By Stephen Champion, BSc (Hons) BVM&S MRCVS,
Veterinary Surgeon, CHAMPIONVET.com
Written for Farming Scotland Magazine, August 2001

We are again approaching the time of year that many large animal vets call the “pneumonia season”. The first call to the practice, usually two to three weeks after the calves are housed from grass in the Autumn, has an all too familiar format. One or two calves hanging back from the feeding trough, the odd cough in the building, or perhaps a calf found dead in the morning, which was fine the night before. This article outlines some of the costs associated with pneumonia, reminds you of some of the culprits and explains the diagnostic procedures your vet may use to identify them.

The costs...

Many attempts have been made over the years to estimate the costs of an outbreak of pneumonia on a farm. This, I believe, is of fundamental importance to farmers, who need to be able to justify the cost-benefits in the prevention and treatment of disease. A recent study commissioned by Pfizer (one of the main manufacturers of pneumonia vaccines!) provides figures representing the ordinary British commercial farm. They found the average cost per ill suckler calf was £82 and the average cost for all calves in the shed during an outbreak was a staggering £74. To save you reaching for the calculator, this means that an outbreak in your shed of 40 bulls and 40 heifers could cost you £6000! The biggest component of this live weight loss (or failure to gain weight) followed by the cost of veterinary drugs and fees. However, when deaths occur, these rapidly become the major cost. In addition, there are “hidden costs” not accounted for in these figures, such as vaccines, rearing calves on other farms and keeping chronic “poor-doers”.

The culprits...

Pneumonia can be caused by a number of different types of organisms: viruses, bacteria or Mycoplasmas. The main viruses responsible are most easily referred to by their abbreviations: BRSV, PI3, IBR and BVDV. All nasties in their own right, they are capable of causing disease by themselves (termed “primary” disease) and damaging the lungs to allow bacteria to invade. Some viruses suppress the immune system so that the calf cannot fight off the invaders to its respiratory tract. Of particularly rapid and dramatic onset, BRSV (Bovine Respiratory Disease Virus) can hit without warning and if seen before death, the calf is often thought to have a “tattie stuck”.

Bacteria are often termed “secondary invaders after viruses have initially damaged tissues of the respiratory tract. However, they are quite capable of causing disease in their own right, and furthermore are often responsible for the ultimate death of the animal. Many of the dramatic lung changes you can see as your vet opens the chest of the carcass are due to bacteria. These almost always belong to a family of bacteria called Pasteurellaceae, related to the bacteria causing pneumonia and sudden deaths in sheep. They live in the respiratory tract of the healthy animal and only cause disease when the animal is subject to stress or viral infection. Thus cattle, like ourselves, are subject to the adverse effects of stress!

There exists a third type of organism that is increasing implicated in calf pneumonia – the Mycoplasma. It is now known to cause very serious disease in its own right, is resistant to several common antibiotics and can evade the immune system. Furthermore, there is no vaccine available to protect against it.

And how we try to find them...

The cause of an outbreak of pneumonia in calves can sometimes be a matter of speculation. To achieve a diagnosis is often difficult and expensive. The bug may have gone by the time you try, or there may be two or even three organisms present at the same time. As a practising vet, I can see the real value of obtaining a diagnosis when faced with an outbreak of pneumonia. It may justify the use of vaccines against viruses, confirm the presence of the devastating IBR virus early in an outbreak and troubleshoot in the event of a failure of a control programme. It also often benefits the farmer from a psychological perspective. If someone has been the victim of a crime, it is only natural to want to identify the perpetrator! Many outbreaks, if not properly controlled, can run on for several weeks. After all these sleepless nights, it can be very frustrating if the causal agent has not been identified. So, how do we do this?

In some many cases of an outbreak of IBR, the virus can be identified from a nasopharyngeal swab (cotton bud up the nose!), which is relatively straightforward and quick. This technique can also be used for the successful identification of bacteria in about 50% of cases, although the value here is only in identifying the susceptibility to antibiotics, as (remember!) these bugs live up the nose anyway!

Blood sampling effected animals may appear the straightforward path to a stress-free diagnosis. Not necessarily so! Firstly, we are looking for a rise in numbers of antibodies to the organism in the blood and for this reason two samples are needed, usually two weeks apart. This can be two long weeks, at a time when the infection is raging through your carefully nurtured livestock. Also, the age of the calves is important, due to interference from colostral antibodies still circulating. The age thus determines the number of samples that should be taken. Take your vet’s advise on this and do not be tempted to take fewer samples than required – it could cost you a whole load of vaccine you don’t need next year!

A technique which I have used successfully on many occasions is called Broncho-Alveolar Lavage (BAL). This has been developed over recent years for use on farm and can provide an accurate and rapid diagnosis of viral disease. Fluids are collected directly from the lungs of the calf (it really does cause little discomfort to the animal!) and need to be sent to the lab for analysis within four hours. A result can usually be obtained within 24 hours, thus enabling a rapid treatment or preventative programme to be instigated. Not all vets use this technique and not all labs are able to process the samples, so check beforehand. Choice of cases for sampling is vital and at least six early, acute cases should be taken, to get a meaningful result.

Finally, much valuable information can be gained from a fresh carcass, so call the vet before you throw it in the pit. He would prefer not to go in after it!

And finally, on treatment and prevention...

This article is primarily concerned with the costs and diagnosis of respiratory disease, but I would like to finish with a few words on treatment and prevention. Treatment is often best based on a firm diagnosis, by one of the methods described above. However, this is not always possible and treatment may have to be initiated without a diagnosis. Your vet should know which antibiotic is best to use and, just as importantly - the million dollar question – which animals it should be used on! It is important that you record the drug details in your medicines book. You should also be aware of the route of administration for follow up treatments, the animal welfare implications, the meat withdrawl period if you are selling stock and the cost!

Prevention is the name of the game where pneumonia is concerned, taking into account welfare and cost-benefits. Avoid stresses to the calves just prior to or at housing, such as castration, de-horning or excessive handling. Check out your buildings. There is a staggering amount of information published on building design, but your first port of call might well be your vet. In addition, the Scottish Agricultural Colleges (SAC) now have a Buildings Design Unit. Key areas to focus your attentions on are stocking density, ventilation, and moisture build-up, all of which can potentially be measured and corrected.

Vaccination of at risk calves reduces dramatically the severity of pneumonia on farms, or can prevent them altogether. It is vital that good advice is obtained on this subject. Every season more vaccines appear on the market from different companies, but the basic principles remain the same. Vaccinate all at risk animals, against the correct disease, by the most effective route of administration and you MUST COMPLETE the course within the specified time in relation to the risk period. Otherwise, don’t bother!

This article has attempted to explain some of the costs and diagnostics associated with pneumonia in calves, and has touched on the treatment and prevention. It is worth remembering that herd health plans, either designed on farm (with the help or your vet) or within quality assurance schemes can provide an incentive to improve management practices and reduce the risk of a serious outbreak of pneumonia.

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