Zoonosis & Shared Infection Flashcards
what type of bacteria is bacillus
gram positive large rods
are bacillus aerobic or anaerobic
aerobes or faculative anaerobes
are bacillus slow or fast growing
very fast growing
large colonies at 24 hours
what is anthrax caused by
bacillus anthracis
what are susceptible to bacillus anthracis
ruminants – highly susceptible
pigs, horses moderately susceptible
carnivores comparatively resistant
birds almost totally resistant
what is the epidemiology of anthrax
Endospore formation most important factor in persistence of anthrax in environment and spread to other animals
Endospores survive for decades in soil
Outbreaks occur in herbivores when pasture contaminated spores
Spores bought to surface by flood, excavation, subsidence, earthworm activity
Infection acquired by ingestion of spores (inhalation, skin abrasion more common in man)
what are the virulence factors of anthrax
Presence of poly-D-glutamic acid capsule and complex toxin
Both violence factors encoded on plasmids
Expression regulated by host temp and carbon dioxide
Capsule inhibits phagocytosis
Toxin consists of 3 antigenic components (protective, edema and lethal factors)
PA acts as the binding moiety for both edema and lethal factor
what is the edema factor of anthrax
calmodulin dependent adenylate cyclase increases cAMP causes build up fo fluid in tissues
also inhibits neutrophilic function
what is the lethal toxin of anthrax and what does it do
Zinc metalloprotease plus PA which act as binding domain
Stimulates macrophages to release IL-1 beta and TNF alpha and cleave MAP kinase
what does the lethal toxin of anthrax cause
Causes swelling, darkening of tissue, edema and necrosis
Septicemia leads to increased vascular permeability, hemorrhage, shock and death
what is the incubation period of anthrax
hours to days
what does anthrax cause in cattle and sheep
septic and rapidly fatal
most animals found dead
what is characteristic feature of anthrax bacilli in the last hours of life
massive bacteremia
how is anthrax diagnosed
Carcasses are bloated, putrefy and do not exhibit rigor mortis
Bleeding issues from mouth, nostrils, anus
Blood collected from animal stained with polychrome methylene blue
Blue bacteria pink capsules
Inoculate agar plates for growth
Characteristic colonial morphology, biochemical tests
what is the apperance of b anthracis after staining
capsule and square ends
what are the forms of anthrax in humans
cutaneous
pulmonary
intestinal
what is the cutaneous form in humans of anthrax
Endospores enter abraded skin — septicemia if untreated
what is the pulmonary form of anthrax in humans
Inhalation of spores
woolsorters disease
what is the intestinal form of anthrax in humans
ingestion of infective material
how is anthrax controlled
Do not open carcass as this will facilitate spore formation and environmental contamination
Report to regulatory authority
Annual vaccination
Stern live spore vaccine, capsule minus toxin +ve in endemic regions
Chemoprophylaxis
Carcass incinerated or buried away from water sources
Contaminated material disinfected in 10% formalin
what is the plague caused by
Yersinia pestis
what type of bacteria is Yersinia pestis
gram negative bacterium
how is the plague infection spread
zoonotic infection in rodents transferred by fleas
organisms in blood of rodents, blood (+ organism) taken up by fleas and flea bites humans (or dogs or cats)
humans infected by flea bites
where is the plague endemic to
africa
asia
USA (southwest and pacific coast)
what species are susceptible to the plague
Varies of different wild rodent species
Prairie dogs are extremely susceptible – 99% mortality
Kangaroo rats in North America
what does the clinical infection of the plague cause
Both dogs and cats in endemic areas
Cats are particularly susceptible and may be a source
- Usually acquired by ingesting rodents
Bubonic, septicemia, pneumonic
what are cats with pneumonic plague a source of
human infection through aerosol generation
human infection can be acquired through cat scratches and bites and fleas
what are the plague syndromes in humans
Bubonic:
- Fever painful lymphadenopathy
Septicemia:
- Fever, hypotension with or without bubonic
Pneumonic:
- Cough, hemoptysis with or without bubonic
Meningitis:
- Fever, nuchal rigidity usually without bubonic
what are virulence factors specific to Yersinia pestis (5)
Fraction 1 (F1) antigen
HPI
Ymt protein on plasmid
His locus
Pla
what are the functions of Fraction 1 (F1) antigen
Capsule around bacteria which prevents opsonization
what are the functions of HPI
for iron acquisition (also Ye and Yp)
what are the functions of HPI of Y pestis
Ymt protein on plasmid is a phospholipase D required for survival in flea gut
what are functions of Hms locus of Y pestis
Hms locus required for efficient transmission to subcut sites
what is the function of Pla plasmid of Y pestis
Pla is plasmid encoded and essential to disseminate from subcut tissue to lymph nodes or bloodstream
how is Y pestis diagnosed
Specimens sent to labs
- Pus, blood, lymph node aspirate
Giemsa stained smears of pus
- bipolar rods
Culture
DFA tests (direct fluorescent antibody)
Passive hemagglutination on paired samples from infected cats
- Rising titre suggests active infection
how is Y pestis treated
Cats with suspected plague isolated
IV tetracycline or chloramphenicol for bubonic plague
Endemic areas dogs, cats routinely treated for fleas
how is Y pestis controlled
Rodent control
Effective human and animal surveillance
Avoid sick/dead animals
Avoid endemic areas or outbreak areas
Vaccination
Isolate human cases
Treat human cases with antibiotics
what is the causative agent of Glanders
Burkholderia mallei
what is Burkholderia mallei
gram negative rod
where is Glanders infection
middle east
india
pakistan
china
mongolia
what is Glanders characterized by
Contagious disease of Equidae
Nodules and ulcers in resp tract and skin
how is Glanders transmitted
Ingestion of food or water contaminated by nasal discharge of infected horses
Inhalation or skin abrasions
what are the clinical features of Glanders in horses
Acute septicemia
- with fever, mucopurulent nasal discharge and resp signs
Chronic disease more common
- Presenting as nasal, pulmonary and cutaneous forms
Ulcerative nodules
- Develop on mucosa of the nasal turbinates and nasal septum
Animals may die after months or recover and shed organisms from RT or skin
Pathogenesis not well defined — organism is dangerous to work with
how is Glanders diagnosed
Clinical signs
Lab diagnosis by sending pus, lesion discharge, blood for serology
Grows on sample media
Serology
Mallein test
how is Glanders treated and controlled
Test and slaughter
Antibiotics inappropriate as treated animals may carry the organism and transmit it
Cleaning and disinfecting
what is melioidosis caused by
Burkholderia pseudomallei
where is melioidosis endemic
Endemic in soil and water in south east Asia
how is melioidosis transmitted
Infection from ingestion, inhalation, skin abrasion from soil/water contact
Opportunistic pathogen, stress-immunosuppression predisposes to clinical disease
what species are susceptible to melioidosis
Many animal species susceptible, including humans
what occurs following infection of melioidosis
Subclinical infection occurs in which the organism may remain latent and then re-activate
Infection may be acute or chronic, septicemic, resp, disseminated and characterized by abscess formation
how is melioidosis diagnosed
Organism may be cultured on blood agar or Ashdowns medium
