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Use of milk for monitoring disease in dairy herds

Herman Barkema Dept. of Production Animal Health

Outline

§ Why do we need monitoring of diseases?

§ How can we use milk for in monitoring?

§ Prioritization of diseases to monitor

Globalization

§ International trade integral part of modern agriculture

§ Increasing dependence on export and import

§ Increasing demand for animal products in developing countries and export from those countries to Canada

Nationally

§ Constant increase in trade of animals and animal products

§ Emergence of new diseases and hardly any eradication of existing diseases

§ Exception: Johne’s disease prevention and control programs

Nationally

§ Diseases are bought and paid for!

§ Also, cattle shows can be a source of infections

§ Freedom of disease is a mixed blessing

§ Minimizing introduction

§ Traceability

Farm-level

§ Different approach Europe and North America

§ ‘closed farming’

§ E.g. Mycoplasma

§ Limitation of within-farm spread of pathogens, e.g. contagious udder pathogens

Within farm

§ A lot of diseases spread from cow to calf

§ Vaccinations are not 100% protective

§ You want to know what diseases you don’t have in the herd

§ You want to know what disease you do have so that you can prioritize control

More organized disease control and certification § Emphasis in North-America on control by

vaccination

§ No good vaccines available for a lot of diseases

§ Only recently introduction of I&R

§ Not a lot of stamping out of diseases

Not only FADs

§ Canada is absolutely not a frontrunner in eradication of disease

§ Northern Europe is free of e.g.: •  Bovine leukosis virus •  Leptospira hardjo

§ Has active eradication programs for: •  Salmonellosis •  Neospora caninum •  Johne’s disease •  IBR •  BVD •  ….

Changes in dairy farming in the last 10 years

§ Larger farms and different housing § Automated Milking Systems § (slow) Increase in organic farms § Bulk tank Somatic Cell Count

•  Change in distribution of pathogens § Bonus programs in some provinces

Increased consumer awareness § Earlier, only interested in the quality of the product.

Now, also wants to know how the product is produced

§ Welfare

§ Environment

§ Zoonotic and possibly zoonotic diseases

Consequences § Dairy industry will have to get used to ‘consumers’ watching

and proactively deal with issues that (may) arise

§ Restrictive use of antibiotics and hormones à focus on prevention and information for monitoring, less on cure

§  “Quality” becomes more and more important, welfare of cows is part of it

§ The number of organic farms increases

§ Control of diseases requires an organized monitoring and control

The very near future

§ Quality not only quantity § Bulk milk SCC will decrease § Strep. agalactiae will disappear in Europe, Canada

and New Zealand § Use of antimicrobials will be more restricted à

focus on prevention and information § How milk is produced will become more and more

important

§ We need to monitor diseases

Good monitoring does not necessarily ensure the making of the right decisions,

but it reduces the risk of wrong ones

Languimer, 1963

History of milk testing

§ Most countries with a developed dairy industry started in the 1970s using bulk milk for: •  Bacteria count •  Somatic cell count •  Mastitis bacteria, particularly Strep. agalactiae

and Mycoplasma

Milk can be tested to assess:

§ Bacteriological quality § Herd udder health (mastitis bacteria) § Foodborne pathogens § Zoonotic agents § Pathogens of animal health significance § Viruses of dairy cattle § Toxins, metabolites, trace minerals § Fat and protein content

Dr. Bhushan Jayarao, 2004

Type of tests used on milk

Milk

Culture

Selective media Enrichment Dip sticks

PCR

Uniplex PCR Multiplex PCR Real-time PCR

Immunoassay

ELISA

Other tests

HPLC Infrared analysis

‘Smelling’ bacteria

Dr. Bhushan Jayarao, 2004

Why monitor disease using DHI or bulk milk samples

§ Sampling and transport has already been paid for

§ A lot of pathogens are shed in the milk

§ A bulk tank sample has milk of all lactating cows

§ The tools are now available to monitor more than one pathogen at the same time

§ It is very cost-effective

Limitations of bulk milk testing

§ Dry cows and young stock are not included

§ Value in large (>200) herds is questionable

§ For interpretation most often quarterly samples are needed

§ Information on management practices needed to interpret results

§ To culture bacteria, samples need to be stored at 4oC and analyzed within 36h

Dr. Bhushan Jayarao, 2004

What could we do right now with bulk milk?

§ Mastitis pathogens: •  Staphylococcus aureus •  Streptococcus agalactiae •  Mycoplasma

§ Quarterly analysis using PCR § If positive, find positive cows using DHI samples

Dr. Bhushan Jayarao, 2004

What could we do right now with bulk milk?

§ Quickscan: •  BVD •  Johne’s disease •  Salmonella •  Neospora caninum •  Bovine Leukosis Virus •  Leptospirosis •  Intestinal parasites •  Liver fluke •  IBR

§ More elaborate monitoring or control program is also feasible for each disease

Dr. Bhushan Jayarao, 2004

Bulk milk à DHI milk samples

§ Bulk milk provides a herd level picture: •  Freedom of disease •  For some disease and indication of the level

§ Individual cow samples: •  Obtain a better picture of the level of infection •  Some diseases good for individual cow data

§ Contamination from cow to cow § Dilution from blood to milk

Bovine Viral Diarrhea Virus

§ PCR •  In spite of vaccination many herds have carriers •  Herds >100 split herd or string samples •  Young stock and dry cows, pooled (max. 50

animals) serum samples •  A certification and/or control program is possible,

but it would include checking young stock for a year

•  Closed herd (or checking animals before they come in) would be necessary

Why provincial Johne’s Disease Initiatives?

§ Most of the Canadian dairy farms are infected § 16% of Maritime cows infected, while 3.4% had

antibodies § 1-2% of beef cows has antibodies, at slaughter

higher § It may be associated with Crohn’s disease in

humans § Effect on farm economics?

§ Potential trade barrier

§ Spin off benefit for other calfhood diseases

Testing for Johne’s disease

§ All Johne’s disease tests, except culture, have to be interpreted on the herd-level

§ The tests are good, it’s the biology of the disease that makes interpretation of testing challenging

§ Antibody ELISA only for individual milk samples. Again, interpretation on the herd-level

§ Milk contaminated by shedding in the milk or contamination at milking

§ PCR works better on bulk milk than culture § Bulk milk testing part of JD prevention and control

program?

Herd JD status program

§ Has to be a national program to work

§ Currently started in Alberta

§ Easy entry, not expensive, not elaborate

§ Not too many levels

§ Herds should not drop too much when one cow is positive

‘A good plan today is better than a perfect plan

tomorrow’

General George Patton Jr.

Salmonella

§ Important cause of diarrhea in humans

§ Lots of problems in cattle; calves and cows

§ Antibodies in bulk milk

§ Notifiable disease in many provinces. What to do if positive?

Neospora caninum

§ Most frequent cause of abortion in cattle

§ Antibodies bulk milk (e.g. quarterly)

§ Antibody ELISA works well

§ Best in combination with serum samples of cows that aborted (and pathology of aborted fetuses)

Bovine Leukosis Virus

§ Many developed countries in the world have eradicated this infection. Others demand negative tests for import

§ Percentage infected herds and animals in Canada increases rapidly

§ Antibodies § CFIA has an existing program - CHAH (Canada

Health Accredited Herd) program with only a few participants

Leptospirosis

§ Most often ‘hardjo’ § Most western European countries have eradicated this disease in dairy cattle § Reduced fertility and sporadic abortions § Occasionally weakly calves that fail to thrive and

‘flabby bag’ or milk with a lot of flakes § Antibodies in bulk milk, If positive, individual

animals § Quite a number of milkers is seropositive. This is a

serious zoonosis: particularly transferred during milking

§ Profound fatigue, severe headache, high fever, muscular aches and pains, sore eyes, nausea and vomiting

Many more possibilities

§ Other pathogens such as Listeria and Coxiella burnetii (Q-fever). Both high prevalence

§ Fertility: •  Pregnancy testing •  Cystic ovaries •  Cycling on not

§ …..

What to do?

§ CanWest DHI has shown that it is one of their priorities to offer diagnostics to monitor diseases

§ Prevalence studies to find out what pathogens are most important

§ Provincial dairy organizations need to determine what should have priority

§ Study what participation can be expected

§ Only monitoring is insufficient. Who will give advise on prevention and control of these diseases?

Don’t wait for provincial programs though

§ Mastitis needs to be monitored

§ Participate in Johne’s disease programs

§ Determine what diseases you have in your herd, prioritize with your veterinarian and make a prevention and control program

How to prioritize

§ Prevalence

§ Impact (economic and human health)

§ Possibility to control

§ Costs

More than milk?

§ DHI organizations have the logistics and the labs

§ For disease control often samples of non-lactating animals are needed: •  Dry cows •  Young stock •  Pathogens that are not shed in the milk •  Antibodies that are too much diluted in milk

§ Beneficial if data come from one source and are combined in reports using animal data

Final words § Possibilities are endless; Canada is well behind the

rest of the developed world § We need coordinated prevention and control

programs § Provincial dairy organizations need to talk with each

other § DHI organizations need to talk with dairy

organizations, government and advising organizations

§ Design programs § Don’t wait for governments and other commodities

to get their act together