Importance of Bacteria in Identifying Bovine Respiratory Disease

Bovine respiratory disease (BRD), which includes respiratory diseases like pneumonia in cattle, is known to cause animal losses and economic impacts in the dairy and beef industry. Specifically, the annual expenses related to BRD are approximately $800-900 M in the US. Multiple factors such as a change in environmental temperature, the presence of bacteria and viruses that infect the lung, and stressful events can make an animal more susceptible to BRD. Though we know which bacteria and viruses infect the lungs of these animals based on bacterial culture on post-mortem lung tissue samples, we still do not have an accurate diagnostic method to diagnose BRD in a live animal. At the farm, the personnel rely on the identification of visual symptoms (such as high rectal temperature, nasal discharge, and decrease in feed efficiency) to determine if an animal has BRD. Nonetheless, these symptoms are not unique to respiratory disease. Additionally, by nature, cattle are considered prey, and by instinct, they will hide their symptoms to not look susceptible to avoid attack by a predator. Thus, without timely detection of BRD, we risk losing the animal or treating sick animals with antibiotics. Thus, it is necessary to develop a BRD diagnostic tool that will not only rely upon visual symptoms alone, but will utilize the presence and abundance of bacteria and viruses that infect the respiratory tract.

How can our research contribute to the process of developing a diagnostic tool to detect BRD?

As an animal science Ph.D. student at Purdue University, Indiana, I’ve been studying the ecology of bacterial BRD pathogens, especially Histophillus somni, Pasteurella multocida, Mannheimia haemolytica and Mycoplasma bovis. These bacteria infect the lung usually after a stressful event for the animal, leading to BRD development. Interestingly, these pathogens can live in the nasal cavity of healthy animals also; thus, it is possible to quantify their abundance without sampling lung tissue post-mortem. I believe that determining the abundance of bacterial pathogens in the nasal cavity could lead to more accurate identification of BRD-affected animals. Additionally, by determining which pathogen is infecting the lung of an individual animal, farmers could give individualized treatment to each animal; thus, improving antibiotic stewardship. Given the expertise of our lab, led by Dr. Tim Johnson, we have been able to collect nasal swabs from healthy and BRD cattle to quantify the abundance of BRD pathogens. For our preliminary study, we collected nasal swabs from a feedlot in Indiana. To our surprise, M. bovis and M. haemolytica had a higher abundance in the BRD animals than in healthy ones, suggesting the importance of these bacteria in detecting disease at that farm. Nonetheless, it is necessary to determine if the same results would be observed at different farms in the United States. As a result, I am currently quantifying the abundance of the BRD pathogens from samples collected from different beef and dairy farms across the country. I expect to be able to infer disease status from the abundance of bacterial pathogens from a nasal swab which will help farmers to better identify their sick cattle.

Being part of the FFAR fellows has completely revolutionized my ideas about agriculture and the importance that we as researchers play in providing solutions to farmer’s problems. Additionally, I have had the opportunity to meet and connect with researchers working on other agriculturally-related research outside of animal science. The FFAR fellows program has equipped me with skills to better communicate my science with different audiences.