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This article was published in 1962
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INSTITUTE OF INSPECTORS OF STOCK OF N.S.W. YEAR BOOK.
The Footrot Eradication Campaign in the Armidale Pastures Protection District
Progress Report - 11/60 to 30/4/62
F. CLARK, B.V.Sc., Veterinary Inspector, Armidale
The Footrot eradication campaign has been in progress in the Armidale Pastures Protection District now for over two years, and it is possibly opportune, at this stage, to review achievements and some of the difficulties encountered. Firstly, however, it is intended to give a brief outline of the history of Footrot in the Armidale district.
The Armidale Pastures Protection District comprises 6,100 square miles and is situated on the New England Tablelands and, on the average, is 3,000 to 4,000 feet above sea level, with a predominant summer rainfall.
Beveridge (1941) states that Footrot was prevalent on the New England Tablelands in 1890 and for several years afterwards. The disease apparently died out in New England during dry times, particularly during the severe 1902 drought, when many sheep died.
Records of the disease in the area for the next 50 years are scanty, but it appears that Footrot was not a problem during this period.
The disease must have been re-introduced on many occasions to New England; in sheep from areas where Footrot is endemic. However, conditions prevailing at the time were unsuitable for the spread and persistence of the disease.
Before the advent of pasture improvement on the New England Tablelands, the pastures consisted of native grasses which came away in the spring and grew during the Summer months, and provided little feed during late Autumn and Winter. Ground cover during Winter months was generally of a dry, open nature. Severe dry periods were common, particularly during the Winter. Many graziers ran only wethers, which were purchased from western districts, normally free of Footrot.
Some 20 years ago the sowing of improved pastures was commenced on New England, and exceptional progress has been made during the last 10 years. This is well illustrated by the stock figures of the Armidale Pastures Protection Board, which show a progressive increase in sheep numbers, from 1,790,508 in 1952 to 2,612,582 in 1961. Cattle numbers also have increased in proportion.
Beveridge (1961) states: "Footrot is much more prevalent on improved pastures than on natural pastures; therefore as pasture improvement becomes more general in Australia, Footrot will become a much more serious economic problem if it is not properly controlled."
These words apply particularly to this District. The establishment of improved pastures on New England has created an environment in which it is suitable for Footrot to become an endemic disease. Unless controlled, it is obvious that the disease will persist now from season to season, and infected flocks will remain a potential source for further spread.
In 1956, the then Veterinary Inspector at Armidale, D. J. Walker, reported that, in the period 1952-56, Footrot had been recorded on 30 properties in this District and, at the time of writing, had been eradicated from 15 of these holdings.
He was able to trace the origin of the disease in all cases and found that in 15 of the 30 outbreaks infection had originated from introduced sheep, in most cases stud ewes and rams from Southern New South Wales.
In 1959, Walker, in a further departmental report, stated that, from 1962 until August, 1959, sheep on 64 holdings were known to have been infected. The disease was still active on 26 holdings and involved 96,300 sheep.
Both Walker and the District Veterinary Officer, A. N. A. Harris realised the potential threat of Footrot as a limiting factor to the benefits of pasture improvement and, as a result, a vigorous extension campaign was initiated. The Armidale Pastures Protection Board and local graziers' organisations were alerted to the menace of the disease and considerable agitation resulted to have additional legal controls imposed and an eradication scheme inaugurated.
Footrot eradication measures were commenced at the beginning of 1960. Additional legal powers under the provisions of the Stock Diseases Act, 1923-1934 and its Regulations were provided by the gazettal of the whole of the Armidale Pastures Protection District as a Footrot quarantine area on 29th July, 1960.
To assist in the eradication work, the Pastures Protection Board appointed an additional Ranger on 31st October, 1960. This brought the full staff available for the campaign to two Rangers and one Veterinary Inspector. Each of these officers was, of course, only able to devote part of his time to the Footrot eradication campaign, as other routine duties had to be performed.
The Board also provided certain equipment for handling sheep. such as portable yards, cradles and footbaths,etc.; the object being that the equipment could be taken to the infected sheep, to avoid moving those sheep to sheep-yards, and thus risking further spread of infection. This equipment has been used extensively. It was never intended that the Board should provide all the equipment for eradication; the above material being used in the early stages of new outbreaks, or in cases where temporary erection in paddocks would assist in cleaning up pockets of infection. Owners are expected to provide their own equipment.,
Since 1st January, 1960, 50 holdings have had sheep infected with Footrot, of these, 36 were infected prior to that date.
The position as at 30th April, 1962, is as follows:
| Total number of holdings on which infection has occurred | 50 |
| Infection still present | 8 |
| Properties where eradication methods deemed successful | 42 |
Methods by which Eradication was Accomplished
| (a) Control by treatment alone | 6 |
| (b) Control combined with disposal of obstinate cases | 26 |
| (c) By disposal of all infected and "in-contact" sheep | 10 |
In this latter group, in four instances no attempt was made at treatment; all infected and "in-contact" sheep were immediately sent to abattoirs once the infection was diagnosed. In the other six cases all infected and "in-contact" sheep were forwarded to abattoirs after an unsuccessful eradication campaign.
At the commencement of the campaign it was decided to give maximum assistance in new outbreaks, and generally to concentrate on the eradication of the disease in the northern part of the District.
Written orders were issued to occupiers, where considered necessary, which prohibited introduction on to or removal from the holding of any sheep without permission. The orders also required the occupier to segregate healthy sheep and infected sheep. and prescribed the treatments to be used. Co-operation of owners in most cases has been excellent.
The dry conditions prevailing in the late Autumn, Winter and early Spring of 1961 greatly assisted the eradication campaign, and it is probable that progress would have been considerably less had a wet season been experienced. However, although the dry conditions assisted eradication by eliminating the spread of infection, they also resulted in the work not being challenged at the time.
Sheep have been checked regularly for Footrot at saleyards and only one infected mob has been detected. These sheep were returned home and, on checking sheep on the property of origin, it was obvious that the disease had been present for a considerable period.
DIFFERENTIAL DIAGNOSIS OF FOOTROT
Many reports of lame sheep now are investigated by the staff of the Armidale Pastures Protection Board.
Foot Abscess or Digital Suppuration is a common disease of sheep running on improved pastures in this area. Usually only one foot is affected and the lameness is much more acute than in Footrot.
Another very common complaint on improved pastures is Separated Wall (shelly hoof or dry separation). Where large numbers of sheep are affected with dry separation, paring time during Footrot control work is increased considerably owing to the difficulty of completely exposing these pockets. In some mobs, practically every sheep is found to be affected with this complaint. In most cases it causes little lameness, although at times it can cause considerable distortion of the horn of the toe and the affected area can even be fly-blown.
Mycotic Dermatitis affecting the feet was found to cause lameness in two instances.
The three conditions described above are not difficult to distinguish from Footrot.
SCALD
Infectious Scald, which has been recorded on a number of properties in this District, presents the greatest difficulty in the differential diagnosis of Footrot.
Diagnosis cannot be based on smears taken from affected feet alone. Infectious Scald will give a very similar smear to Footrot; thus the two diseases cannot be differentiated by that means, or course, a negative smear supports the assumption that neither disease is present, provided a comprehensive range of smears has been taken. Clinical history and subsequent development of the lesions must be taken into account. Infectious Scald causes a varying amount of under-running of the sole of affected feet, but does not proceed to the advanced separation of sole and wall from the under-lying soft tissues, as occurs in Footrot.
When fairly advanced, Footrot also can be differentiated from Scald by the often considerable amount of greyish necrotic material present between the separated hard tissues and the under-lying soft tissues, Footrot also has a characteristic, unpleasant smell.
When advanced Footrot lesions are present, a diagnosis is relatively easy on clinical grounds alone. The difficulty is that early Footrot cannot be differentiated from Scald with certainty on clinical grounds or by smears.
DISPOSAL OF INFECTED SHEEP
There are no provisions for infected on "in-contact" sheep to be yarded and sold by auction for slaughter. Thus, movements must be made direct from the holdings to the abattoirs. Where large numbers of sheep are involved, it has been possible to attract buyers to the holdings and obtain reasonable prices. However, in many instances the numbers of sheep to be disposed of are small and owners are often obliged to accept sacrifice prices.
If the eradication campaign is ever extended to other Districts, with a higher incidence of infected flocks than Armidale, it would appears that it would be essential to have some provision in saleyards, such as Flemington, for the sale by auction of infected sheep. This, of course, would involve separate unloading races and quarantine yards to avoid spread of infection.
TERMINATION OF CONTROLS OVER AFFECTED SHEEP
The eternal problem is: When should control measures be lifted from a holding? How can we be sure Footrot is eradicated? Under dry conditions, when frequent challenges to the efficiency of eradication measures are not forthcoming, the decision may be a difficult one.
To be certain of eradication, the challenge of a wet season is needed. The recent wet conditions in this District have challenged work done on several properties during the dry period, when the feet of every sheep in the previously infected mobs were examined. This work has withstood challenge to date.
POSSIBLE RE-INFECTION FROM ADJOINING DISTRICTS
Footrot is known to be present or to have been present recently on several properties in the Ward's Mistake area of the Glen Innes District and the Nundle area of the Tamworth District. Both these areas are in close proximity to the boundary of the Armidale Pastures Protection Board. Should Footrot not be eradicated in these areas, they will provide a possible source of re-infestation in the Armidale District.
AVAILABILITY OF TRAINED STAFF
Only two Rangers and the writer are available to carry out the field work. The best it has been possible to maintain equals about about one man, full time, on Footrot.
It should be stressed that the incidence of infected holdings in the Armidale District, at its maximum, was only 21 per cent, approximately. Even this low percentage of infection places heavy strain on the Board's resources, both financial and in personnel. To eradicate Footrot from a District in which a large number of properties was involved would necessitate many more Inspectors, and would be beyond the resources of a Pastures Protection Board.
It is pointed out that the Armidale Pastures Protection Board receives no additional finance to conduct its Footrot eradication programme, and the additional expenses associated with the campaign were, to a large degree, responsible for the increase in the 1962 rating.
It is considered that much better progress would have been made in the campaign if an additional specialised officer had been available, full time, for Footrot eradication work. However, Board's finances would obviously not allow such a step.
ERADICATION METHODS
The standard methods of eradication of Footrot, based on the findings of Beveridge and others, are well known and need not be elaborated. However, it is considered that too much effort is spent on curing infected feet when the time could be spent more profitably on prevention of spread. Infected sheep are best segregated and slaughtered on the property or despatched to abattoirs.
The most efficient method of eradicating Footrot from a property is the disposal for slaughter of all infected or "in contact" sheep. Where this cannot be done, if possible the sheep should be drafted and all infected sheep sold for slaughter and the balance regularly treated to avoid further spread. If the incidence of infection is too high to permit this second method economically, then treatments should be carried out with the object of selling infected sheep for slaughter as soon as the numbers are low enough. It seldom is economical to pare more than two or three times.
In Western Australia, where an eradication campaign has been in operation for some time, the best method of eradication was found to be the total removal and sale of all carriers for slaughter. This method is encouraged and is now the method most commonly employed. The segregation and treatment of carriers as a hospital flock is not encouraged and is employed now, in Western Australia, when the sheep have a particular value; such as in stud flocks or in the case of young crossbred ewes, which are costly and difficult to replace.
The Footrot campaign, to date, in this District has been reasonably effective. Primary objectives in limiting Infection to the area south of Walcha, where there are now two main pockets of infection, involving eight properties, have been achieved largely.
This progress was aided greatly by the active sympathy of the stockowners generally, who had previously pressed for an eradication campaign, and, in the vast majority of cases, promptly notified lame sheep.
Many people have given assistance and thanks are especially due to the District Veterinary Officer, A. N. A. Harris, B.V.Sc., who has been in close collaboration at all times. I. L. Johnstone, B.V.Sc., and N. P. H. Graham, B.V.Sc., also have provided much helpful advice.
The enthusiasm displayed and field work undertaken by both the Rangers of the Armidale Pastures Protection Board, Mr. A. Foster and Mr. A. Ford, also is appreciated.
Reference:
- Beveridge, I. W. (1941) — C.S.I.R. Aust. Bull. 140