Course: Winter Health | Last Updates: 7th October 2015
Calf pneumonia can have a significant impact on the productivity and profitability of both dairy and beef herds.
The disease leads to reduced growth rates in cattle, increased calf mortality, increased labour requirements to look after affected calves and added costs from treatment.
And even if the animals do survive an outbreak, pneumonia can cause long-term problems because lung function is impaired.
By and large the disease affects younger animals, but it can also pose a threat to adult cattle, particularly in the dairy herd.
By understanding the factors which initiate pneumonia, farmers can take steps to minimise them and reduce infection rates across the herd.
What is pneumonia?
Pneumonia is an inflammation of the lungs, which can cause permanent damage and even death in cattle. Pneumonia can be viral or bacterial in origin, but most often viral infection is first followed by bacterial infection.
The virus or viruses impair the animal’s ability to get rid of the bacteria they are exposed to, allowing the bacteria to gain entry to the lungs and cause further damage.
What causes it?
Pneumonia is typically caused by a combination of factors including stress, housing and ventilation quality and the presence of the causal viruses and bacteria.
The most common viruses that cause pneumonia are respiratory syncytial virus (RSV) and parainfluenza type 3 (Pi3), which are present in most cattle herds.
The third virus is infectious bovine rhinotracheitis (IBR), which is less prevalent, and can cause disease in cattle of any age, but is more typically seen in older calves
It often occurs when groups of cattle from different sources or groups are mixed or housed in large herds and can cause severe tracheitis, even in adult cattle, leading to death.
The final virus to consider is bovine viral diarrhoea (BVD).
Although it does not cause damage to the lungs and airways, it can impair the disease resistance of the group, leading to more serious infection.
With RSV and Pi3 always present in groups, infection requires other triggers which compromise immunity and create an environment in which disease can thrive.
Most commonly, pneumonia affects calves when they are weaned and housed for the first time as it puts them under stress.
Sheds with poor ventilation or dusty bedding are other risks, as are those which are under- or over-stocked, resulting in huddles of animals with poor immediate air flow.
Mixing new groups of cattle will also introduce greater risk, by increasing their exposure to different pathogens and impairing their ability to resist disease.
Although very occasionally calves living outdoors which are infected with RSV or Pi3 suffer severe infections which can prove fatal, the majority will suffer from a raised temperature and mild clinical signs for a few days before, in most cases, making a full recovery.
But those infected indoors, where air quality is poorer, will struggle to clear inhaled dust and organisms from their respiratory tract while under the burden of infection. This then provides ideal conditions for bacteria to colonise the airways and multiply.
The most common bacteria involved in pneumonia outbreaks are Mannheimia haemolytica, Pasteurella multocida, Histophilus somni and Mycoplasma bovis.
These start to colonise the upper respiratory tract and move down towards the lungs, triggering a case of pneumonia.
Toxins produced by the bacteria and by the body fighting the infection cause tissue damage which, if left untreated, can prove fatal.
What are the symptoms?
Cattle infected with RSV and Pi3 viruses will often look well, but will have a temperature of more than 39.5C.
The first sign of disease is usually loss of appetite, so farmers should take the temperature of any animal which is off its food.
Some may develop nasal discharge, a cough, or both and are later likely to suffer from rapid and laboured breathing.
It usually takes two to three days for initial infection to develop into bacterial colonisation and pneumonia, but stock can deteriorate extremely quickly from apparently healthy to seriously ill within hours.
Where there are one or two calves showing obvious signs of pneumonia, four to five times more in the same group are likely to be in the early stages of infection and presenting high temperature.
How is it treated?
An animal showing clinical signs of infection should be treated with antibiotics, as should any other animals showing raised temperatures.
Usually, a broad spectrum antibiotic is used, but cases involving Mycoplasma bovis may be more difficult to treat due to a different sensitivity to antibiotics.
Mycoplasma bovis is, therefore, the most likely bacteria to be associated with low-grade, persistent pneumonia in calves.
Once treated, relapses of the disease can occur, most commonly because initial treatment was not early enough to prevent damage in the lungs.
Once tissue has died it cannot deliver the antibiotic, leaving pockets within the lungs which go untreated.
The bacteria in those areas therefore survive the treatment and go on to re-colonise in the airways, resulting in a relapse.
When this happens the animal may potentially need another course of treatment.
How can infection be prevented in the first place?
As with all disease, prevention is better than cure and there are many steps farmers can take to reduce the risk of a pneumonia outbreak.
The first step is to identify routines which are stressful to youngstock and try to manage them in a way which will keep the animals as stable as possible. Don’t wean, castrate, dehorn and house stock all in the same period. You want to make as few changes as possible and always think of the wellbeing of stock when making those changes.
Check for nutritional deficiencies such as vitamin E and selenium, which will weaken the animal’s immune system.
Young calves should all receive 10% of their bodyweight in good-quality, first-milked colostrum within 12 hours of life to provide vital immune defence.
Ensure housing is well-ventilated, but not draughty and stock to the right density to prevent huddling or overcrowding.
Minimising the level of disease threat is also important, particularly BVD, which is a common trigger for pneumonia as it depresses the immune system for several weeks.
BVD control can be achieved through vaccinating the breeding cows to prevent the birth of persistently infected (PI) calves, and testing young stock to ensure good control is being achieved. When buying in calves from farms of unknown BVD health status then testing and vaccination of the calves themselves may be required.
Where there is risk of pneumonia, youngstock should be vaccinated against RSV. Your vet can advise on whether your herd is at risk of Pi3 or IBR and vaccinate accordingly.
Different vaccines can be administered at different ages, so farmers should formulate their vaccination programme in discussion with their vet.
- Plan your control programme before the pneumonia season begins
- Identify potential stressors and environmental factors which precipitate the disease
- Take advice from your vet about how best to deal with the issue on your farm: depending on your operation, vaccination may be a priority over tackling issues with housing.
- If you do vaccinate, ask your vet for a written vaccination and treatment programme and rigorously stick to it.
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