DISEASE E&E (Disease Emergence 2) Flashcards
Human demographics/behaviour:
-how we interact with animals
Ex. bush meat trade and Ebola virus
Monkeypox outbreak US 2003:
-various reservoir hosts (rope squirrels, tree squirrels, poached rats, dormice, various monkeys)
-human-human transmission was limited (‘stuttering chains’)
How did monkeypox get into US?
-having contact with infected prairie dogs purchased as pets
>touching sick animal
>receiving a bite or scratch
>cleaning cage or touching bedding of sick animal
What was the source of monkeypox?
-shipment of animals from Ghana
-stored in close proximity to prairie dogs
Examples of how people conceal animals, trying to get them into the country:
-ceramic garden gnomes
-hollow books
-computer hardware
-prosthetic leg
-behind or among legal cargo
What are the most potent factors that drive disease emergence?
-human activities
International travel:
-swifter movement of people, animals, and pathogens over large distances
-transportation of vectors
-9/11 caused a delayed outbreak and prolonged influenza season
-human migrants
-intensification of animal and plant trade
FMD 2001 UK outbreak:
-first discovered at a pig slaughter plant
-farmer was probably feeding illegal food waste (ex. restaurant waste)
>restaurant was probably getting illegal meat from Asia
-sheep on the farm also got infected
-went to sheep market, where it spread even more
-2-3 weeks before they found the first case
Ecology of food production:
-done on a global basis
-networks and pathways within these systems are not well described
-we have a very limited understanding of the complexities of these systems
Ex. one pen of 300 at a feed lot would have at least 100 farms
Prior to BSE:
-several TSE’s (transmissible spongiform encephalopathies) were known in humans
>CJD
>Kuru
Kuru:
-seen in tribe in New Guinea
-“to tremble with cold”
-the disease was infectious and probably spread through cannibalistic practices
What is special about TSEs?
-prions (proteinaceous infectious particles)
Natural uninfectious prion proteins:(PrPc)
-is found in cells of normal animals
>function is unclear
Infectious prion protein (PrPsc):
-folded into a different shape
*change in 3D shape of protein makes it incredibly stable
What happened in UK (BSE)?
-first known cases were on a dairy farm then found on more
-meat and bone meal (MBM) hypothesis
Meat and bone meal (MBM) hypothesis:
-all cases had been fed MBM
-explained breed and geographic differences
>guernsey: high incidence (feed mill used MBM)
>jersey: low incidence (feed mill did not use MBM)
-risk of exposure to calves was 30x
3 theories for origins of BSE?
- Originated from a scrapie-like agent from sheep
- Caused by spontaneous genetic mutation of the PRP gene of cattle
- Originated from another mammalian species with a TSE, who’s carcass was rendered and incorporated into MBM
Why was feeding of MBM so widespread?
-freely available
-was needed: no other easily available cost-effective source of protein feed in the UK
-commonly included as a protein source in calf starter rations
MBM freely available:
-massive reduction in UK sheep flock
-there was no market for cull sheep beyond rendering
BSE infected cows goes to slaughter or dies on farm:
-infective material
-brain
-spinal cord
-tonsils
-eyes
-small intestine
*food contamination
*rendering plant
BSE infected cow cycle:
- Infected cow
- Dies or sent to slaughter
- Food contamination OR
- Rendering plant
- Meat and bone meal
- Feed mill
- Fed to ruminants
British epidemic steps to try stop it (BSE):
- First verified case
- Feed ban introduced
- SBO ban
- Mammalian MBM ban
- Feed security assured
SBO ban:
-specified bovine offal
-can’t use other parts besides the skeletal muscles
2 ways BSE spread:
- Ship cattle
- Shipment/movement of MBM around the world
How did BSE get to North America?
-did not import MBM from UK, most of it came from USA
-Saler cow was imported from UK, and many others from UK and Ireland
>CFIA culls
>some were already dead and went to rendering plants
Measures to stop BSE in Canada:
- Ruminants MBM ban to ruminants
- SRM removal (food contamination)
- SRM removal (rendering plant)
SRM removal:
*specified risk material
-infective material
-brain
-spinal cord
-tonsils
-eyes
-small intestine
MBM movement:
-simply a commodity
-traded and moved across borders
-commodity brokers look for opportunities to buy and sell it
-once it moves to another country, it quickly loses it’s identity of origin
Microbial adaptation and change:
-emergence of antimicrobial resistant bacteria as a result of human usage of antimicrobial drugs in both humans, horses and pigs
-antigenic ‘drift’ of various influenza viruses
Breakdowns or deficiencies in public health infrastructure:
-though as an important factor in developing countries, but can still happen in North America
Ex. Cholera outbreak in Haiti after earthquake
>outbreak of Cryptosporidium in North Battleford, SK
>mumps outbreak in university students in Canada (lack of vaccination of specific cohort of children)
Outbreak of Cryptosporidium in North Battleford, SK:
-2001
-50 people hospitalized
-waste water treatment plant was upstream from the surface water treatment plant
>sedimentation failure in water treatment plant
>Doctor noticed the increased cases of diarrhea
Walkerton, ON, 2000 (surface runoff with E.coli and campylobacter jejuni):
-entered a well supplying drinking water
-bacteria was from cattle manure spread (best management practices were in place)
-the well was chlorinated less than the amount required
>manually monitored: employees just made fictitious entries
-2300 cases of gastroenteritis, 7 deaths
