Zoonotic Disease

Question 1

Zoonotic disease definition

Answer 1

infections that are transmitted between humans and other animals

Question 2

Factors influencing zoonotic infections

Answer 2

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).

Question 3

Causative organisms in the plague

Answer 3

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

Question 4

Yersinia pestis features

Answer 4

• 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

Question 5

Y. enterocolitica/Y. pseudotuberculosis cause…

Answer 5

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

Question 6

animal reservoirs of Y. pestis

Answer 6

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

Question 7

Enzootic foci

Answer 7

-stable rodent-flea reservoirs of infection

Question 8

epizootic plague

Answer 8

results from introduction into a new susceptible mammal population

Question 9

zootic plague

Answer 9

transmission from animal host to humans

Question 10

Location of plague cases in US and world

Answer 10

Southwestern US and Colorado from May-October

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

Question 11

Clinical features of bubonic plague

Answer 11

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

Question 12

Clinical features of septicemic plague

Answer 12

fever, hypotension

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

Question 13

Clinical features of pneumonic plague

Answer 13

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

***transmitted human to human

Question 14

Diagnosis of plague

Answer 14

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

Question 15

Tx of plague

Answer 15

streptomycin; supportive care

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

Question 16

Prevention of plague

Answer 16

rodent and vector control

-killed vaccine gives short term protection to high risk indiv

Question 17

Tularemia: associated animal; how infectious is it?

Answer 17

• 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

Question 18

Features of Francisella Tularensis

Answer 18

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

Question 19

Groups commonly infected with F. tularensis?

Answer 19

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

Question 20

Does F. tularensis spread person-to-person?

Answer 20

NO!

Y. pestis can: pneumonic plague

Question 21

Clinical features of F. tularensis

Answer 21

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.

Question 22

Diagnosis of F. tularensis

Answer 22

• cultures need special media

- serologies positive in most pts by 1-2 weeks

Question 23

Tx for F. tularensis

Answer 23

streptomycin or gentamicin;
alternatives: tetracycline, chloramphenicol and fluoroquinolones

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

Question 24

Causative organism in Lyme disease?

Answer 24

Borrelia burgdorferi

Question 25

Features of Borrelia burgdorferi

Answer 25

- loosely coiled spriochete - difficult to culture - evades immune effector cells and crosses intracellular junctions

Question 26

Reservoirs of Borrelia burgdorferi and location

Answer 26

``` 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

Question 27

lyme disease: cutaneous features

Answer 27

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

Question 28

lyme disease: MSK sx

Answer 28

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

Question 29

lyme disease: neurologic features

Answer 29

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.

Question 30

lyme disease: cardiac sx

Answer 30

conduction block

Question 31

Diagnosis of Lyme disease

Answer 31

- 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

Question 32

Tx of Lyme disease

Answer 32

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

Question 33

Lyme Vaccine

Answer 33

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

Question 34

Correcting card

Answer 34

Correcting card