Dairy suckler farmers and practising vets should not rule out the possibility of Johne’s disease impacting on weanling cattle that are scouring and losing weight over a consistent period of time.
This follows the confirmation by Agri-Food and Biosciences’ Institute (AFBI) veterinarians of Johne’s in a seven-month-old Friesian heifer, who was recently submitted for post-mortem analysis.
According to the history provided, there were also several other calves on the farm with similar clinical signs.
The disease is caused by a bacterium, which is similar to that responsible for bovine tuberculosis. Johne’s is normally associated with older cattle, but not always.
AFBI’s head of Disease Surveillance and Investigation branch, Dr. Barry McInerney, said:
“In the case of the young animal submitted to us, the disease was confirmed on the back of the pathology work that was undertaken. This included a histological examination of tissues taken from the animal.
“It’s a process that takes a number of days to complete. The calf might have contacted the disease through its mother’s milk or by ingesting contaminated dung.”
“Johne’s is a very complex health condition, both to confirm and to manage. It is one of five main endemic diseases that are in Northern Ireland, having a severe economic and welfare-related impact on the local cattle industry.
“The others are: Bovine viral diarrhoea (BVD), leptospirosis, infectious bovine rhinotracheitis (IBR) and neosporosis.”
Johne’s disease
According to the AFBI veterinarian, Johne’s can be confirmed by way of a blood test. Alternative options are dung and bulk milk tank testing.
The latter option simply helps to identify the presence of the disease at farm level.
Minimising the spread of the disease centres on the prevention of stock from coming into contact with contaminated milk and dung.
Johne’s infection develops slowly and the signs of disease vary depending upon the stage of infection, but begins with reduced productivity, followed by weight loss, scour and ultimately, emaciation and death.
Signs of Johne’s are typically seen in animals that are between three and five-years-old. But, they can occasionally be seen in animals that are younger than two-years-of-age.
As the animal gets older, the signs become more obvious. An infected animal may also have increased susceptibility to other disease before the obvious signs occur.
There is no effective treatment or vaccination for Johne’s disease.
Infection can contribute to reduced milk yield and increased susceptibility to other conditions, such as infertility, even before the more obvious signs of disease appear.
Infected cattle may be culled due to poor productivity before a diagnosis of Johne’s disease. Therefore, Johne’s disease can be an unrecognised cause of excessively high cull rates.
Barry McInerney pointed out that AFBI’s Cattle Health Scheme provides a pathway to manage and control Johne’s at farm level.
In Northern Ireland, there is a voluntary, industry led control programme managed by Animal Health and Welfare NI.
Due to the young age of the weanling submitted to AFBI, Johne’s was not high on the initial list of differential diagnoses. It was only through submission for post-mortem examination that the disease was confirmed.
This demonstrates that Johne’s must be kept in mind as a differential weanling calves of this age, especially if there is a known history of the disease on the farm.
McInerney concluded: “This case demonstrates the value of submitting animals to AFBI for post-mortem.
“The diagnosis of disease and surveillance for other potential diseases, not only has value at farm level but also added value for the wider livestock sector.”
