Clinical Case Review: Calf Diphtheria in Feeder Cattle

By: Dr. Kip Lukasiewicz, Dr. Tom Noffsinger, and Dr. Dan Thomson, Production Animal Consultation

Calf diphtheria is a disease that affects the larynx or voice box of cattle (figure 1). Most commonly, diphtheria cases occur in young, light weight cattle. The causative agent is a bacterium named Fusobacterium necrophorum which is an anaerobic organism that is also commonly cultured in foot rot and liver abscess cases.

Fusobacterium necrophorum is present in the environment and the gut of cattle without causing disease (a commensal organism). However, if some sort of insult or irritant creates an opportunity for these bacteria to colonize, a disease process can occur. Cuts in the skin between the hooves can lead to foot rot, and a small ulceration in the surface of the larynx can lead to calf diphtheria.

Cattle with diphtheria are first noticed by the sounds that occur when they try to breathe. The plaque that is formed by the bacteria growing on the larynx along with the swelling of the larynx itself obstructs the windpipe and makes it difficult for cattle to breathe.

The noise heard with diphtheria cases occurs when the cattle draw in a breath or inspire air. Noises heard during inspiration indicate that the problem in the respiratory tract is not in the lungs and is located in the upper respiratory tract. Noises heard during expiration, or when the cattle breathe out, indicate the problem is located in the lungs or the lower respiratory tract. Cattle with diphtheria will exhibit difficult and noisy breathing patterns. They generally do not run a temperature or have any other clinical signs. These cattle can be confused with cattle suffering from tracheal edema, and proper diagnostic methods should be utilized to rule either of the syndromes out.

Recently, we had a feedlot experience a seasonal outbreak of calf diphtheria. It occurred in the spring of the year with cattle presenting with difficulty breathing, failure to respond to treatment with antibiotic and subsequent death. The veterinarians diagnosed calf diphtheria based on plaques and lesions found on necropsy at the feedlot (figure 2).

However, the cultures coming back from the diagnostic laboratory were not positive Fusobacteria in the results. Therefore, four head of cattle experiencing diphtheria clinical signs were transported to the Veterinary Health Center at Kansas State University College of Veterinary Medicine. The cattle were 70 to 100 days on feed which was typical for what the cowboy and doctoring crew at the feedlot had been observing.

When the cattle arrived, they had normal rectal temperatures but were having difficulty breathing. Clinicians used an endoscope to examine the lesions in the upper respiratory tract in two of the four animals. Again, laryngeal plaques and swelling were present causing obstruction of the airway in both cattle examined (figures 3 and 4). Also, plaques were present in the lining of the nasal sinuses indicating a sinus infection (figure 5). Deep nasal swabs were used to culture the larynx and nasal passages of two of the cattle. Nasal passages only were cultured in the two non-scoped steers. Blood samples were obtained for complete blood cell counts and serum biochemistry diagnostics.

All four cattle were positive for F. bacterium from the cultures taken at the KSU VHC. Not only did we isolate the Fusobacterium but in three of the steers no other bacteria were found in the nasal passages or the larynx.

Cattle had elevated white blood cell counts but most everything else was normal. Cattle were treated with dexamethasone to try to decrease the laryngeal swelling and treated with a macrolide to control the Fusobacteria. Cattle were transported back to the feedlot and responded well to therapy.

Questions exist on factors that predispose cattle to laryngeal infections and life threatening swelling of the vocal folds. Viral infections, feedstuff irritation, vasculitis and en