Vector-borne bacterial diseases

Describe the general characteristics of Rickettsia, Ehrichia, Anaplasma, and coxiella

• Obligate IC pathogens

• Gram-negative but stain poorly, Giemsa stain better

• Arthropod vectors except coxiella

• Respond to tetracyclines (Doxycyline), and chloramphenicol

Pathogenesis of Rickettsial diseases

No known toxin or immunopathology, however cells are destroyed → Causes leakage of blood into tissues → Rash (Blood gets stuck in the dermis, which causes rash)
Also → Organ and tissue damage

RMSF, infectious agent, vectors and seasonality and reservoires

Infectious agent: Rickettsia rickettsii

Seasonality: April to september

Vectors: Ixodid ticks (saliva) - Prolonged exposure to the tick is necessary

Reservoirs: Ticks and rodents, humans are accidental hosts

Describe the RMSF rash

Starts and wrists and ankles and spreads towards the trunk.

Similar rash in HFMD and 2ndary syphillis

Rickettsia rickettsii diagnosis

Fluroescence antibody for Ags

PCR (in reference labs)

RMSF treatment

Tetracycline and chloramphenicol

Epidemic typhus: Reservoir, Vectors, epidemiology

Reservoir: Humanss and flying squirrels

Vectors: Squirrel fleas and human body louse

Epidemiology: Associated with unsanitary conditions (War, famine…)

What are the clinical manifestations of Epidemic Typhus

Rash that starts on the Trunk and spreads centrifugally but spares the palms and soles.

*The rash is maculopapular, progressing to petechia and may be hemorrhagic

Epidemic typhus complications

Myocarditis, delirium (typhos = smoke (Smoking crack leads to delirium))

Epidemic typhus convalescence and mortality

May take months, and mortality rate is as high as 60-70%

Rickettsia prowazekii diagnosis

Weil-Felix antibodues - OX19 (however isolation can be dangerous)

Murine/Endemic Typhus causative agent, epidemiology, vector, reservoir

Causative agent: Rickettsia typhi

Reservoir: Rat, (Humans accidental hosts)

Vector: Rat flea

Epidemiology: Ocurs worldwide,

R. typhi incubation

1-2 weeks

Murine typhus clinical manifestation

Sudden onset fever, chills, headache, myalgia + Centrigually-spreading rash (also spares palms and soles)

Murine typhus severity

Mild, and resolves spontaneously

Ehrlichia and Anaplasma diseases

Human monocytic ehrlichiosis - E. chaffeensis: VECTOR: Lone star tick RESERVOIR: White-tailed deer

Human granulocytic ehrlichiosis - E. ewingii: VECTOR: Deer/dog ticks RESERVOIRS: White-tailed deer

Human granulocytic Anaplasmosis - A. phagoctophilium: VECTOR:

Ehrlichiosis and Anaplasmosis diagnostics

We will find Mulberry-like inclusions in either monocytes (E. chaffeensis), or, granulocytes (E. ewingii and A. phagocytophilium)

Coxiella burnetii characteristics

It’s stable - Endospore-like

Coxiella burnetii epidemiology

Causes Q fever, a profession-linked disease (Ranchers/ Vets)

Found in infected animals’ milk and animal placentas

Transmission: AEROSOLS from cattle/sheep amniotic fluid

C. burnetii clinical manifestations

Acute Q fever: Asymptomatic or mild flu-like symptoms
→ Severe cases: Atypical pneumonia, hepatosplenomegaly, liver granulomas.

Chronic Q fever: Endocarditis (Always due to chronic), and possible T3HS
→ Poor prognosis

*Common cause of culture-negative endocarditis (Coxiella and HACEK)

Laboratory diagnosis of Coxiella burnetii

Coxiella burnetii has 2 different antigenic forms based on LPS differences:

Acute Q fever: We should find Phase II IgG and IgM antibodies
Chronic Q fever: We should find Phase I IgG antibodies

*Note: Anti-phase1 antibodies titer above 800 is considered diagnostic for Q fever endocorditis

Coxiella burnetii treatment

• Acute Q fever - Tetracycline

• Chronic Q fever - Combination

Is there a vaccine for Q fever

Yes

Bartonella characteristics and epidemiology

G-, aerobic, bacilli

Bartonella henselae Transmission + symptoms

Acquired from cat scratch or cat fleas. Leads to headache, fatigue, poor appetite, fever, scab, or pustule at scratch site + Regional lymphadenopathy

Cat-scratch treatment

The disease is motly self-limited, but we can use Azithromycin to reduce the duration of lymphadenopathy

Trench fever

Caused by Bartonella quintana → Cause asymptomatic or severe disease

Characteristics: Sudden onset of recurrent fever, chills, headache & myalgia.
#Severe pain in tibia (shin-bone fever), with symptoms peaking at the 5-day interval
#Maculopapular rash on the trunk sometimes

Note: Quintana = 5 for 5-day fever

Bartonella quintana epidemiology

Vector: Human body louse

Reservoir: Humans

*Associated with war and famine

Trench fever diagnosis and treatment

Diagnosis: Clinical picture + Biopsy/serology/ PCR
- Conventional culture used to be gold standard, but it’s hard so low sensitvity
- Western Blot on blood

Treatment: Doxycyclin & Gentamycin (If suspected endocarditis)