REPORT ON DISEASE OF SHEEP’S TEETH

Press, Volume XCVIII, Issue 29058, 21 November 1959, Page 8

REPORT ON DISEASE OF SHEEP’S TEETH

[By

M. C. ARMSTRONG,

Government Veterinarian, Timaru)

During recent years veterinarians in the Department of Agriculture have investigated a dental disease of sheep commonly known as pyorrhoea, and referred to as Parodontosis or Enzootic Parodontal disease by the veterinary profession. The disease is characterised by a chronic inflammatory process in the periodontal membrane of one or more teeth, resulting in pain, looseness of teeth, reluctance to graze and consequent starvation. In some seasons it may be an important cause of wastage. Investigations have been largely confined to the Bulls-Santoft area of the Manawatu and to the Fairlie, Pleasant Point and Morven areas of South Canterbury. Veterinarians in charge of the areas concerned have utilised research facilities available at the Wallaceville Animal Research Station and the Pathology Department of the Otago University Dental School in order to define the nature and causes of the disease. Parodontal disease was first investigated in New Zealand by Armstrong and Gray near Fairlie in 1952. R. M. Salisbury did the laboratory work at Wallaceville and the disease was recorded in the New Zealand Veterinary Journal of March, 1953. At that time the disease was considered to resemble Vincent’s Angina or Trench Mouth in humans. First Cases The first cases were observed in the spring of 1945 when some unthrifty ewes were found diseased in the mouth when yarded for drenching. No more cases were observed until February, 1952. when several ewes and some rams became affected. In the 1952 outbreak the disease appeared to arise at the gum tooth margin of molars and/or incisors. There was ulceration of the gum and penetration of the infection down into the alveolus with involvement of all the periodontal tissues and eventual expulsion of the tooth. No

specific infective agent could be isolated and the disease could not be transmitted to healthy sheep by contact or by artificial inoculation. In South Canterbury there were no more opportunities for investigations until the autumn of last year when the disease was reported in several flocks near Fairlie. During the autumn to spring period this disease was identified on 18 farms in the Fairlie district, one near Pleasant Point and one near Morven. The incidence varied from 2 to 8 per cent., the highest being about 140 cases in 1700 sheep. In the majority of cases sheep recover slowly but they seldom make good sheep. The death rate would average about one in every five affected. In North Since about 1954 the disease has also been observed and investigated in some flocks in the Bulls area of the Manawatu. The disease in the Manawatu differs in minor respects from that in South Canterbury, but the basic nature of it is the same. For instance, in South Canterbury, inflammation of the gum margin is observed frequently and the disease affects rams and ewes of various ages from hoggets onwards. It is also seen in the different breeds of sheep peculiar,to the farming areas involved. The breeds of sheep affected in South Canterbury have been Romney, Cheviot, Corriedale, Border Leicester, and various crossbreds. In the Manawatu. the flocks concerned are all Romney, the affected sheep are four-tooth or older and, all cases were in ewes apart from one ram. The soil, types affected vary greatly from fertile clay downs to low lying silt loams, to very stony silt loams and to some sandy soils. There is no apparent relation to soil type or carrying capa(fity or to the degree of development of the property. Molars and incisors or either molars or incisors may be affected, but the animal declines more rapidly

when the molars are affected. Pathological studies reveal localised degeneration and shrinkage of the tissues surrounding the tooth. A crevice in the gum degenerates to form a deep pocket impacted with food which tends to surround and detach the tooth. In advanced stages inflammation of the jaw bone may occur with resultant hard bony swellings which often distort the face. If the tooth drops out then healing takes place but there is less chance of this happening with deep rooted molars. Affected sheep can be recognised by irrigation in the mouth causing jaw movements of an unusual nature (mouthing), reluctance to masticate, a foul smelling mouth, missing, loose or displaced teeth and perhaps lesions on the gums. Pathological studies indicate it is primarily a bone disease which begins in the superficial tissues and then extends to bone at an early stage. It is essentially localised and does not spread to all teeth. It most commonly affects premolars and molars. Bacteriological studies have been unable to find any evidence of specific infective agents that can transmit the disease to healthy sheep. Biochemical studies have so far revealed no significant findings in the nutritional and mineral field. Radiographical findings have supplemented and confirmed the pathological picture.

Seasonal Nature

In South Canterbury the disease is definitely of an extremely seasonal nature. In the present season the disease is almost completely absent and this is all the more significant because the previous season was the worst ever recorded. It is considered that this disease will be a very difficult problem to solve and that it is probably a hormonal, metabolic or nutritional disease, possibly some mineral deficiency, rather than an infective or contagious one.