Pneumonia in Lambs

Written by Bas van Luijk, Veterinarian at East Coast Farm Vets

---

If you notice coughing lambs while they stand in the yards, snotty noses when drenching, or if you have pleurisy listed on kill sheets, you are not alone.

Pneumonia (Ovine pneumonia (or “viral pneumonia”) is detected in an average of 28% of lambs’ lungs at slaughter but rates can vary greatly, affecting 6%-80% of animals in each line. The most severely affected (an estimated 7% of lambs) take an average growth rate check of more than 50 grams per day.

It can be frustrating if you’re not seeing the expected growth rate in your lambs, despite excellent feed quality and availability. If you have a robust worm drenching program and know that your drenches are effective, are monitoring facial eczema spores in your paddocks and grazing appropriately it can be frustrating if you’re still not being rewarded for your efforts.

Pneumonia in lambs and hoggets is a multi-factorial disease involving both pathogens and external factors such as stress, environmental changes and concurrent disease.

In acute cases, sheep may be found dead, or found lagging behind the mob displaying signs of respiratory distress.

If you find the odd dead lamb in the paddock it is well worth getting a post mortem carried out to investigate further. We check the lungs – these should be light pink and spongy and not attached to the chest wall or heart by firm tags. Affected lungs change to a dark firm tissue that resembles the colour and texture of the liver. Sometimes we find pus in the chest cavity or around the heart and abscesses when cutting into the lung tissues.

Unfortunately once affected, there are no satisfactory treatments and any animals that develop pleurisy (from the severe pneumonia) will have adhesions on the rib cage for life and the damage cannot be reversed. Lambs will remain ill-thrifty, carcasses will be downgraded at the works and expect deaths in the paddock. The best approach is to limit stressors that predispose lambs to develop pneumonia.

While the viruses (like parainfluenza) and bacteria (like Manheimia haemolytica) which cause pneumonia circulate in all populations of sheep year-round, environmental and animal risk factors come together mainly in the summer months to trigger clinical disease.

Poor summer feed quality, heat stress (including high humidity, long musters, dusty yards), shearing lambs on the day of weaning, purchasing and mixing different groups of lambs and transporting them have all been shown to increase the risk of pneumonia.

In the absence of specific preventative measures, you can minimise pneumonia by addressing risk factors.  Strategies could include:

• Muster during cooler times of day

• Concreting or covering yards to minimise dust and provide shade during yarding

• Delay shearing lambs until after weaning

• Provide good quality feed to lambs over late summer

• Avoid yarding for long periods in close confinement

If lambs are already coughing make sure you don’t push mobs too hard; if you see lambs open-mouth panting you are already increasing the risk for them to run into problems.

Preventing/controlling other diseases such as facial eczema, endophyte toxicity (staggers), and Haemonchus (barber’s pole), all of which put lambs under increased stress during the late summer/autumn will help the lamb to better deal with an infection as well.

This article was published in the Gisborne Herald on 08/02/25.