CONTENTS Foreword General Conclusions Regarding the Intradermal Method of Testing Cattle. 98 Present Status of the Intradermal and Ophthalmic Tests in the United States. 100 Local Tuberculin Reactions and Their Use for Diagnosis in Human and Veterinary Practice Technic of the Intradermal Method Kind and Strength of Tuberculin for Intradermal Use Precautions against the Deterioration of Tuberculin Lack of Uniformity in Tuberculin Alcoholic Precipitated Tuberculin Autopsy Notes PAGE 97 101 102 104 105 106 107 109 111 The Local Reaction to the Intradermal Injection in Cattle 117 The Thermal Reaction to the Intradermal Injection in Cattle 118 122 Results of Retests 127 Description of Cases which Reacted to the Intradermal but did not React to the Subcutaneous Test 129 Discussion of Cases which Reacted Thermally to the Subcutaneous, but 133 134 Use of the Intradermal Tuberculin Test on Swine Conditions under which the Intradermal Test is Preferable TABLES PAGE Table 1. Results from the Intradermal Use of Various Solutions of Tuberculin 110 Table 2. Results of Intradermal Tests and Autopsies 112 Table 3. Intradermal Tests with Koch's Old Tuberculin and Precipitated 113 Table 4. Typical Cases Selected to Show that Cattle React Thermally to the Intradermal Test 119 Table 5. Showing Tests in Six Herds in which Thermal Reactions Resulted from the Intradermal Injection 120 Table 6. Results of Successive Intradermal Tests 121 Table 7. Comparison of One Thousand Tests by the Intradermal and Sub cutaneous Methods 124 Tables A B, and C. Results of Intradermal Tests by European Veterinarians. 126 ILLUSTRATIONS Plate 1. Figures 1 and 2, Syringes for the Intradermal Test. Figure 3, Calipers for Measuring the Reaction Plate 2. Figures 1 and 2, Position for Injecting Intradermally Plate 4. Measuring Intradermal Reactions Plate 5. Unusually Large Intradermal Reactions Plate 6. Figure 1, Swelling caused by Disinfectant. Figure 2, Reaction 145 146 147 148 149 150 151 152 FOREWORD In all ages, trees and grasses have been the most important products of the soil. The efficient, economic utilization of grass and similar forage, which can be accomplished only by the use of domestic animals, is one of the world's great problems. It is a basic problem in California. Animals are necessary to utilize the grass on its vast ranges, including valleys, foothills, and mountains, and also to utilize one of the most important products of irrigation-alfalfa. The production of butter fat is almost an economic necessity wherever alfalfa is extensively raised. Domestic animals, however, do more than convert. into edible form the products of the soil. They help to maintain its fertility: first, by returning to it essential fertilizing ingredients and, second, by permitting a more diversified system of agriculture. Obviously one of the most important factors in the efficiency of this living machine is its health. If animals when grown are unfit for food, in so far as this occurs it becomes a tax upon every pound of wholesome beef. If the average usefulness of a cow extends only through three periods of lactation, as is claimed to be the fact in some milch dairies, the cost of producing every pound of butter fat and every bottle of milk is thereby increased. The most disastrous disease among cattle is tuberculosis. It is a menace that no stockman or dairyman can afford to ignore. Its control is a problem that every state must seek to solve as surely as it must endeavor to develop an abundant food supply. Of the eight thousand head of cattle examined under the direction. of the veterinary division of this Station, approximately twenty-five hundred have reacted to the tuberculin test. The loss from this disease in California alone is estimated at over half a million dollars per year. The loss appears to be increasing. Reports of meat inspectors in San Francisco and Los Angeles indicate that the proportion of cattle from certain ranges, which are affected with tuberculosis, has increased from 1 to 5 per cent in five years. The Agricultural Experiment Station has resolutely set itself to study this problem with all the resources at its command. It is going to be a long, hard road to travel. A thorough study of the conditions under which this insidious disease is spread among domestic animals must be made. Then a sane, rational, comprehensive system of public control must be organized. All evidence points to the fact that it must be on lines not heretofore generally attempted in this country. Up to the present time the most efficient weapon with which to combat tuberculosis in cattle has been the tuberculin test. A description of the usual method of performing this test was published by this Station in Bulletin No. 199, entitled "Bovine Tuberculosis," which may be obtained free upon application. This method, however, of performing the tuberculin test by injecting the tuberculin subcutaneously has not proved effective in all cases. It cannot be applied satisfactorily to young calves or to wild range cattle, while during the hot season in some of the interior valleys the test has been unsatisfactory even when applied to docile dairy cows. A recent modification of the tuberculin test, called the intradermal method, is especially adapted to these conditions. This bulletin deals with the best technic and the proper strength of the tuberculin to be used in this new method, as well as its accuracy as compared with the usual subcutaneous method. The intradermal method is believed to constitute an important step in the control of tuberculosis in both cattle and hogs. However, it should be clearly understood that a method of discovering the disease, which any tuberculin test is, is not, in itself, a method of controlling it. When the proper knowledge has been obtained of the conditions under which the disease spreads, a system of husbandry must be developed which will ensure the maintenance of healthy animals. THOMAS F. HUNT, Director. GENERAL CONCLUSIONS REGARDING THE INTRADERMAL METHOD OF TUBERCULIN TESTING CATTLE The intradermal method of tuberculin testing cattle as first applied by the French investigators Moussu and Mantoux37 and as used under California conditions by Ward,50 Baker, Longley23 and others has many advantages over the usual method. Since the reaction to tuberculin when injected intradermally depends upon a swelling at the point of injection and not on a rise of temperature, it is to be preferred to the subcutaneous under all conditions that are liable to modify the tuberculin temperature curve, such as unusual surroundings, very hot weather, or fatigue from a long journey. It can be satisfactorily applied to young calves and wild range cattle and is especially useful in testing cattle during the hot season in the interior valleys of this state under conditions that render the subcutaneous method of testing unsatisfactory. It excels the subcutaneous method in economy of time, labor and materials. From our observations in applying 4926 intradermal tests, including retests, to 4001 head of cattle, 1614 of which reacted, the results being checked by 1000 subcutaneous tests and 341 autopsies we conclude that under average dairy conditions the intradermal equals the subcutaneous method in accuracy, provided a 5 per cent, or stronger, solution of alcoholic precipitated tuberculin is used and the test is performed by an experienced operator. We do not advocate the substitution of the intradermal for the subcutaneous method by a veterinarian until he has become skilled in its use by practice and observation. The practitioner can easily accomplish this in the routine of his work by applying the two tests simultaneously. Such a procedure cannot injure the accepted subcutaneous method in any way, although it may modify the local intradermal swelling to some extent. Tuberculous cattle usually react thermally, as well as locally to intradermal injections, even when very small doses of tuberculin (1 to 10 miligrams) are used. If temperatures are taken at two-hour intervals from the eighth to the twentieth hours following the intradermal injection it will be found that most of the cattle which react locally will also react thermally. Since neither the intradermal, the subcutaneous, nor the ophthalmic method will detect every case of tuberculosis when applied independently, the maximum number of reactors can only be detected by applying the combined tests. This may be done by applying the intradermal and subcutaneous tests simultaneously or by administering the intradermal test alone and retesting all of the non-reactors after an interval of at least seven days. The ophthalmic test may also be advantageously combined with either or both of these tests. The ophthalmic test alone is unsuitable for use under the average California dairy conditions, except when only a few animals are to be tested and they can be kept confined under shelter. For official tuberculin testing where a high degree of efficiency is necessary a combination of the three tests would be desirable. The intradermal method is especially adapted to the testing of swine. |