Lamb performance at this time of year can be severely hindered by enzootic pneumonia (aka Viral Pneumonia). This is an infection of the lungs and is generally caused by bacteria and viruses.
The main signs are respiratory in nature; coughing, exercise intolerance, breathing difficulty, and nasal discharge. Other signs may include lethargy, depression, or even sudden death. It is also possible that lambs will be suffering from pneumonia sub-clinically (i.e. not showing signs, but still affected).
The disease tends to occur in outbreaks, often greater than 20% of a mob becomes affected. It is not uncommon for many of the affected animals to die or require euthanasia. Surviving animals may be ill-thrifty for life; studies have shown weight gains to be halved in lambs with lung damage from pneumonia.
The most significant risk factors for pneumonia are generally stress, crowding, and dust i.e. any yarding event. Shearing on the day of weaning is one of the most risky management practices for spreading pneumonia. Other risk factors include high temperature, excessive exercise, low immunity, and high parasite burden.
If you are suspicious of pneumonia causing problems in your sheep, it is easily confirmed on post-mortem examination. If you open up the chest cavity there will often be large amounts of fluid, potentially with the lungs stuck to the chest wall. Cutting into the lungs will likely reveal pus/fluid. If you are having a pneumonia outbreak get hold of us for advice, or book a vet visit to confirm.
Treatment can sometimes be of some benefit in affected animals. However, it is generally accepted that the risk of yarding animals for treatment potentially outweighs the benefit.
Prevention is most important. There are currently no effective vaccines.
Improving management practices is the best bet to limit the cost of pneumonia in your flock. These recommendations are all based around reducing stress, crowding, and dust:
- Keep time of yarding to a minimum
- Small mob sizes reduce stress and dust inhalation
- Sprinkle yards before use
- Avoid shearing lambs at weaning
- Shift stock early morning; it’s cooler and there might be a dew to keep dust down
- Reduce pressure when shifting them- let them go at their own pace.
When worried about pneumonia, some farmers use “long acting” drenches to reduce yarding frequency. These tend to be “Barber’s Pole” type drenches (e.g. Exodus, Genesis ultra). They do provide some persistency against Barber’s pole, but often not against the many other worm species affecting sheep production.
The risks of this strategy are:
- The long acting drenches used at this time of year tend to only have persistent activity against Barber’s Pole worm. Other species of worm can cause significant sub-clinical and clinical disease in the time that the drench is only killing Barber’s Pole. Higher worm burdens at the next drench in the sheep may increase the risk of pneumonia, or you may suffer worm related production losses.
- Long acting drench use provides a very significant risk of drench resistance.
Because of this, I still believe a standard 28 day drench program in combination with some careful management should give the best all-round results. It is all a delicate balance and is best dealt with on a farm by farm basis.
Give your local Anexa Vet a call if you would like further advice.