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Infectious Disease Unit 2 > Zoonotic Disease > Flashcards

Zoonotic Disease Flashcards

1
Q

Zoonotic disease definition

A

infections that are transmitted between humans and other animals

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2
Q

Factors influencing zoonotic infections

A
  1. Transition from hunter-gatherer societies to agrarian societies
  2. Domestication of animals
  3. Increased population density
  4. Modification of the environment
  5. Emergence of immunosuppressed populations
  6. Many of these organisms can and have been used as bioterrorist weapons (e.g. Y. pestis, B. anthracis).
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3
Q

Causative organisms in the plague

A

Yersinia pestis
“Black Death” refers to purpura.
Hallmark of plague: is DIC with cutaneous petechiae, purpura and ecchymosis.

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4
Q

Yersinia pestis features

A
  • introduced in US by rats on ships arriving in SF from China
  • facultative bipolar-staining Gram-negative bacillus belonging to the Enterobacteriaceae
  • has plasmids containing virulence factors (w/ complement resistance determinants and secreted proteins called “YOPS”–a tyrosine phosphatase that subverts normal activation mechanisms of phagocytic cells)
  • antiphagocytic capsule
  • iron/hemin uptake systems
  • coagulase fibrinolysin that facilitates transmission from fleas
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5
Q

Y. enterocolitica/Y. pseudotuberculosis cause…

A 
(less virulent relatives of Y. pestis)
enterocolitis
arthritis
septicemia
mesenteric adenitis
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6
Q

animal reservoirs of Y. pestis

A
  • urban and forest rodents
  • fleas usually transmit disease to humans
  • domestic cats can provide connection b/t sylvatic (forest) foci and human populations.
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7
Q

Enzootic foci

A

-stable rodent-flea reservoirs of infection

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8
Q

epizootic plague

A

results from introduction into a new susceptible mammal population

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9
Q

zootic plague

A

transmission from animal host to humans

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10
Q

Location of plague cases in US and world

A

Southwestern US and Colorado from May-October

Currently prevalent in Africa, South America, SE Asia, India

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11
Q

Clinical features of bubonic plague

A

fever, painful lymphadenophathy (bubo, most commonly of groin, axilla, or neck).
Results from the bite of a flea on the arm or leg.

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12
Q

Clinical features of septicemic plague

A

fever, hypotension

rapidly fatal, frequently results from the ingestion of large numbers of organisms

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13
Q

Clinical features of pneumonic plague

A

can be primary or secondary to hematogenous spread, rapidly fatal.

***transmitted human to human

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14
Q

Diagnosis of plague

A

Wayson/Giemsa/Gram strains of a bubo aspirate; bubo/blood/sputum culture with confirmation by fluorescent antibody; serology

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15
Q

Tx of plague

A

streptomycin; supportive care

alternative: tetracycline, chloramphenicol and fluoroquinolones
* Need to be effective against intracellular pathogens

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16
Q

Prevention of plague

A

rodent and vector control

-killed vaccine gives short term protection to high risk indiv

17
Q

Tularemia: associated animal; how infectious is it?

A
  • rabbit associated illness
  • one of most infectious bacterial organisms known (Infectious dose less than 50 organisms applied to unbroken skin; 5-10 organisms by respiratory route)
  • less severe disease than Y. pestis
18
Q

Features of Francisella Tularensis

A

small, aerobic, pleomorphic Gram-negative coccobacillus

virulent strains require cysteine for growth;

3 biotypes

The ability to survive intracellularly, aided by bacterial phase-variation, is believed to be important in pathogenesis.

cellular immunity is required for recovery.

Transmission: arthropid vectors or infected rabbits

19
Q

Groups commonly infected with F. tularensis?

A

hunters/trappers, meat handlers, veterinarians, farmers, lab workers; peak incidence in summer (ticks) and December (hunting)

20
Q

Does F. tularensis spread person-to-person?

A

NO!

Y. pestis can: pneumonic plague

21
Q

Clinical features of F. tularensis

A

flu-like symptoms, persistent remitting constitutional symptoms lasting weeks.

GLANDULAR – lymph node only ULCEROGLANDULAR – necrotic ulcer with tender regional lymph node
OCULOGLANDULAR – from direct inoculation of eye
PHARYNGEAL – can be mistaken for streptococcal/EBV infection
TYPHOIDAL – systemic disease without localizing findings, requires a high dose from ingestion to cause disease.
PULMONARY – can result from inhalation or from hematogenous spread of another kind of infection.

22
Q

Diagnosis of F. tularensis

A
  • cultures need special media

- serologies positive in most pts by 1-2 weeks

23
Q

Tx for F. tularensis

A

streptomycin or gentamicin;
alternatives: tetracycline, chloramphenicol and fluoroquinolones

Prevention: avoid exposure (don’t eat infected rabbits)

24
Q

Causative organism in Lyme disease?

A

Borrelia burgdorferi

25
Q

Features of Borrelia burgdorferi

A
  • loosely coiled spriochete
  • difficult to culture
  • evades immune effector cells and crosses intracellular junctions
26
Q

Reservoirs of Borrelia burgdorferi and location

A 
white-footed mice and deer
Ixodes tick (2 year life cycles-- humans are infected by bites from ticks in the nymph stage)
  1. Northeast
  2. Upper Midwest
  3. Far West
    Also: Europe, Scandinavia, Russia, China, Japan, Australia
27
Q

lyme disease: cutaneous features

A

spreading erythema with pale center at the site of a tickbite is called “erythema chronicum migrans” (“bulls eye rash”)

28
Q

lyme disease: MSK sx

A

joint symptoms may be present early, but frank large joint arthritis (esp. knee) usually occurs months after exposure

29
Q

lyme disease: neurologic features

A

manifestations of aseptic meningitis, encephalitis, cranial or other radiculoneuritis, or myelitis may be seen weeks to months or even years after the onset of infection.

30
Q

lyme disease: cardiac sx

A

conduction block

31
Q

Diagnosis of Lyme disease

A
  • clinical features
  • serology in later disease (but can’t distinguish between previous and active disease)
  • ELISA w/ confirmation by Western blot

Rule out infection with: Babesia, Ehrlichia or tick-borne encephalitis

32
Q

Tx of Lyme disease

A

doxycycline is effective in early disease, and also treats possible co-infection with Ehrlichia

alternatives: amoxicillin, cefuroxime, azithromycin

parenteral ceftriaxone x2-4 weeks used in neurologic infection

Prevention: insect repellant and check for ticks

33
Q

Lyme Vaccine

A

No longer available. Why?

  • costly
  • effectiveness less than 80%
  • 1,000 adverse event reports filed against it (arthritis-like side effects among other complaints)
  • caused 4 deaths
34
Q

Correcting card

A

Correcting card

Infectious Disease Unit 2 (22 decks)

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