Exam 1 Flashcards
Paratenic host
- intermediate host required for completion of lifecycle
* no development of parasite occurs
Percutaneous
o Made, done, or effected through the skin
Sporotrichiosis Basics & effects on humans vs cats
o Sporothrix schenkii o Dimorphic fungus o Soil saprophyte o Can be gotten from rose garden pokes o Reverts to yeast in tissue (37 degrees C)
Humans
• Nodular, ulcerative pyogranulomatous dermatitis.
• Nodules along lymph channels near surface of skin.
• Infrequently can affect lungs, joints, CNS
Cats
• Nodular, ulcerative pyogranulomatous dermatitis
• Adult cats are usually resistant
Sporotrichiosis Diagnosis, Treatment, Client Education
Diagnosis
• Cytology on exudates from lesion
• Looking for polymorphonuclear things
Treatment
• Itraconazole
Client Education
• potential for transmission from cat lesions.
• Wear gloves; wash hands
Classification of zoonoses based on hosts
Direct zoonoses
• One vertebrate host
• Transmission through contact, aerosol, vehicle, or mechanical vector
Cyclozoonoses
• 2 vertebrate hosts
Metazoonoses
• Biological vector
Saprozoonoses
• Has an environmental stage
Mycobacterium Species
M. tuberculosis:
• Human-to-human (elephants)
M. avium complex:
• disseminated disease in immunocompromised patients.
M. avium paratuberculosis:
• Johne’s disease, Crohn’s Disease?
Other “Atypical mycobacterial diseases”
• M. marinum (fish), M. chelonae (pedicures)
M. leprae:
• leprosy, human-to-human Armadillo-to-human
Reservoir & Hosts for M bovis
Reservoir for M bovis
• Cattle
• Does not multiply outside host
Hosts • Cattle, humans, swine, goats, dogs, rarely cats • White-tail deer, elk, bison • Badgers in the UK • Brush-tailed possums in New Zealand
Transmission of M bovis
Infected bovine to non-infected
• Aerosol or milk
Infected bovine to humans
• Mostly milk worldwide but more aerosol in US
Infected bovine to other animals
• Raw milk or aerosol
Humans to non-infected bovine
• aerosol
Vaccine for M bovis
- BCG vaccine
- Attenuated strain of M bovis
- Used for humans
- Can stimulate immune system in cancer patients
- Can cause infection in AIDS patients
Diagnosis of M bovis
• Histopathology of lesions using acid-fact stain will be (+)
for ALL Mycobacteria
Live animals
• Skin (antigen) testing
Postmortem
• Culture, PCR (NVSL)
Testing for M bovis in different species
- Done by accredited vets or state/fed vets
- Done for interstate or international shipment
Cattle bison goats
• Caudal tail fold test
Camelids
• Axillary skin region
Cervids
• Single cervical test
Performing a caudal fold test
- Inject 0.1 purified protein derivative, tuberculin Ag ->
- Return and read in 72 h +/- 6 h
- Vet who made the injection must be vet who reads test result.
- determine results by observation and palpation of site
US State Accreditation for Dz’s
- USDA-APHIS-VS regulate inter-state (between states) movement of livestock
- States regulate intra-state movement (state’srights)
- used for Bovine TB, Brucellosis, Equine Infectious Anemia
- Uniform rules are developed to control diseases
- Status is given to areas (states) free of disease
- Movement between areas (states) is less restricted when status is “free”
Basics of M avium & M tuberculosis
M avium
• No Federal control program
• environment is Reservoir
M tuberculosis
• Maintained in Humans & NH primates
• Some other animals are susceptible pigs, dogs
What does a (+) caudal fold test mean & what are the regulations?
Positive response
• delayed hypersensitivity ->
• TH1/macrophage response (cell mediated) ->
• Swelling ->
• Means the animal has been exposed
• Responder: (+) response
• Reactor: reacts specifically to M. bovis
Regulations for positive reactions • Reactors sent to slaughter • Post mortem inspection • No lesions -> pass carcass for cooking • Lesions -> condemn carcass
Taenia saginata (Cysticercus bovis) & Taenia solium (Cysticercus cellulosae) life cycle, & hosts
Lifecycle in human • Tissue cyst in animal -> • human eats undercooked meat & ingests cysticerci -> • shed eggs in feces -> • animal picks up eggs
Definitive Hosts
• House adult tapeworms
• T. saginata - Humans
• T. solium- Humans
Intermediate Hosts
• House larvae
• T. saginata – cows
• T. solium – swine
T. saginata & T. solium Dz in humans & control
Disease in humans • Taeniasis • rarely clinical • Human cysticercosis • serious, CNS and ocular
Control • Prevent infection in animals • Prevent access to human feces • Treat human cases • Meat inspection • “Measly beef” • Condemn carcass if severe • If can trim, require freezing or cooking before sale. • Cook meat well done
Rickettsia rickettsii (Rocky Mountain Spotted Fever); basics, hosts, & transmission
o Prefer endothelial cells -> vasculitis & rash
o Comes from Dermacentor & Rhipicephalus ticks
o Transmitted transovarian or transstadial
o Ticks infected for life
Hosts
• Wild rodents, lagomorphs, dogs. Opposums, humans
• Humans & dogs are dead end
Transmission
• Tick bite
Rickettsia rickettsii Dz in humans Vs animals
Dz in humans • Incubation: 2-14 days • Fever, chills, muscle • joint pain (flu-like) • Rash • Vasculitis • Tx greatly shortens clinical course • 15-20% fatal if not Txed • Most frequently reported rickettsial dz in U.S.
Dz in animals
• Inapparent in most wildlife
• Dogs: fever, abdominal pain, depression, lethargy, anorexia, neurological signs
• Thrombocytopenia
Rickettsia rickettsii Diagnosis, Treatment, Control
Diagnosis:
• Serology (paired sample)
• Isolation of organism from blood
• PCR
Reportable disease in humans in the U.S. G.
Treatment:
• Tetracycline, Doxycycline
Control
• Vector control
• Tick removal
Definitive Vs Intermediate Host
Definitive
o organism in which the parasite reaches the adult stage and reproduces sexually.
Intermediate
o organism which harbors the sexually immature parasite.
Management of Dogs, Cats, & Ferrets Exposed to Rabies
Unvaccinated
• Euthanize
OR
• Strict quarantine for 4 mo. (D + C) 6 mo. (F) ->
• vaccinate w/in 4 days or 1 month before release ->
• If unable to do at entry, extend isolation to 6
mo.
Vaccinated
• revaccinate w/in 4 days ->
• keep under owner’s control and observe for 45 days
Vaccinated, but not current
• case-by-case evaluation
Management of Livestock & Horses Exposed to Rabies
Previously vaccinated
• Revaccinate immediately ->
• Observe for 45 days
Unvaccinated
• Euthanize immediately
OR
• Close observation for 6 mo
Euthanized immediately after exposure
• Eat meat
Management of Animals that Bite Humans
Cat, dog, ferret
• 10 day observation
• do not vaccinate
• euthanize & test if develop rabies signs
Other animals
• Usually euthanize and test
Pre & Post Exposure Rabies Prohylaxis Humans; vx options
Pre
• People @ risk
• 3 injections @ days 0, 7, 21e
Post determined by • Biting species • Geographic location • Circumstances • Type of exposure
Rabies Biologics
• human diploid cell vaccine (HDCV), IM or ID (deltoid region)
• Purified Chick Embryo Cell Vaccine (PCEC)
• HRIg - neutralizing antibody
Protocol for Humans Post Exposure to Rabies
If not previously Vxd
• Wound cleaning
• 4 IM vaccinations (0, 3, 7, 14)
• HRIG on day 0 around and into the wounds.
• Any remaining volume injected IM at site distant from vaccine site.
If previously Vxd
• Wound cleaning
• 2 IM vx on day 0 & 3
• No HRIG
If Pregenant
• No indication of fetal harm due to Vx
Brucellosis abortus Basics Reservoir, other hosts, in humans, transmission
Reservoir
• Cattle bison elk
Other hosts
• Humans, horses, dogs
In humans
• Undulant fever or Malta fever and arthritis
• Raw milk or direct contact with infected animals or their fluids.
Brucellosis abortus Vaccine
- RB-51
- Approved for cattle in 1996
- Live Culture
- Rifampin & Penicillin resistant strain of B. abortus
- replaced the Strain 19 vaccine in cattle
- Antibodies to RB-51 can be differentiated from “wild type”
- Can cause abortion in bison
What to do if a human comes into contact with RB-51
- Prompt medical attention
* 3-week course of doxycycline
Disadvantages of Brucella Vx Strain 19 Still Used in Elk
Cattle
o abortion and orchitis
Humans
o Milder disease than field strain
o Accidental (usually self)
inoculation
o Human transmission not naturally transmitted
• Persistent titers
Brucella Suis Basics & Effects on Humans
o Focal granulomatous lesions in bones and joints
o Can cause endometritis, infertility
o USDA Eradication
Program
o No quarantined swine (domestic) herds left in the U.S.
Effect on Humans
• Pathogenic
• Direct contact w/ infected pigs
• Cases in hunters of feral swine
Brucella Suis State/Federal Eradication
- All intact swine >6mo must test (-) for brucellosis or originate from brucellosis-free herds
- All state currently brucellosis free
- Feral swine surveillance program
Brucella melitensis
o Effects goats, sheep, camelids o Not in US o Most pathogenic for humans o B. abortus VX does not protect o No approved VX o Also established in cattle in some European & middle eastern countries
Brucella canis
o Effects dogs
o Only ~30 cases ever reported
o Risk to humans very low
o Causes discospondylitis
Brucella Ovis
o Primarily causes epididymitis in rams
o Not zoonotic
o Shed in high numbers in uterine fluids -> abortion
o Transmitted orally through milk or fluids
Brucella & Food Safety
o Unpasteurized milk main source of human infection worldwide
o Meat not known to be source of infection
o Killed by cooking, acid pH, autolytic changes
Transmission & Entry for Brucella SPecies
Inhalation (respiratory)
• Organism aerosolized when shed in high numbers in uterine fluids and urine.
• Most common route for humans
Conjunctiva
Percutaneous
Venereal
• Important rote for suis & canis
In utero
• Causes abortion
Three Types of Human Brucella Infection
Acute
• Flu like symptoms
Chronic
• Localized in bones, joints, endocardium
Abortion
• Occasionally causes abortion
Brucella Diagnosis & Treatment
Diagnosis
o Serology on live animals (exposure)
o Culture/PCR of fetal tissues on abortions
o Culture/PCR on blood of other suspect antemortem cases.
o Warn the lab if suspect Brucella
Treatment
o No treatment for livestock
o Antibiotics for humans
Brucellosis Control Program
o Uniform rules o VX o Animal ID (right ear) o Testing protocol o Regulatory agency to enforce
Vaccinating Cows for Brucellosis
o Vaccinate females at 4-12mo
o Must clear vx before pregnancy
o Do not vx bulls
o If bull is vx’d on accident -> castrate or cull
o If neither option above -> give prophylactic antibiotics
Testing, Slaughter & Quarantine for Brucella
o Test (+)
-> sent to slaughter if healthy
o Animals exposed to
(+) animals -> quarantine ->
o test
quarantined ->
o Usually, entire herd must test negative on 2 sequential tests
->
o If high rate of infection in the herd, may depopulate
Species of Chlamydia & Dz caused
Chlamydophila felis
• Rhinitis & conjunctivitis in cats
Chlamydophila abortus
• Abortion/weak neonates in sheep, goats, cattle
Chlamydopjila psittaci
• Conjunctivitis, respiratory, GI in birds
Terminology for Chlamydophila psittaci
o Psittacosis: disease in humans
o Ornithosis: disease in humans from non-psittacine birds
o Avian Chlamydiosis: disease in birds
2 Types of Chlamydiosis in Humans
Chlamydia trachomatis
• most common STD in developed countries
• Leading cause of preventable blindness worldwide
Chlamydia pneumoniae:
• asymptomatic to severe upper and lower respiratory disease
• Clinically, very similar to psittacosis
Chlamydiosis in birds; Basics & Transmission
o Most or all birds susceptible
o Most common in psittacines and pigeons
o May be asymptomatic carriers or mild to severe illness
o May cause significant death loss in turkeys and ducks
Transmission
• aerosol (feather dust, aerosolized feces)
• ingestion,
• fomites (feed and water)
• Some birds shed intermittently (when stressed)
• Incubation period of 3 days to weeks
Chlamydiosis in birds; Clinical Signs & Diagnosis
Clinical signs • ruffled feathers, • off feed, • ocular and nasal discharge, • respiratory signs, • conjunctivitis, • green droppings, • neurologic signs
Diagnosis • Mostly PCR • Culture • Direct smear & stain • Immunohistochemical stain
Chlamydiosis in birds; Treatment/Control & Necropsy Findings
Treatment & Control • No vaccine • Tetracycline or doxycycline • Quarantine and medicated feed • Wild birds and rodents excluded • Clean and disinfect
Necropsy Findings
• Air sacs cloudy and thick
• Liver enlarged, scattered white foci (necrosis)
• Spleen enlarged
Avian Chlamydiosis in Humans; Basics & Symptoms
o Reportable in humans o Can spread person to person o fever, chills, headache o Sometimes respiratory distress and pneumonia o Severe cases: heart, liver, CNS signs
Avian Chlamydiosis Treatment & Control
- Antibiotic treatment
- PPE
- Respirator (N95)
- Dampen bird carcasses
- Dampen pigeon feces
- Do not allow children to touch dead birds
Chlamydophila felis
o Common cause of conjunctivitis in cats
o Vaccines can reduce clinical signs but do not prevent shedding
o May occasionally cause keratoconjunctivitis in humans
Chlamydophila abortus; basics, symptoms in humans, treatment
o Common cause of abortion in sheep and goats
o Transmitted to humans oral or aerosol
o Organisms shed at lambing
o Can cause abortion in humans
o Vaccine may reduce abortions
o Tetracycline or doxycyline
Q Fever Basics
- Coxiella burnetii,
- obligate intracellular Gram(-)
- resistant to environmental stress
- remain viable for weeks to months in environment
- Worldwide distribution
- Started in Australia
How is Coxiella burnetti different form Ricketssia
o Resistant to elevated temps, UV light, chemicals
o Does not tend to cause rashes in humans
o Does not REQUIRE vector transmission, but can be vector- borne
Hosts & Transmission of Q Fever
Hosts
o most have asymptomatic
infections
o sheep, goats, cattle, cats, dogs, wildlife, ticks
o In ruminants, abortions or stillbirths, up to 50% of flock can be affected in sheep
o Large number organisms shed at parturition
Transmission
o Shed in feces, milk, urine,
o persist in environment & spread by wind
o Arthropods (ticks): bite by an infected tick is rare
o human to human: rare
Q fever in Ruminants
o Bacteria localizes in MG, LN,
placenta, uterus
o May be shed in subsequent births and lactations
o Infection may be subclinical or cause anorexia, late abortion
Diagnosis of Q Fever
Post Mortem Pathology
o Infection involves mostly the
placenta
o Grey-brown placental exudate
o Necrotizing vasculitis
Other Ways to Diagnose
o impression smear of cotyledons stained by acid- fast stain (Geimsa)
o Serology: ELISA, CF, Immunohistochemistry, IFA
(rising titer)
o PCR placenta (this is how it is diagnosed mostly now)
o Culture rarely attempted
Treatment & Prevention of Q Fever in Ruminants
o Efficacy of antibiotic treatment questionable (oral tetracycline)
o Minimize contact with wildlife, minimize new animals into flock
o Isolate pregnant animals in an outbreak
o Bury or burn placentas, aborted fetuses
o Clean and disinfect (10% bleach) birthing areas
o Consider PPE/ respirator when cleaning birthing area
o Rodent control (good practice for many diseases)
o Do not allow dogs and cats to contact birth material
o Do not move heavily pregnant or new dams off farm
o Biosecurity (limit access)
Q Fever in Cats; basics, diagnosis, treatment
o Cats have caused infections in
humans
o Cats exposed via aerosol, tick bites, or ingestion of aborted ruminant placenta/fetus
o high numbers in placenta of cats and may persist in uterus for weeks after birth
o Cats often subclinical, but may abort
Diagnosis
• serology (increased
titer) may be performed
Treatment
• Tetracycline and chloramphenicol may be used to treat
Basics of Q Fever in Humans
o Primarily affects those that work with animals, hides and wool
o Higher seroprevalence in > 40 years old
o Males> females
o Age 60+: highest risk for Q fever
in U.S.
o More common in immunosuppressed people
o reportable
Symptoms of Q Fever in Humans
Symptoms
• acute or chronic
• Incubation period several days to several months or even years
• Most cases are asymptomatic
• Flu-like symptoms, severe headache, chills, fever, sore throat, chest pain (and, thus, may be under-reported)
• Usually self-limiting,
• severe pneumonia may occur in elderly, immunosuppressed patients
Treatment for Q Fever in Humans
- Early antibiotic treatment may shorten illness and decrease complications (doxycycline)
- Long term treatment (years) for chronic endocarditis
- 4A vaccine is available in Australia for those in high risk occupations
Chronic Q Fever in Humans
- rare
- Months to years after acute infection
- Endocarditis, encephalitis, pneumonia, hepatitis, osteomyelitis
- Usually in people with heart conditions
Triad of Infectious Dz
o Presence of a disease-causing agent is rarely sufficient to cause disease
o Genetic predisposition usually requires environmental factors too
o Incidence of infection depends on the
interrelationship of the host, the pathogen, and the environment
o vector plays an important role in disease transmission
Basics of Lyme Dz
o Most common tick borne dz
o Emerging dz
o reportable in humans & animals
o spirochete Borrelia burgdorferi or rarely B. mayonii
o Infected tick bites, stays on host 48 hours
o Incidence higher in children than adolescents, young adults
Lyme Dz Symptoms in Humans
- Most cases: bulls-eye rash (erythema migrans), flu-like symptoms.
- Can be cutaneous, arthritic, neurologic, cardiac symptoms
- 60% cases: Lyme arthritis of knees
- Days to weeks following infection or months to years!
Lyme Dz Symptoms in Dogs
• Most do not get disease
Acute
• intermittent, recurring lameness, fever, anorexia, lymphadenopathy, swollen joints
Renal failure
• Bernese Mountain Dogs & Labs have high Ab levels and immune complex in kidney cause severe inflammation
Lyme Dz; Diagnosis in Dogs
- Over diagnosed
- History, clinical signs, R/O other diseases, lab tests, epidemiology, response to tx
Ab detection:
• ELISA then positive samples tested by Western Blot (WB differentiates natural infection vs. vaccination)
C6 peptide assay:
• specific for infection-induced Ab (may be false-negative shortly after infection)
Serology:
• long incubation, persistence of Ab, disassociation of Ab response from clinical dz make dx by blood testing alone difficult
Bacterial isolation:
• difficult, time-consuming (6 weeks) and often negative
PCR (joints, skin tissue etc.)
• may be used, often negative
Lyme Dz; Diagnosis in Humans
- Serology w/ western blot
* For IgM & IgG
Treatment & History of Lyme Dz
Treatment
• Doxycycline or ampicillin
History
• Arthritis & rash in children in Lyme, CT ->
• Suspected rickettsia ->
• Found spirochete Borrelia burgdorferi
Lyme Dz Maintenance Cycle/Reservoir; ticks responsible
Tick vector
• Nymph infects human
• Adult infects dogs
Ixodes scapularis
o NE & Midwest
o 25-50% infected
Ixodes pacificus
o West Coast
o 1-5% infected
Rodent reservoir
• Mice have bacteria
• Deer feed ticks
• Animal to animal transmission not possible
Control & Vx Recommendations Lyme Dz
Control
• Avoid ticks
• Osp A Canine Recombinant Lyme vaccine
Recommendations on Vx
• Don’t Vx in non-endemic areas
• Use tick prevention instead
Giardia Basics
- Many species
- Protozoan
- Humans: Giardia duodenalis (G. intestinalis, G. lamblia)
- Dogs: Giardia canis
- No environmental replication, cysts persist
- Dogs & cats carry A & B that can infect humans
Giardia Transmission
o cysts shed in feces ->
o Cysts can survive for months in cold water ->
o Ingestion of cysts in contaminated water or food
–>
o Human-to-human transmission
– Primary source of human infections
o Animal-to-human transmission
– Only if assemblages A&B
Giardia in Humans; basics & acute/chronic symptoms
o Most common intestinal parasite in humans o 1-3wk incubation o late summer o Asymptomatic carriers o Re-infection common
Acute Symptoms
• Cramps, nausea, V/D, gas, dehydration
Chronic Symptoms
• Weight loss & malnutrition
Giardia Diagnosis in Dogs & Cats
o Do 3 fecal samples due to intermittent shedding
o Direct fecal smear
o Zinc sulfate fecal
floatation
o Fecal IFA & ELISA- SNAP test
o PCR- only method to determine Assemblage (Rarely done)
ELISA SNAP Giardia Test
o Warm to room temp
o Check results @ correct time
Giardia Treatment in Humans Vs Animals
Humans:
• Metronidazole,
• Tinidazole
• nitazoxanide
Animals:
• Metronidazole,
• fenbendazole,
• albendazole
Giardia Prevention
o Good hygiene o Avoid potentially contaminated water o Prevent contact w/ feces o Diagnose & treat infections o Giardia vx for dogs/cats resists oocyte shedding (discontinued)
Leptospirosis Basics & Transmission
- Spirochete Leptospira
- Gram (-)
- Greater than 200 serovars
- Does not replicate outside of the host
- maintained in environmental water sources, mud, and wet soil for extended periods
- Global distribution
Transmission o Urine, blood, tissue, contaminated soil/water into abraided skin or mucosal surface o In utero o Horizontally through semen o Lab transmission o Floods
Leptospirosis Clinical Signs
o Hepatic dz o Red water o Renal failure o Abortion o Mastitis o Uveitis in horses
Leptospirosis Diagnosis & Treatment
Diagnosis o Clin Path for renal and hepatic disease o Kidney biopsy o Serology o FA & IHC of abortions or necropsy o PCR of urine & water o Culture (very slow weeks)
Treatment
o doxycycline,
o penicillin,
o oxytetracycline
Leptospirosis Prevention
o Water sanitation
o Hygiene: protective clothing, hand- washing
Vaccination
• Swine, Cattle, Dogs
• Not cross protective
• Controversial to recommend
Cattle Producer Leptospirosis Control Recommendations
o Vx for several serovars
o Vx calves 3-6mo to avoid maternal Ab
o Boost bi-annually
Basics of Tularemia
o Francisella tularensis o Gram negative, aerobic coccobacillus o Hardy, non-spore-forming o Category A bioterrorism agent o North Americ & Eurasia o Survives well in H2O, moist soil, decaying carcasses
2 Maintenance Cycles of Tularemia & Reservoir/Hosts
Maintenance Cycles
o Rabbits/hares/ticks
OR
o Voles, mice, squirrels, muskrat/direct contact or contaminated aquatic environment
o Reservoir
Lagomorph, wild rodents, ticks (transovarian)
o Hosts
• MANY species
Transmission of Tularemia
o Biological vector: Dermacentor & Amblyomma ticks
o Mechanical vector: deer flies, mosquitoes
o Directcontact: bites, secretions
o Inhalation
during lawn mewing, shearing rabbits
o Ingestion of infected animals, contaminated food
o Lab BL3 to culture
o No person-to person transmission
Why is Tularemia Used as a Bioterrorism Weapon
o Easy to acquire o Stable in the environment o Intentional contamination of food and/or water o Aerosolization o Multiple species infected
4 Presentations of Tularemia in Humans
Ulceroglandular infection
• An ulcerative skin lesion with lymphadenopathy
Pharyngeal infection:
• via ingestion
• cervical, submandibular, mediastinal lymphadenitis;
• exudative pharyngitis, oral ulcers
Septicemia (typhoidal)
• hepatomegaly, splenomegaly
Pneumonic
• via inhalation
• Radiographic and clinical evidence of pneumonia, pleuritis,
• 60% fatal if not treated
basics & 3 forms of Tularemia in Animals
o Fever, lethargy, anorexia, stiff gait, increased pulse and respiration, coughing, vomiting, diarrhea and pollakiuria
incubation:
• 3-5 days, (1-14 days)
Ulceroglandular form:
• cutaneous ulcers & regional lymphadenopathy
Septicemic form:
• hepatomegaly, icterus, sheep
Pneumonic form:
• rare
Tularemia Diagnosis, Treatment, Control
Diagnosis o Serology: 4-fold change o Culture of blood, aspirate, exudate or biopsy o Direct FA o PCR
Treatment
o Doxycycline, tetracyclines, chloramphenica, ciprofloxacin
o Resistant to Beta-lactams: Penicillin & cephalosporins
Control o Prevent pets from hunting rodents/rabbits o Tick control o PPE around infected animals o Food hygiene o No Vx
What is an Emerging Dz
o Appearance in new host o Changes in pathogen’s underlying epidemiology o Evolved strains o Recent & 1st entry into a host o Increased incidence
Factors of Pathogens Contributing to Emergence of Dz
Antimicrobial resistance
• Transformation
• Transduction
• Conjugation
Genetic adaptation & change • Nucleotide substitution • Natural selection • Recombination • Reassortment
Factors of Humans Contributing to Emergence of Dz
Human demographic changes • Increased human contact • Increased contact with wildlife • Intensification of agriculture • Population displacement
Human behavior
• Sexual practices, IV drug use: HIV
• Intent to harm: Anthrax, Botulism
• Domestication of animals: Toxoplasma
Human susceptibility to infection
• Immunocompromising conditions: HIV, cancer
• Nosocomial infections: SARS, Ebola, MRSA, MERS-CoV
• Transplants/infusions: HIV, Cryptococcus neoformans, Baboon cytomegalovirus
• Implants/surgical instruments: vCJD, fungal meningitis in contaminated steroid injections
What does R sub 0 mean in Emerging Dz
o <1 = limited spread
o 1 = endemic
o >1 = epidemic
