Misc Infections

    .

     

     

    Tick-Borne Diseases

    Introduction

    • List: (Source: MKSAP)
    • Disease Pathogen Vector Predominant US Distribution
      Lyme Disease Borrelia burgdorferi Deer Tick Northeast and north central US
      Babesiosis Babesia microti Deer Tick Northeast and north central US
      Southern tick-associated rash illness Unknown Lone Star Tick Southeast, south central, mid Atlantic
      Human monocytic ehrlichiosis Ehrlichia chaffeensis Lone Star Tick Southeast, south central, mid Atlantic
      Human granulocytic anaplasmosis Anaplasma phagocytophilum Deer Tick Northeast and north central US
      Rocky Mountain Spotted Fever Rickettsia rickettsii Dog Tick Contintental

     

    Lyme Disease

    • Epidemiology:
      • LymeDisease.png
    • Borrelia burgdorferi sensu stricto
      • Transmitted to humans via nymphal deer tick
      • Very small tick, 50% of patients remember being bitten by a tick
    • Has 3 distinct stages:erythemamigrans.jpg
      • Stage I: Early localized (3-30d)
        • Erythema migrans at site of tick attachment (visualize) in 3-30 days.EM noted in 70-80% of pts.
          • Lesion expands over days, and center clears (can present atypically)
        • If early localized stage not treated, can get spirochete-emia, and get "early disseminated".
        • DX: CLINICAL Visualization of skin lesion. (Testing is negative)
      • Stage II: Early disseminated (3-6w)
        • Spirochetemia.
          • Myalgia, headache, fever, fatigue, lymphadenopathy.
            • Can involve:
              • Heart: Lyme myocarditis - 5% of untreated pts.  Can create 1st deg AV block or a complete block. Reversible.
              • CNS - palsys, aseptic meningitis, radiculopathy etc..
          • Multiple erythema migrans (in sites other than tick bite)
        • Incubation, can have multiple erythema migrans lesions distinct from site of tick.
        • Diagnosed: initial ELISA (Sn, not Sp), confirm with Western Blot (antibodies - WB is very Sp)
          • Restricted to IgM testing for Borrelia burgdorferi restricted to pts with 1mo of symptoms. because IgM without IgG  = false positive.
        • Can have cranial nerve palsies, meningitis, myocarditis.
      • Stage III: Late (months to years) (60% of untreated pts)
        • Arthritis (first episode and recurrent) often knee - Commonly mistaken, but the fact is that arthritis is only seen in late stage
          • Migratory monoarticular/oligoarticular inflammation.  Improves spont. and recurs in the same joint, most commonly the knee (85%).
          • Can do Lyme PCR of synovial fluid to diagnose (even after treated)
        • Encephalopathy or encephalomyelitis (rare)
          • PCR of CSF has LOW sensitivity, negative test does not exlude dx.
          • Encephalopathy, deficits in cognition, short term memory.
          • Diagnosed: CSF pleocytosis and positive ratio btwn CSF to serum antibodies, or positive PCR (consider experimental).
        • Diagnosed: Same as "Early Disseminated"
           
      • NOTE: The finding of antibody in patients with non-specific symptoms of fatigue or myalgia with an unlikely exposure to a vector tick represents false positive.
      • NOTE:  Testing without symptoms after a tick bite is NOT indicated.  
      • NOTE:  Serum antibodies remain positive indefinitely, cannot monitor treatment.
    • Diagnosis:
      • Early Localized: Inspection only. (Clinical)
      • Early Disseminated and Late:
        • Initial ELISA (Sn, not Sp), confirm with Western Blot (antibodies - WB is very Sp)
          • Restricted testing for IgM to Borrelia burgdorferi, restricted to pts with 1mo of symptoms suggestive of signs/symptoms of Lyme who had contact with endemic area. because IgM without IgG  = false positive, so cannot test too early before IgG has time to accummulate.(?)
    • Treatment:
      • Doxycycline 100mg BID x 14 days
        • Empiric doxycycline recommended for erythema migrans.  Agent of choice.
      • Cardiac or Neurologic Involvement:
        • Ceftriaxone 2g daily
      • Alternatives:
        • Amoxicillin 500mg TID
        • Cefuroxime 500mg BID
        • Ceftriaxone 2g daily
    • Post-Lyme Disease Syndrome
      • Erroneously called "Chronic Lyme Disease -> challenging.
      • Pts with confirmed Lyme with persistent constitutional symptoms despite abx treatment.
      • Supportive therapy, but prolongued duration of repeated abx are ineffective and strongly discouraged.
        • Counsel patients... many people online endorse long-term treatments.

    Babesiosis

    • Protozoal infection
    • Similar as Lyme, transmitted by same vector.
    • Edemic to north-western and mid-western regions of US.
    • Person to person can transmit (tranfusion of blood product)
    • Protozoan persists in erythrocytes
    • Symptoms:
      • Most are asymptomatic
      • Range from self-limited febrile illness to fulminant multi-organ system failure + death. 
      • Mild: Fever, hemoysis (hepatoplenomegaly, jaundice)
      • Severe:  AKI, high-output HF, circulatory collapse
    • Risk factors for severe infections: older age, HIV, immunocompromise, asplenia.
    • Labs:
      • Hemolysis - Macrocytic anemia (large retics), bili, haptoglobin, LDH, low platelets, elevated liver enzymes.
    • Diagnosis:
      • PCR using whole blood specimen (better than direct microscopy).
      • Historically did direct microscopy for intra-cellular parasites, but cannot distinguish from malaria.
    • Treatment:
      • All symptomatic patients with lab confirmation.
      • Asymptomatic with documented persistence of parasites > 3mo.
      • Combination Mitoquinone+azithromycin, quinine + clindamycin
      • Exchange transfusion >10% paracitemia

     

    STARI (Southern Tick Associated Rash Illness)

    • STARI clinically indistinguishable from early localized form of lyme disease.
      • However, geographically different: South-east mid atlantic and south-central US
      • And negative testing for Borrelia burgdorferi
    • Looks like Lyme disease, but unknown pathogen, treated the same.  (Lone Star Tick)
    • Symptoms:
      • EM skin lesion + fever, headache, myalgia
      • Early localized: clinical diagnosis
    • Treatment:
      • Doxycycline
      • Disease progression to later stages, not reported if not treated.

     

    Ehrlichiosis & Anaplasmosis

    • Two:
      • Human Monocytic Ehrlichiosis
      • Human Granulocytic Anaplasmosis
    • Clincally similar tick-borne rickettsial diseases in US.
    • Both occur 1-2 weeks after innoculation characterized by:
    • Symptoms:
      • non-focal febrile illness + fever, headache, myalgia, fatigue.
      • Skin lesions <30% in ehrichiosis and even less anaplasmosis
        • Most common is maculopapular rash, but petechial eruption such as Rocky Mountain Spotted Fever described.
      • Meningoencepalitis more frequent in 20% of pts.
    • Labs:
      • Triad:
        • Leukopenia (Lymphopenia)
        • Low plts
        • Elevated Liver Enzymes
      • Serology can be negative in acute infection, positive 2-4w post-infection.
      • Often this triad leads people to think its cholecystitis leading to unnecessary surgery
      • If CNS involvement: CSF: Lymphocytic pleocytosis with mildly elevated protein concentration.
    • Treatment:
      • Empiric antibiotics started prior to lab confirmation
        • Doxycycline 100mg BID x7-14d --> treats both.  (delays = worse outcomes)
        • Symptoms respond in 24-48hrs, consider alternative dx if not better.

     

    Rocky Mountain Spotted Fever

    • Tick-borne rickettsial disease throughout US.rockymountainspotted.jpg
    • Incubation period following infection 2-14d.
    • Symptoms:
      • Fever (almost always)
      • + often headache, myalgia, confusion, GI symptoms
      • Petechial rash (90% of patients, but present at onset of fever in 15%)
        • Non-blanching macules on wrists/ankles that progress to petechial skin eruptions involving trunk, palms, soles, SPARE FACE!
        • Do not occur in 10% of patients, can delay early detection.
    • Labs:
      • Thrombocytopenia.
      • Elevated transaminases
      • Leukocyte counts are normal! (LOW in Ehrlichiosis and Anaplasmosis)
      • CSF (if meningoencephalitis): Lymphocytic pleocytosis
    • Diagosis:
      • Serology, but seroconversion lags behind symptoms (4-fold rise of titre, or seroconversion considered diagnostic)
        OR
      • Skin biopsy: immunohistochemical staining shows Rickettsia
    • Treatment:
      • Doxycycline started emprically when suspected. (DO NOT withhold even if serologically negative)

     

    Plague

    • Yersinia pestis
    • Endemic to SouthWestern US --> large reservoir of rodents (transmitted by flea bite)
    • Pathognemonic: "Bipolar staining gram-negative bacillus - giving the apperance of a closed safety pin"
    • Category A Bioterrorism Agent
    • Three clinical syndromes:
      • 1.  Pneumonic plague, occurring with inhalation of bacteria
        • Most fulminant and lethal - direct inhalation of respiratory droplets of infected animals/people.
        • Need treatment in 24hrs --> 100% fatal
      • 2.  Bubonic plague, characterized by purulent lymphadenitis near the inoculation site (more common in the naturally occurring zoonotic form of infection)
        • Intensely painful swollen group of lymph nodes (bubo) - 85% of cases.
      • 3.  Septicemic plague, a septic presentation that can arise from either of the other syndromes. 
    • Treatment:
      • Gemtamicin, Streptomycin
      • Post-exposure proph: Doxycycline, Ciprofloxacin
      • (See detailed reference for more info)
    Tag page (Edit tags)
    • No tags
    Page statistics
    11230 view(s), 9 edit(s) and 14170 character(s)

    Comments

    You must login to post a comment.