Key Microbial Causes of Sudden Death – Anthrax

Question 1

What are the important control measures following an outbreak of anthrax?

Answer 1

• Carcass disposal
• decontamination
• vaccination
• restriction of movment of both animals and people

Question 2

What are the 4 broad classifications of sudden death in ruminants?

Answer 2

1. Acute infections
2. intoxications
3. metabolic and nutritional causes
4. physical or environemtnal disasters

Question 3

Should a post mortem be done in a suspected anthrax case?

Answer 3

No

Question 4

When factors might make you suspect anthrax?

Answer 4

If they die suddenly and have one or more of the following occur:
- Blood oozes from one or more body orifices and sites of predation (e.g. eyes, anus, udder)
- Blood from the carcase does not clot
- There is a history of anthrax at any time on the property
- The property is located within the anthrax belt
- Any rapidly fatal disease of herbivores – rule out anthrax

Question 5

What is the first thing you do when you suspect anthrax?

Answer 5

Notifiable disease, so notify appropriate people

Question 6

What does B. anthracis look like?

Answer 6

• ## Large, blunt ended, gram +ve rods, capsulated (lose capsule when cultured)

Question 7

List the differences between clostridium spp. and B. anthracis.

Answer 7

• Both spore forming gram positive rods
• Bacillus spp. will grow in air, whilse clostridium spp will only grow anaerobically
• B. anthracis have a capsule in vivo (loses this once cultured) while clostridium spp. do not have a capsule

Question 8

What is this?

Answer 8

B. anthracis with a capsule (in vivo)

Question 9

When is B. anthracis spore forming?

Answer 9

• Under aerobic conditions
• this is the vegetative state
• central endospores mean that they are highly resistant

Question 10

Are the spores of B. anthracis resistent? How can they be destroyed?

Answer 10

• Yes, they have central endospores which are highly resistant
• can survive 2-3 decades in dried cultures
• remain viable in siul for >100 years
• freezing has little effects
• Destroyed by: boiling for 30 mins, dry heat at 140C for 3 hours. Chemical disifectants need to be used at high concentrations for a long time

Question 11

Where is B. anthracis found?

Answer 11

• Survive as spores in animals or animal products and in soil.

Question 12

How might B. anthracis spores be brought to the surface of the soil?

Answer 12

• Higher risk of heavy rain after drought - flooding
• excavation
• subsidence of earthworms

Question 13

When do B. anthracis spores germinate?

Answer 13

• Spores germinate & bacteria multiply when exposed to high temperatures, moist conditions & when there is a lack of other soil-living bacteria

Question 14

How does B. anthracis enter the host?

Answer 14

• Ingestion of spores
• through scratches or wounds
• Inhalation
• mechanical trasnmission with biting insects (rare)

Question 15

What are the VFs of B. anthracis?

Answer 15

Both the capsule and toxin are required for virulence
- Capsule: resistant to phagocytosis
- Toxin: 3 thermolabile protein antigenic components (protective antigen, oedema factor and lethal factor)

Question 16

What differences do we see in anthrax infection between ruminants vs pigs and dogs?

Answer 16

• Pigs susceptible to oedema factor while pigs are susceptible
• Sudden death in ruminants, longer timecourse in pigs
• Few spores required to cause disease in ruminants, many spores required to cause disease in pigs

Question 17

Explain the pathogenesis of B. anthracis in ruminants.

Answer 17

 Cows happily grazing but ruminants are the species MOST susceptible to anthrax  Ingest spores present in the environment (relatively FEW spores are required to cause disease)  enters through abrasions in mucous membranes  Initially stays localised & causes little oedema (rel. resistant to Oedema Factor) but then get a build up of toxin  invades bloodstream and causes septicaemia (bacteria and toxins)  lethal factor comes into play

Question 18

How does anthrax present in dogs and cats?

Answer 18

The same as in pigs, longer clinicial course, exposure through ingestion of infected meat, oedema factor plays a greater role.

Question 19

Are horses more or less susceptible to anthrax comparred to cattle and sheep?

Answer 19

Less susceptible, see signs of enteritis and colic or localised oedema.

Question 20

What are the three forms of disease caused by anthrax in humans?

Answer 20

• Cutaneous form
• pulmonary form
• intestinal form

Question 21

What risk/protection level is anthrax?

Answer 21

Notifiable disease, protection level 4

Question 22

How does an anthrax immunochomatographic test (ICT) work?

Answer 22

• hand held “cow-side” test
• Contains capture antibody against anthrax protective antigen & an inbuilt control
• Blood collected and mixed with sample dilution buffer then placed in the sample well - gives a result in about 15 mins

Question 23

Can you use an ICT test <48 hours after death?

Answer 23

If the sample collected < 48 hours since death, sensitivity close to 100%. If used > 48 hours after death, sensitivity decreases; however, any positive ICT can still be regarded as a true result.

Question 24

How is a postive ICT test confirmed?

Answer 24

• Blood or aqueous humour sent to the lab
• ear notch sent to lab if blood cant be sampled
• culture (needs to be in a PC3 lab)

Question 25

How could you diagnose the localised form of anthrax?

Answer 25

• ICT
• Aspirate fluid from the local affected lymph nodes

Question 26

Is it possible to treat anthrax?

Answer 26

Yes, but needs to be done quickly.
Penicillin is the drug of choice

Question 27

What are some control measures for anthrax?

Answer 27

• Vaccination
• regulr monitoring
• immediate notification if disease is suspected
• isolation/quaratine
• making and maintaining records to assist in disease tracing
• appropriate disposal of carcasses

Question 28

How can anthrax be prevented?

Answer 28

• Vaccination: non-envapsulated, avirulent, spore vaccine
• Carcass disposal: do in accordance with AUSVETPLAN
• Host immunity following infection: permanent immunity following infection if the animal survives

Question 29

What other Bacillus spp. are there? Are they of a concern?

Answer 29

• Bacillyus cereus: causes gangrenous mastitis in cattle. Opportunistic infection
• Other Bacillus spp.: umbiquitous in environment. Usually associated with a contaminated sample if grown in the lab