CO129-562-12 Dysentry epidemic- recommendation to enforce compulsory pasteurization of milk 7-6-1937 - 17-8-1937 — Page 37

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vaccines takes time to develop, necessitating immediate removal of calves from their dams and strict isolation before vaccination and for a period subsequently. Also the immunity only lasts for from six to twelve months and must be renewed periodically by revaccina- tion. While, therefore, vaccination may afford a means of raising healthy stock from heavily infected herds, the attention, skill and expense needful for its success cannot be less than in the scheme of eradication based on the tuberculin test. Furthermore, it must be remembered that animals which have been vaccinated with tubercle bacilli, either living or dead, react to the test for a variable, sometimes long, period subsequently. Such animals would, there- fore, have to be excluded from a scheme of eradication based on the test, and could not be permitted to enter tuberculosis-free herds, as it would be impossible to decide whether a reaction was due to the vaccine or to a natural infection following on the decline of immunity.

147.

(b) Other diseases of cattle.

Other diseases besides tuberculosis may be attacked by the methods which we have just described, provided that there is a test that can reveal them in their early stages. This condition is fulfilled, in the case of contagious abortion, which is disclosed by a blood agglutination test, and of chronic streptococcal mastitis which can be discovered by a bacteriological examination of milk samples. Johne's disease cannot yet be identified with any certainty before clinical symptoms appear, and concerted steps to eradicate it must await further research.

148. In many respects contagious abortion and chronic strepto- coccal mastitis lend themselves more readily to eradication than does tuberculosis. The loss occasioned to farmers is even more severe; at the

same time the precautions which the farmer himself may take against the spread of infection in his herd are possibly simpler and more effective. Every attempt, therefore, on the part of individual farmers to eliminate these diseases from their herds is to be encouraged. But a concerted scheme should not apply to more than one disease at a time. For otherwise either the government scheme must apply to animals free from all the diseases, which would seriously reduce the number of herds which could be looked to for supplies of disease-free cattle, or separate schemes must be operated concurrently for each disease. This course would lead to great administrative complications. If two diseases were dealt with there would be four classes of animals; those with both diseases, those with neither, those with the first disease but not the second, and those with the second disease but not the first. A government scheme would have to arrange that no animal should come into contact with any animal belonging to a different class. This, however, we believe to be impracticable. We hold, therefore, that the various diseases must be dealt with by the state successively and not concurrently, whatever course

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individual farmer may adopt. The first disease to be dealt with officially must be tuberculosis because of its great danger to public health.

VI. THE PASTEURISATION OF MILK.

149. The proposal to make the pasteurisation of milk compul- sory raises two distinct questions. Much of the milk consumed in large towns is already heat-treated to prevent it souring before it reaches the consumer. To substitute in the interest of public health a special form of heat-treatment for those at present in use, though as shown in paragraph 163 this would raise a number of important technical problems, would not greatly interfere with the interests of individuals. But these interests would be seriously affected if pasteurisation were made compulsory in and around large towns and throughout towns of smaller size, where raw milk is to-day sold in competition with heat-treated milk. Here the raw milk is produced on land with labour the price of which is enhanced by proximity to a town. But it is not burdened with heavy transport charges; it is distributed directly by the owner fresh from the cow;* and it avoids the cost of heat-treatment. It is therefore able to compete with milk produced more cheaply but further from the town. The compulsory pasteurisation of milk produced and sold under these conditions is a quite different question from a change in the method of heat-treatment.

(a) Compulsory pasteurisation in areas now largely consuming raw milk.

150. Compulsory pasteurisation of milk throughout Great Britain would involve in many areas the widespread replacement of raw milk by treated milk. But raw milk has its determined advocates who base their case partly on its alleged nutritional superiority and partly on the discouraging effect that compulsory pasteurisation would have upon efforts to produce clean and disease- free milk.

151. The ambiguous results of large-scale feeding experiments, and the uncertainty of deductions from more theoretical considera- tions lead us to the conclusion that there is not sufficient evidence to support the presumption that pasteurisation is harmful from the point of view of human nutrition. In view of the fact that innumerable healthy children are to-day reared on a diet containing no unpasteurised milk, we do not feel that the suggestion that pasteurisation may at some future time be shown to have bad results should be given much weight in deciding on the general merits of pasteurisation as a safeguard to public health.

152. It has been argued that if farmers knew that their milk was to be pasteurised, they would relax their efforts to produce a safe and clean milk. In considering this argument it is essential

*

There is a demand for such milk from a section of the public.

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