Autumn sees a seasonal rise in cases of pneumonia, with both individual animals and groups being affected.
Most at risk are bought-in weanlings. but home-reared cattle, both dairy and beef, are also at risk, particularly at housing.
The obvious costs of pneumonia include treatment costs, your time, and the cost of animals that don’t survive.
Less obvious costs are reduced weight gain and performance in recovered animals that may have residual lung damage.
These animals cost more money to finish and usually produce a less valuable end product.
Dairy heifers that go on to calve and milk are more likely to produce less milk and to survive in the herd for fewer lactations.
Studies have shown these ‘hidden’ losses to be far greater than the more obvious ones mentioned earlier.
Finally, a pneumonia outbreak like any disease, causes worry and stress that cannot be measured in financial terms.
In this week’s article, we will look at the disease agents involved and the methods of diagnosis.
Next week, in Part Two, we will turn our attention to the risk factors involved in pneumonia and how to prevent occurrence, including vaccination.
Disease agents causing pneumonia
There are a number of different viruses and bacteria associated with pneumonia in cattle, including IBR, RSV, PI3 and Corona virus, to name the viruses, and the bacteria, Pasteurella, Mannhaemia, Histophilus and Mycoplasma.
The clinical appearance of an animal may give clues to suspect one virus or bacteria over another.
IBR is a virus that affects the upper airways, often leading to a discharge from the nose and eyes, red inflamed muzzle, and a high temperature.
RSV and PI3 are viruses that affect the lower airways, leading to inflammation in the lungs, and respiratory distress.
Bacteria can also be the primary cause of pneumonia, and also affect the lower airways.
However, most pneumonias consist of mixed infections of viruses and bacteria.
The primary agent could be a virus like IBR which could be followed by a secondary bacterial infection like Pasteurella.
It is also important to remember that some of the bacteria are normal inhabitants of the upper airways of cattle, but can cause infection secondary to other agents.
As well as examining the animals,there are a number of diagnostic tests available to your vet to determine the exact agent(s) involved.
Nasal swabs can be taken from cattle with pneumonia and can be used to test for both bacteria and viruses.
In general, you need fresh cases, that is, animals with high temperatures and clear discharges, to obtain best results, particularly when it comes to viruses.
Many animals can be swabbed, and the swabs pooled at the lab for testing.
This is more economical, and increases the chance of obtaining a result.
A result in two or three days can be very useful, however, occasionally a negative result can be disappointing, meaning the test failed to pick up anything.
Lung washes involve flushing saline into an animal’s lungs, and sending the fluid sucked back out to the lab for testing.
This method can offer a better chance of making a diagnosis, but is obviously more time consuming and invasive.
Blood testing is more useful as a way of looking back in time to check which viruses a group of cattle have been exposed to.
For example, blood testing last year’s weanlings to check for antibodies to see what viruses they have come in contact with in their lifetime, helps in making decisions on vaccination of stock in the future.
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