Interesting snippets from the 2nd Paratb forum August 8th 2009 &10th International Colloquium on Paratuberculosis 9-14 Aug 2009

Margaret Good SSVIPeter Mullowney SVI

Mike Collins

Reasons to Cull ELISA Strong-Positive Cows

• Likely to go clinical next lactation• Likely not to complete a full lactation• Decreased production next lactation• Likely carrying an infected fetus if PG• Heavy shedders = highly infectious• Will contaminate maternity pen causing

more infected heifers

Susceptibility to MAP

• Windsor and Whittington, 2099, Vet J

Age No cattle

% Clinical JD

% Lesions

<6 mos 57 47% 74%

6-12 mos

26 38% 50%

>12 mos

57 18% 19%

• Young calves (<6 mos) less resistant to infection than older cattle

• Older cattle can become infected

Brian Kirkpatrick presented on a Whole genome association study for Holstein susceptibility to MAP infection Possible SNP associations with paratuberculosis susceptibility identified in multiple locations

Scott Wells University of Minnesotapresented on Age related susceptibility

M. Paratuberculosis common in environment surrounding dairy farms

In Austria J. Khol• Assigned correct status to 70%

herds by environmental sampling & culture.

• 3 consecutive samples 80% of herds assigned correct status.

• All herds with high within herd prevalence detected.

• Accurate & economic screening method

• Minnesota dairy farms• (Raizman et al., JDS,2004)

– Positive cow alleyways on 77% of infected farms– Manure storage on 68% of infected farms

• US dairy farms (USDA-APHIS-VS NAHMS Dairy 2007)

– 68% of herds test-positive. Cow level prevalence 4.8% with 18.8% of those heavy shedders

– Pooled environmental samples positive if at least one heavy shedder

– Most cost effective for medium sized herds <10% prevalence was pooled faecal culture 10 or 5/pool.

• Cornell univ. Checked suspect ‘pass through’ and found most were confirmed infected in tissue samples (low shedders may be infected by super-shedders as they did share strains)

Maarten Weber (GD The Netherlands)

• Compared slurry pit (91% +ve) & cow alley (87% +ve) culture in 222 known +ve herds with at least 1 culture +ve cow.

• 5-13% herds false negative.

Sampling cow alleys!! (Ian Gardner)

Rebecca Mitchell did a meta-analysis of calves and Map

• Historically calves not considered an important source of MAP• Experimental infection data indicates calves often have an

infectious period.• Mathematical models would suggest that challenge dose dependent

shedding may result in self-propelling endemicity (backward bifurcation)

• 17 studies Published between 1953 and 2007 Total of 197 animals• Found• Experimentally infected calves shed in 2 phases – early, followed

by a carrier non shedding period then a late shedding phase• Strong relationship between dose and duration of early shedding is

sufficient to allow backward bifurcation ( an increase in effective reproduction ratio relative to basic reproduction ratio once prevalence reaches a specific threshold)

• Endemic infection can be sustained at reproduction ratios which would not support introduction.

Vangenugten looked at birth clusters of Map• Confirmed: Calves from test-negative dam that were

born within 10 days following the calving of a shedding dam were 5 times more likely to become a MAP shedder later in life compared to calves that were not exposed. (Benedictus et al. 2007)

• Birth clusters appear to be present and contribute a large proportion of incident cases of MAP to a dairy farm operation:– 10 day cluster most prevalent (calving pen?) (pooled colostrum?)– 60,90,120 clusters also observed (calf-to-calf?)

• MAP control program with an emphasis on calving pens and a test-and-cull program virtually eliminate birth clusters.

• Perez took illeo-caecal valves of 15,546 extensively reared calves 8-12mths old slaughtered out of 137 herds in Spain.

• Microscopic examination for lesions and acid fast organisms (ZN) (PCR confirmatory on a sample of +ves)

• Demonstrated the method as efficient in detecting lesions in sub-clinical animals

• Lesions in 444 calves 2.83% and if herds with at least one detection were considered positive 49.63% herds are positive

Off-site rearing of dairy heifers to reduce Johne’s disease risk (Ian Gardiner)

ELISA positive Mortality and Culling

Cohort No. first lactation

Positive (%) lacs 1 and 2

Positive (%) herd test

Birth to first calving (%)

First 3 lactations (%)

ON (reared on infected farm)

601 4.6 18/307 (5.9)

194/797 (24.3)

319/601 (53.8)

ON/OFFOff inf farm at 5 months

581 3.6 16/365 (4.4)

210/791 (26.5)

292/581 (50.3)

OFF/OFFReared offsite

638 2.3 10/461 (2.2)

148/797 (18.6)

257/638 (40.3)

Jason Lombard presented on the results of the JD herd management Project

began in 2003• Primary Objective

– Evaluate effect of long-term management on control of JD

• Status (2009):– Seventh and final year of study– 17 States have enrolled herds– 66 dairy herds (~175,000 animals) – 16 States– 23 beef herds (~30,000 animals) – 11 States

Similarly Preliminary Results presented by Sorge on the Canadian voluntary JD risk assessment control programme showed a within herd fall in prevalence

** based on JD milk ELISA test positive or suspect cows

Maximum apparent within-herd prevalence (n=159)In 2005/07: 42%. In 2008/09 18.9%

Based on 159/240 herds Apparent Prevalence1st Test(05/07)

2nd Test(08/09)

Within-Herd Prevalence**

2.4±4.9 1.6±3.0

Lactation 1 0.8 0.7

Lactation2 1.6 1.4

Lactation ≥3 2.0 1.6

Preliminary Results• Herds with individual calving stalls have a lower

prevalence (1.4%) than those without (3.6%) (p=0.022)

• The more cows that were calving together, the higher the prevalence of JD test-positive cows at the 2nd test (p=0.042)

• The prevalence dropped MORE in herds using individual cow maternity pens (-1.2%) than in herds not using individual calving pens (+0.2%) (p=0.042)

• Poor Hygiene throughout the farm (i.e., all age groups) was associated with higher prevalence

• Purchase of cows in last 10 years before ’05-’07 was associated with increased JD prevalence in ’08-’09 (p<0.05)

-Preliminary Results-

Trier presented on a Danish co-op with an ‘experience’ group of farmers as part of the JD control

Experience Group• 8 groups of geographically based farmers• The co-op rep., a Facilitator and the Local advisor

(veterinarian or other)• Meet Twice a year on a different farm of one

participant each time• The farmer shows the farm and tells how he

attempts to control MAP• Participants provide feedback and make

suggestions for alternatives

• The facilitator– Ensures all major risk areas are discussed– Summarize the advice given by the group

members– Brings new knowledge– Encourage the farmers

• Valuable to the Co-op– Feedback from the farmer– Areas that need focus– Where are the obstacles?– Demonstrate success in controlling MAP

• Valuable to the farmer– Focus– Helps to find solutions– Gives ideas– High motivation– Education– Engage the advisers– Commitment to the group

Conclusion

• Improved routines

• The quality of the discussions has improved

• The knowledge of infection protection has improved

• Meetings are valuable to the farmers

• Kruze (Chile) demonstrated a lag time of two months from spreading slurry contaminated by map and finding of map in water samples.

• Map leaching favoured by light soil textures and increasing rainfall

• Dhand (Australia) suggest that under experimental conditions that Map adsorbs to a range of soil particles influenced by soil pH.

Phage based detection of MapUniv. Nottingham and Vet service Cyprus

• Used fast plaque TB from biotech normally used for sptutum sampling in humans

• No decontamination steps therefore no loss of organisms (VISAVET said decontamination reduces colony counts by 2.5log)

• Milk samples TBC indicated Map detected in non-clinical cows was not a result of faecal contamination

• Phase based test more sensitive than culture• UK – 54 samples; 19(35.2%) phage +ve only 1% PCR and

none culture• Cyprus – 225 samples; 218 +ve phage, 50 PCR, 2 culture• Phage also detects M. bovis in milk

Conclusions1. Map was detected and cultured from diaphragm muscle of

paratuberculosis infected cattle destined for human consumption

2. In general there was a positive association between the severity of the enteric lesions, clinical signs of paratuberculosis, heavy bacterial load in intestinal tissues, fecal shedding of Map and the presence of disseminated Map infection in diaphragm muscle.

3. Two of the positive animals did not show clinical signs associated to paratuberculosis and one was not confirmed as fecal shedder, suggesting that meat from both symptomatic and asymptomatic animals could potentially represent a source of exposure to Map to humans.