ZOONOSES

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ZOONOSES PAUL A. GULIG, PH.D.
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I. Encounter - What all of these diseases have in
common is the animal reservoir. Humans are
usually an accidental, dead end host. There are
a couple of exceptions, and one related disease
(typhus) has only a human host with an arthropod
vector. Most are not transmissible between
humans. With the exceptions of Lyme disease,
Rocky Mountain Spotted Fever and Ehrlichiosis,
these are extremely rare in the United States
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II. Entry - Many are through the bite of an
arthropod vector, some from an animal bite some
from inhalation of contaminated materials or
animal droppings, some from ingestion of
food. III. Spread - All of these infections
spread beyond the initial site of inoculation and
become systemic to varying degrees. IV. Multiplic
ation - many are fastidious and require special
media, the rickettsia require tissue culture.
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V. Evade defenses - Since most of these
infections spread, phagocytes and complement must
be dealt with. Most are intracellular pathogens,
and many are intracellular pathogens of
phagocytes VI. Damage - inflammation,
intracellular cytotoxicity, few have overt
exotoxins. VII. Spread to new hosts - see. I. -
humans are usually a dead-end host.
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Borrelia bergdorferi A. gram-negative
spirochete
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B. Disease - Lyme disease (Lyme borreliosis) -
thousands of cases per year C. Diagnosis -
clinical presentation and serology D.
Encounter/entry - deer tick bite nymphal stage
(very small) more likely than adult mice are
immediate reservoir, but deer are essential for
tick life cycle E. spread - yes - through
skin and body
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F. Damage - 1. Stage one Early infection - 3
- 30 days after bite - Bull's eye rash - erythema
chronicum migrans, painless flu-like symptoms -
fever, chills, myalgia, fatigue, headache
secondary skin lesions possible arthralgia
endothelial infection 2. Stage 2 Early
dissemination - weeks to months later -
neurologic and sometimes cardiac involvement
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3. Latent stage 4. Third stage chronic -
arthritis of large joints also chronic
progressive neurological disease immune response
to persistent bacterial antigens? 5. Autoimmunit
y ?
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G. Spread to new human hosts no H. Vaccine
discontinued because of poor sales!
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RICKETTSIACEAE A. General characteristics 1.
Gram-negative coccobacilli (Giemsa stain best)
2. 4 genera in this class a. Rickettsia b.
Bartonella c. Coxiella (does NOT cause skin
rash) d. Ehrlichia
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RICKETTSIACEAE 3. Unique characteristics a.
All transmitted by arthropods except i.
Bartonella direct contact ii. Coxiella
aerosol inhalation (Q fever) b. Obligate
intracellular parasite of i. Endothelial
cells Rickettsia ii. Leukocytes other
genera.
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Rickettsia rickettsii a. Disease - Rocky
Mountain spotted fever (mainly in eastern US),
100s of cases per year in U.S. b. Clinical
manifestation i. Acute onset of fever,
headache, myalgia, abdominal pain ii. Rash
(macular, petechial) begins on palms and soles,
ankles/wrists and spread to truck. iii.
Aseptic meningitis, conjunctivitis, ARDS.
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Rickettsia rickettsii c. Diagnosis i.
Clinical diagnosis by typical rash ii.
Immunofluorescent stain of skin/tissue biopsy.
iii. serological test iv. (old Weil-Felix
test - detect cross-reactive antibodies to
Proteus).
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d. Encounter/entry - wood tick and dog tick from
dogs or rodents tick is both vector and
reservoir e. Spread - yes - through body
causing vasculitis use actin polymerization like
Listeria and Shigella f. Multiplication -
requires tissue culture unlike Chlamydia - no
developmental stages, but escapes vacuole to live
within cytoplasm
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g. Evades defenses - intracellular h. Damage
- 2 - 6 day incubation period infection of
vascular endothelium resulting is rash,
hemorrhage, thrombosis, and edema (macules
progressing to petechial lesions) rash spreads
from hands and feet to trunk (presence of rash on
palms and soles - unique characteristic) can be
fatal if untreated i. Spread to humans - no
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Other Rickettsia (name recognition)
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Ehrlichia chaffeensis (100s of cases/yr) -
transmitted by tick - asymptomatic to fatal -
Classic presentation fever, headache, myalgia.
- Infects white blood cells. - Important lab
test thrombocytopenia, leukopenia. lt50 develop
rash. - Serological test - anti-Ehrlichia
antibodies
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Bartonella henselae 1. cat scratch disease -
benign local lymphadenopathy 2. bacillary
angiomatosis (AIDS) - proliferative vascular
lesions in dermis and internal organs 3.
Diagnosis - Biopsy/stain, PCR, serology
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Bacillus anthracis A. Gram-positive rod, aerobic
spore former B. Disease - anthrax cutaneous,
inhalation, ingestion - (usually only a few cases
of cutaneous in U.S. each year) C. Diagnosis -
epidemiology, culture, chest X-ray for
inhalation D. Encounter - exposure to animal
products contaminated with stable spores E.
Entry - breaks in skin and lungs F. Spread - yes
throughout blood with inhalation, possible with
cutaneous
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G. Evasion of defenses 1. poly-glutamate
capsule (exception to carbohydrate rule)
antiphagocytic 2. toxins inhibit phagocyte
function H. Multiplication 1. spores
germinate in macrophages 2. vegetative cells
replicate extracellularly
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I. Damage - potent cytotoxic A-B exotoxins 1.
B portion protective antigen (PA) 2. A
portions a. Lethal Factor (LF)
protease interferes with signal
transduction b. Edema Factor (EF) - adenylate
cyclase interferes with PMN motility 3.
Holotoxins a. PA LF Lethal Toxin b.
PA EF Edema Toxin
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1. cutaneous - entry at skin papule
progressing to vesicle, ulcer, ultimately an
eschar (black lesion) and edema - called a
"malignant pustule" rarely fatal 2. lung
(Wool sorter's disease) flu-like illness
progressing rapidly to respiratory distress,
cyanosis, edema of neck and chest, shock, fatal
if untreated J. Spread to humans - No
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Pulmonary Anthrax
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Biologist Dies Of Plague In Arizona Man Performed
Necropsy On Infected Mountain Lion POSTED 537
am PST November 11, 2007 PHOENIX
-- A wildlife biologist at Grand Canyon National
Park most likely died from the plague contracted
while performing a necropsy on a mountain lion
that later tested positive for the disease,
officials said Friday, reported WCVB-TV in
Boston. The death last week of 37-year-old Eric
York triggered a health scare that led to 49
people who had contact with him being given
antibiotics as a precaution. None have shown
symptoms of the sometimes-fatal disease. York,
who worked in the park's cougar collaring program
and grew up in Massachusetts, became ill on Oct.
30 and called in sick for a couple of days before
being found dead in his home on Nov. 2. Testing
after his death was positive for the
plague. York's symptoms were consistent with
pneumonic plague, the most serious but least
common form of plague. The biologist had skinned
the lion and was exposed to its internal organs
during the necropsy he performed three days
before developing symptoms, said David Wong, an
epidemiologist for the U.S. Public Health
Service. The cougar, which had died from the
plague, was believed to have remained in
back-country areas where park visitors wouldn't
normally go, officials said.
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Yersinia pestis A. Gram-negative rod (bipolar
staining on Gram-stain) B. Disease - Bubonic or
pneumonic plague 1. bubonic - swollen, painful
lymph nodes, fever, septic shock in later
stages 2. pneumonic - flu-like illness
progressing to mucoid, bloody sputum dyspnea,
cyanosis rapidly fatal C. Diagnosis - culture,
stain of tissue/sputum, or serology
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D. Encounter 1. urban cycle (none in U.S.) -
fleas from rats (bubonic), human-human
(pneumonic) - with pneumonic plague - a human
with pneumonic disease can spread the organisms
via respiratory droplet - highly communicable
(requires isolation) 2. sylvatic cycle - fleas
from prairie dogs, deer mice, or rats less than
50 cases per year in western U.S. E. Entry -
bite on skin (bubonic) or lungs (pneumonic)
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F. Spread - yes - to draining lymph nodes
causing buboes (swollen, painful), through blood
throughout body (lungs can become infected by
septic emboli to for pneumonic plague) G. Evade
defenses, multiplication 1. after flea bite
grows within macrophages 2. then becomes
extracellular 3. deacylation of LPS -
antiinflammatory
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H. Damage - endotoxin shock-like symptoms due to
infection throughout the body (high fever,
myalgia), bubonic usually fatal if untreated
pneumonic 100 fatal if untreated I. Spread to
new human hosts - yes in pneumonic plague
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Eh, whats up Doc?
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Francisella tularensis A. Gram-negative rod B.
Disease - Tularemia (Rabbit Fever) after
ingestion - influenza-like to typhoid fever-like
syndrome with fever ulceroglandular form - ulcer
at inoculation, adenopathy at regional nodes
other localized sites possible C. Diagnosis -
usually NOT cultured to prevent lab infections
serology usually done
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Francisella tularensis D. Encounter and entry -
many different wild animals - rabbits deer,
rodents usually through arthropod vector but
also by direct contact with animal (e.g. skinning
a rabbit), inhalation (very low i.d.) or
eating E. Spread - yes, from the site of
inoculation into the regional lymph nodes F.
Evasion of defenses/multiplication -
multiplication in macrophages
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Lawnmower Tularemia The term lawnmower
tularemia was first used about a decade ago to
describe two cases of pneumonic tularemia in
adolescent males who ran over a dead rabbit while
mowing a grassy area. Neither youth touched the
remains of the animal, suggesting an aerosol of
bacteria was sufficient to cause infection. Both
individuals were hospitalized, treated with
streptomycin, and recovered. Hence, in endemic
areas, use of protective clothing and face masks
may be warranted. (A.S.M. News)
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LEPTOSPIRA 1. Microbiology spirochete,
detected by dark field 2. Disease biphasic
illness a. First phase bacteremic 1 week
i. Nonspecific fever, headache, conjunctival
suffusion, GI complaints, myalgia, rash ii.
bloodstream ? organs (liver, kidney) ? jaundice,
hemorrhage, renal failure iii. Resolution of
fever - humoral response (immune phase).
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LEPTOSPIRA b. Second phase immune phase
occurs 2 days after the first phase 1-4 weeks
aseptic meningitis, conjunctivitis, diffuse
lymphadenopathy, hepatosplenomegaly. c. Weils
syndrome (icteric leptospirosis) after first
phase triad hemorrhage, jaundice/hepatitis,
renal failure. Creatinine phosphokinas (CPK)
extremely high due to myositis.
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5. Spread to human host No 6. Damage a.
Toxin - displaces long-chain fatty acids from
host endothelial cells -gt breakdown of blood
vessel wall ? spirochete dissemination. b.
Thermolabile hemolysin.
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Brucella abortus A. Gram negative rod,
coccobacillus B. Disease - Brucellosis
(undulate fever, Malta fever) - very rare
(couple of 100 cases in U.S.) - fever, back or
limb pain splenomegaly - long course
(months) C. Diagnosis - culture or serology
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Brucella abortus D. Encounter - occupational
exposure to infected animals (ranchers,
slaughterhouse, veterinarians), contaminated
milk no arthropod vector E. Entry -
inhalation, ingestion, cuts in skin F.
Multiplication, evade defenses - lives within
macrophages in reticuloendothelial system
(spleen, liver, lymph nodes, bone marrow), avoid
killing by PMNs likes erythritol
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3. Diagnosis a. Culture CSF, blood, urine
low yield b. Dark field microscopy () only
during early infection. c. Serology ELISA
4. Encounter/entry a. Ingestion or contact
with contaminated urine from infected domestic
animals (dogs, sheep, cattle, goat, sheep) or
rats. b. Broken skin and mucous membrane.
c. Occupational hazard for farmers,
veterinarians, hunters.
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Sorry that this is such a ZOO!