ARCHIVE FILE

---

---

INSTITUTE OF INSPECTORS OF STOCK OF N.S.W. YEAR BOOK.

The Milk Ring Test for Brucellosis

By PETER T. DIPLOCK, B.V.Sc. Veterinary Inspector, Warialda - Inverell

Comparatively little use appears to have been made in Australia of the Milk Ring Test, or ABR Test for Brucellosis in cattle, although it has been found a useful tool in some overseas countries, provided its limitations are taken into account.

The test was first developed by Fleischhauer in 1937 while endeavouring to develop better diagnostic methods for Brucellosis (Gilman and McAuliff 1956.)

Recent experience in Sweden has shown that it is of considerable value as a preliminary screening test and its use in that country has allowed the rapid selection of infected herds in which individual blood testing can be applied (Bjorkman and Bengton 1962).

In view of these reports and following come experience with this test in New Zealand, some limited work with the ABR test was recently carried out at Warialda with a supply of antigen provided by the Director of Veterinary Research, Glenfield.

TECHNIQUE

The Commonwealth Serum Laboratories, who produce the necessary antigen in Australia, give the following instructions for carrying out this test: Collect a sample of whole milk. This should be taken from the pooled milk of all milking cows in the herd. A drop of stained suspension is added to each ml of whole milk. (The test is qualitative and there is, therefore, some latitude as to the amount of suspension added. The optimum is in range 0.02 to 0.03 ml for each ml of milk).

In practice 2 ml of whole milk is put into a test tube of ⅜" to ½" diameter. Add the suspension and thoroughly shake. Allow to stand undisturbed for one hour at 37 degrees C or room temperature.

READING THE TEST

When the milk contains Br. abortus agglutinins the stained bacteria are first agglutinated and then carried to the surface in the cream. In a positive test the cream therefore becomes deeply coloured. The intensity of the colour varies with the amount of suspension added and the amount of agglutinins present in the milk.

The degree of reaction may be noted in accordance with the following table:

INTERPRETATION

Any degree of positive reaction (i.e. plus plus plus, plus plus, or plus) indicates the presence of one or more infected animals in the herd.

Reaction	Cream Ring	Milk Column	Agglutinins Present
+ + +	Intensely coloured	White	+
+ +	Intensely coloured	Incompletely decoloured	+
+	Coloured ring still present	Not noticeably decoloured	+
O	No colour in cream	Fully coloured	O

DISCUSSION:

The ABR test or Milk Ring Test, depends upon the agglutination of a coloured antigen added to the milk. In the positive test the agglutinated antigen adheres to the fat droplets, forming a coloured cream layer as the cream rises, while in the negative test, the antigen remains dispersed in the skim milk layer and the cream is white (Anon. 1955.)

It is emphasised however, that this test is essentially a herd test since it is less accurate than the blood test to determine the status of the individual animal (Gilman and McAuliff 1956.)

CONCLUSION:

The ABR test or Milk Ring Test, described above has the following advantages:

1. It provides a reasonably accurate and rapid test for determining the status of a herd, particularly when carried out frequently, and if there are relatively few infected herds in the area.

2. It will permit detection of infected animals even though the organism has not localised in the udder.

Its disadvantages are:

1. It will not detect infection in bulls, dry cows, or non-lactating heifers.

2. If unwisely applied and interpreted, it can only lead to confusion and loss of confidence in the established methods of control.

REFERENCES:

1. Anon. (1955). "The Merck Veterinary Manual", p. 444 (Merck & Co. Inc., Rahway, N.J., U.S.A.)
2. Björkman, G. and Bengtson, H. (1962) — J.A.V.M.A., 140: 1192
3. Gilman, H. L. and McCauliff, John L. (1956), “Diseases of Cattle". p. 547 (American Veterinary Publications Inc., Evanston, III.)