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INSTITUTE OF INSPECTORS OF STOCK OF N.S.W. YEAR BOOK.
BRUCELLOSIS OF SWINE
By R. O. C. KING. B.V.Sc.,
R. M. Kinross Veterinary Research Officer.
Introduction: Brucellosis of Swine, first reported from New South Wales in 1932 by the author, has been recognised since December, 1940, as occurring in our swine herds much more frequently than was previously known.
Surveys of swine carried out over the period 1932-40 did not indicate the true extent of the disease because such surveys were taken
(a) at bacon factories and abattoirs, where the majority of pigs slaughtered are young;
(b) in the country, where we now know the disease is less widespread than close to the large cities.
We know, from the results of work carried out since December, 1940, that the disease is most prevalent in mature breeding swine and in the districts close to the city of Sydney. Our information cannot be regarded as complete, however, and Stock Inspectors are urged to keep the survey work on Brucellosis of Swine constantly in mind. The disease is known to occur in several country districts and may well be more widespread than is now known.
Cause of the Disease:
Brucella suis, an organism closely related to, but distinct from, Brucella abortus.
Symptoms:
This disease is not characterised by abortion of the young, although this phenomenon may be seen. It is more frequently associated with sterility of both male and female and with early death of suckers born at full term. Wherever considerable mortality of sucking pigs in the first month to six weeks of life is encountered, this disease should be suspected. Sterility of sows or boars is not so frequently reported by stockowners, chiefly because so few of them keep correct records of their breeding herds, but where it comes under notice Brucellosis should also be considered as a possible cause. The author, during nine months of field work on this disease, encountered only three boars which the owners considered to be "poor breeders." All three animals proved to be infected when subjected to the agglutination test.
Other symptoms seen less commonly are abortion of the young, white mucopurulent discharge from the vulva of sows, enlargement of one or both testicles of boars and abscess formation in almost any site in the body. Occasionally, such abscesses may develop in the bones of the spinal column and cause varying degrees of paralysis.
Lesions:
Apart from the abscess formation previously mentioned, lesions appear to be the exception rather than the rule so far as New South Wales experience has shown. Necrosis of the mucous membrane of the uterus in animals which abort and, according to foreign authors, even in female animals which are not pregnant may be encountered. In the male, necrosis of the tissues of the genital organs may occur. In the majority of cases studied in New South Wales to date, however, lesions have been conspicuous by their absence and have only been encountered in the genital organs of three of the reacting boars seen by the author.
Appearance of health is no indication of freedom from Brucellosis of Swine.
Method of Spread of the Disease:
As with Brucellosis of Cattle, so with Brucellosis of Swine the movement of untested pigs is the most important method of spread of the disease from herd to herd. Too much stress cannot be laid on this point at the present time when swine breeding is extending under stimulus of war conditions. Owners should be urged to breed their own replacement stock and to buy only a minimum number of animals for breeding. Such purchased animals should always come from Brucellosis-free herds.
From the point of view of control of all diseases, buying of store pigs is always a very risky proceeding and should be discouraged. Permitting the home boar to serve sows from untested herds or sending sows to untested herds for service may also introduce the disease.
Uncooked pig meat offal is dangerous as Brucella suis is widely distributed throughout the body of the infected pig.
In exceptional cases the farmers' boots may transfer infection from farm to farm and disinfection should be practiced when a farmer (or Stock Inspector) visits any piggery.
Within the herd the boar is one of the most important spreaders of the disease. He may develop the disease by mating with infected sows and may then transmit it to clean sows by mating. Brucella suis is commonly passed in the urine of infected boars and where the boar runs with the sows this is an added danger. The organism may also be passed onto the ground in urine by the infected sow. Discharge and or aborted foeti also contaminate ground and the meat-eating and rooting habits of pigs render them particularly susceptible to infection present in the ground.
Control:
Slaughter of reacting pigs and eradication of the disease by repeated tests at 30 day intervals is the only method of control at our disposal at present. Infected pigs cannot be sold for slaughter because it is known that Brucella suis is commonly distributed widely throughout the body of the infected pig and is more dangerous to man than Brucelia abortus. Some authors consider it is the most dangerous of the three Brucella species for man.
This policy, adopted by the Department of Agriculture from the outset of control of this disease, is vindicated by the fact that during 1939 a slaughterman at Homebush Abattoir died as a result of Brucella infection. Unfortunately, the species of Brucella was not typed in this instance but, nevertheless, this occurrence serves as a warning of what could happen.
Further, a porker class pig, aged four months, and reacting to the agglutination test, was recently slaughtered at the Veterinary Research Station, Glenfield, by the author. No gross lesions of disease could be found at post-mortem examination but Brucella suis was isolated from every group of lymph glands in the body and from several of the internal organs.