Infectious diseases and health schemes

Johnes Disease

Johnes disease is caused by the bacterium mycobacterium avium pparatuberculosis.

Cattle are susceptible to infection when they are newborn calves. The infection is mainly transmitted in the infected cow’s milk and faeces.

This is why it is especially important to ensure that milk and colostrum from Johnes-positive animals are not fed to calves, and that the areas where cows will be calving down is kept clean and free of faeces.

Unfortunately, Johnes disease is endemic across the country, and many farms will have a level of disease.

Even if you don’t see clinical cases of Johnes disease – such as progressive weight loss, a reduction in milk yield and profuse pipestream diarrhoea in animals usually four to six years old – subclinical Johnes disease could be impacting your profits by reducing the fertility and milk yield in your animals, and increasing the incidence of mastitis and lameness.

Johnes disease can be tested for in samples of milk, blood or faeces. However, the results must be interpreted with caution, as the bacteria is shed from the faeces intermittently, and the antibody levels in the blood of infected cows also fluctuates.

As such, it is important to do regular testing, so that we can build up a picture of the prevalence of disease in the herd, and to be sure that we have detected infected cattle.

Here at Penbode we have several vets accredited on the Action Johnes Scheme. We can arrange to visit your farm and discuss which control measures would be most suitable to your herd, and help you implement those changes.

Bovine Viral Diarrhoea (BVD)

BVD is a viral disease which results in abortion, subfertility, weak calves and respiratory disease.

The virus is shed in faeces, semen and nasal secretions. When a naïve cow comes into contact with the virus from one of these sources, the following may occur:

• If the cow is not pregnant à scouring, reduction in milk      yield – mild to no signs

• If the cow is in the first trimester     of pregnancy à abortion and reduced fertility. If the      foetus survives to full term it will be born as a persistently infected      animal (a PI calf).

• If the cow is in the second trimester     of pregnancy àabortion or congenital abnormalities

• If the cow is in the third trimester     of pregnancy à the calf may be weak or healthy at      birth, but abortions generally do not occur

In all cases, the cow will produce antibodies to the BVD virus approximately two weeks after infection.

PI Calves do not recognise the BVD virus, and so do not mount an immune response to it.

This is because it was present within the calf’s bloodstream during the development of the calf’s immune system, and so the white blood cells do not recognise it as foreign.

As such, these calves will never produce antibodies to the BVD virus, but they will have a circulating amount of virus, or antigen, in their blood.

These animals are weakly, fail to thrive, and are a source of infection to the rest of the herd. To eradicate BVD from a herd, these animals should be identified and culled.

PI calves, if they live long enough, can also develop mucosal disease. Any offspring from these animals, if they survive to adulthood, will also be persistently infected.

The presence of BVD in a herd can have huge financial implications due to the reduction in fertility, reduction in daily liveweight gain of calves and loss of calves. Fortunately there are several measures available for the control of the disease.

At Penbode, we have several accredited vets on the BVD Stamp it Out scheme. We can organise to come to your farm and conduct an investigation into the level of disease in your herd.

Based on the results of this, we could organise a PI hunt to identify any persistently infected animals which are acting as a source of infection. Alternatively, if you have no BVD on your holding, we could arrange vaccination of the herd and/or tagging and testing to monitor prevalence of the disease.

Leptospirosis

Leptospirosis is caused by one of two serovars of the leptospira hardjo bacteria.

The signs most commonly seen are a reduction in milk yield with the udder becoming soft and flabby, and milk becoming clotted or blood-tinged.

Infected cows will abort their pregnancy, often towards the end of the gestation, or may give birth to weak sickly calves.

Leptospirosis can persistently infect the uterus, resulting in sub- or infertility, reducing conception rate.

The disease is transmitted via contact with aborted tissues and urine passed by infected cows. It is also possible for a bull to be a carrier of infection and to pass the disease on to any cows that he serves.

Sheep are symptomless carriers of leptospirosis and so may also pass infection to cattle. Some cows might only shed the bacteria in their urine for a short time after infection, whereas others could shed the bacteria intermittently for their whole lifetime.

A herd is at higher risk of infection with leptospirosis if any of the following practices take place:

• Sharing a bull

• Co-grazing with sheep

• Shared water sources

• Keeping an open herd.

It is important to remember that leptospirosis is a zoonotic disease – this means that it can be transmitted to humans and cause disease.

The signs of human infection include a headache and flu-like symptoms. The people most at risk are milkers, due to their being exposed to the cows’ urine whilst in the parlour.

Bulk tank screens can be useful to detect the level of disease prevalent on your farm.

For the reasons outlined above, it may be prudent to vaccinate your herd against leptospirosis.

This prevents colonisation of the renal tract, which prevents infected cattle from shedding the bacteria in their urine, thus reducing the risk to human health, and the reproductive tract, so reducing the effects on fertility and preventing infection of the unborn calf.

If you are interested in this, please contact us and we will order the vaccine for you.

Bovine Respiratory Disease

Diseases of the respiratory tract in cattle remain a major cause of economic loss and welfare concern in the UK cattle industries, resulting in:

• Lifelong reduced growth rates

• Increased use of medicines

• Delay in age at first calving

• Reduction in subsequent milk yields

• Higher mortality rates

Often respiratory infections begin with viral damage to the lungs.

This provides the perfect environment for bacteria to grow and so we see further damage. Symptoms that could indicate bovine respiratory disease include:

• Smaller, poor-growing calves

• Nasal and ocular discharge

• Fever

• Coughing

• Abortion

• Milk drop

As with many diseases, prevention is much better than cure. We can provide vaccines to prime the immune system against these viral and bacterial pathogens, should the body come under attack. Our VetTechs can also help administer them.

The environment plays a major role in the transmission and propagation of infectious respiratory disease.

Ventilation, temperature and moisture are the three main environmental factors that influence respiratory pathogens.

Good ventilation relies on the stack effect, with warm air from the animals rising and escaping through outlets at the top of buildings and fresh air entering from the sides to take its place.

Cobwebs and tiger stripes are evidence of poor ventilation in sheds. We can assess ventilation in housing by visiting farms to collect the following data:

• Number of livestock in the building

• Area of floor space per animal

• Average body weight of the animals

We can also assess if the inlets and outlets for airflow provide a good environment for your cattle. With this information we can advise ways you could adapt your current set up to make improvements and reduce the risks and impacts of BRD.

Infectious Bovine Rhinotracheitis (IBR)

IBR is caused by bovine herpes virus and is highly contagious.

It can cause an upper respiratory tract infection which can lead to a fatal pneumonia. Other signs include conjunctivitis, milk drop and abortion.

Once an animal becomes infected with IBR, it remains infected for life, only showing signs of the disease under periods of stress, much like cold sores in humans which are also herpes viruses.

This makes animals who have been infected but aren’t currently sick the highest risk to your farm when buying in.

Vaccination can help protect animals but it will not stop those already infected continuing to shed throughout their lives. The best way to ensure you are not buying in IBR is to buy from IBR free accredited herds.

You can become an accredited herd through various health schemes. More information can be found here: 

https://www.checs.co.uk/diseases/infectious-bovine-rhinotracheitis-ibr/

IBR has been eradicated in various European countries. In the future, herds will have to prove they are IBR free in order to trade live cattle in these markets.

TB

TB testing is a big part of all farmers’ and vets’ lives in the South West. While some of you are fortunate and only have an annual test others see us every 60 days for short interval testing.

Our trained TB advisors can offer free telephone recommendations to our clients to help prevent TB breakdowns in herds that are currently clear, as well as discussing trade options and measures to prevent repeated infections for farms currently under restriction.