Penny Young, ASAS/ASAP Intern
An article by Roy Lewis posted late last year on Grainews identified two lesser known pathogens that are emerging as causes of respiratory disease in cattle. The article also highlights how management practices are important in helping to minimize the impact of these diseases, given there is little specific prophylaxis or treatment available.
One of the agents identified was a Coronavirus, a virus family most commonly associated with scouring in new calves and winter dysentery in mature cattle. However, the virus can also cause respiratory disease. While this respiratory disease is typically milder or subclinical, it poses threats to calves’ health as it can infect the respiratory epithelium, which can increase susceptibility to secondary bacterial infection. It also poses a problem because large amounts of the virus are secreted in the nasal mucus, allowing the disease to be easily spread to other cattle, especially amongst housed animals.
While vaccines containing coronavirus exist for scours, no respiratory vaccines containing the virus are currently on the market. Hence to prevent disease, it is vital that the immune systems of the calves are kept in top form as immunocompromise due to vitamin/mineral deficiency, stress or parasites may increase the risk of coronavirus respiratory infection. This is especially important to consider when bringing many susceptible animals together, such as newly weaned calves moving to a feedlot. This kind of non-specific protection through improving immunity is crucial given there is no specific defense or treatment offered. Rigorous vaccination programs for other respiratory diseases is also important as Coronavirus is commonly seen in association with the other, more prominent, respiratory viruses and bacteria.
The second pathogen discussed by Lewis was Bibersteinia trehalosi, which may be an emerging pathogen in the US and thus is of significance to Canada. The bacterium causes pneumonia that is difficult to distinguish from the M. hemolytic type post-mortem, yet is somewhat distinctive in its ability to cause rapid death in adult cattle. While these rapid deaths can partially be explained by ill-preparedness for respiratory disease in adult cattle, it is also concerning because the disease is very acute, giving antibiotics little time to be effective. It also appears that some strains of the organism are resistant to many different antibiotics.
While some cross-reactive protection has been observed in cattle vaccinated with a Mannhaemia haemolytica vaccine, there is no vaccine currently available against pneumonia caused by B. trehalosi. Given that there appear to be difficulties with antibiotic treatment, good surveillance of herds is critical, especially in housed animals. Post mortems should be performed and culture completed where farmers are seeing poor responses to vaccines and increased death rates, or if the sudden deaths from respiratory disease are observed in adult cattle. Lewis also recommends farmers stay abreast of advances in early detection prevention and treatment of respiratory disease, as progress is continually being made.
1. Hanthorn, Christy Jo, “Pathogenicity of Bibersteinia trehalosi in bovine calves” (2014). Graduate Theses and Dissertations. Paper 13974, p. 17 http://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=4981&context=etd