Bulk Tank Milk Testing for Johnes Disease
Bulk tank milk testing
The Department of Agriculture, Food and the Marine (DAFM) is conducting ongoing national screening on bulk tank milk (BTM) samples for a range of animal diseases, including Johne’s disease.
The purpose of this page is to support and provide information to dairy herd owners who receive advice from DAFM of a positive result to Bulk tank milk test screening for Johne’s disease.
Bulk tank milk testing
Screening has been conducted twice per year, in spring and autumn, since 2019. A milk sample from each milk supplier is provided by all Irish dairy processors to DAFM, which conducts the laboratory testing.
BTM samples are tested by ELISA, looking to detect antibodies against MAP, the bacteria that cause Johne’s disease.
The test applied to BTM samples will detect antibodies only if herds a relatively high proportion of animals releasing l antibodies into the milk; many infected herds will have negative BTM test results because they do not yet have a sufficient level of antibodies in the bulk milk samples. Therefore, a negative result provides very little assurance that a herd is free of infection, and should not be taken as evidence of freedom.
Positive test result
One or more positive BTM results for Johne’s disease indicates that the herd is very likely infected with Johne’s disease, and at a relatively high proportion of infected animals (high prevalence).
A positive BTM result should be interpreted carefully, in consultation with the herd’s regular veterinary practitioner who is familiar with the herd’s health profile. Rarely, other factors such as recent TB testing or exposure to closely related bacteria in soil or water may cause positive BTM results.
Further assessment and testing of the herd will give a clearer picture of whether infection is present.
DAFM is notifying owners of herds with positive results to BTM testing for Johne’s disease. The purpose of this notification is to advise of the result(s) and to recommend joining the Irish Johne’s Control Programme.
What is Johne’s disease?
Johne’s disease affects primarily ruminant animals (cattle, sheep, goats, camelids), but can also infect other species. It is caused by infection with bacteria called Mycobacterium avium subsp. paratuberculosis (MAP). Animals generally become infected by ingesting (swallowing) MAP, and cattle are much more susceptible to infection as calves than as adults.
- Herds infected with Johne’s disease can have reduced milk production (volume and solids), and higher rates of mastitis, infertility and lameness, even before the severe signs of disease in individual animals become apparent.
- Individual infected animals with advanced disease show drop in milk production, severe weight loss, diarrhoea and bottle-jaw, leading to death.
Spread and progression
- Cattle are usually infected as calves by ingesting MAP bacteria from colostrum or milk or from their environment.
- The bacteria are shed in dung from infected cattle, mostly as adults, to contaminate the local environment including bedding, and udders and teats. The bacteria may be shed directly into colostrum and milk within the udder; or colostrum and milk may be contaminated from soiled surfaces of teats, calf lips, milking equipment, milk containers or hands.
- As well as housing, the contaminated environment can include pastures that have been grazed by adult cattle or have been spread with slurry, and also fodder made from those pastures. Calves may also be infected before birth.
- Infection progresses slowly. For two years or longer, infected animals usually remain without apparent disease and are test-negative. Progression of infection to disease (wasting and scouring, etc.) is usually triggered by stress, most commonly in dairy cows due to peak milk output in the second to fifth lactations. Other stressors such as calving, movement to a new herd, bullying, and concurrent disease may be factors.
- Shedding of infection from an animal increases as infection progresses, but can occur before disease becomes apparent. Within a herd, spread of infection is typically slow at first, but gradually increases as more calves become infected each year.
- Keys to controlling infection are to identify high-risk animals (mostly test-positive animals) for isolation and removal, and hygienic conditions for calving and calf-raising. The key to preventing infection is to maintain a closed herd.
Irish Johne’s Control Programme
The IJCP will help clarify whether a BTM positive result is truly due to infection, and will enable cost-effective actions for the long-term benefits of control.
It will assist with either reducing the level and impact of infection where present, or protecting uninfected herds against becoming infected. The programme also reduces calf mortality, improves calf health and farm biosecurity for participating herds, enhancing Ireland’s reputation for high standards in milk production.
This is a voluntary national programme with funded supports for on-farm activities. It provides for a trained approved veterinary practitioner (AVP) nominated by the herd owner to work in collaboration. This work involves animal testing, assessment and planning of practicable controls to minimise the impacts of JD.
The programme is supported by a cross-industry Implementation Group, which includes representatives from all industry partners including your milk processor and farmer organisations.
JD can significantly affect profitability of dairy herds (estimated at €2,000 per year on average even in the absence of obvious disease) and the information and actions available to you under the IJCP are practical and cost-effective.
The IJCP comprises the following components for all dairy herds:
- An annual veterinary risk assessment and management plan (VRAMP) conducted in collaboration between the herd owner and AVP, and fully funded by DAFM. A VRAMP will:
- identify risks that apply to a herd for introduction and spread of infection, such as cattle introductions and calf hygiene, and
- note agreed changes towards the most practical and cost-effective controls to suit the particular farm.
- Annual whole herd testing (WHT) of all eligible animals (those aged two years and above) using individual blood or milk samples. Financial support is provided toward the costs of the WHT, at the rate of €2.75 per tested animal initially. This rate is maintained for test-positive herds, but reduces over time in subsequent rounds for test-negative herds.
- Follow-up (ancillary) testing of dung samples from animals with positive or inconclusive results to the screening WHT. This testing is fully funded under the programme by DAFM, being paid directly to the AVP and testing laboratory.
- Herds that have one or more positive ancillary test results are confirmed as infected and are provided with further AVP input and advice through a fully funded TASAH (targeted advisory service on animal health) assessment.
How to join the programme
There is no cost to join the IJCP. You can easily join by:
- On-line registration or phone Animal Health Ireland (091 507 648) for more information.
For advice that is specific to your herd, contact your preferred veterinary practitioner.
Useful programme leaflets, including:
- ‘10 Good Reasons’ Factsheet – A leaflet showing the benefits to all Irish dairy herds from joining the programme
- Flowchart – Displays the components described above, and provides links to detailed information on how to take each step along the flow
- Planning your Milk Test – Guide to scheduling herd testing using milk samples, to ensure all programme requirements are met.
Your milk quality advisor can explain why your co-op encourages Johne’s control, to improve your bottom-line and to enhance Ireland’s reputation for high standards in milk production.
If you are milk recording, your milk recording organisation can show how testing of the milking herd is convenient and cheap (although non-milkers aged two years and over must also be tested by your veterinary practitioner).
Contact Animal Health Ireland by phone on 091 507 648 or by email to firstname.lastname@example.org.