Bovine Respiratory Disease:Preventive Measures Save Profits

The exact causes and progression of bovine respiratory disease (BRD) are often unclear. But what is certainly clear is that it remains one of the biggest profit drains within the cattle industry – annual costs are estimated at more than one billion dollars.

This well-known pneumonia is the number-one sickness in calves, stockers, and feeder cattle. As a result, death loss and treatment costs go up, while average daily gains go down. Often, treated cattle also have poorer feed conversion and lower-quality and less-tender carcasses.

BRD is an extremely virulent disease and aptly known as a complex because it involves environmental, viral, and bacterial factors. It is caused primarily by two different organisms, Mannheimia haemolytica (formerly called Pasteurella haemolytica) and Pasteurella multocida.

Some species of bacteria are commonly found in the environment, and even in the animal, but do not create problems unless other factors such as stress or another disease are present. M. haemolytica and P. multocida are two such species. Normally found in the upper respiratory tract, these infections may be spread through direct, nose-to-nose contact, or through feed and water contaminated by other infected cattle.

The typical pathogenesis of cattle pneumonia involves stress, and probably an initial respiratory viral infection, fol-lowed by a secondary bacterial infection of the lower respiratory tract. When calves are in situations where they are stressed, such as at weaning, commingling, or shipping, pathogenic bacteria, M. haemolytica and P. multocida, are able to set up shop and replicate.

In the United States, M. haemolytica serotype 1 is considered the main bacteria responsible for the clinical signs and lesions of severe bovine pneumonia (shipping fever), particularly disease that is seen within the first week to 10 days after stress. P. multocida is less likely to cause the classic lung lesions that are found with shipping fever, but it is still a disease that has an economic impact on performance.

M. haemolytica-induced pneumonia is characterized by severe lung lesions that can develop very rapidly. Symptoms include coughing, nasal discharge, high fever, depression, and sometimes death. Early detection of this disease is important in order to avoid damage – often beyond repair – to significant portions of the lung.

Vaccination effective component

According to Derek A. Mosier, DVM, of the Department of Diagnos-tic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, various strategies, including preconditioning and retained ownership, have been used to reduce the impact of M. haemolytica as a major contributor to BRD. But depending on the situation, “M. haemolytica vaccination can be an ef-fective component in a strategy to reduce the incidence of BRD,” he says.

Many vaccines, such as AgriLab’s Express5®-PHM, that are intended to re-duce the incidence of BRD incorporate combinations of antigens including viral agents (eg: Bovine virus diarrhea virus, Infectious bovine rhinotracheitis virus, Parainfluenza virus, Bovine respiratory syncytial virus, and others), and other bacteria (eg: Pasteurella multocida) along with M. haemolytica.

The goal of these vaccines, Mosier explains, is to inhibit both the predisposing agents of BRD as well as M. haemolytica. Other vaccines that exclusively target M. haemolytica are intended to stimulate the production of high levels of immunity to key portions of the bacteria.

A critical factor in vaccinating for M. haemolytica is timing. Mosier explains, “Cattle which enter the feedlot environ-ment with high antibody titers to M. haemolytica have better performance and less respiratory disease than those with low M. haemolytica titers.

“Since maximum titers to M. haemolytica usually don’t occur until 2 weeks following vaccination, the best results are obtained when cattle are vaccinated 2-3 weeks prior to shipment to a feedlot. Vaccination at the time of arrival is not generally as effective at preventing pneumonia soon after ar-rival, but may be of value for inhibiting disease whose onset occurs 2-3 weeks or more following arrival.”

He adds that antibodies to M. haemolytica often rapidly decline after their peak, and can decrease to pre-vaccination levels within 6-8 weeks. Therefore even though many M. haemolytica vaccines are licensed for a single dose, they may need boostered in order to optimize antibody titers at the period of greatest stress.

Because production situations vary, it’s important to consult with your veterinarian to determine the specific vaccination protocols that will be most effective for your beef-cattle operation. For additional information on Mannheimia haemolytica and BRD, see page 19 in the Winter 2007 and page 20 in the Fall 2007 Bovine Health Watch magazines.