Networks and disease control Flashcards
Movement of animals
- movement and trade of animals important part of economy
- leads to risk of spreading disease between farms
- understanding contact and trade patterns is important in disease control activities
Risk factors for large livestock disease outbreaks
- high density areas of livestock (Southern Alberta (Beef), Lower FV (dairy cows, poultry), SE manitoba (pigs))
- long distance and high frequency movements (50 million animals on road each day in canada)
- comingling (auctions, community pastures, livestock, shows/competitions)
- Inconsistent application of biosecurity
Stakeholders in Large animal economy
- livestock producers
- industry organizations
- associated sectors (feed mills, auction etc)
- CFIA (federally reportable diseases)
- Provincial CVOs (provincially reportable diseases)
- vet organizations
AHEM II
- meeting of all the stakeholders
- creates awareness and building capacity for response to serious animal disease emergencies in Canadian livestock sector
Health of animals act
- 31 diseases
- CFIA must respond and have a program
- allows authorities to control, eradicate and prevent entry of disease
- allows regulation of movement of animals, people, vehicles in respect of places or areas infected with serious animal disease
** If disease has known presence in canada, then focus is control and eradication
**If disease is foreign to Canada, then focus will be importing controls, active surveillance, and emergency preparedness
Reportable diseases
- outlined in Health of Animals Act and Reportable diseases Regulations
*animal owners, vets, labs required to report (confirmed contamination or suspected contamination) - report to CFIA
Reportable Sask diseased
- anthrax
- chronic wasting diseases
- rabies
Notifiable Sask diseases
- West nile
- salmonella
- lyme disease
Lots of others
Notifiable diseases
those that require monitoring for trade purposes, or to help industry detect or understand their presence in Sask
**most cases, no action is taken in response to the confirmation of a disease
World Organization for Animal Health (WOAH)
- 167 member countries
- 5 geographic regions
- Canada 1952; US 1976
- cooperation between nations to counter disease spread
- set animal health standards
2017 Porcine Epidemic Diarrhea outbreak (Manitoba)
- April 2017 to October 2017
- 80 infected herds, 11 high risk areas
- causes diarrhea and extremely high levels of mortality in young pigs
- weekly testing (198 premises, 1500-1700 samples per week)= 8x the normal lab testing levels
- trace in/out surveillance
Trace in/out Porcine Epidemic Diarrhea
to stop spread, need to examine all aspects of contact
- manure companies
- processing crews
- feed trucks
*these crews/companies often work for multiple farms and have potential to spread between farms
Premises ID
specific ID for each location that cares for livestock; part of traceability system
allows for better tracking because everyone registered and can be notified easily
Porcine epidemic diarrhea outbreak spread risks
- direct animal movement
- recurrent PEDv from recovered pigs
- premises biosecurity gaps
- transport and high risk premised
- area spread and weather
- deadstock
- manure and manure application
- feed and feed movement
Networks
- network of people/animals/herds connected by potential disease transmission events
Network map- connects nodes (animals, people or herds) and represents a road map where disease can travel
Disease “social” netowrks
- every disease has its own social network
- highly dependent on form of disease transmission (diseases with similar transmission routes may have similar networks; different transmission routes likely very divergent)
Ex. divergent route= BSE vs. Foot and Mouth
Contact tracing
- major part of disease control efforts with reportable disease (foot and mouth, TB, PED, BSE)
- start at node of infection and identify all contacts and test them for disease or protect them with vaccination and quarantine
What places would nee premises ID?
- farms
- pastures/community pastures
- hatcheries
- abattoirs
- zoos
vet hospitals/labs - livestock and poultry research facilities
Importance of Premises ID
- rapid notification of livestock stakeholders
- help prepare for animal health and food safety emergencies
- facilitates rapid evacuation of animals in event of natural disaster
- help track animals in emergency
- reduce impact of emergency
- help maintain or provide fir greater market access
What do you need a premises ID for?
- buy medications
- complete movement documents (manifests and permits)
- sell livestock
- apply for grants, licenses, programs
Animal movement and traceability
- varies by industry
- animals leaving a location must be identified with approved tag before leaving
- Canadian Livestock Tracking System, Canadian Cattle ID Agency (CCIA), PigTRACE (tags and tattoos)
Measuring animal movement networks
- hard to measure
- rarely have information completely identified which means contact tracing is highly labour intensive and difficult
BUT can make a huge difference in disease control if it works
Analysis of swine movement
- one truck shared by 4 farms in overall network
- more than 50% of shipments on any day, the same truck used for more than one shipment
Reproductive Ratio
R= number of cases generated per existing case
R<1 outbreak contracts
R> 1 outbreak expands
**changes over time and is not consistent between cases
Hubs effect on Reproductive ratio
- hubs or super spreaders can have great influence on network and spread of disease
Ex. horse shows, auction markets act as superspreaders for disease
Spread and control
- exponential by nature
*Therefore, importance of blocking or preventing spread (biosecurity).
- We are often not aware of “saves” because they are cases that don’t happen and we cannot see
- Ex. wear a mask
Trace forward and trace back during disease response
- find one case, quarantine to prevent further spread
- Trace forward: locate other cases by testing individuals linked to first identified case (ex. daughter of first case)
- Trace back: possible to find cases that may have led to the first case found. If we can implement something to control individual further back, can possibly prevent further spread within other branches
Early detection in spread
- the further back, earlier cases that we can find and implement control can have huge impact on how much transmission occurs
Two ways to flatten curve (disease transmission)
- increased biosecurity barriers/control
- Earlier detection: implement controls when fewer cases
Exponential factors
- disease spread
- control of spread
