Zoonotic Infections Flashcards
zoonosis
an animal disease that is transmissable to humans, who are usually an accidental host
how is anthrax an animal reservoir?
we come in contact with the spores in the environment
emerging infectious disease
infection that has newly appeared in the population, or has existed but is rapidly increasing in incidence or geographic range
name 5 ways that zoonoses can be transmitted
direct skin penetration (micro-breaks in the skin), bites and scratches, inhalation, ingestion, vector-borne
name 2 zoonotic infections transmitted by direct skin penetration
anthrax, tularemia
microbiology of leptospirosis
spiral shaped aerobic spirochete seen by dark-field microscopy or culture (takes a long time)
how prevalent (generally) and in what part of the world is leptospirosis usually found?
most common bacterial zoonosis wordwide, usually in tropical countries
what are the two major sources of leptospirosis acquisition?
recreational exposure & traveling
name 4 risk factors for leptospirosis
fresh water swimming, hiking, rafting, fishing, poor sanitation, flooding, urban overcrowding (infected rats), farming
what are the common symptoms of leptospirosis?
abrupt onset fevers, rigors, myalgia, and headache, some get GI symptoms and cough, some are asymptomatic
how do you diagnose leptospirosis?
blood and CSF cultures are positive for the first 10 days of illness, urine becomes positive after that until day 30; can also identify by serology
name a bacterial and a viral zoonotic organism that is transmitted by animal bites and scratches
Pasteurella multocida (GNR - cats, dogs) & rabies virus (bats, skunks, raccoons, etc.)
what organism is responsible for cat scratch disease/fever?
bartonella henselae (fastidious, slow growing GNR)
epidemiology of cat scratch disease
found worldwide, effects more children, usually transmitted by kittens, fall/early winter, 13% of head/neck masses
what are the clinical manifestations of cat scratch disease?
wide variation; local infection with swollen regional lymph nodes, fever of unknown origin, skin papule at site of inoculation
how to diagnose cat scratch disease
culture requires specific media, histo can be helpful, PRC not very sensitive
microbiology of pasteurella multocida
gram-negative coccobacilli that are small, non-motile, and non-spore forming; aerobic and facultative; grow on blood agar; catalase, oxidase, indole, and sucrose POSITIVE
clinical manifestations of pasteurella
soft tissue infections (painful, swollen), bone and joint infections from cat claws, respiratory infections
how to diagnose and treat pasteurella
culture blood or body fluid on sheep blood agar, treat with penicillin
rabies virus
neurotropic bullet-shaped segmented negative strand RNA virus that binds to nicotinic ACh receptors
pathogenesis of rabies
retrograde passage up local motor and sensory nerves to DRG and CNS, spread back to organs, saliva from the CNS
why does rabies have such a long incubation period?
because its retrograde migration is very slow
what animals transmit the rabies virus worldwide? In the US?
worldwide usually dogs, wild animals in the US because we vaccinate our pets (raccoons on the east coast)
what happens once symptoms of rabies appear?
progressively worsening encephalopathy, come, and death
how can we diagnose rabies?
viral PCR of saliva, skin biopsy; can find antibodies in serum/CSF
what can be seen in a brain biopsy of someone who died of rabies?
negri bodies: eosinophilic inclusion bodies in cytoplasm of nerve cells
how to prevent rabies pre- and post-exposure
pre-exposure: 3 IM vaccine injections; post-exposure: wound care, immunoglobulin to the site, 5 doses of vaccine over one month
zoonotic infections transmitted primarily by inhalation
plague, Q fever, tularemia
what is the agent responsible for tularemia?
francisella tularensis (gram neg coccobacilli – requires time and cysteine to grow, but hardy in nature)
pathogenesis of tularemia
small inoculum, replicates in macrophages, capsule protects against serum-mediated lysis, type IV pili, LPS does NOT have classic endotoxin
what animals are the host for tularemia?
LOTS, including rabbits, ticks, deer flies, mosquitos, voles
where in the US is tularemia particularly prevalent?
Martha’s Vineyard, midwest
clinical manifestations of tularemia
2-10 day incubation, abrupt onset of fever, chills, headache, and malaise with swollen LN being the most common sign (6 major clinical syndromes, but most have ulcerogladular ds which has papulo-ulcerative lesion)
microbiology of plague bacteria
enterobacteriaceae family, non-motive, non-spore forming gram negative coccobacillus; microaerophilic
how to do humans acquire the plague?
bites by rodent fleas, infected domestic cats, aerosols, humans with plague
how to dx the plague
culture, serology, rapid diagnostic test
Q fever is caused by what organism?
coxiella burnetii (short pleomorphic strict intracellular rod – host cell is macrophage)
mammals infected with Q fever shed large amounts of organism is their?
milk and birth products
how is Q fever acquired?
contaminated aerosol, bioterrorism, transplacental, sexual, soil and standing water (SO BASICALLY EVERYTHING)
clinical presentation of Q fever
looks like pneumonia, flu, or hepatitis; can become chronic
diagnosis of Q fever
serologic: 90% have antibodies by week 3 (IgM and IgG for acute, high levels of IgG for chronic)
treatment for Q fever
14 days of doxycycline (acute) or 18 months if chronic
