Pneumonia in milk-fed dairy calves is a common problem caused by a mixture of pathogens and associated management or environmental factors.

But, writes Colin Mason, of SAC Consulting Veterinary Services, in Dumfries, recent disease surveillance results have shown a rise in the number of cases linked to the bacterium mycoplasma bovis and, within the industry, this seems to be increasing.

The infection is only part of the pneumonia complex, but it is important. While we still have some things to learn about it our understanding of many aspects of the disease process is good.

These facts about it can be used to help disease control:

• Mycoplasma species are bacteria but, unlike many bacterial species, they do not have a cell wall. This has significant effect on the choice of antibiotics that can be used so appropriate diagnosis and antibiotic selection through veterinary health planning is especially important.

• In conjunction with other pathogens mycoplasma bovis can often produce a chronic type of pneumonia with coughing and it is not uncommon to see relapses in individual cases some time after initial treatment. A common sign is reduced growth rate and thin, coughing calves which calls for further investigation.

• The infection can also cause other disease syndromes in cattle, such as arthritis and mastitis in adult cows. In milk-fed calves, another common clinical sign is middle ear disease which can show as an ear droop and a head tilt. This is a clinical picture we have seen more of in recent years.

• Mycoplasma bovis is most commonly spread in milk from carrier cows, either through the air from coughing calves or in the nasal discharge from affected calves.

• It is believed infection first gets in to a group of uninfected calves through milk/colostrum from carrier cows that may be clinically normal. The present cost-saving practice of feeding cows’ milk and, in particular, waste milk could be increasing the spread of this on some units. So, waste milk should not be fed and cows’ milk and colostrum can be pasteurised to help with control.

• Another significant risk of potential infection and disease spread is with feeding and handling equipment, and, in particular, rubber teats. Hygiene, particularly in automatic feeding systems, is of critical importance.

• Once the infection is established within a group of calves it is important to control any airborne spread. Two things to consider are:

1, Instead of offering a continuous flow of young calves into mixed age groups, try and create stable groupings managed as an ‘all in and all out’ system.

2, To protect the rest of the group and better manage treatment of individual animals consider isolating single or small groups of calves that are identified as having pneumonia.

In future, the use of vaccines and producing and then selling cattle known to be free of mycoplasma bovis may help control the spread and impact of this disease – and may even be a selling point.

Remember, though – like all health problems – diagnosis, treatment and prevention need to be tailored to each farm’s specific requirements and ongoing discussions with your veterinary surgeon are crucial.