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The Rural Voice, 1991-10, Page 16Copper Base ROYALE BULBS made by PHILIPS Guaranteed 6000 hours Also Available •Energy Saving Lights •Heat Bulbs, etc. THE DUTCH STORE 519 482-7302 55 Albert St. CLINTON FARM AND MUNICIPAL DRAINAGE Clay & Plastic Tile Installation – Backhoe Service CaII Wayne Cook Zurich 519-236-7390 PARKER & PARKER LIMITED Quality Service Competitive Rates 12 THE RURAL VOICE DIA ENZOOTIC PNEUMONIA OF CALVES by DR. A. J. REHMTULLA VETERINARY LABORATORY SERVICES Not to be confused with specific viral pneumonias such as those caused by IBR, PI3, adeno or respiratory syn- cytial viruses (RSV) alone, nor with shipping fever complex discussed pre- viously (November, 1990), the enzoot- ic or so-called "virus" pneumonia of calves is a more common endemic in- fectious problem of gradual onset and slow progression. It occurs primarily in housed dairy calves and occasional- ly in nursing and pastured beef calves under six months of age. The extent of infection and severity will vary from farm to farm and from season to season. Whether on a cer- tain farm this year's calves will or will not get enzootic pneumonia, or if it will be severe, is a result of a combin- ation of several major factors that in- clude: • opportunity for exposure to infectious agents. (Are cattle of differ- ent ages mixed?); • immune status of the calves. (Was colostrum available to calves before weaning?); • environ- ment and housing. (Is microclimate of calves inside the barn constant., non - fluctuating?) Let us examine these factors indi- vidually first and then collectively. • Infectious agents — primarily bo- vine viruses (but also mycoplasmas and chlamydia) such as P13, RSV, ad- eno, rhino, reo and herpes viruses are ubiquitous — which means they are present everywhere where cattle are kept. Also, adult animals can carry these agents without showing clinical signs. Viruses in exposed calves can persist for up to two months. • In calves home raised or pur- chased at around 10 days of age, col- ostral immunity is declining when they are about six weeks of age, foll- owing which they are most susceptible to infection (i.e. — between the ages of two to five months). • Barn environment becomes criti- cal, particularly in winter, when calves are housed continuously. If crowded in poorly designed buildings without adequate ventilation, the combination of close contact amongst calves, lack of air movement, inadequate supple- mental heat, and high relative humidi- ty all result in conditions ideal for aer- osol or droplet transmission of infec- tious agents between calves. It is important to remember that in absence of stress, the effects of viruses and mycoplasmas by themselves are minimal, and uncomplicated infection which results two to four days after exposure to these agents causes only slight cough, mild fever, little nasal clear discharge, and transient rapid breathing. These mild episodes usual- ly go unnoticed and calves recover un- eventfully in about seven days, as lung tissue undergoes healing. However, during these two weeks, if stress occurs due to inadequate ven- tilation, high humidity, and chilling, then secondary bacteria entering down the upper respiratory passages invade lung tissue already mildly damaged by virus before it has had time to heal, and this results now in a severe puru- lent bronchopneumonia, mostly attri- butable to this bacterial superinfection. Calves now with clinically severe disease show signs of high fever (107°F), laboured breathing, severe coughing, and much creamy nasal discharge. They gradually become thin and eventually die or have to be destroyed as advanced cases seldom respond to antibiotic treatment. It is greatly accentuated in cold, crowded, humid, and poorly ventilated condi- tions. To obtain conclusive diagnosis of enzootic pneumonia and specific early treatment and preventative control measures recommended for individual situations, assistance of your practis- ing veterinarian and diagnostic labora- tory should be sought. Their recom- mendations should be implemented, as the disease can reach outbreak propor- tions and become very difficult and costly to overcome once it becomes endemic on a farm.0 We have tried to keep our topics timely and informative. However, we would welcome any suggestions from readers for future topics. We would also invite interested persons to take a tour of the facilities at the Diagnostic Laboratory at Huron Park. We would ask that you make prior arrangements by phoning 228-6691, Ext. 276.