Miller - Zoonoses

Question 1

Rickettsia and related microbes

Answer 1

• Very short rods (barely visible under scope)
• Obligate IC parasites
• Structurally similar to G- (express LPS), but gram stain poorly
• RICKETTSIA, ERLICHIA, COXIELLA
• Pathogenesis: 1) vasculitis, particularly at site of infection, 2) skin rash from edema/hemorrhages, 3) fever/petechiae suggest endotoxin, 4) no exotoxins or cytolytic enzymes

Question 2

Rocky Mountain Spotted Fever (Rickettsia rickettsii)

Answer 2

• Transmitted by variety of ticks, esp. dog ticks (GA, NC, VA) -> dogs/rats are a reservoir
• Children: spring and summer; 95% of rickettsial disease in the US
• CLINICAL: acute onset of flu-like sxs, muscle soreness in calves, rash starting at ankles/wrists and spreading to palms, soles, trunk
  1. Delirium, coma, DIC, edema, circulatory collapse in severe cases (25% fatality untx)
• DIAGNOSIS: Weil-Felix serology w/proteus Ags, IFA (attached image) can be used
• TREATMENT: Doxycycline

Question 3

Epidemic Typhus (Rickettsia prowazekii)

Answer 3

• Hum-to-hum transmission via lice feces; not in US
• CLINICAL: sudden onset of flu-like sxs, rash from trunk to extremities (not on palms/soles), 10-60% untreated mortality, myocarditis, CNS involvement, death from vascular collapse or bac pneumonia
• DIAGNOSIS: IFA, ELISA (4x INC in titer)
• TREATMENT: Tetracycline or Chloramphenicol

Question 4

Endemic (murine) typhus (Rickettsia typhi)

Answer 4

• Rat flea, small mammals (rats, possums)
• CLINICAL: similar, but less severe sxs than epidemic typhus, rash in 50% of pts, rare fatalities even if untreated
• DIAGNOSIS: symptomology + serology
• TREATMENT: Doxycycline

Question 5

Erlichia chafeensis

Answer 5

• Human monocytic erlichiosis: lone star deer tick that replicates in monocytes
• CLINICAL: flu-like sxs, rash in 60% of children and 30% of adults, fatality rate 1.8%
• DIAGNOSIS: blood smear w/morulae in monocytes (attached image), confirm w/serology
• TREATMENT: Doxycycline

Question 6

Anaplasma phagocytophilia

Answer 6

• Human granulocytic anaplasmosis, aka RM spotless fever -> Ixodes blacklegged ticks
• CLINICAL: flu-like sxs, uncommon rash (and may indicate co-infection w/B. burgdorferi), and trouble breathing, hemorrhage, renal failure, neuro problems in severe cases (<1% mortality)
• DIAGNOSIS: blood smear -> look for morulae in granulocytes
• TREATMENT: Doxycycline

Question 7

Coxiella burnetti (Q fever)

Answer 7

• Obligate IC G- bacillus in cattle, sheep, goats -> transmission via contaminated milk, ticks, spores
• Almost every country, but low incidence
• PATHOGEN: very infectious (ID₅₀ <10), closely related to Legionella (and lives in macros)
• CLINICAL: 30-50% asymptomatic, acute febrile illness (atypical pneumo w/<2% mortality), liver/heart may be involved, chronic infection -> endocarditis or granulomatous hepatitis and 100% fatal untreated
• DIAGNOSIS: serological (rising Ab titers)
• TX: spontaneous resolution or Doxycycline

Question 8

Borrelia burgdorferi (lyme disease) epi

Answer 8

• Flexible, motile spirochete (darkfield, Giemsa, or silver stain); blood cultures usually (-), but culture from tick vector (see attached) usually (+)
• 30-50% I scapularis culture (+) vs. 2% I pacificus; main reservoir sm animals, like white-footed mouse
• Nymphal stage ticks (very small) during summer mos: 24-48 hrs of feeding required
• 80% of cases in NY, CT, PA, and NJ; most common vector-borne disease in US

Question 9

Borrelia burgdorferi (lyme disease) pathogenesis, diagnosis, and treatment

Answer 9

• PATHOGEN: skin to blood (bacteremia) to various organs (heart, joints, CNS), no exotoxins/enzymes, Ag variation of outer surface proteins (OSPs) to survive in different hosts (tick, mouse, human, etc)
• DIAGNOSIS: ELISA (sensitive, but false +’s), confirm by Western blot, PCR
• TREATMENT: early -> tetracycline or amoxicillin; late -> IV cephalosporins or penicillin G
  1. Used to be a vax to OSP-A; discontinued

Question 10

Borrelia burgdorferi (lyme disease) clinical presentation

Answer 10

• STAGE 1 (acute): erythema migrans (attached) in 75% of pts (3-30d post-transmission), painless, non-pruritic, flu-life sxs may occur, arthralgias, 2^o skin lesions (no rash until tick released usually)
• STAGE 2 (wks-mos later): cardiac, neuro -> myocarditis/heart block, acute septic meningitis and facial N palsy (bilateral Bell’s palsy HIGHLY suggestive)
• STAGE 3 (chronic): arthritis of lg joints, chronic progressive CNS disease

Question 11

What do you see here?

Answer 11

Bell’s palsy of lyme disease

Question 12

What is this?

Answer 12

Bell’s palsy of lyme disease

Question 13

Relapsing fever

Answer 13

• B. hermsii (Ixodes tick) & B. recurrentis (body louse; rare in US) -> most endemic in high desert of Western US (rodents, sm mammal reservoirs)
• PATHOGEN: Ag variation of OSP responsible for relapsing disease, no o/virulence factors detected
• CLINICAL: 1-wk fever that recurs 2 wks later, and can repeat up to 10x, skin rash uncommon
• DIAGNOSIS: blood smear, serology can be confirmatory (but often useless)
• TX: Tetracycline

Question 14

Leptospira interrogans

Answer 14

• Tightly coiled, fine spirochetes sometimes visible via darkfield
• EPI: rodents, livestock, pets (DOGS), bugs shed in urine (contaminating soil), swimming or consuming contaminated water (triathlons, adventurers, farmers, urban poor), mucosal or cutaneous inf
• PATHOGEN: skin to bacteremia to organs, Ag variation (relapsing sxs)
• CLINICAL: flu-like sxs + conjunctivits, which wane, then -> aseptic meningitis, liver damage (jaundice), kidney dysfunction (uremia) Weil’s disease, and/or lung hemorrhage
• DIAGNOSIS: hx, clinical signs, marked rise in IgM titers, isolation from blood/urine culture (unreliable)
• TX: Penicillin G (vax 4 livestock, pets = prevention)

Question 15

What are these from? Describe clinical presentation.

Answer 15

• Fever + tender, enlarged nodes (front image) on same side as scratch -> papule at site of scratch may precede this
• Long disease, but typically resolves w/o ABs
• Endocarditis, encephalitis in small percentage
• Immunocompromised: bacillary angiomatosis can occur in skin and visceral organs (see attached image)

Question 16

Cat scratch disease (Bartonella heneslae)

Answer 16

• EPI: sm, pleomorphic G- rod w/polar flagellum (oral flora of many cats) that needs specialize culture medium to grow
  1. Cat fleas may also transmit (but not really hum-to-hum or urine/feces); mostly children
• PATHOGEN: low virulence, usually self-limiting
• DIAGNOSIS: serology, culture (uncommon), Warthin-Starry silver stain for pleomorphic rods in biopsy tissue, patho exam to distinguish bacillary angiomatosis from Kaposi’s sarcoma in HIV/AIDS context
• TX: none, unless severe lymphadenitis -> Azithromycin (or Doxy or Erythromycin)

Question 17

Bacillus anthracis

Answer 17

• Anthrax toxins, spore former, cattle/sheep (Wool-sorter’s disease), person-to-person or cutaneous
• Cutaneous form: 5-20% mortality untx, but <1% w/tx (also pneumo and GI disease; see attached)
• CLINICAL: 2-12d incubation (sometimes only hrs), painless papule w/edema, inflam, then blistering and necrosis (ESCHAR w/in hrs) -> fever, dizziness, heart palpitations, lymphangitis/sepsis w/o tx
• DIAGNOSIS: fluid sample, Abs or toxin in blood, CXR w/mediastinal widening if pneumo version
• TX: Cipro for 60d (bc can live in macros) + Ampicillin, Penicillin G, Meropenem, Rifampicin, or Vanc, if severe disease

Question 18

Burkholderia pseudomallei (meliodosis/Whitmore’s)

Answer 18

• Facultative, IC G- rod in SE Asia, N Australia soil, rice paddies, & muddy waters (enzootic/cutaneous)
• PATHOGEN: anti-phago capsule, cell lysis (and mvmt bt cells w/o going EC), latency (Vietnam war)
• CLINICAL: 2-3d or yrs incubation, most commonly pneumo (fever, chest pain, normal sputum), consolidations or upper lung, can become septic (20-50% mortality, even when tx)
• DIAGNOSIS: isolation from blood, urine, sputum, etc., Abs in acute-phase/convalescent serum
• TX: Ceftazidime for 8 wks (6 mos if IS’d), resistant to many ABs (like Gentamicin; can aid in dx)

Question 19

Francisella tularensis

Answer 19

• IC, G- rod w/LPS not recognized by TLR 4 (type A)
• EPI: tick, blood-blood w/many types of animals (roadkill, lawn mower), survives for long time in H₂O, AR, MO, MA (Martha’s Vineyard)
• PATHOGEN: highly contagious (low LD₅₀), skin infection = ulceroglandular disease (1-3% mortality), pneumo type w/30-60% mortality (can become this from skin type), pronounced LAD (front image)
• CLINICAL: sudden onset flu-like or prolonged low-grade fever and adenopathy, 75% ulceroglandular
• DIAGNOSIS: agglutination, fluorescence, culture rare (bc so contagious); military unlicensed vaccine
• TX: Streptomycin

Question 20

Yersenia pestis (epi, pathogen)

Answer 20

• IC (V and W Ags), G- encapsulated rod w/bipolar (safety pin) stain
• EPI: rodents/prairie dogs via fleas, person-to-person aerosolized, 99% of cases in SE Asia
• PATHOGEN: buboes (swollen nodes), bacteremia and abscesses in many organs, F-1 capsular Ag to protect from phago, endotoxin (LPS: DIC, cutaneous hemorrhages), Yops via type III secretion INH phago and cytokine production by macros/polys, exotoxin

Question 21

Yersenia pestis (clinical, diagnosis, tx)

Answer 21

• CLINICAL: buboes (swollen nodes) near bite, extreme fatigue, collapse, coughing up blood, septic shock and pneumo possible (inhalation or septic emboli), untx bubonic fatal in 50% of cases, and untx pneumo fatal in 100% of cases
• DIAGNOSIS: smear/culture from bubo pus, Giemsa or Wayson stain for safety-pin appearance, fluorescent Ab stain, rise in Ab titer to envelope Ag
• TX: Streptomycin + Tetracycline, or just Strep (don’t wait for + culture)
• VAX: partial protection against bubonic, but not pneumo (military in Vietnam war, but not recommended for tourists; killed vax)