Necrotic laryngitis or calf diphtheria

beEf 911 The outcome is usually successful, but producers should be careful not to stop treatment too early

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Over the years, most producers have had a sporadic throat infection in their calves. These are the ones with an extremely loud inspiratory and expiratory sound, which can be heard across the pen. They generally have extended-neck breathing and are in various forms of respiratory distress.

The cause is generally an infection of the throat or larynx area in turn caused by the same bacteria which can often cause foot rot. The initiating cause is usually an abrasion to the throat caused by rough feed or an oral ulcer. This is why seldom do we see these cases in outbreak form.

Sporadic cases are the norm and can occur from young calves right up until 18-month-old cattle in the feedlot. The younger cattle with a soft oral lining are therefore most susceptible to these abrasions. The oral ulcerative lesion could have even started from sharp teeth and them inadvertently biting the inside of their cheeks. I am sure we have all done this from time to time or bitten our tongue so we all know how these injuries could occur.

The organism gains entry this way and over time an abscess is formed around the laryngeal cartilages. This combined with the surrounding swelling significantly reduces the respiratory passage. What you, in a sense, are hearing is like a whistle when the calf is breathing.

Veterinarians have varied treatments over the years depending on what they have found to be most effective. The larynx is mostly cartilage and as a result the blood supply and hence the ability to get antibiotics to the site of the infection is not good. Drugs from the potentiated sulphonamides to penicillin and more recently drugs such as the macrolides (Zuprevo & Draxxin) or florphenicol (Nuflor) have been tried. Make sure if you have a case to get the advice of your veterinarian as to what drugs have worked the best and for how long.

Veterinarians will often recommend either a steroid such as dexamethasone or an NSAID (non-steroidal anti-inflammatory drug) such as banamine or metacam to name a couple. These and the antibiotics are all prescription drugs, which is why you need your herd veterinarian involved.Maintain antibiotics

If caught early and treated aggressively response is favourable. I have found in numerous cases the producer notices it quickly enough but stops treatment too early and a relapse occurs. In my experience, even if clinical signs have subsided substantially I continue treatment for several more days. The steroids or NSAIDs are stopped after a few days but the antibiotics are kept on board for the duration.

In chronic cases or those unresolvable with drugs some can be saved with an emergency tracheotomy and laryngeal surgery where the abscess is peeled out and the proper diameter to the wind passage is re-established. These cases of course carry a guarded prognosis but leaving these calves and doing nothing is grave indeed. You will have such a restriction that the eyes seem bugged out from straining to breath.

There is only one other condition I know of that mimics necrotic laryngitis. Large calves that are born backward and have a hard pull may break some ribs. As the first few ribs heal it may cause a restriction on the windpipe and the same clinical signs. These generally cannot be helped and although a tracheotomy may provide temporary relief, the actual problem cannot be corrected.

With the price of cattle ever rising, keep in mind something can be done or at least tried on these calf diphtheria cases. Try to not wait too long before treatment is initiated and remember to finish the course of antibiotics your veterinarian recommends. As a salvage operation laryngeal surgery can be done but most cases will clear up with good, sound medical treatment. A few will recover but will still have a distinctive whistle especially when run a bit. This will be permanent for the rest of their life but they still will do well enough in the feedlot.

About the author

Contributor

Roy Lewis practised large-animal veterinary medicine for more than 30 years and now works part time as a technical services veterinarian for Merck Animal Health.

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