Bovine Tuberculosis
Dr. Rick SmithAssistant State Veterinarian over Ruminant Programs
Bovine TB Program CoordinatorMDARD
Overview• 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 testedo 17% caudal fold response rateo 13% gamma interferon - 6 mo. +
2013 Saginaw Co.TB positive dairy herd
Gratiot & Midland Co.TB positive herds
Arenac & Huron Co.TB positive feedlots
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
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 10-mile 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: oHerd plan to test lateroFeedlot 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-Gratiot-Midland-Arenac County circleso 11,438 cattle tested
No further disease discovered !
2014 Circle Testing• 1st Huron County circle test (Bay
Port) o3 mile - 24 premises in databaseoMarch 31 - September 30
• 2nd Huron County circle (Port Hope)o3 mile - 24 premises in databaseoMay 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
herdo 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 2012Stress of heat and drought in summer
of 2012Stress of calvingSpatial stress – tight quartersFeeding 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 tagsBecause Saginaw farm’s 2012 bull calves
were not identified with RFID tags it complicated the trace investigation
• Not feeding unpasteurized milk to calvesAt 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?