Preventing and reducing calf pneumonia
Bovine respiratory disease (BRD) is a complex disease entity, of which pneumonia is the main feature. Each year in Ireland, respiratory disease is the most significant cause of deaths among calves greater than one month of age. Interactions between the animal, infectious agents (commonly referred to as bugs) and the environment can result in lesions in the lungs. The clinical cases you see on your farm with the classical clinical signs of respiratory disease such as coughing, high temperature and nasal discharge are only the tip of the iceberg, as there are often subclinical cases.
The economic implication of respiratory disease is not only restricted to treatment cost and mortalities but significant long-term impacts, both for dairy and beef animals. Heifers and beef animals with a history of respiratory disease have the potential for reduced milk yield (up to 525L) in their first lactation and reduced growth rates (up to 108g/day), respectively.
Common INFECTIOUS agents
What are the common infectious agents associated with pneumonia in calves and weanlings? Respiratory syncytial virus (RSV) and parainfluenza-3 (PI-3) are viruses commonly associated with BRD. RSV can be transmitted from adult cattle to the highest-risk group of younger stock, two weeks to nine months of age, resulting in severe clinical signs such as difficulty breathing. On the other hand, PI-3 is associated with mild clinical signs. A primary viral infection can predispose cattle to bacterial colonisation in the lungs, for example with Mannheimia haemolytica. M. haemolytica is a commensal organism (occurs naturally in the upper respiratory tract of cattle). Interactions with both viruses and bacteria can result in more severe outcomes.
To optimise calves’ immunity, vaccination for respiratory disease is recommended as it will stimulate their immune system and produce antibodies. It will reduce infection and clinical signs of pneumonia. It is important to store, handle, and administer vaccines correctly and follow the correct vaccine protocol.
Vaccination
Vaccination programmes vary depending on the vaccine used. For example, a vaccine that protects against both viral and bacterial agents namely Pl-3, RSV and provides the broadest protection against Mannheimia haemolytica – which is often the principal bacterial agent implicated in pneumonia – is advised. Bovilis Bovipast RSP is an example of such a vaccine and its primary course involves two subcutaneous injections of 5ml administered four weeks apart. For calves, the second injection should be given two weeks before the known risk period of weaning, housing or sale. For bought-in weanlings the vaccine can be administered any time after arrival, ideally allowing a short rest period of 24 hours before handling and followed up with a second dose four weeks later.
Such a vaccine provides the broadest protection available on the market to M. haemolytica as it is the only cattle vaccine licensed to protect against both serotypes A1 and A6. We should not underestimate the importance of A6 serotype as one study of beef bulls, demonstrated that M. haemolytia serotype A6 accounted for 63 per cent of isolates within 40 days of arrival at a fattening facility. This vaccine incorporates IRP technology which ensures early onset of protection and reduces the multiplication of M. haemolytica thereby reducing clinical signs of pneumonia.
To reduce the incidence and severity of respiratory disease within your herd it is vital to implement a correctly timed vaccination programme. Vaccination alone is not sufficient to prevent disease but must be in conjunction with good husbandry practices. Contact your veterinary practitioner for further information and to discuss vaccination programmes suitable to your herd.