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This article was published in 1948
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INSTITUTE OF INSPECTORS OF STOCK OF N.S.W. YEAR BOOK.
Tuberculin Testing of Pigs
K. V. BYRNE, B.V.Sc., Inspector of Stock, Tamworth.
As references to this subject have been infrequent in recent Australian veterinary literature, it is considered possible that a few comments on it might be of interest.
It is mentioned that the incidence of Tuberculosis generally in the Central Riverina is very low, clinical inspections of dairy herds for the presence of the disease, for example, only resulting in a locating of affected animals on rare occasions; condemnations for this disease during recent years in the district being as follows:-
| 1940 | 3 |
| 1941 | 5 |
| 1942 | 2 |
| 1943 | 2 |
| 1944 | Nil |
| 1945 | Nil |
| 1946 | Nil |
That these figures are a true indication of the position is suggested by the experience of Meat Inspectors in the abattoirs of the Leeton and Wade (Griffith) Shires. These two towns are among the few of their size where all meat slaughtered for local consumption is subjected to regular and competent meat inspection, each Shire employing for the purpose a Health Inspector who has the additional qualification of being a trained and experienced Meat Inspector.
At both these abattoirs Tuberculosis rarely is seen, not infrequently the whole year passing without any condemnations for this disease at all. From time to time, however, an affected beast is encountered; the incidence being a small fraction of 1 per cent.
Unfortunately, precise figures covering a lengthy period cannot be given as the only statistics available are those for 1946 and 1947 at Leeton. These are:-
| Cattle slaughtered | Affected with Tuberculosis | Pigs slaughtered | Affected with Tuberculosis | |
|---|---|---|---|---|
| 1946 | 1300 | 2 | 179 | nil |
| 1947 | 1543 | 1 | 518 | 26 |
The figures for 1946 are typical of an average year; the high pig condemnations for 1947 resulting from the outbreak which forms the subject of this article.
Attention first was drawn to the property concerned when in a consignment forwarded from it the heads of four pigs were condemned for Tuberculosis. This occurrence was reported by the Health Inspector to the writer, the first reaction in view of the rarity of Tuberculosis in the area being to entertain the possibility that the lesions may have been in the nature of those described by Hankin (1937). However, a few days later a total condemnation of three further carcases from the same owner proved the presence of a high incidence of Tuberculosis.
A visit was made to the property, therefore, and it was found that on the piggery in question 45 pigs were being run under conditions of the poorest hygiene. All pigs, however, appeared to be in excellent health and condition.
The matter of how such a high incidence of Tuberculosis should have developed in the piggery then received attention, but no definite conclusion was reached on the point. The piggery had been in action for approximately two years; foundation stock being obtained in ones and twos in a number of different country saleyards. With the exception of an occasional small quantity of milk obtained from one cow the pigs had been grain-fed throughout. A tuberculin test of this cow gave negative result. The pigs were not in contact with any other animals, and no poultry existed on the property. The most likely conclusion presenting itself, therefore, was that the owner, in obtaining his foundation stock, purchased an infected animal or animals, the disease spreading from that source.
It was decided to submit the remaining pigs on the property to the tuberculin test and this was carried out on one boar, 11 gilts, 4 sows and 15 six-weeks-old suckers. The only pigs on the property not tested were 15 suckers under one week of age. The method of testing was by the simultaneous intradermal and ophthalmic test: intradermal tuberculin being used for the latter also. The animals were restrained by means of the usual iron bar and running wire loop device: the intradermal injection being made on the medial edge of the ear, approximately half-way between the tip and the base. The ophthalmic test was initiated by squirting a few drops of tuberculin into the eye.
This portion of the work was carried out by Veterinary Officer B. King and the writer, the reading of the ophthalmic test being performed by the latter the following day.
In reading the ophthalmic test the presence of any muco-purulent discharge was considered to be a positive reaction, a watery or nil discharge being considered negative. On this basis nine pigs were held to be positive.
At the seventy-second hour the intradermal test was read by Veterinary Officer King and the writer, when 11 pigs were considered to be positive reactors. These 11 included the 9 which had been considered to be positive to ophthalmic test, and two negative to that test. However, a watery discharge was present in these two at the time of reading the ophthalmic test, but such a discharge was present in the big majority of the tested animals; many pigs showing such a discharge therefore being also negative to the Intradermal test.
Subsequently a further sow which the owner had on another holding was tested by the writer with both the ophthalmic and intradermal tests and this animal showed no discharge at all at the reading of the ophthalmic test, but gave a very marked positive reaction to the intradermal.
It is mentioned that in the case of all positive reactors except one the swelling of the injected ear was so marked that the Interpretation of the test was obvious at a glance. In the exception the swelling was not so pronounced but the difference between the injected and the non-injected ear was still sufficiently great to allow a decision to be made without hesitation.
In view of the high incidence of the disease in this piggery and because of the fact that the premises were only leased by the owner the latter decided that he would establish a new piggery elsewhere with fresh stock and retain his existing pigs in quarantine until they were disposed of by slaughter.
The reactors were disposed of immediately, nine being sent through the local abattoirs where all were found to be affected with Tuberculosis. The three remaining reactors were unsuitable for slaughter and were destroyed on the property, where a post-mortem also revealed marked tubercular lesions in each case.
It is mentioned here that one non-reacting pig which went through the abattoirs at the same time as the reactors had the head rejected by the local Health Inspector because of the presence of Tuberculosis in the submaxillary lymph glands.
The concluding history is that the owner destroyed the suckers which were not tested and fattened to the porker stage the 15 tested suckers, all of which were negative reactors. Condemnations for Tuberculosis in the latter subsequently were one carcase and one head.
Reference:
Rankin, T. H. (1937). Aust. vet. J., 13 : 241.