vectorborne diseases Flashcards
what is the most common vector-borne dz in the US?
lyme dz
how is lyme dz transmitted?
Borrelia burgdorferi via Ixodides, a small tick
how long must the tick feed to transmit the spirochete?
24-36 hours
what is the first stage of a lyme dz infection?
early localized infection that occurs 7-10 days after the original bite
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describe stage 1 of lyme dz
- erythema migrans: flat or slightly raised red lesion that expands over several days, typically with central clearing (bull’s eye) -about 25% of pts done have this
- common sites are the groin, thigh, axilla, and it typically resolves in 3-4 weeks w/o tx
- 50% of pts experience flu like sx
stage 2 of lyme dz?
early disseminated infection that occurs days to weeks later
what are the clinical manifestations of lyme dz
- involve the skin, CNS, MSK system
- HA, stiff neck, fatigue, malaise, intermittent musculoskeletal sx
- cardiac: pericarditis, arrhythmias, heart bock
- neurologic: aseptic meningitis, bell palsy, encephalitis
what is stage 3 of lyme dz?
late persistent infection that occurs months to years later
what occurs in stage 3 of lyme dz?
- MSK dz, CNS and PNS,
- skin manifestations
what are MSk dz sx of late persistent lyme dz?
joint pain w/o objective findings, frank arthritis, chronic synovitis
most likely immunologic cause
what are CNS adn PNS sx of late persistent lyme dz?
- subacute encephalopathy (memory loss, mood change)
- axonal polyneruopathy (paresthesias, encephalopathy)
- leukoencphalitis (cognitive change, paraparesis, ataxia, bladder dysfxn)
what are skin manifestations of stage 3 lyme dz?
acrodermatitis chronicum atropicans: bluish-red discoloration of distal extremities w/ atropy (seen in europe, not in US)
dx studies for lyme dz
antibody testing via immunofluorescent assay or ELISA techniques
western as confirmatory test
when will IgM go away in lyme dz? IgG?
after 6-8 weeks; will last indefinitely
problems with diagnostic testing in lyme dz
-tests lack sensitivity: the probability of a false-positive test may be greater than that of a true-positive test
what dz may cause fals-positive tests for lyme dz?
RA, SLE, mono, endocarditis
what should early lyme dz dx be based on?
clinical presentation
how is late dz dx lyme
by objective evidence of clinical manifestations and laboratory evidence of dz
what are other lab tests that can be done for lyme
-CSF, synovial fluid analysis, aspirations, or bx
how is lyme dz treated (early dz)
- doxy
- alternatives: amoxicillin, cefuroxime, ceftriaxone, cefotaxime
how is late/chronic lyme dz treated?
- may need IV drugs
- difficult to dx and difficulte to resolve
what is a complication of lyme dz?
Post Treatment Lyme Disease Syndrome:
+muscle and joint pains, cognitive defects, sleep disturbance, or fatigue
+Likely due to autoimmune response
+No further antibiotic treatment indicated
+Ongoing studies, very controversial topic for some patients
how do you prevent lyme dz
Avoid heavily wooded areas
Use of DEET or permethrin repellants for skin & clothing
Wash/bathe after being outdoors to get rid of crawling ticks
Tick check – also check pets, outdoor gear
what is the appropriate removal of the tick
Tweezers as close to skin as possible, steady pressure to remove
Try not to twist, don’t want to leave mouthparts in skin
Wash area with soap and water
No vaseline, fingernail polish, matches, etc!
*can also put clothes in dryer for an hour to kill ticks
Rocky Mountain Spotted Fever?
Rickettsia rickettsii that is carried by
the American dog tick (Dermacentor variabilis), the Rocky mtn wood tick, and the brown dog tick
when do sx of RMSF first show up?
2-14 days after exposure
where does RMSF most commonly occur?
the eastern US
what are the initial clinical findings in RMSF?
-abrupt onset HA/Fever
what may occure in hte first 2-14 days after exposure in RMSF?
fever. chills, N, V, maylagia, restlessness, insomnia, irritability
less common: couh, pneumonitis, delirium, sz, stupor, coma
what does RMSF rash look like?
90% of pts; flushed face, injected conjuctiva
-appears 2-5 days after the onset of fever as small, flat, pink, macules on the wrists, forearms, and ankles
spreads to include the trunk and sometimes the palms and soles
The red to purple, spotted (petechial) rash of RMSF is usually not seen until the sixth day or later after onset of symptoms and occurs in 35-60% of patients with the infection
why is the rash on the palms and soles very concerning
BAD SIGN AS THIS IS PROGRESSION TO SEVERE DISEASE, can lead to vasculitis, organ damage and permanent neurological defects
what are less common PE findings in RMSF?
splenomegaly, hepatomegaly, jaundic, myocarditis, uremia, acute respiratory distress syndrome and necrotizing vasculitis
what may you see on a CBC and CMP of a pt with RMSF?
leukocytosis, thrombocytopenia, hyponatremia, proteinuria, hematuria
transiet rise in aminotransferase, bilirubin
what will a CSF analysis reveal in a pt with rMSF?
pleocytosis (increased WBC) and hypoglycorrhachia (low glucose level)
when wil you see a rise in antibody titers in RMSF?
second week of illness
what is the gold standard for laboratory confirmation of RMSF?
IFA and paired tests showing four-fold increase in IgG
what should the paired immunoglobulin tests show?
First sample early in disease, second drawn 2-4 weeks later, along with +IgM
IgM by itself can simply be a false positive
PCR test – blood or scrape rash lesion
May also see hyponatremia, thrombocytopenia and elevated liver enzymes
what is the treatment of RMSF?
mild cases go away in the 2cd week
tx with doxy or chloramphenicol hastens recovery
what pt population may have poor outcomes in RMSF?
advanced age and pts with atypical features
death is caused by penmonitis or respiratory or cardiac failure
what is RMSFsequelae?
seizure, encephalopathy, peripheral neruopathy, paraparesis, bowel r bladder incontinence, cerebellar dysfxn, vestibular dysfxn, hearing loss, or motor deficites
toxoplasmosis?
toxoplasma gondii is a prtozoan parasite
how is toxoplasma transmitted?
- food/waterborne
- animal to huma
- mother to child
- rare: transplants
- undercooked meats, contaiminated soild, infected water, kitty litter
who is more likely to get toxoplasmosis?
pts that are immunocompromised
CD4 counts less than 100 are at greater risk of both acute or reactivated dz due to prior exposure
what should you warn people that may be at risk of contracted toxo?
Cats play an important role in the spread of toxoplasmosis. They become infected by eating infected rodents, birds, or other small animals. The parasite is then passed in the cat’s feces in an oocyst form, which is microscopic. So those at risk should not clean litter box – or wear gloves if they do, along with scrupulous handwashing and avoidance of inhaling dust/soil.
what are some fetal toxoplasmosis sx?
miscrriage, stillbrith, congential anomalies, such as retinochoroiditis, mental disability, seizures, macrocepahly,
what can toxoplasmosis present as?
encephalitis, retinochoroiditis, PNA
how do you test for toxoplasmosis?
Can be very complicated, especially for congenital
IgM is often a false positive test
IgG titers need to show 4 fold increase to demonstrate active disease
Many antibody tests (ELISA) simply report the result as “positive
what is the definitive test for toxoplasmosis?
direct visualization
what is the treatment for sympotmatic toxoplasmosis? in asx healthy pple? in HIV infected
- symptomatic: pyrimethamine and sulfadiazine puls folinic acid
- healthy: none
- HIV: tx and prophylaxis
what can be used for toxoplasmosis prophylaxis?
bactrim
