Hendrick: Treatments have advanced for cases of diphtheria in calves
Upper respiratory problems in cattle include diphtheria – an infection or inflammation of the vocal folds of the larynx at the back of the throat.
The infection, called necrotic laryngitis, and swelling from inflammation can restrict the airways and make breathing difficult. In acute cases the calf may die of suffocation.
Steve Hendrick of Coaldale Veterinary Clinic in Coaldale, Alberta sees quite a few cases of diphtheria in cow/calf operations and in feedlots.
“It’s not something we deal with every day, but it happens fairly frequently, and today there are some better ways to treat severe cases,” Hendrick says.
“We think trauma opens the way for infection and inflammation, such as eating abrasive feeds,” Hendrick explains. “Trauma could also be caused by using a tube feeder on baby calves.”
“If the surface of that tube is rough instead of smooth – such as if it got chewed or is forced abruptly into the throat – it may scrape or irritate the larynx,” he says.
The infection is generally caused by pathogens in the environment. They simply need an opportunity to invade the tissues, Hendrick says.
“The main ‘bug’ that causes diphtheria is Fusobacterium necrophorum, which is the same one that causes foot rot, liver abscesses and is often found in the gut and upper respiratory tract,” he says, noting viruses such as infectious bovine rhinotracheitis (IBR) may be implicated in diphtheria. “In feedlots we often see diphtheria in conjunction with Histophilosis.”
Histophilus somni is a bacterium that lives in the nasal passages of cattle and sometimes causes an acute, often fatal, septicemic disease, especially if it becomes complicated with other infectious agents.
Due to swelling in the larynx, which narrows the opening, the calf makes more effort for every breath after diphtheria infection.
“Air must pass those swollen folds, so they are also constantly getting more irritated with each breath, rubbing against each other,” he says.
Ranchers may hear the calf wheezing and at first may believe he has pneumonia. However, observation of the respiratory effort can distinguish between diphtheria and pneumonia, says Hendrick.
He describes a calf with pneumonia has trouble pushing air out of damaged lungs, whereas a calf with diphtheria makes more effort to draw the air in through the narrowed airway.
Additionally, a calf with diphtheria often drools frothy saliva because he has trouble swallowing, and saliva may continually drip from his mouth.
“He’s so busy trying to breathe he can’t take time to swallow. Extra salivation can also be due to irritation from sores in the mouth as well as the throat,” Hendrick says.
Hendricks adds sometimes the infection is in the mouth and not in the throat, which is not as much problem for the calf because he can still breathe.
The larynx area serves as a valve, sending food down the esophagus and air down the windpipe. When calves breath, the valve stays open. However, when the calf has trouble breathing, he doesn’t take time to swallow, says Hendrick.
“If swelling in the throat closes the airway, he suffocates,” he says. “If the calf is wheezing and struggling for breath, staggering from lack of oxygen, it becomes an emergency.”
Diphtheria is most common in calves, but older animals are sometimes affected, Hendrick notes. A mature animal has a larger throat and windpipe, however, and may not have as much trouble breathing if this area becomes swollen.
“The infection may still affect the larynx and, in some cases, may cause enough scar tissue in the vocal folds to affect the voice,” says Hendrick.
Some cows lose their voice and can’t bawl as loudly anymore.
“Infection in the larynx is generally responsive to oxytetracycline,” Hendrick advises. “This antibiotic has good distribution throughout the body. We also have good luck with penicillin.”
He added some people prefer to use the newer, longer-lasting drugs because they don’t need to treat as often, but oxytet or penicillin works well.
“There are several antibiotics that can be used, and our choice may depend on our ability to catch that calf and how often we want to try to do that,” he says.
Recovery from diphtheria may take a long time, Hendrick says, noting that every breath continues to damage the swollen larynx.
He continues, blood supply to the area is also limited, which makes getting enough antibiotics to the infection more difficult. Treatment may have to be continued for several weeks.
Sometimes it may take as long as a month of treatment, to get a calf over this problem, but there’s a way to help those persistent or serious cases.
“A tracheostomy insert can by-pass the swollen, irritated larynx and allow the calf to breathe through a hole in his windpipe. A veterinarian can place it into the calf’s windpipe below the larynx. We have great success with this in both baby calves and in feedlot calves,” he says.
“If the calf is suffocating, installing this insert allows him to breathe,” Hendrick continues. “When we take that constant irritation away, within a couple weeks or a month, the calf has healed, and we don’t need to keep treating with antibiotics that long.”
“Usually the infection is gone after a couple weeks’ treatment, and this breathing by-pass takes away the irritation so the larynx can heal,” he explains.
“Producers need to talk to their veterinarian regarding treatment and what might be recommended,” Hendrick explained. “Usually if treatment can be started early, if we can treat these animals for a week or two, we can clear it up. With many other types of infections, we are often ok with just three or four days of antibiotic coverage, but diphtheria is persistent.”
“Don’t stop treatment until it is completely cleared up,” says Hendrick.
Anti-inflammatory medication is also important, to reduce the swelling and irritation in the throat. This can ease the calf’s breathing and also help irritated tissues start to heal.
“Often we recommend using dexamethasone as a single dose at the beginning, to help reduce that swelling. We don’t repeat it because prolonged use of steroids tends to hinder the immune system, but the dexamethasone can make a difference for the calf,” Hendrick says.
A number of non-steroidal anti-inflammatory drugs can also be used.
“Discuss drug use with a veterinarian to treat the calf as soon as we realize he has a problem,” says Hendrick.
Heather Smith Thomas is a correspondent for the Wyoming Livestock Roundup. Send comments on this article to firstname.lastname@example.org.