellant: *Diethyl toluamide* application on exposed skin surfaces

Treatment & Control of Epidemic Typhus

Treatment: doxycycline Prevention: - delousing with insecticides - personal hygiene - improved living conditions - WHO supervision

Brill-Zinsser disease

aka *Recrudescent Typhus* or *jail fever* - This occurs after the person recovered from epidemic typhus & reactivation of the Rickettsia prowazekii which remained latent for years. - Mild illness and low mortality rate.