Dealing with Diphtheria in Calves
How to Treat A Respiratory Disease in Calves
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Diphtheria in calves is generally more serious — and more noticeable — than in adult cattle. Diphtheria is an upper respiratory disease and is an infection and/ or inflammation of the vocal folds of the larynx (voice box) at the back of the throat. Infection in that area (called necrotic laryngitis) and swelling from inflammation can be serious if it restricts the airways and makes breathing difficult. Swelling impairs breathing because air must travel through the larynx to get into the windpipe and down to the lungs.
Trauma opens the way for infection and inflammation. This may be caused by eating abrasive feeds like stemmy weeds or woody plants, calves chewing on sticks or eating coarse straw, or the use of a tube feeder on baby calves. If the surface of the tube is rough instead of smooth (which can happen if it gets chewed on when putting it into the calf’s mouth), or if it is forced abruptly into the throat, it may scrape or irritate the tissues of the larynx.
Infection is generally caused by bacteria in the environment. Some of them commonly inhabit the upper respiratory tract. They simply need an opportunity to invade those tissues. The main pathogen that causes diphtheria is Fusobacterium necrophorum — the same one that causes foot
rot and liver abscesses in cattle and is often found in the gut and upper respiratory tract.
There is also possibility that viruses such as infectious bovine rhinotracheitis (IBR) may play a role because they can damage the outer lining of the respiratory tract and open the way for bacterial infection. In feedlots, veterinarians commonly see diphtheria in conjunction with Histophilus somni (a bacterium that lives in the nasal passages of cattle). This pathogen sometimes causes an acute and often fatal septicemic disease, especially if it becomes complicated with other infectious agents.
Many of the respiratory bacteria, including Histophilus, Manheimia, Mycoplasma, etc. can also cause infections in the larynx as well, but Fusobacterium is the one we find in most cases of diphtheria, especially in young calves.
The calf usually shows difficulty breathing. Due to swelling in the larynx which narrows the opening, the calf must make more effort for every breath. The incoming air has to pass through those swollen folds, so those tissues are constantly getting more irritated with each breath, rubbing against each other.
If you are near the calf, you can hear wheezing. At first glance you may think he has pneumonia because he is struggling for breath, but if you observe the respiratory effort you can tell the difference. A calf with pneumonia has trouble pushing the air out (of damaged lungs), whereas a calf with diphtheria is making more effort to draw the air in, through the narrowed airway.
Also, when dealing with diphtheria in calves, the calves will often be drooling frothy saliva because they have trouble swallowing; saliva drips from their mouths. If they are so busy trying to breathe, they can’t take time to swallow, and the saliva keeps drooling. Extra salivation can also be due to irritation from sores in the mouth as well as the throat. Sometimes the infection is mainly in the mouth and not in the throat, and in that situation, that’s not as much of a problem for the calves because they can still breathe.
The larynx area serves as a sorting valve, sending food down the esophagus and air down the windpipe. Most of the time, a person or animal is just breathing; the valve only closes off the airway as we swallow. When a calf has trouble breathing, he doesn’t take time to swallow.
If swelling in the throat closes the airway too much, the calf suffocates. If he is wheezing and struggling for breath and staggering from lack of oxygen, this becomes an emergency. You may need to slice through the windpipe below the larynx (carefully cutting between the ribs of cartilage surrounding the windpipe — with a very clean, sharp knife), to create an opening for the calf to breathe through.
Diphtheria in calves is more common than in adult cattle, but older animals are not completely immune and sometimes can be affected. 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 cause enough scar tissue in the vocal folds to affect the animal’s voice. Some cows lose their voice and can’t bawl as loud anymore.
Infection in the larynx is generally very responsive to oxytetracycline because this antibiotic has good distribution throughout the body. Penicillin is another broad-spectrum antibiotic that works for this type of infection. Some people prefer to use the newer, longer-lasting drugs because then they don’t need to treat as often, but the traditional drugs work very well.
There are several antibiotics that can be used, and your choice may depend what your veterinarian recommends, and also on your ability to catch that calf and how often you want to try to catch and treat him.
It may take a long time to overcome this infection however. Every breath can continue to damage the already-swollen voice box which is why it
takes a long time to heal. Blood supply to this area is also limited which makes getting enough antibiotics to the infection more difficult. Treatment may need to be continued for several weeks.
It is important to talk to your own veterinarian about diphtheria in calves regarding treatment and what might be recommended. Usually if treatment can be started early, and continued for a week or two, it can be cleared up. With many other types of infections, it may take just three or four days of antibiotic coverage, but diphtheria is persistent. You should not stop treatment until it is completely cleared up. If you stop too soon, the calf will relapse, and then the infection is much harder to treat successfully and you may lose the calf.
Sometimes it takes as much as a month of treatment, to get the calf over it, but there is a new way to help those persistent and serious cases. Some veterinarians now use a tracheostomy insert, to bypass the swollen, irritated larynx and allow the calf to breathe through a hole in his windpipe. This insert comes in two pieces, and your veterinarian can place it into the calf’s windpipe below the larynx.
This gives the calf instant relief and he can breathe. When that constant irritation (air being forced past the swollen folds of the larynx with every breath) is removed, within a couple weeks or a month the calf has healed and you don’t need to keep treating him with antibiotics that long. Usually the infection is gone after two weeks of treatment and the breathing bypass takes away the irritation so the larynx can heal.
This can be an effective way to help a calf heal if the infection doesn’t respond enough to the initial week or two of antibiotics and is still having trouble breathing or isn’t improving adequately. The insert requires monitoring, because it may plug up occasionally with mucus.
The windpipe is lined with cilia — tiny hairlike projections that constantly move any mucus/debris up from the lungs so the animal can swallow it and get rid of it. Some of that mucus ends up in the insert and may plug the hole. If it starts to plug, you’ll hear the calf making a wheezing sound, since the mucus is obstructing the breathing hole. If that happens you need to take the insert out and clean it, but once it’s clean the calf can breathe again.
Just as important as antibiotic treatment is anti-inflammatory medication to reduce swelling and irritation in the throat. This can ease the calf’s breathing and also help the irritated tissues start to heal. Talk to your veterinarian about what to use. Often dexamethasone is recommended as a single dose at the beginning, to help reduce swelling. You shouldn’t repeat
it, however, because prolonged use of steroids tends to hinder the immune system.
Another good anti-inflammatory is DMSO (dimethyl sulfoxide). A few cc of DMSO mixed with a little warm water and squirted into the back of the mouth (for the calf to swallow) gives fairly instant relief by reducing the swelling. It has an advantage over dexamethasone because the DMSO-water “gargle” can be repeated as often as necessary.
There are also some non-steroidal anti-inflammatory drugs that can be used, but they are not as effective. Discuss this with your veterinarian and treat the calf as soon as you realize he has a problem. If you identify these cases early, treat them long enough, and help them breathe if necessary, you can save these calves.
Have you had to deal with diphtheria in calves in calves? We would love to hear from you in the comments below.
Originally published in Countryside March/April 2020 and regularly vetted for accuracy.