Calf Diphtheria

Also known as: Necrobacilosis

Introduction

This is a disease associated with Fusobacterium necrophorum, which is a strict anaerobic bacteria found everywhere in the environment. The disease is usually trasmitted by oral ingestion of the bacteria. It is often a secondary invader, meaning prior tissue damage must have to occur for the bacteria to gain entry, however it can be a primary pathogen in some cases. There are two forms of calf diptheria; oral and laryngeal.

Oral form - common yet sporadic in occurrence and is often associated with poor hygiene especially in housed calves that are bucket fed, although it can occur in calves at pasture. Calves are usually less than three months old and the disease is often predisposed to by teeth eruption, rough feed, poor use of dosing gun or presence of a concurrent disease.

Laryngeal form - is less common can be seen in animals of all ages, but particularly calves up to the age of one year.

Clinical Signs

Swelling of the rostral cheek and salivation are the main clinical signs.

Upon physical examination, there may be a foul smell emitting from the mouth and deep necrotic lesions may be found on the cheek or tongue. These irregular shaped ulcers will be covered by a thick, diphtheritic membrane. In severe cases, sloughing of the tongue may occur.

If the larynx or pharynx are involved, swelling may lead to dyspnoea and the presence of pneumonia. These animals will also be pyrexic. They usually die fairly quickly as exudate may block the airways.

Diagnosis

Unhygienic housing conditions, poor general health, along with clinical signs and signalment of the animal are indicative of the disease.

Thorough oral examination with a gag is required for a definitive diagnosis. Differential diagnoses may include Foot and Mouth Disease Virus, foreign bodies, Papular Stomatitis and BVD mucosal disease. Appearance of the lesions should exclude all of the above differentials.

Treatment and Control

The animal should be isolated from the herd and cross contamination between its and others' feed buckets and equipment should be prevented.

Treatment with anaerobic specific antibiotics should commence immediately, either parenterally or orally for three to five days. In the laryngeal form, treatment should continue for longer.

Control focuses on hygiene with recommendation to disinfect all feed buckets regularly and improve the quality of feed.