Bovine Tuberculosis

Dr. Rick SmithAssistant State Veterinarian over Ruminant

ProgramsBovine TB Program Coordinator

MDARD

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 rate

o 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 later

oFeedlot 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 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 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?