Rickettsial diseases Flashcards
Classification of Rickettsia?
- small
- gm -
- non-motile
- rod -to-coccoid-shaped bacterium (why you cover with broad spectrum, doesn’t just fit into one category)
- similar to chlamydia
- size of a large virus
What does it mean that Rickettsiae is an obligate intracellular bacterial parasite?
- steal ATP, unable to produce sufficient energy to replicate extracellularly
What does cell wall of rickettsiae resemble?
How rickettsiae is transmitted?
- gram - rods
- in arthropods (insects), rickettsiae grow in gut lining, often w/o harming host, require an arthropod vector (except for Q fever)
- human infection results from either an arthropod bite or contamination with its feces
- circulate widely in bloodstream (bacteremia)
- infecting endothelium of blood vessel walls (this produces clotting -> petechiae)
What cells do Rickettsiae infect?
- endothelium of blood vessel walls
Pathophysiology of Rickettsial disease?
- typical lesion: vasculitis, Rickettsia has a tropism for endothelial cells that line blood vessels
- damage in endothelial lining of vessel wall where organism is found
- damage to vessels of skin results in characteristic rash
- edema and hemorrhage caused by increased capillary permeability
- most Rickettsia cause rashes, high fevers, and bad HAs (always have meningitis as differential)
What are most of the rickettsial diseases in the U.S.?
- Tickborne
Common presentation of rickettsial diseases?
- most have fevers, arthralgia, rashes and HAs
- some cause vasculitis (petechiae, purpura)
- see in children
- Hx is huge!!!!
What is the primary method of dx of Rickettsial disease?
- Hx of insect bite
What is the confirmation of your clinical dx of rickettsial disease?
- based on measuring immunological titers to the infecting organism, and this may take weeks to develop
Hx that might reveal rickettsial disease?
- outdoor activities during April- Sept., particularly in areas with high uncut grass, weeds, and low brush can increase risk for tick bites
- the include recreational pursuits
- occupational activities that involve persons being in brushy or grassy areas that might be inhabited by ticks
- vegetation that borders roads, trails, yards, or fields also are potential areas that might be inhabited by ticks.
- In endemic areas (where the agents causing TBRD are present at all times), even children who play in grassy areas in backyard are at risk.
What would be good to know about your community?
- what types of insects reside in your community
- what types of arthropod-borne diseases have been reported in your community
What are the Rickettsial diseases in the US?
- Rocky Mountain Spotted Fever
- Rickettsial pox
- Endemic Flea-Borne Typhus ( Murine Typhus)
- Epidemic Louse-Borne Typhus
Rocky Mountain Spotted Fever:
pathogen, geography, insect vector, and other carrier?
- Rickettsia rickettsii
- Western Hemisphere US (especially mid-Atlantic coast)
- tick
- rodents, dogs
Epidemic (louse-borne) Typhus: pathogen, geography, insect vector, and other carrier?
- Rickettsia prowazakii
- Central and NE Africa, Central and S. America
- louse
- Human body, flying squirrels
(more severe typhus)
Endemic (murine) typhus: pathogen, geography, insect vector, and other carrier?
- Ricekttsia typhi
- small focus (US: SE gulf)
- Flea
- rodents
(mild)
Rickettsial pox (causes an eschar): pathogen, geography, insect vector, and other carrier?
- Rickettsia akari
- U.S.
- mite
- mice
Clinical presentation of Rocky Mountain Spotted Fever?
- acute onset of nonspecific sxs: ex - fever, severe HA, myalgia, and prostration
- rash appears 2-6 days later, merciless that frequently progress to petechiae (wood tick or dog tick)
- ***Rash usually appears first on hands and feet and then moves inward to the trunk
- 90% of kids have rash
- rash may be of short duration
- localized to a particular region of the body
- rash completely absent or atypical in up to 20% of RMSF cases
- DDX: syphillis (RPR), hand, foot, and mouth, meningitis
What can the rashes turn into in Rocky mountain spotted fever if left untx?
- can become necrotic tissue, looks like DIC, TTP
- if don’t tx aggressively -> can lead to death
- transmits bacteria in 6-10 hours after bite so early dx is key
Work up for RMSF?
- CBC: thrombocytopenia
- chemistry panel: hyponatremia, elev AST, hyperbilirubemia
- may need spinal tap to study CSF and rule out meningococcus
LP: mild increase WBC, low glucose
** tip off: AST elevated
DDX of RMSF?
- difficult
- 40% of pts don’t recall tick bite
- rash may be confused with that of measles, typhoid, ehrlichiosis, or most impt: meningococcemia
- need blood cultures and exam of CSF
- mortality: 70% in elderly (myocarditis)
can be fatal in kids too if left untx
Tx for RMSF?
- delay in tx can lead to severe disease and fatal outcome
- is susceptible to tetracycline-class abx:
Doxy- DOC
in pregnancy: chloramphenicol (dangerous AEs) - optimal duration of therapy hasn’t been established
- current recommendations for RMSF are tx for at least 3 days after fever subsides, and until evidence of clinical improvement is noted, which is typically for a minimum course of 5-7 days
- severe of complicated disease might require longer tx courses
When does Epidemic Louse-Born Typhus occur?
- caused by Rickettsia prowazekii, parasite of body louse
- in US -> flying squirrels are an extra human reservoir
- crowded, unsanitary, famine, war
- considered bioterrorism agent
Sxs and signs of Epidemic louse-borne typhus?
- prodromal malaise, cough, HA, arthralgias, and CP (pleuritic chest pain) during incubation period of 10-14 days
- abrupt onset of chills, high fever, and flu like sxs progressing to delirium and stupor (looks like flu that progressed to pneumonia)
Lab findings in Epidemic Louse Borne typhus?
- CBC: thrombocytopenia
- CMP: elevated liver enzymes, proteinuria, and hematuria (leaky kidneys, not filtering very well)
- CXR: patchy consolidation (could also be mycoplasma or fungal)
What is Brill-Zinsser Disease?
- R. prowazekii can survive in lymphoid tissues after primary infection, and years later, produce recrudescence of disease
- this phenomenon can serve as pt source for future outbreaks
- more gradual onset than primary, fever, and rash are of shorter duration, and the disease is milder and rarely fatal (main concern: contagious)
Tx of Epidemic louse-borne typhus?
- doxy
- chloramphenicol
MOA of Doxy?
- protein synthesis inhibitor at 30s subunit
side effects: discoloration of teeth, and stunted bone growth
Chloramphenicol MOA andAEs?
MOA: protein synth. inhibitor at 50S
- gray baby syndrome
- aplastic anemia
- hemolytic anemia
Endemic (murine) typhus signs and sxs?
- Rickettsia typhi
- transmitted from rat to rat via the rat flea (same flea as bubonic plague)
- urban
- gradual onset, less severe sxs, and shorter duration of illness than epidemic typhus
labs, Dx, and Tx of endemic (murine) typhus?
- same as epidemic louse-borne typhus
labs: CBC: thrombocytopenia
CMP: elev liver enzymes, proteinuria and hematuria (ineffective kidney filtration) - CXR: patchy
tx: doxy and chloramphenicol
What would be a pro to getting endemic (murine) typhus?
- makes you immune to epidemic louse-bourne typhus which is much more severe
Transmission of Rickettsialpox?
Rickettsia akari
- transmitted to humans via mites that ride on mice
signs and sxs of Rickettsialpox?
- mild, self-limited, febrile illness that starts with an initial localized red skin bump
- bump turns into a blister and days later: fever and HA develop, and other vesicles appear over body
Tx of Rickettsial pox
responds well to Doxy
- get sticky mouse traps
What is cause of Q fever?
- Coxiella burnetii
What is Coxiella burnetii?
- gram - intracellular organism
- Coxiella burnetti (formerly known as rickettsia, but now considered a proteobacteria)
What does Coxiella burnetii infect?
- infects cattle (usually spread by milking), sheep and goats
- in man = Q fever
- highly resistant spore stage that is transmitted to humans when animal tissue is aerosolized or ingestion of contaminated milk
- doesn’t need vector
Signs and sxs of Q fever?
- begins suddenly with fever, sever HA, cough, and other flu like sxs
- ***pneumonia develops in about 50% of pts
- **Hepatitis is frequent enough that combo of pneumonia and hepatitis suggest Q fever
- Q fever is acute disease: recovery is expected even in absence of abx therapy
chronic Q fever: endocarditis: culture will be negative, high risk pts: heart valve disease, valve replacement
lab findings in Q fever
- CBC: may have leukocytosis
- CMP: elev. LFTs
- CXR: may be more prominent than what physical signs suggest - patchy pulmonary infiltrates (like mycoplasma)
- echo: rule out endocarditis
DDX with Q fever?
- Viral, mycoplasma, and bacterial pneumonitis, legionnaire disease, kawasaki disease, tb, psittacosis.
** think Q fever in cases of unexplained fevers with negative blood cultures in association with embolic or cardiac disease especially with suspicious history, no rash hepatitis, and pneumonia presentation
Tx and prognosis of Q fever?
- doxy
Hydroxychloroquine and doxy for endocarditis - even when untx: mortality rate is low unless endocarditis develops
Lyme disease?
- spirochete, but tick transmitted disease
- corkscrew shaped, but larger than Treponema
- Borrelia burgdorferi
Where is lyme disease seen?
- NE, midwest and NW US
- Ixodes tick
- takes 24 hours to transfer infection
- similar to syphilis (can have chancre but it won’t be painful)
- can disseminate to heart, CNS, joints, CN 7 palsy, fatigue, can develop chronic arthritis
- ddx: think lupus
Signs and Symptoms of lyme disease?
- recognize sxs in person who has been exposed to ticks in area endemic to lyme disease
- Erythema migrans, bull’s eye
- Ha or stiff neck
- arthralgias, arthritis, myalgias, arthritis is often chronic and recurrent
Dx of lyme disease
- Erythema migrans, bull’s eye, leading edge of rash bx
- culture is really difficult, usually use levels of antiBorrelia burgdorferi abs to help make dx
- ELISA and western immunoblotting
Tx of Lyme disease?
- doxy or PCN family abx are currently most effective ab for treating the disease
- is vaccination available but withdrawn in 2002 due to poor sales
When should you be thinking a rickettsial disease?
- high fevers, arthralgia, and rashes
RMSF rash?
- starts at wrists, ankles, sole and palms and spread to the trunk
Lyme disease differentiation?
- bulls eye: erythema chronicum migrans
Rickettsialpox skin findings?
- red skin bump turns into blister
