Rickettsia/Lyme Disease/Zoonotic Disease Flashcards
Describe Rickettsia
intracellular infection of endothelial cells with perivascular lymphocytic infiltrate (perivascular cuffing)
General characteristics of Rickettsia
small, gram-neg. obligate intracellular bacteria that inhabits ticks, mites, fleas or lice
What appears at the inoculation site of a rickettsia infection
dark, swollen, crusted lesion (eschar)
where do rickettsia multiply?
mainly in small vessel endothelia
severe manifestations of rickettsial infection are due to
vascular leakage secondary to endothelial cell damage
What do rickettsial infections not have
no exotoxins or endotoxins (LPS is nontoxic)
What immune response is responsible for rickettsial infections
cytotoxic T-cells
Epidemic typhus method of transmission
head lice
prisons, concentration camps, refugee camps
symptoms of epidemic typhus (R. prowazekii)
begins with centrifugal rash followed by CNS involvement in the form of apathy, dullness, stupor, and even coma
high fever, chills, cough, rash, severe muscle pain, sensitivity to light, delirium
severe epidemic typhus
gangrene of fingers, nose, earlobes
fatalities with epidemic typhus increased with
G6PD deficiency (african americans)
syndrome related to epidemic typhus transmitted by fleas on rodents
murine typhus
important pathological markers for epidemic typhus
mononuclear cuffing of vessels, ecchymotic hemorrhages of affected organs
Rocky mountain spotted fever
R. rickettsi; tick bite
What kind of tick carries R. rickettsi
ixotid or hard ticks - American Dog Tick, Rocky Mountain Wood Tick
Disease progression of rocky mountain spotted fever
incubation period 7 days
high fever for 2-3 weeks, nausea, vomiting, headache muscle pain restlessness, insomnia
describe rocky mountain spotted fever rash
extends over entire body, including palms and soles; rare eschar
begins on periphery (palms, wrists, soles) and spread to trunk, neck and face
major cause of death with rocky mountain spotted fever
noncardiogenic pulmonary edema
morphology of rmsf
perivascular mononuclear infiltrate
necrosis, fibrin extravasation, and thrombosis of small blood vessels and arterioles
foci of necrotic skin
microthrombi, microinfarcts in brain
Where is scrub typhus group endemic
Far east, china, india
scrub typhus group caused by
Orientia (formerly Rickettsia) tsutsugamushi
scrub typhus is transmitted by
lice
Ehrlichiosis (Erlichia chaffeensis or Anaplasma phagocytophilum)
no eschar, rare rash
infects neutrohpils or monocytes, not endothelial cells
characteristic histology or Ehrlichiosis infection
cytoplsmic inclusions (morulae) - shaped like mulberries, masses of bacteria
Ehrlichiosis transmitted by
dog ticks, and deer ticks
Describe lyme disease (Borrelia burgdorferi)
spirochetes transmitted to man by tick bites from animals or lice (man to man)
type of tick that carries lyme disease?
tick of the white-tailed deer, which also infects dogs, horses and people
how does borrelia avoid host production of antibodies
shift antigenic markers
local lyme disease lesion progresses to
bacteremia and chronic inflammatory lesions in distant organs
lyme disease skin rash shows
vasodilation with dense perivascular inflammatory infiltrates of mononuclear leukocytes
prevention of lyme disease
OspA vaccine commercially available forhigh risk groups; vector avoidance;
therapy: doxycycline
pathogenesis of lyme disease
bacteremia disseminates the spirochetes to many organs with focal necrosis, hemorrhages
late manifestations include chronic arthritis, polyneuropathy, and encephalitis
primary disease of lyme disease
initial bulls-eye lesion appearance with spreading erythematous margins and a blanching center known as erythema chronicum migrans
fever and constitutional symptoms
secondary lyme disease
bacteremic dissemination of spirochetes
most victims complain of joint disease weeks to months after initial inoculation o the organisms
also muscle, pain, cardiac arrhythmias, meningitis with CN involvement
tertiary lyme disease
CNS, cardiac, and skeletal involvement in later stages
morphology of lyme disease
lymphoplasmacytic infiltrates
synovial hyperplasia with lymphocytes and plasma cells
onion-skin arteritis
Describe Borrelia recurrentis (relapsing fever)
spirochete; transmitted by human lice (B.hermsii) or rodent ticks (B. recurrentis) to humans
Describe the disease characteristics of relapsing fever
1-2 week latent period; shaking chills, fever, headache and fatigue
fatal disease is accompanied by massive enlargement of spleen and liver
successive attacks of borrelia recurrentis is from
results from the ability of the organism to express new surface antigens; with each wave of attack, the body must make new antibodies to clear the organism
Describe the plague organism
gram-negative bacillus
mode of transmission of the plague
arthropod bite; man’s an accidental victum of cycle where organism spreads among wild animals; especially rodents “sylvatic cycle”
Forms of Disease from the Plague
- minor plague - prominent lymphadenopathy and constitutional symptoms
- bubonic plague - buboes (most common form)
- pneumonic plague - hemorrhagic, necrotizing pneumonia primary or secondary to (2)
- septicemia (rapidly fatal)
Pathologic mechanisms of the plague (Yersinia pestis)
rapid proliferation of organisms within lymphoid tisues
injection of toxins (YOPs) that kill host cells - inhibits actin and cytokines
necrosis of tissue and blood vessles; swelling of lymphoid tissue
striking leukocytosis; septicemia/DIC
Tularemia (Francisella tularensis)
pleomorphic gram-neg coccobacillus; facultative, intracellular
How do you get tularemia
contact with rabbits or rabbit skins; direct contamination of skin or conjunctiva by organism
forms of disease from tularemia
- ulceroglandular tularemia: local skin lesion ulcerated pustule enlargement of lymph nodes, bacteremic phase
- primary or secondary pulmonary infection with ilar lymphadenopathy
- oculoglandular form
Pathologic mechanisms of tularemia
purulent necrosis and granulomatous reactions, leukocytosis not striking
fatalities associated with endotoxin-like reactions
Pet-related diseases
pasteurela multocida (cats) Bartonella henselae (cats) Toxoplasmosis (cats) Chlamydia psittaci (birds) Leptospirosis (dogs) rabies (wild dogs, raccoons, foxes, skunks, coyotes)
Live-stock related diseases
Bacillus anthracis (sheep and goats) Listeria moncytogenes Brucella (goats, cows, pigs, dogs) Q fever (ticks from sheep and cattle) Glanders (pseudomonas mallei)/Meliodosis (Pseudomonas pseudomallei) - horses, donkeys and mules
Pasteurella multocida
gram neg. coccobacillus present in the oral cavity of many species
rapidly developing cellulitis, abscesses, sepsis
systemic infections require IV Abx (augmentin)
Bartonella henselae (Cat-scratch disease)
self-limited bacterial infection giving rise to localized lymphadenopathy
associated with kittens and fleas
Bartonella henselae in people with AIDS
bacillary angiomatosis
multiple skin nodules with vasular proliferation distinct from Kaposi’s sarcoma
Ornithosis (Chlamydia psittaci)
inhalation of dust-borne contaminated excretia from birds
pneumonia may involve severe dyspnea
interstitial inflammation with edema, hyperemia, mononuclear infiltration
lethal generalized disease caused by Chlamydia psittaci
marked by focal necrosis in liver and spleen; diffuse mononuclear infiltrative changes in kidneys, heart and brain
Salmonellosis transmitted by
turtles, reptiles
Toxoplasmosis gondii is an
obligate intracellular protozoan
Clinical syndromes of toxo
- infection of mother in 1st trimester leads to severe disseminated infection - transplacental transmission
- congenital or 3rd trimester infection may lead to chorioretinitis and blindness
- AIDS or immunosuppressed: encephalitis
pathogenesis/pathology of toxo
- able to infect all types of cells; binds to laminin receptors on host cells
- in normal person, infection is characterized by lymphoid hyperplasia
- extensive destructive lesions of the CNS as well as liver, heart lungs and adrenals in immunosuppressed/neonates
- reaction of latent infection in AIDS
Describe the disease caused by Leptospira interrogans
mild disease: acute, self-limited febrile illness with biphasic fever and meningeal irritation; conjunctival irritation and hyperemia
Leptospirosis is a common disease in
dogs
organism excreted in urine; also transmitted by direct contact with water contaminated with animal products, urine; hazard to campers and swimmers
lymphocytic atypical meningitis
severe leptospirosis with jaundice, bleeding and renal failure
Weil’s disease
pathogenesis of Leptospira interrogans
leptospirae quickly disseminates through the liver, spleen kidneys CNS with little cellular reactions, resembles viral meningitis
Rabies caused by
rabies virus transmitted to humans by contamination of open wounsd or mucous membranes by saliva from infected animals
rabies lesions characterized by
presence of Negri bodies in nerve cells; can only be diagnosed by direct examination of brain tissue from infected animal
lymphocytic choriomengintis virus
hamsters and other pocket pets/immunosupressed
Anthrax organism
highly pathogenic, encapsulated, gram-positive, large spore producing rod
Anthrax mode of transmission
contact with animals, animal hides, or animal products, particularly sheep and goats
forms of disease from anthrax
- cutaneous disease - small hemorrhagic pustule develops into black eschar with very painful lymphadenitis
- pulmonary disease - woolsorter’s disease; extensive pneumonia with serofibrinous exudation, development of septicemia
pathologic mechanims of anthrax
antiphagocytic activity, edema factor, cytotoxic factor
antrax infections associated with
leukopenia, bacteremia may give rise to meningitis, electrolyte imbalance, hemoconcentration and DIC leads to death
Main point of anthrax as a weapon of biological terror
potential weapon of biological terrorism due to stability in environment, high virulence and ease of respiratory transmission
Listeria monocytogenes
small gram positive rod, facultative psychrophile, microaerophilic motile rode
Forms of disease from listeriosis
- abortion; maternal infection may be inapparent
- neonatal sepsis with leptominingitis
- meningitis in immunosuppressed adults
pathologic mechanisms of listeria
exudative meningitis with numerous gram positive rods in CSF
Brucellosis organism
gram neg aerobic coccobacilli
method of transmission of brucellosis
contact with infected tissues (esp aborted fetuses and placentas)
unpasteurized milk and milk products
occupational exposure for veterinarians, meat workers
Pathologic mechanism of brucellosis
intracellular habitat and macrophage activation is essential for halting their growth
Q Fever (Coxiella burnetti)
- headahce, cough, myalgia, lymphadenopathy, hepatosplenomegaly
- rare pneumonias
