Bovine Tuberculosis Dr. Rick Smith Assistant State Veterinarian over Ruminant Programs

Bovine
Tuberculosis
Dr. Rick Smith
Assistant State Veterinarian over Ruminant Programs
Bovine TB Program Coordinator
MDARD
Overview
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Background of Saginaw TB infection
Outcomes at infected farms
Trace investigation outcomes
Circle testing and outcomes
How the Saginaw herd infection happened
Lessons learned
What about Michigan’s TB Free Status?
Questions & Answers
Background
• February 19 - cow discovered at slaughter
• February 25 - Saginaw herd quarantined
• February 28 - slaughter cow bovine TB
positive
• March 12 - Michigan strain of bovine TB
Ante-Mortem Test Results
• March 4-7 - herd TB tested
o 17% caudal fold response rate
o 13% gamma interferon - 6 mo. +
2013
• March 25 Saginaw dairy
• May 1 - Gratiot &
Midland herds
• September 5 Arenac feedlot
2014
• February 27 Huron feedlot #1
• April 3 Huron feedlot #2
2013 Saginaw Co.
TB positive dairy herd
Gratiot & Midland Co.
TB positive herds
Arenac & Huron Co.
TB positive feedlots
Outcomes - Infected Herds
• June 7 - Small freezer beef herd depopulated in
Midland County.
• June 19 - Small dairy beef herd depopulated in
Gratiot County.
• August 8 - Saginaw dairy herd completed
depopulation.
• February 3 - Arenac feedlot complete depopulation
with assistance from law enforcement
• Bay Port & Port Hope feedlots in process of
depopulation
Trace Investigations Outcomes
• State and Federal veterinarians followed 248
traces to 198 unique farms that were linked to
the infected farms and feedlots
• Three TB affected herds were found as a result
of these investigations – Gratiot, Midland,
Arenac herds mention on previous slides
• 78 of the 198 herds needed to TB test - 17,209
head of cattle
Circle Testing
• Public Act 466 requires circle testing
• Typically 10-mile circles
• Three overlapping 10mile circles - Saginaw,
Gratiot, Midland
• Feedlot circles - 3 miles Arenac, (2) Huron
Circle Testing
• All cattle herds in circle must be tested
within 6 months, unless:
o Herd plan to test later
o Feedlot agreement to only to sell to slaughter
• Herds not under quarantine until the day
the actual TB testing begins
• Once the testing is completed the
quarantine may be released
What to Test in Circle Test?
• Cattle and bison 12 months of age and older
• All non-natural additions
• Goats that are comingling with the cattle or
bison that are 6 months of age and older
• Captive cervids that are comingling with the
cattle or bison that are 12 months of age and
older
2013 Circle Testing Outcomes
• 107 farms tested in Saginaw-GratiotMidland-Arenac County circles
o 11,438 cattle tested
No further disease discovered !
2014 Circle Testing
• 1st Huron County circle test (Bay Port)
o 3 mile - 24 premises in database
o March 31 - September 30
• 2nd Huron County circle (Port Hope)
o 3 mile - 24 premises in database
o May 6 - November 6
How Saginaw Herd Infection Happen
• Genetic testing of TB found in Saginaw herd
linked Saginaw herd’s infection to bovine TB
found in wildlife (deer, raccoons, opossums)
and cattle in NE Lower Peninsula’s Modified
Accredited Zone
• To date all wildlife testing in Saginaw region
has been negative
How Saginaw Herd Infection Happen
• Trace investigation found that Saginaw herd
last purchased milking cows in mid-90s
• Market records
• Three different source herds that had provided
the Saginaw herd with bulls were TB tested 6,085 head of cattle all tested negative
How Saginaw Herd Infection Happen
• Most likely source of infection was from a cow
purchased in mid-90s, perhaps from dispersal
sale in TB zone
• Similar case found in November 1993 at
Isabella County dairy through slaughter
surveillance
• Smith et al - JAVMA, August 1, 2013
o one infected animal introduced into dairy herd
o 6 to 19.42 years to discover the infection through
slaughter surveillance
How Saginaw Herd Infection Happen
• Multiple factors likely involved in causing the
infection to spread through the herd during
the summer of 2012
Stress of heat and drought in summer of 2012
Stress of calving
Spatial stress – tight quarters
Feeding unpasteurized milk to calves.
How Other Herd Infections Happen
• Gratiot - infection introduced from feeding
infected unpasteurized milk from Saginaw dairy
• Midland - infected animal originated from
Saginaw dairy
• Arenac - infection introduced by feeding
unpasteurized milk from Saginaw dairy at Gratiot
farm in 2012
• Huron County feedlots - infected cattle from
Saginaw herd purchased
Lessons Learned
• Important to identify all cattle moving off
Michigan farms with RFID tags
Because Saginaw farm’s 2012 bull calves were not
identified with RFID tags it complicated the trace
investigation
• Not feeding unpasteurized milk to calves
At least two of the three other farms found with
TB were infected by feeding unpasteurized milk to
calves
What About Michigan’s TB Free Status?
Questions?