Zoonosis Flashcards
one health
worldwide initiative that recognizes that human health is connected to animal health and our shared environment
when was one health first used?
in 2003-2004 associated with SARS (severe acute respiratory disease) emergence and then subsequently by the spread of highly pathogenic avian influenza H5N1
who was the 1st president for one health?
Dr. Mahr from ISVMA
zoonosis
diseases passed between animals and humans
at least 61% of human pathogens are zoonotic
reverse zoonosis
pathogen that humans can pass to animals
endemic
usual level of disease in a geographic area
epizootic
disease cases in animals in excess of normal
animal version of an epidemic
epidemiology
study of disease
reservoir host
living organism that harbors a pathogen
amplification host
host that develops high concentration of pathogen
sentinel
organism that reacts to contaminant/pathogen before impact to people
seroprevalence
number of seropositive individuals in a population
herd immunity
increasing proportion of resistant individuals which decreases susceptible population
what are sentinels used for?
they are good epidemic indicators and bioterrorist event indicators
seropositive
presence of an organism or antibodies
allows us to predict epidemics
sylvatic transmission
animals living in their native habitat get sick and it spills over to us
domestic transmission
animals residing in our homes/work get sick and then we contract it from them
peri-domestic transmission
overlap of species disease transmission
spill-over
when disease amplifies in its natural cycle to a level to where it spills over into humans
direct contact disease transmission
bite, scratch, contact with infected tissues
ex: rabies, Q-fever, ringworm, herpes B
indirect contact disease transmission
food/water borne or touching infected object (fomite)
ex: Salmonella, E. coli, Giardia
aerosolization disease transmission
inhalation, contact with respiratory droplets
ex: brucellosis, psittacosis
vector-borne disease transmission
mosquitoes, ticks, fleas
ex: Rocky Mountain Spotted Fever, West Nile Virus
what 4 things do we look for when tracking a possible bioterrorism threat?
- clustering of illness of humans or animals
- unusual age distribution
- illness outside usual season
- disease unusual for geographic area
case fatality rate (CFR)
proportion of infected animals that die from a disease
CDC rating pathogen system
CDC rates agents by how easily they are disseminated, mortality rate, and public panic they cause
CDC category A pathogens
easily transmitted person to person, high mortality, potential for public panic and social disruption
why would livestock be targeted for bioterrorism?
it would be disastrous for our food supply
class A bioterrorism
extremely infective to animals and humans, easy to procure from animal reservoir, can easily be grown in large quantities
aerosolized dispersal can lead to extended infections of potentially fatal pneumonia and food/water contamination
prions
causes bovine spongiform encephalitis, chronic wasting disease, scrapie, Creutzfeldt-Jakob disease (vCJD)
dermatophytosis
“ringworm”
fungal infection starts as red, itchy, scaly circle
40 types of fungi can cause ringworm: trichophyton, microsporum spp.
tx: antifungals for 2-3 weeks
toxoplasmosis
cat eats infected prey
protozoal parasite
T. gondii burrows into walls of the cat’s small intestine forming early stage cells called oocysts that the cat eliminates in feces usually for a period of 2-3 weeks
can cause abortions in pregnant women as well as birth defects and AIDS in immunocompromised people
how are protozoans transmitted?
accidental ingestion (usually water)
Giardia hosts
dog, cat, cattle, pig, primates
Cryptosporidia hosts
large animals, wildlife
reptile strain not shown to be zoonotic
shows acid fast positive
Balantidium hosts
pigs, primates
Sarcocystis hosts
cattle, pigs
Chagas
American trypansomiasis
seen in tropics, causes sleeping sickness
flagellate protozoan that transmits through vector or contaminated food
vector: kissing bug; bite then defecate near bite
commonly seen in poverty, vet occupation, hunters
Chagas CS
acute phase: flu-like symptoms with chagoma and/or romanas
indeterminant phase: asymptomatic for 5-40 years, parasite disappears from blood
chronic phase: organ failure, fatal if untreated, causes abortions in pregnant women
Scabies
sarcoptes scabiei
transmisison: direct contact
self limiting in humans
CS: rash, itching
control by treating animal source
serious outbreak in animals when they are immunocompromised
larva migrans
transmission: fecal-oral
toxocara, Ancylostoma, Strongyloides, Baylisascaris
Toxocara
common dog roundworm
Ancylostoma
dog hookworm that causes cutaneous larval migrans
Strongyloides
moves more quickly through the skin
Baylisascaris
poor prognosis especially if it enters the brain, eye, lung
humans CS: cough, wheezing, abd pain, strabismus, blindness
Hydatidosis
Echinococcus: tapeworm
proglottids are identical to Taenia
hosts: dogs, wolves, herbivores
transmission: fecal-oral
can take up to 20 years for symptoms to occur
cysts mostly found in liver, lungs, or brain
Trichinosis
round worm
host: pigs
transmisison: ingestion
common from eating wild game, especially where beef is mixed with a little pork
Schistosomiasis
“Bilharzia”, snail disease
seen in tropics, not US
host: snail
transmission: contact with fluke
in US we have “swimmer itch” related fluke
Leptospirosis
spirochete
transmission: direct (shed in urine), indirect (environmental)
can’t live in dry environment, requires high humidity
control by vaccinating, antibiotics, good hygiene, don’t drink stream water
Leptospirosis animal CS
icterus, bloody diarrhea, renal failure
Leptospirosis human CS
mild form: non-specific CS
severe form: multi-organ failure/meningitis
Tuberculosis (TB)
humans susceptible to all 3 strains
cell-mediated hypersensitivity
Mycobacterium bovis TB strain
rare transmission in US
hosts: cattle, deer
M. tuberculosis strain
reverse zoonosis
hosts: humans, birds, elephants, mammals
prolonged contact with actively infected individual
M. avian TB strain
causative agent of Johne’s disease
host: birds
seen in patients with Crohn’s disease
Q-fever
Coxiella Burnetti
can live in environment for 6 months
sheep and goats are the most common reservoir
transmission: aerosol
Q-fever animal CS
subclinical or spontaneous abortions
Q-fever human CS
50% subclinical, 50% flu-like symptoms
hepatitis, encephalitis
chronic form: endocarditis (infection of heart valves) which leads to night sweats, fatigue, shortness of breath, weight loss, limb swelling
Q-fever tx
long-term antibiotics
Q-fever prevention
hygiene, pasteurization, vaccines
cat scratch fever
Bartonella henselae
host: felids
cats become infected through flea bites, fights with infected cats, or blood transfusions
most cats are subclincal
transmission to humans: cat bites/scratches
cat scratch fever human CS
lymphadenitis, abscess at lesion, fever, malaise, splenomegaly
cat scratch fever tx
supportive care
difficult to eliminate with antibiotics
most human cases are self limiting
psittacosis
Chlamydia psittaci
associated with pet birds
called ornithosis when not from a psittacine
transmission: fecal dust, direct contact (bites, beak-to-mouth contact)
psittacosis CS
flu-like symptoms that initially mimic typhoid fever, prostrating high fevers, joint pains, diarrhea, conjunctivitis, nose bleeds, low WBC levels
rose spots called Horder’s spots may develop and can turn into pneumonia
bird fanciers lung
immune mediated
hypersensitivity pneumonitis caused by inhalation of bird dropping extracts and antigens in feathers
high mortality
Lyme disease
Borrelia Burgdorferi
midwestern/eastern US: Ixodes scapularis or deer tick are main vectors
primary reservoir host: white footed mouse
ticks in nymph stage cause the most cases due to their small size and painless bite
tick life stages
egg —> larva —> nymph —> adult
each stage after hatching they suck blood then drop off and enter dormant period, then molt to enter the next stage
how do you remove a tick?
gasp tick as close to skin as possible and pull straight out
save for ID
Lyme disease animal CS
lameness, lymphadenitis
Lyme disease erythema migrans
appears at the site of the tick bite ~ 7-10 days afterwards
CS: red papule that expands into a large lesion, fever, myalgia, arthralgia, malaise, headache, stiff neck, lymphadenopathy
can cause development of dyspnea, uveitis, and memory loss
Lyme disease erythema migrans secondary smaller migrans CS
secondary smaller lesions form 3-5 weeks after bite along with facial nerve palsy, dizziness, syncope, chest pain, palpitations, dyspnea, uveitis, meningitis
Lyme disease late stage CS
autoimmunity, arthritis, meningitis, encephalitis
Brucellosis
undulant/malta fever or Bang’s disease
caused by Brucella spp. (B. abortus in cattle, B. canis in dogs)
transmission: direct contact, ingestion, inhalation
very resistant to environmental changes
Brucellosis animal CS
abortions, orchitis (inflammation of testes), lymphadenitis
Brucellosis human CS
undulating fever, muscle and joint pain, lymphadenitis, meningitis/carditis
fatal if untreated
anthrax
“wool sorters disease”, Bacillus anthracus
spore formers that are released from dead/dying host
over 1,200 strains
very resistant
wool sorters have contact with spores in sheep’s wool and can get cutaneous form
what are the 3 different forms of anthrax?
- cutaneous: spores found on animal products or in soil
- ingestion: contaminated meat
- inhalation: spores on animal products or terrorism
anthrax inhalation phases
1st phase: flu-like symptoms
2nd phase: dyspnea, bloody vomit/diarrhea, sepsis, death within 24-36 hours
Rocky Mountain Spotted Fever
Rickettsia rickettsi
tick vector: American dog tick in this area (Dermacentor), Brown dog tick in South (Rhipicephalus)
takes a while to transmit: minimum 4 hours
found in small animals and wildlife
Rocky Mountain Spotted Fever dog CS
flu-like symptoms
severe form: neurologic signs, bleeding, heart damage
Rocky Mountain Spotted Fever human CS
flu-like symptoms followed by rash and neurologic, pulmonary, and circulatory damage
Tularemia
rabbit fever
Francisella tularensis is a highly infectious bacterium that causes it
can survive 3-4 months in mud, water, or dead animals and is infective for > 3 years in frozen rabbit meat
US reservoir hosts: cottontail rabbits, ticks, deer flies
transmission: aerosol, insect bite, direct contact, ingestion
Tularemia BTT and prevention
BTT: food, water, aerosol
prevention: avoid mowing over dead animals, wear gloves when handling sick animals, insect repellent
Tularemia animal CS
swollen lymph nodes, ulcers, diarrhea, weakness, dyspnea
Tularemia in humans
ulceroglandular is most common form: skin ulcer appears at site of transmission
glandular form: lacks ulcer
transmission: vector bite, contact with infected animal
all cases start with flu-like symptoms but can progress to pneumonic if untreated
Tularemia: oculoglandar and oropharyngeal forms
oculoglandular transmission: eye (ex: butchering an animal and rubbing eye); CS: irritation and inflammation of eye, swelling of lymph glands in front of ear
oropharyngeal transmisison: contaminated food; CS: sore throat, mouth ulcers, tonsillitis, swelling of lymph glands in neck
Tularemia: pneumonic and typhoidal forms
pneumonic transmission: aerosol or secondary to untreated forms, most serious form; CS: cough, chest pain, difficulty breathing, lung infiltrates
typhoidal: non-specific combination of other forms; CS: fever, myalgia, malaise
plague
Yersinia pestis
natural cycle in wildlife but spill-over occurs when there is epizootic
hosts: rodents, rabbits, cats (cats particularly susceptible)
dogs are incidental hosts and don’t usually become ill but can bring home fleas
vector: fleas
plague CS
Bubonic plague: buboes (swollen lymph nodes), flu-like symptoms, toxemia
septicemic from flea bite: purpura, epistaxis, hematuria, DIC, tissue necrosis
pneumonic: person to person transmission, least common form
plague tx
must begin within 24 hours of symptom onset for survival to be likely
