Animal Health Matters: Viruses are making the rounds in people and cattle alike
Cold and flu season is upon us. This year, in addition to influenza, another respiratory virus is getting a lot of press: respiratory syncytial virus, or RSV. A surge in the number of people sick with RSV is stretching hospital capacity in some parts of the country.
Respiratory syncytial viruses constantly circulate throughout the population. For most of us, it’s just one of the viruses responsible for the “common cold” – the runny nose, cough, and sore throat that most of us will encounter at least once this winter. The term “syncytial” refers to the virus’ tendency to make infected cells morph together into what’s referred to as syncytia (visible only through a microscope).
For other people, however, an RSV infection can mean a trip to the hospital – or worse. In children less than a year of age, the infection can extend beyond the upper respiratory tract to cause inflammation in the small airways and lung tissue. When this happens, it becomes more difficult for oxygen to get to the bloodstream. Labored breathing and wheezing are the result, sometimes severe enough that supplemental oxygen or a ventilator is needed. The elderly or people with chronic lung disease are also at risk of these severe infections.
Cattle producers and their veterinarians are also familiar with RSV, but not the kind that affects little kids. Bovine respiratory syncytial virus (BRSV) causes similar respiratory problems in cattle. (Fortunately, this cattle version doesn’t infect people, and the people version doesn’t infect cattle). Just like RSV in people, BRSV circulates regularly among the cattle population, occasionally emerging to cause illness in an unlucky segment of the population.
There are some similarities between this cattle version and its human counterpart. Bovine respiratory syncytial virus tends to affect younger animals, and causes fever and difficult breathing, too. The lower airways and deeper lung tissue are affected in cattle. Fluid and inflammation cause the connective tissue between lung sections to swell with fluid, further exacerbating the calf’s ability to breathe. Some of the most miserable-looking sick calves I’ve encountered in practice have been those with BRSV infections.
Since viruses don’t respond to antibiotics, treatment for both human and bovine RSV relies on supportive care such as fluids and anti-inflammatories. However, BRSV, in addition to causing problems by itself, is one of the viruses that set a calf up for infections from the more common pneumonia germs such as the bacteria Mannheimia and Histophilus. Similar to the actions of other viruses such as IBR (“red nose”), BRSV makes it easier for those bacteria to grow in the calf’s system and damages the calf’s inborn defenses. Therefore, BRSV infections very frequently turn into bacterial infections.
So while human physicians don’t need to treat their RSV patients with antibiotics, veterinarians do. If they don’t, full-blown bacterial pneumonia will result. Additionally, it’s hard to tell an uncomplicated viral infection from bacterial pneumonia; both look very similar “on the hoof.” While our human health counterparts have all sorts of diagnostics to determine whether their patient’s infection is bacterial or viral in nature, those aren’t often feasible or available for cattle.
There is one other big difference between human RSV and BRSV. There is not a vaccine for RSV in people, but BRSV vaccines in cattle are very widely marketed and available. They are used in calves of all ages, and are available in intranasal or injectable forms in combination with other respiratory disease pathogens. A typical beef calf program includes vaccinating beef calves at branding time, with boosters at pre-weaning and weaning. Dairy calves get intranasal vaccine at a young age, then strategically after that, to coincide with pen moves and other stresses. Adult cows often receive BRSV in their reproductive vaccines. BRSV does not affect reproduction, but it might help cows produce colostrum that can better protect the baby calf.
When a child contracts RSV, it’s usually just bad luck that they encountered an infected person who spread it to them. The same can be said for calves and BRSV to a certain extent. But in calves, pneumonia prevention – whether due to BRSV or some other germ – is something largely under our control. Using the right vaccines at the right times will help, but reducing stress and providing good nutrition and a comfortable environment is just as important.
Russ Daly, DVM, is the Extension Veterinarian at South Dakota State University. He can be reached via e-mail at firstname.lastname@example.org or at 605-688-5171.