Transcript OVINE JOHNE’S DISEASE (OJD)

LHPG 2014 CONGRESS
2 - 4 JUNE, SKUKUZA
CONTROL OF OJD USING COSTEFFECTIVE, PRACTICAL AND
ACCEPTABLE MEASURES
Prof Gareth Bath
Convenor: Small Stock Health Advisory Body (SSHAB)
and Emeritus Professor,
Faculty of Veterinary Science
University of Pretoria
BACKGROUND
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First SA identification in cattle 1923
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First SA identification in sheep 1967
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Probably imported by Department of Agriculture
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Escaped from Animal Institutes in 1980s
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Became a problem in Western Cape commercial
flocks 1990s
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First survey done
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Current regulations promulgated
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Vaccination of positive flocks allowed in about 2003
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Small Stock Health Advisory Body 2005
Small Stock Health Advisory
Body (SSHAB) 2005
PARTICIPANTS
National Wool Growers’ Association (NWGA)
2
National Emerging Red Meat Producers’ Organisation (NERPO)
2
Red Meat Producers’ Organisation (RPO)
2
Livestock Health and Production Group (LHPG)
2
SA Federation Stud Breeders’ Society (SAFSBS)
2
SA Stud Book (SASB)
1
SA Federation of Livestock Auctioneers (SAFLA)
2
Convener
1
PRINCIPLES FOR ACCEPTABLE
OJD CONTROL MEASURES
• Protect interest of infected flocks
• Protect interest of uninfected flocks
• Practical, affordable measures
THE NEED FOR CHANGE
• Current regulations unworkable
• Unintended consequences (dishonesty)
• No or little monitoring of sales
• Allegations of vaccine dispersal
• No other country has had success
• Major countries (and OIE) do not regulate
• Zoning indefensible without surveys
• State has not acted with vigour on OJD
ORIGINAL PROPOSALS FROM
SSHAB TO DAFF (2008)
• Extensive consultation over 3 years
• Proposals based on consensus
• Tried to have a system based on zoning
• Needed whole-hearted support from DAFF &
Provinces
• No action for over 2 years
• Problems of management changes at DAFF
• Decided to draw up workable system
• The nature of the disease point to industry-based
control measures
SUMMARY OF OJD CONTROL
PROPOSALS: July 2008
1.
Targeted Detection Surveys
2.
OJD Control Areas
3.
Other areas of South Africa
4.
Detection and Testing
5.
Liaison and Review
CURRENT PROPOSALS FROM
SSHAB TO DAFF (2010)
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Abandon zoning as unworkable
End quarantine of positive farms
Change status from controlled to notifiable
Separate Ovine from other forms of JD
Notification of outbreaks
Vaccine supply simplified but still subject to
veterinary prescription
Information of vaccines, sales must be recorded
Sales of live sheep must only be done with a
Vendor Declaration
Draft of proposed Regulations supplied
Moratorium requested
OJD VACCINE PURCHASE
DECLARATION
• Competence
• Flock regarded as OJD Positive
• Doses commensurate with flock size
• Permanent unique ear tags
• No removal of vaccine reaction
• Use only on own sheep
• Vendor Declaration with sales
• Sales to be recorded
CALCULATE COST/BENEFIT
OF VACCINATION
Consider annual deaths first
current cost of vaccine/sheep
_________________________ X 100 = percentage of annual deaths to justify vaccination
current price of breeding ewe
Examples:
R15__
R1500
X 100
= 1 % annual mortality
R30__
R1500
X 100
= 2 % annual mortality
R30_
R750
X 100
= 4 % annual mortality
R20__
R4000
X 100
= 0.5 % annual mortality
ADD OTHER COSTS &
CONSIDERATIONS
• Cost of raising extra replacements
• Cost of early deaths, less lambings per ewe
• Effects on flock structure
• May lose 8 – 10, even 15% adults annually
OTHER RISK FACTORS
• buying policy (unvaccinated sheep)
• sheep (especially lambs) concentrations on
grazing
• moisture – retaining pastures
• type and timing of rain
• use and timing of irrigation
• ambient humidity at lambing
• temperature range
• feeding system (on ground or raised)
• water troughs
OJD VACCINE
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Gudair (Virbac)
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Killed oil adjuvant
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Lowers losses by 90%
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Lowers carriers by 90%
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Lowers shedding by 90%
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Authority & prescription - SV
OJD VACCINE (cont):
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Only for infected flocks
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Single injection in lambs
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Permanent identification
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Subcutaneous in neck
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Severe reactions possible
VETERINARY GUIDANCE FOR
PRESUMED OJD-NEGATIVE FLOCKS
• Owners must be OJD-aware
• Never buy sheep without prior advice
• Never buy sheep from speculators
• Always demand a Vendor Declaration
• Ensure that the implications of each point in the
Vendor Declaration is well understood
• If in doubt, then rather do not buy
• It only takes one apparently healthy carrier sheep
• The signs of OJD may take 5-10 years to become
apparent
• The property becomes permanently OJD positive
• Never accept any verbal assurance on OJD status
• Explain to breeders that testing for OJD will be to
their benefit - the lowest of risk categories
• Emphasize that there is no such thing as “no risk”
DRAFT VENDOR DECLARATION
1. I hereby declare that I am the owner or authorised representative of the sheep on sale and
am competent to make this declaration
2. The sheep for sale are clearly identified in the accompanying description.
Yes NONo
YES
3. The sheep for sale were born on my farm.
YES
Yes NONo
4. The farm has a closed flock policy.
YES
Yes NONo
5. know the signs of the disease and to the best of my knowledge, all of my
properties are free of cases of Ovine Johne’s Disease
6. I have actively looked for Ovine Johne’s Disease and have had tests done
for this.
7. To the best of my knowledge, my immediate neighbours and farms in my
magisterial district of my farm(s) are free of cases of Ovine Johne’e
Disease.
8. The sheep on my properties have been vaccinated against Ovine Johne’s
Disease and are appropriately identified as such.
YES
Yes NONo
YES
Yes NONo
YES
Yes NONo
YES
Yes NONo
9. If vaccinated, the number of years that the vaccinations have been done is
years
years
NOTE: Vaccination does not mean freedom from OJD, vaccinated animals can still be carriers.
Buyers should consult their veterinary advisor before any purchases
Signature: _______________________________
Date: _______________________________
Farm:____________________________________
District: _____________________________
Owner or Authorized representative:________________________________________________________________________
CURRENT (2014) COST OF OJD
PFS TEST
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About R500 / pool
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With 7 pools, about R3 500 / farm
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Target older, thinner sheep
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Cost of transport, sampling etc? R2 500
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Maybe around R6 000 / farm
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This is the price of one good ram
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Divide farm cost by number of rams sold
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If 100 rams, cost / ram = R60
CAN WE “ERADICATE” OJD
FROM A FARM?
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Yes, depopulate for 18 – 24 months
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This is not a practical option
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Reinfection remains a problem
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May be possible (South Australia)
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Vaccinate for 5 years (lower infection on farm)
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Test and cull (like bovine TB)
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May be able to classify farms by risk category
CURRENT SITUATION (May 2014)
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OJD positive flocks may trade live sheep
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SSHAB meetings via NAHF with DAFF
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Vendor declaration gathering support
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Pooled Faecal Sample test to detect OJD in
flocks under testing
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Targeted Detection Surveys in breeder flocks
and communal areas have support
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Vaccine sales have plummeted!
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Support from industry and veterinarians is
essential
END
1. TARGETED DETECTION SURVEYS
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Western Cape Province
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Western Cape Province
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Known OJD area
Other areas
Other Provinces
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High risk areas
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Sellers of breeding stock
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Known diagnoses
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Goats (& wildlife?)
2. OJD CONTROL AREAS
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Identify and declare areas
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All farms included
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Exemptions possible
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Free trade within area
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Movement records to be kept
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Free importation of sheep
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Written vendor declarations
OJD CONTROL AREAS (continued)
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Vaccination strongly recommended
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Clear, unique, permanent tags
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Advise purchase of vaccinated sheep
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Vaccinate (if not done before)
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Live sheep can be sold directly for slaughter
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Embryos, semen & OJD-free sheep: strict
safeguards
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Breeders must take responsibility
3. OTHER AREAS (OJD “FREE”)
• Vendor Declaration: risk factors
• Detection surveys needed
• Encourage breeders to test
• Good management practices
• No vaccination allowed
• No purchase from control areas
• OJD awareness promoted
4. DETECTION AND TESTING
• Standard procedures
• Authorised laboratories
• Multiple tests – confirmation
• Histological, bacteriological and PCR
• Flock, not individual tests
• Logistics and budgeting crucial
DETECTION AND TESTING (continued)
• State to pay for surveys
• Subsidisation recommended
• Protocols required
• Abattoir monitoring and traceback
• Research needed
5. LIAISON AND REVIEW
• Strong liaison essential
• All parties included
• Positive attitude needed
• Everything open to review
• 3 Principles to be used
• Helpline required for advice
• Suitable supervisor required