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2008 Johne’s Disease Proficiency Panel‐Retest

General Summary

There were 65 USA laboratories and 6 International laboratories that

participated in the 2008 Johne’s disease proficiency panel. These laboratories were sent

118 individual kits and 27 pooling kits, as USA laboratories are required to check each

method used for official testing. Table 1 lists the kit performance by method tested and

Table 2 further divides the liquid media culture into each testing platform.  

Table 3 lists the causes for labs not passing the individual kits. Sensitivity issues

continue to be the most common problem laboratories encountered followed by false

positives on confirmatory PCR.  Five laboratories chose to reorder more kits (4 using

direct PCR, 1 using liquid media) after they were notified they may not pass. Four out of

five labs passed on the second kit. Both the original and repeat tests are included in

Tables 1 and 3.  Results included in this report do not include methods that laboratories

passed on the recalled 2008 Proficiency panel released in February of 2008. Please see

the specific report on the recalled panel for that information.

Table 1. Summary kit results* for the 2008 Johne’s Disease  

Proficiency Panel Retest sent to laboratories in June, 2008.

# passed (%)

# not

passing (%)

# not

returned (%) Total

Individual kit

Direct PCR 35 (70%) 13 (26%) 2 (4%) 50

Liquid 24 (75%) 5 (16%) 3 (9%) 32

HEY 20 (55%) 13 (36%) 3 (8%) 36

Total 80 (67%) 29 (24%) 11 (9%) 118

Pooling kit

Direct PCR 10 (91%) 0 1 (9%) 11

Liquid 8 (67%) 2 (17%) 2 (17%) 12

HEY 4 (100%) 0 0 4

Total 22 (81%) 2 (7%) 3 (11%) 27

*In order to pass kits must meet the criteria listed in the 2006 Uniform  

Program Standards for the Voluntary Bovine Johne's Disease Control  

Program.  

Table 2. Liquid media culture system results for the 2008  

Johne’s Disease Proficiency Panel Retest sent to laboratories  

in June, 2008

# passed

# not

passing

# not

returned Total

Individual kit

Trek ESP 19 2 1 22

MGIT 960 3 3 2 8

Bactec 460 2 0 2

Total 24 5 3 32

Pooled kit

Trek ESP8 2 2 1

Total8 2 2 1

2

2
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Table 3. Primary reason for kits not passing the 2008 Johne’s Disease  

Proficiency Panel Retest

Direct

PCR

Liquid

media

HEY

media

Misclassified a negative sample as

positive 3 21

Missclassified the M. avium spiked

sample as positive 0 0 2

Missed 5 or more low/ moderate

shedders (lack of sensitivity) 10 2 3

Missclassified a high shedding sample

as negative 0 0 3

A critical sample was contaminated N/A 1 1

Multiple reasons cited above 0 03

Total 13 5 13

Kit composition and sample selection

All kits contained the same cows and replicate samples.  The negative samples

were from cows located in beef herds that have done extensive testing for Johne’s

disease and have high biosecurity. Cows were located in Georgia (ST10, 1, ) North

Dakota (68) and Montana(492922).  The positive samples were from a commercial dairy

in New York (14, 18, 315, 318), a commercial dairy in Iowa (443, 447) and at NVSL (68,

834). Samples were cultured 3 times on each method (MGIT 960, Bactec 460, Trek ESP,

HEY solid media, and direct PCR.)   

Table 4. Kit composition, sample designation and average colony counts from participating

laboratories and the National Veterinary Services Laboratories using HEY media

Cow ID

# reliplicates

in kit

Average of lab

colony counts

per tube (St.

Dev)

Range of all

lab results

NVSL

colony

counts per

tube ? Sample designation

1 2 0.0 (.132) 0 ‐ 1 0 Negative‐ (Critical)

68 2 0.0 (.110) 0 ‐.75 0 Negative‐ (Critical)

492922 2 0.0 (0) 0 0 Negative‐ (Critical)

ST10* 1 NA NA 0Negative‐ (Critical)

834 2 0.0 (.112) 0 ‐.75 0 Eliminated

3000 3 0.7 (1.07) 0 ‐ 5.75 3 Low

14 2 1.3 (2.6) 0 ‐ 18.3 6 Low

18 2 5.0 (5.7) 0 ‐ 23 13 Moderate

86 2 6.6 (6.4) 0 ‐ 25 39 Moderate

318 2 TNTC 6‐TNTC 480 High‐ (Critical)

315 2 TNTC 0.25 ‐ TNTC 1725 High‐ (Critical)

443 2 TNTC 0 ‐ TNTC 6075 High‐ (Critical)

477 2 TNTC 0 ‐ TNTC 7850 High‐ (Critical)

*Sample spiked with Mycobacterium avium ?

Colony counts by NVSL were determined by averaging results from 3 cultures for each cow. For high

shedders, the inoculum was diluted 10‐x

  until colony counts were under 100 per tube
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Criteria for passing

According to 2006 Uniform Program Standards for the Voluntary Bovine Johne's

Disease Control Program (Johne’s UMR),

(http://www.aphis.usda.gov/animal_health/animal_diseases/johnes/downloads/johnes‐umr.pdf ) all

negative and high shedders must be classified (positive/negative) correctly. In order to

be considered a critical high sample, 50% of laboratories using solid media must identify

those samples as having >50 colonies per tube. There were 7 critical negative, 7 critical

positive samples and 1 positive control sample in the kit.

Furthermore, 70 % of participating laboratories must correctly identify a sample

in order for it to be included for grading purposes. Only 4 of 214 samples from cow 834

were identified as positive, therefore both samples from this animal were eliminated.

This cow resides at NVSL and has been culture positive previously.

The final criterion for passing is 70% of all non‐critical samples (low and

moderate shedders) must be identified as positive. There were 9 non‐critical samples

left in the kit, Therefore a minimum of 6 of the 9 non‐critical samples must be identified

as positive.   

Participating laboratories will also receive a detailed report of their laboratory’s

individual performance separately.  

Any questions about this report can be directed to either:

Beth Harris, M.S., Ph.D.

USDA/APHIS/NVSL

Head, Mycobacteria and Brucella Section

1800 Dayton Ave.

Ames, IA 50010

Office: 515.663.7362

Beth.N.Harris@aphis.usda.gov   

Suelee Robbe‐Austerman, DVM, PhD

USDA/APHIS/NVSL

VMO, Mycobacteria/Brucella Section

1800 Dayton Ave.

Ames, IA 50010

Office: 515.663.7837

Suelee.Robbe‐Austerman@aphis.usda.gov