NECROTIC LARYNGITIS (CALF DIPHTHERIA)

Etiology.Necrotic laryngitis representsan atypical site of infection by the anaerobeFusobacterium

necrophorum, the organism responsible for calfdiphtheria. Calf diphtheria is an infection of the softtissue in the oral cavity following mucosal injury causedby sharp teeth in calves of 1 to 4 months of age.

The infection spreads amongcalves fed from common utensils or those in such closecontact that they may lick one another.

Signs.

Low-grade fever (103.0 to 104.5° F/39.44 to 40.28° C)

abscesses in the cheek region

mild salivation

refuse solid feed

inspiratory dyspnea

painful short cough

both inspiratory and expiratory dyspnea

A necrotic odor may be present on the breath

Diagnosis. Endoscopy is helpful in confirming thediagnosis. In some calves, the lesions can be seen by usingan oral speculum, but endoscopy is much easier andless stressful for the patient. If the calf is in extreme dyspneaor is anoxic or cyanotic, a tracheostomy should beperformed before endoscopy. The larynx will be foundto be uniformly swollen and may appear to have cartilaginousdeformities in chronic cases. Thelaryngeal opening always is narrowed, and mucosal necrosiswill be present in acute cases. Chronic cases mayhave laryngeal deformity and airway narrowing, but thenecrotic, infected cartilage may be covered by normalmucosa.

Treatment. Long-term therapy is required becauseinfection of cartilaginous structures usually exists. Acutecases should be treated with penicillin (22,000 U/kg IM,twice daily). A tracheostomy is essential for treatment ofcalves that have severe dyspnea. This will provide a patentairway and rest the infected larynx from further exertionalirritation while the infection is controlled. Theprognosis for acute cases is fair.

Chronic cases have a poor prognosis because laryngealdeformity and cartilaginous necrosis or abscesseswithin the laryngeal cartilage already have developed.

Treatment is similar to that described for acute cases butshould be extended to 14 to 30 days in patients valuableenough to warrant treatment, or the necrotic cartilageshould be surgically removed or debrided. A tracheostomymay be necessary for the reasons listed above, andsome clinicians recommend concurrent treatment withsodium iodide in the hope of penetrating the deepseatedinfection of cartilage. A. pyogenes frequently contributesto or replaces F. necrophorumas the causativeorganism in chronic infections because these two organismsare synergistic. For valuable cattle with thechronic form, referral to an expert surgeon familiar withthe tracheolaryngostomy technique described by Gasthuysshould be considered.