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Calf pneumonia costs the UK cattle industry millions every year and is of huge financial significance. These losses arise from the cost of treatment, reduced weight gain, increased labour and most significantly from calf deaths. The disease is multifactorial which means that viruses, bacteria, husbandry and management factors have an essential role in outbreaks. The key in dealing with this disease is PREVENTION which is also the most cost effective approach.
RSV (Respiratory Syncytial Virus), Pi3 (Parainfluenza virus 3) and IBR (Infectious Bovine Rhinotracheitis) are the most common cause of respiratory disease and are usually responsible for initiating pneumonia. BVD (Bovine Viral Diarrhoea) does not directly cause pneumonia but causes widespread suppression of immunity like many other diseases, leaving the calf more susceptible to other infections. RSV can cause very acute disease, meaning that the first few calves affected often die following a short period of severe respiratory distress before treatment can be instigated. IBR is caused by a Herpes virus which is highly infectious and spreads from nose to nose contact, in air over short distances and indirectly on clothing, equipment or semen. The most common clinical signs include fever, watery/discharging eyes, nasal discharge and ulceration, milk drop in adult cattle and death. The virus can lie dormant after intial infection for a long period until times of stress when they often relapse and start shedding virus again. IBR is also an important cause of abortion. Pi3 tends to cause milder infections but leaves the animal susceptible to the other viruses and bacterial infection.
The bacteria capable of causing penumonia are often found in the normal nasal passages of healthy calves but cause severe lung damage and often death when they are allowed to penetrate into the lower airways. The most important bacteria are
Mannhaemia haemolytica (Pasteurella), Pasteurella multocida, Histophilus somni and Mycoplasma bovis. These bacteria usually cause pneumonia following viral infection but can act alone when ventilation or husbandry is poor.
Lungworm also known as HUSK is caused by Dictyocaulus viviparus which is a roundworm affecting grazing cattle of all ages. The disease is usually seen in mid-late summer following a grazing period. All cattle are susceptible unless immunised through natural pasture challenge or from vaccination. Clinical signs vary from occasional coughing to severe respiratory distress and death depending on the numbers of larvae ingested during a short period. The disease has an incubation period of about three weeks and once clinical signs are present the health of the animal is already severely compromised because of the damage the worms cause to lung tissue. In dairy cattle milk drop may be the only early sign but by the third week, badly affected cattle stand in a characteristic head-extended position with rapid shallow breathing and frequent coughing.
The first sign of pneumonia is often reduced feed intake (not coming forward to the trough). It is usually the associated fever (temp. greater than 39.5 degrees C) which causes the anorexia and a watery nasal discharge may be noted at this point. Coughing is usually the next sign and increased effort to breathe (heaving). The nasal discharge often becomes thicker and cloudier at this stage and the animal is clearly ill. As the disease progresses severe respiratory effort becomes apparent as the animal is starved of oxygen and death is often the result. If the calf does survive, the lungs will usually be too badly damaged to repair and the animal will remain ill-thriven and suffer recurrent bouts of pneumonia.
Ventilation is extremely important and is affected by the number and size of the inlets and outlets, height of the building (and surrounding buildings), direction the building is facing, drainage and the stocking density. A well-ventilated building will appear fresh without smells of ammonia or slurry gasses and cobwebs should not be present. Sources of dust should be avoided and rations should be ground and mixed in a separate area. A "SMOKE" test can be carried out to assess how effective the ventilation is.
Vaccines are an important way of helping control pneumonia as long as they are not substituted for good management and environment. Vaccination programmes should be timed so they are completed about a month ahead of the main risk period (e.g. housing) so their immune systems are ready for a fast specific response at time of challenge. A large range of vaccines are now on the market which means the correct vaccine should be available for your individual farm requirements and can be ordered through County Vets.
WARNING - 90% of UK farms have one or more of the respiratory viruses, so if buying in animals from different sources, pneumonia is a constant risk!
Farmers will often be required to treat the occasional case of mild pneumonia but if large numbers of calves are affected or if the disease is severe, veterinary attention should be sought. A response should be seen following an appropriate antibiotic in the first 24 hours. Sometimes treatment of all the calves in a particular group should be carried out but antibiotics MUST be used responsibly and should only be given following veterinary advice. Anti-inflammatories should be used alongside antibiotics as these are important in reducing inflammation in the lungs and also reduces the fever present.