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While everyone has their own ideas concerning the cost of calf respiratory disease, there were no UK, multi-centre studies as to the actual costs on-farm.

Recently, Pfizer Animal Health sponsored an independent study by National Animal Disease Information Service-veterinary surgeons, who recorded in detail 12 calf pneumonia outbreaks.

The survey involved weekly on-farm visits for the duration of the outbreak and then a final visit one month after the end of the disease occurrence. The 12 farms studied in depth were in four different practices and involved eight herds with calves from dairy herds and four from suckler herds. Overall 325 calves were treated for respiratory disease out of 428 within the studied groups producing a morbidity rate of 76 per cent and overall mortality of 2.6 per cent.

As might be expected, the actual costs were very variable ranging from £8.60 per ill calf in a vaccinated herd to £345 per sick animal in a herd which had to have their animals contract reared off the premises. Overall, the average cost in the outbreaks involving calves born in the dairy herd and reared as replacements or for beef was a minimum of £43.25 per ill calf and £29.60 per calf in the at risk group. In general, outbreaks tended to cost more when they were protracted, even when clinical signs where not pronounced. Costs also rose as mortality occurred.

Surprisingly, in this study the severity of outbreaks did not contribute greatly to the outbreak costs, provided the outbreaks were not protracted.

The average proportion of costs attributable to treatment was 22 per cent, and that to production losses was 26 per cent.

The suckler herds produced different results. In the outbreaks recorded, morbidity was very high (90 per cent), the sample was small, but it did appear that costs were probably related more to the severity of the outbreak than in the dairy-bred calves. The average proportion of costs attributable to treatment was 31 per cent, and that to production losses was 40 per cent. Again mortality was a major contributory factor to average costs and was higher in these herds at 4.5 per cent.

Each outbreak appeared to have been precipitated by weather changes and usually involved damp and mild conditions. Many of the herds had various other management factors which were thought to contribute to the respiratory disease outbreak, such as poor ventilation within the buildings, different age groups within the same airspace and sub-optimal feeding regimes. When the organisms involved were examined, respiratory syncytial virus (RSV) was present in eight outbreaks, parainfluenza III (Pi3) was seen in five and Pasteurella spp was involved in three.

The frequent veterinary visits and increased supervision necessitated by the trial protocol helped to prevent more serious illness in many animals and also prevented deaths. The increased veterinary involvement also instigated alterations in buildings to improve ventilation, and changes to management and feeding regimes, All these changes greatly benefitted the calves, which would not otherwise have happened. At this time of great economic pressures on all farmers, the veterinary surgeon was shown to be only the third or fourth most costly input in outbreaks of pneumonia but often was the major contributor to influence the course of disease.

HOW TO GET THE BEST FROM YOUR VACCINE

• keep it in the fridge (between 2-8 ˚C)

• don’t freeze the vaccine

• always check the vaccine is still in date

• reconstitute vaccine pellets with the correct amount of diluent to ensure correct doses are given

• when a vaccine has been reconstituted, use the whole vial immediately

• don’t use chemically sterilised syringes or needles as they can inactivate the live virus

• if vaccinating large numbers of animals, change needles regularly

• avoid vaccinating unhealthy animals

• try to be as ‘clean’ as possible with your vaccination technique

• read the instructions on the package insert

• if in doubt - take advice from your vet

• use vaccines according to manufacturers instructions

• make sure cattle receive the full vaccine course

VIRAL PNEUMONIA - STILL A MAJOR PROBLEM ON UK FARMS

The results of a blood sample survey carried out by Pfizer between 1994/98, show that the risk of viral pneumonia is still high. Of those farms tested, 89.4 per cent showed exposure to RSV, IBR or Pi3 viruses.

Why are cattle susceptible?

Cattle are extremely sensitive to pneumonia because of their small lung volume (typically 1/3 of the volume of a horse of equivalent weight) and the less well developed blood supply within the lung. Consequently, the respiratory system copes with the basic oxygen need, but has limited spare capacity to react to extreme conditions such as attack by viruses and bacteria.

Prevention is better than cure

By the time you notice your calves coughing they will already have started to suffer the significant damaging effects associated with viral pneumonia, and all you can hope to do at this stage is minimise your losses by treating. So it makes sense to prevent disease rather than wait for it to happen.

How can viral pneumonia be controlled?

Many pneumonia outbreaks are due to initial viral infection which can damage the respiratory system. To control viral pneumonia and its economic consequences, it is essential to control the viruses involved. The most successful control strategies include management and vaccination.

• Management - aim to reduce the virus load in the environment by reducing stocking rate and improving ventilation, improving calf purchasing arrangements and avoiding mixing age groups in a single airspace will also help.

• Vaccination - stimulate the calves’ natural defence mechanism so they can resist attack from viruses causing pneumonia. Calves which have been vaccinated mount a faster, more specific and powerful defence against the virus. If they do become infected they shed less virus to infect the others in the same airspace. This reduces the spread of infection and the rate of a severe outbreak.

IBR - WHAT IS IT AND HOW DOES IT AFFECT YOUR HERD?

Infectious bovine rhinotracheitis (IBR) is a common form of viral pneumonia, caused by bovine herpes virus 1.

IBR is highly contagious and all ages of animal are potentially at risk.

In calves, the initial signs of IBR may be coughing, high temperature and a general dullness. Affected calves have a reduced appetite and consequently show a reduced weight gain.

Infected animals often show a profuse nasal discharge, which contains the virus, and is therefore a good source of infection for other cattle.

Due to the damage caused by the IBR virus, the respiratory system is more susceptible to attack by secondary bacterial pathogens, leading to severe pneumonia.

IBR is also seen in adult cattle, particularly heifers, at stressful times, such as calving or housing. These cattle may show all the symptoms seen in calves, but an early sign of infection is a drastic fall in milk yield. Abortions may also occur. Since the infected cow will shed the virus, she is a good source of infection to her own calf and other susceptible cattle: immediately isolate affected animals where possible.

CALF PNEUMONIA - CAUSES AND CONTROL

Calf pneumonia is caused by a range of pathogens such as viruses (RSV, Pi3 and IBR), bacteria (including Pasturella pp, Haemophilus somnus) and mycoplasmas and can be triggered by risk factors such as warm wet weather, buying in calves mixing age groups, poor ventilation, stress and high stocking densities. We know that 90% of UK farms have one or more of the respiratory viruses, so when buying in multisource calves, viral pneumonia is a constant risk. It is also important to recognise the other risk factors that may lead to an overwhelming challenge. Vaccination programmes should be timed to occur ahead of the main risk period so that the calves immune systems are ready for a fast specific response at the time of viral challenge.

Mycoplasma bovis can act as an immunosupressant by destroying the protective lining of the upper respiratory tract and affecting white blood cells, so allowing other pathogens to infect the lungs.

Where there is a necessity to house calves of mixed age groups in the same air space, it is a good idea to house the younger calves upwind of the older calves, or to try and create a barrier between air spaces to limit air movement.

Control

Pneumonia vaccines available from Pfizer Animal Health protect against the three major viruses that cause respiratory disease in calves: RSV, Pi3 and IBR, but as you know there are also other factors that influence the development of pneumonia, namely bacteria, mycoplasmas, and housing factors such as ventilation and humidity. In order to maximise the benefit of vaccination it is important to consider husbandry matters and identify areas for improvement.

The costs of respiratory disease include obvious ones like vet visits drug costs, deaths and the additional labour required for treatment. More importantly perhaps are the hidden costs: loss of daily live weight gain, increased time to reach finished weight, and lost opportunity costs (of labour that could have been used elsewhere and capital). Add to this the stress and frustration of dealing with respiratory disease, especially on a large scale, and the answer must be to enforce a practical and effective respiratory disease control programme with input from the veterinary surgeon, and other consultants where necessary.

To control respiratory disease (a) the risks should be reduced by improving management wherever possible, and (b) enhance the calves’ immune systems by ensuring good general health, adequate nutrition and using respiratory vaccines where appropriate.

Vaccination should be timed to allow the calves immune system to be primed and ready for action before challenge.

First vaccinations should take place a few days after arrival on farm to avoid too much stress on the day of vaccination.

If the presence of RSV, Pi3 or IBR is confirmed on your farm then vaccination is recommended. Rispoval™ RS protects against RSV, Imuresp™ RP protects against Pi3 and IBR, and Tracherine™ will protect against IBR depending on which viruses are present. The timing of vaccination should occur so as to prepare the calves for the time of challenge i.e. if the pneumonia generally occurs in December, then the vaccination course should be completed two weeks before that. It should also be realised that the full benefit of viral pneumonia vaccination will only be gained when husbandry issues are tackled so as to reduce the risk.

Vaccination is a way of optimising the ability of the animal’s immune system to fight off infection before it causes disease. However, the effective control of respiratory disease also involves minimising the number of viruses and bacteria in the calves environment and airspace. This involves looking at the animals’ environment for ways to improve features such as ventilation.

If the vaccines are stored correctly, used as directed and the "quarantine" recommendations followed, then the level of respiratory disease should be significantly reduced. Pneumonia is usually caused by an interaction between viruses and bacteria. Viruses cannot be killed with antibiotics: it is the animals’ own immune system which gets rid of them. Any attempt to control respiratory disease MUST be two-pronged (a) to increase immunity by ensuring that calves receive an adequate amount of high quality colostrum in the first four hours of life, and that they are in a good plane of nutrition and (b) to reduce the challenge – by isolation methods, good ventilation and vaccination.

Another important feature of disease control is by prompt treatment of clinical cases to ensure that the bacteria causing pneumonia are killed. In general, a broad spectrum antibiotic, effective against most respiratory bacteria will be prescribed by the veterinary surgeon, on the basis of farm history +/- laboratory samples.

Correct use of calf pneumonia vaccines before the period of viral challenge can give protection against RSV, Pi3 and IBR viruses. Often it appears that viruses act as a primary pathogen, entering the lung to cause the initial damage which may be secondarily invaded by opportunistic bacteria. Therefore it is logical to assume that if we protect against the major viruses that we will in turn help to prevent bacterial pneumonia.

Vaccinating autumn born sucklers

For autumn born calves that receive challenge at a young age Pfizer recommend that calves are vaccinated at one and four weeks of age with Rispoval™ RS, and at one week with Imuresp™ RP. Depending on circumstances, a third dose of Rispoval™ RS may be recommended at 16 weeks. This will protect against all three of the major pneumonia causing viruses; RSV, Pi3 and IBR.

Vaccinating spring born sucklers

For spring born calves, the challenge is usually seen a few weeks after winter housing so it is recommended that calves are vaccinated with two doses of Rispoval™ RS and one dose of Imuresp™ RP and that the course is complete two weeks before housing. For practical reasons it may be more realistic to give the second dose of Rispoval™ RS at the time of housing.

Vaccinating store cattle

A store cattle system is typically one of high inputs. There are a number of respiratory disease risk factors associated with this type of system:

1. Cattle arrive from multiple sources, so this means that most respiratory pathogens (including viruses, bacteria, mycoplasmas) are being brought in.

2. Cattle are housed in large groups and this increases the chance of pathogens spreading.

3. Cattle are mixed prior to vaccination which means that the pathogen "pool" has more chance of spreading.

4. Concurrent disease will cause some degree of stress and make cattle more likely to succumb to respiratory disease.

5. Ventilation has to be addressed; wide ridge outlets and breathing roofs help to create an outlet. However, even if these were incorporated, it could be that on a still day the atmosphere may be humid outside the shed, so contributing to the likelihood of cattle developing respiratory disease.

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