Anthrax Flashcards
Where does the name of anthrax come from?
“coal” from the black colour of the cutaneous lesions
What does anthrax mainly have a history of?
Bioterrorism
What are the four main ways that anthrax can be transmissed into humans?
- Cutaneous
- Inhalation
- Gastrointestinal
- Any groups at risk (wool sorters, bone processors, slaughterhouse workers)
What is the main transmission of anthrax?
Spores found in the soil
What are the peak anthrax zones and weather?
- Any soil with a pH under 6
- wet spring, followed by a hot, dry period
- Grass or vegetation damaged by the flood-drought sequence
What does oxygen exposure do to anthrax?
Formation and contamination of spores
What are the clinical features of cutaneous anthrax in humans?
- 95% of all cases globally
- Incubation: 2 to 3 days
- Spores enter skin through open wound or abrasion
- Papule > vesicle > ulcer > eschar (dry, dark scab)
- Case fatality rate 5 to 20%
- Untreated – septicemia and death
What is the anthrax lifecycle?
- Spores are uptaken from feed or water, they enter via lesions in the GI tract
- bacterial multiplication in the spleen
- endothelial breakdown of blood vessels
- release of bacilli and toxins in the bloodstream
- death
- shedding into the environment and sporulation of the released vegetative cells
- exposure of new hosts via scavengers, wind etc.
What species is a dead end host in anthrax transmission?
Humans
What are the four ways human transmission of anthrax can occur?
- Cutaneous- contact with infected tissues, wool, hides etc.
- Inhalation- tanning hides, processing wool/ bone
- Gastrointestinal- undercooked meat
- Groups at risk- wool sorters, bone processors
What three ways is anthrax transmissed in humans?
- Spores (not vegetative cells) - the natural reservoir is in soil- no soil replication = no saprophytic lifecycle
- Anthrax zones (any soil rich in organic matter)
- Anthrax weather (wet spring followed by a hot, dry period, grass or vegetation damaged by the flood-drought sequence)
- Cattle are primarily affected
Where are anthrax bacteria present in the carcass?
They are not present in a closed carcass
They are present in haemorrhagic exudate from the mouth, nose and anus
Oxygen exposure = causes sporulation
How do animals mainly transmit anthrax bacteria?
- Ingestion- contaminated soil or contaminated meat
- Inhalation
- Mechanical (via insects)
What are the clinical features of cutaneous anthrax?
- Spores enter the skin via open wounds or abrasion
- dry, dark scab
- untreated it can cause septicaemia and death
What are the clinical features of inhalation anthrax?
- Nonspecific/ initially- causes mild fever
- Second phase- severe respiratory distress, dyspnea, cyanosis, medaistinal widening
- case fatality is 75-90% if left untreated
What are the clinical features of gastrointestinal anthrax?
- Severe gastroenteritis
- consumption of uncooked or contaminated meat
- case fatality= 25-75%
- ulcers, intestinal lesions, abdominal pain, vomiting
What are the three forms of anthrax?
- Peracute
- Acute
- Sub-acute/ chronic
What are the clinical features of anthrax in ruminants?
- Death, tremors, bloody discharge, pharyngeal and lingual edema
What are the clinical features of anthrax in equine?
- Fever, anorexia, colic
- swelling in the neck
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What are the clinical features of anthrax in pigs?
- Acute disease is uncommon, causes localised throat swelling
- Anorexia, Vomiting, Discharge
What are the clinical features of anthrax in carnivores?
- They are realtively resistant but may be due to the ingestion of contaminated raw meat
- fever, anorexia, weakness, necrosis and edema of the upper GI tract
What is the microbiology of anthrax?
- large, gram-positive rod,
- faculative anaerobe
- non-motile
- has two forms, vegetative and spore
- belongs to the bacillus cereus family
What does anthrax sporulation require?
- Poor nutrient conditions
- Presence of oxygen
- Host dead tissues to become anerobic
The spores are very resistant, they can survive for decades- be taken up by the host and germinate
What are the two key anthrax virulence factors?
- Capsule made up of D-glutamic acid
- Toxins that are complexes of proteins
What are the three anthrax toxins that together make the lethal combination?
- Protective antigen
- Oedema factor
- Lethal factor
What do OT and LT cause?
cardiovascular dysfunction
-Ot causes hypotension and increases vascular permeability
LT- comprimises heart performance- may cause DIC
What are the two mechanisms of virulence?
- Plasmids
- Vaccine strains
How might you diagnose anthrax?
- Sample blood or other fluids from the carcass
- grow on blood agar
- colonies are usually white/grey- look like a string of pearls
How may you prevent/ control the spread of anthrax?
- Veterinary supervision/ trade restrictions
- Isolate sick animals
- Discourage scavengers
- insect control/ repellants
- prophylactic antibiotics
- vaccination
What should you do if anthrax is suspected?
- Do not open the carcass
- take samples of peripheral blood
- isolate the animal/ carcass
What should you do if anthrax is confirmed?
- Legal powers to control the spread of disease, movement restrictions, incinerate the carcass, moniter in-contact animals
- local authorities may pay for disposal of diseased carcasses
How can you disinfect anthrax?
- Spores are resistant to heat, sunlight
- gas or heat sterilisation
- gamma radiation
What kind of vaccines are available for anthrax?
Both attenuated and live vaccines
