M. bovis may play bigger role in BRD that originally thought

By Daniel W. Scruggs

DVM, Diplomat ACVP

The scientific community has done an admirable job of trying to make sense of the multiple bacterial, viral, immunologic and environmental factors that converge in cattle to produce the condition known as Bovine Respiratory Disease Complex or BRD. As the name indicates, it is not a simple relationship, and while there may be some common factors in BRD, there are a lot of variables that account for the unpredictability of prevention strategies and treatment responses seen with BRD.

Mycoplasma bovis has emerged as one of those factors that previously was thought a minor contributor to BRD, but is now receiving more attention as a major cause of treatment failures and chronics in cattle. Mycoplasma bovis (M. bovis) is not a new organism, nor is its contribution to BRD a new story. M. bovis was first identified in the 1960s and since then has been isolated mainly from lungs of cattle with chronic pneumonia, as well as from cattle with joint and ear infections, and dairy cows with mastitis.

Historically, M. bovis was considered a major cause of pneumonia in young nursing dairy calves, but its role in respiratory disease in feedlot and stocker cattle was unclear, other than the fact that it was commonly isolated from chronic pneumonias.

In the last 6 to 7 years, clinical signs of M. bovis have become more frequent in some classes of feeder and stocker calves, with reports in some groups of cattle experiencing high incidences of respiratory disease, poor treatment response and excessive numbers of chronics. Ear and joint infections are also seen, but usually respiratory disease is more common in beef calves. Recent studies have shown that a large percentage of cattle with acute pneumonia are infected with M. bovis, indicating that it plays a role in the early events of BRD, not just in chronics as was previously supposed. Unfortunately, it is difficult to tell if cattle are infected with M. bovis on initial treatment for BRD.

Cattle infected with other bacteria typically associated with BRD (Mannheimia haemolytica, Pasteurella multocida, Histophilus somni) are often infected with M. bovis as well, which may compromise the expected treatment response.

Cattle infected with M. bovis alone may not appear as obviously sick as cattle with other bacterial causes of pneumonia, and as such may not be treated early in the course of the disease. Delay in treatment of M. bovis can result in lung changes that will take a long time to heal. When dealing with cattle at high risk of BRD, and especially those cattle at high risk of M. bovis infection, it makes sense to utilize antibiotics that are effective against the major causes of BRD, including M. bovis, and to deploy those antibiotics as early in the treatment process as possible.

Discuss with your veterinarian what role M. bovis may be playing in your cattle operation, and as always rely upon their advice on the most effective and responsible use of veterinary products to meet your animal health needs.

Editor's note: Cattle Call is brought you by cattle health professionals to keep you informed about current issues important to cattle producers. Daniel W. Scruggs is a veterinarian with Pfizer Animal Health.

Date: 10/26/06

	Web hpj.com

Copyright/Privacy
Copyright 1995-2008.  High Plains Publishers, Inc.  All rights reserved.  Any republishing of these pages, including electronic reproduction of the editorial archives or classified advertising, is strictly prohibited. If you have questions or comments you can reach us at High Plains Journal 1500 E. Wyatt Earp Blvd., P.O. Box 760, Dodge City, KS 67801 or call 1-800-452-7171. Email: webmaster@hpj.com