During a visit to the property of a district landholder early in May, 1956, and on another matter, the case of a stud ram was mentioned, which some six weeks previously had commenced losing its cud and salivating. At this time it was suggested that a partial oesophageal obstruction could have been responsible for the condition.
Some eight days later another call was received from this owner, who reported that six cross-bred weaners and four cross-bred ewes were showing similar symptoms to those shown by the ram. These sheep were portion of a mob of 200 ewes and weaners and were running on improved pasture on a river flat which was heavily contaminated with Noogoora Burr (Xanhem chinense). In all, a total of 12% of the mob became affected.
The ram earlier referred to appeared to have improved considerably by this time.
Ante-mortem, the only obvious symptoms were salivation and staining of the lips a greenish colour, by partially masticated food material. All affected sheep showed a large cud held in the mouth.
No obvious lesions could be observed in the mouth or elsewhere, but in oral speculum was not available at the time.
On post-mortem examination, necrotic ulcers, varying in size from 1-2 cm. diameter and with a small amount of thick yellowish white pus in the depths, were observed on the lateral and dorsal surfaces of the base of the tongue. The number of such ulcers in each affected sheep varied from two to four.
Examination of Gram stained smears from these ulcers showed numerous Gram negative organisms morphologically resembling F. necrophorus; with many Gram positive staphylococci and short and medium chain streptococci.
According to Hagan (1947) a number of members of the genus Fusiformis are common saprophytes in the human mouth, and often are associated with troublesome inflammations.
In Australia, Gorrie (1948) has recorded necrotic lesions similar to those observed in this case; in the pharyngeal region and following careless use of balling guns for the administration of phenothiazine pellets.
Seddon (1953) also has reported Necrobacillosis in sheep following drenching in this country.
Cases of necrotic types of gingivitis in dogs and cats, similar to Vincent's Angina of man, have been recorded by Coffin (1947) as being due to Fusiform spp. in association with spirochaetes, and this author uses the term Fusospirochaetosis for the condition he describes.
The primary factor in the pathogenesis of the majority of cases of necrobacillosis of the oral cavity would seem therefore to be trauma; either of a mechanical nature or due to some associated organism possessing the ability to penetrate intact mucous membrane.
As drenching had not been performed on the weaners in the case reported here, and as the last drench given to the ewes concerned was administered some 2 to 3 months prior to symptoms appearing, it seems not unlikely that the heavy pasture contamination with Noogoora Burr was the factor responsible for the primary injuries to the mouth; and that these primary injuries opened the way for infection by organisms normally saprophytic in the mouth of the animals concerned.
An outbreak of Necrobacillosis of the tongue in sheep is reported, in which the primary injury appeared to be due to the burrs of Xanthium chinense.