Upper respiratory problems in cattle include diphtheria—infection/inflammation of the vocal folds in the larynx at the back of the throat. Infection and swelling are serious if it restricts the airway. Air must travel through the larynx into the windpipe, and swelling or trauma to this area makes it difficult to breathe.
Dr. Lee Meyring, a veterinarian in a cow-calf practice in Steamboat Springs, CO, says the main thing with diphtheria is to identify it early. “If you don’t halt the infection and inflammation soon enough, scarring in the larynx can be a problem.”
Many people have a hard time telling the difference between diphtheria and pneumonia. In both situations the calf has trouble breathing, but with pneumonia it’s difficult to force air out of impaired lungs. The calf may grunt with every forced exhalation, often with little, short breaths.
A calf with diphtheria has a hard time drawing air in through a narrowed airway. The greatest respiratory effort is inhaling. “He’ll have his head and neck extended, trying to open his airway a little more because he can’t get enough air,” Meyring explained.
Another sign is drooling, because the throat is swollen and it’s difficult to swallow. The calf may still be bright and alert because this is not a systemic infection like pneumonia, but he might not be nursing because it’s hard to swallow—or to try to breathe at the same time he’s trying to suckle. “The calf with diphtheria usually doesn’t have a fever; often the main clue is noisy breathing,” says Meyring.
Cases are sporadic. “We may have several years without any and then a year with more cases, depending on weather and other factors. It is the same bacterium that causes foot rot and the incidence of diphtheria is similar. When it’s wet and muddy, the pathogen is more accessible,” says Meyring.
Calves also chew on things, and if they’re eating coarse feeds, nibbling on straw or anything abrasive, this may scrape the lining of mouth and throat and open the way for infection. Just like foot rot, the pathogen can’t enter unless there’s a break in the skin.
“I tell producers that, if they have a case of diphtheria, they should be prepared to see a few more. On some ranches I’ve treated three or four calves over the course of a spring, and sometimes they’ve never seen a case before. It tends to go in cycles,” he said.
Monitor young calves closely. “You might not notice one with diphtheria until the cattle are moving. Then you can see one is slow and having trouble breathing. You can also hear wheezing, as he struggles to get enough air.”
For diagnosis, if you aren’t sure, but suspect a calf might have diphtheria, Meyring suggest putting a little pressure over the larynx (voice box). “If you press on the outside of the throat with your fingers, you can shut off the airway completely. It’s so swollen it only takes a little external pressure to close it off. In a normal calf you can’t press hard enough on the larynx to shut off the airway,” he says.
Treatment
Immediate treatment is best, to minimize damage and scarring in the airway. In an acute case, a calf may suffocate. “Swelling can shut the airway off quickly. Anti-inflammatory medication such as dexamethasone (to reduce the swelling) is very important for the diphtheria calf,” says Meyring.
In an emergency, when the calf is unable to breathe, a tracheostomy can be done, slicing through the windpipe below the larynx (carefully cutting between ribs of cartilage surrounding the windpipe—with a clean, sharp knife), for the calf to breathe through. “This enables the calf to breathe immediately (incoming air bypasses the swollen-shut larynx),” he says.
A stainless steel tracheostomy insert can be used to keep the incision open and bypass the swollen, irritated larynx and allow the calf to breathe through the hole in his windpipe. This insert comes in two pieces, and your veterinarian can place it into the calf’s windpipe below the larynx.
“I’ve also used the handle of a plastic milk jug to make a tube that fits into the trachea. It goes down into the windpipe, and we suture the plastic to the skin, to hold it in there several days and hope the swelling in the vocal cords will subside enough to allow the calf to breathe normally again.
“The commercial inserts have a rounded tube to insert, and a flat edge for suturing to the skin, to hold it open. We use a piece of gauze as an air filter to make sure no foreign material goes into that breathing hole,” Meyring explains.
Bypassing the larynx, allowing the calf to breathe through the hole in his trachea, removes the constant irritation (air being forced past the swollen folds of the larynx with every breath). You need to keep treating with antibiotics until the infection is gone, and stubborn cases may take a couple weeks or a month.
Early intervention is best, to reduce swelling (for easier breathing and less irritation of vocal cords) and address the infection before it creates much damage and scar tissue. “If the calf has impaired breathing even after the infection has healed, he can’t keep up with the herd for summer grazing. The calf is eating and doing ok but has no endurance—can’t get enough air for exertion.”
If you don’t treat diligently, or if you quit too soon, the calf may relapse and is harder to treat—needing a longer course of antibiotics and anti-inflammatory medications.
“Many people use oxytetracycline (which works well against this bacterium) or penicillin, but I’ve had good luck with Nuflor if you catch it early. The antibiotic must be given several times, because sometimes when you think the calf has recovered and stop medication, he relapses.
“Penicillin must be given twice a day, whereas some of the other drugs can be given every other day. Nuflor is labeled for the tougher foot rot cases, and the same is true when using it for diphtheria,” said Meyring.
“I usually use dexamethasone daily for three days and give long-acting antibiotics at least three times-–providing at least a week’s coverage and sometimes longer,” he said.
Don’t keep giving dexamethasone more than three days because it starts to inhibit the immune system, but you can keep administering antibiotics for as long as it takes to get the calf fully recovered. If the calf is still having trouble breathing you can use a little DMSO (dimethylsulfoxide) mixed with warm water as a drench after you stop the dexamethasone. DMSO is an anti-inflammatory that reduces swelling but does not hinder the immune system, and can be given as many days as needed. Use of DMSO in food animals is controversial and some veterinarians will not prescribe it. Others, like Meyring, recognize its value, especially in a young calf that won’t enter the food chain for a long time, if DMSO might help save its life.
“The key to resolving diphtheria in calves is early detection and diligence. If you treat for just a few days, they relapse. People have told me they had to treat some calves a long time and the calves finally get over it, and it may be partly due to the calf getting bigger, and the airway is getting larger—and he can breathe better in spite of remaining scar tissue. — Heather Smith Thomas, WLJ correspondent
