UNIVERSITY OF CALIFORNIA AGRICULTURAL EXPERIMENT STATION 
 COLLEGE OF AGRICULTURE BENJ ' '° E WHEELER - •■"«•«" 
 
 THOMAS FORSYTH HUNT, Dean AND DIRECTOR 
 BERKELEY H. E. VAN NORMAN, Vice-Director ano Dean 
 
 University Farm School 
 
 CIRCULAR No. 205 
 August, 1918 
 
 BLACKLEG 
 
 WITH NEW METHODS FOR ITS PREVENTION 
 AND TREATMENT 
 
 By GEO. H. HAET 
 
 Blackleg is one of the common and probably the best known of any 
 of the infections diseases of cattle. Most cattlemen of any experience 
 under range conditions have come in contact with the disease. It is 
 prevalent throughout the western range country of the United States 
 and is quite generally distributed throughout the world. Few, if any. 
 live stock counties in California are entirely free from it. Some 
 have claimed such freedom for years, only to find on careful investi- 
 gation that animals, supposed to be dying from other causes, were in 
 reality infected with this disease. It is the common cause of sudden 
 deaths in bovine animals between six months and two years of age, 
 and when such animals are dying it should be the first disease to be 
 considered in ascertaining the cause. While it is more prevalent on 
 the ranges, young cattle on dairy pastures in some sections of this 
 state have to be regularly vaccinated to prevent losses. 
 
 CAUSE AND METHOD OF INFECTION 
 
 The cause of the disease is a rod-shaped micro-organism known as 
 the Bacillus of Blackleg. This organism is strictly anaerobic, mean- 
 ing that it will not multiply in the presence of the oxygen of the air. 
 When it meets with unfavorable conditions, it forms spores which are 
 the resting stage of the bacteria and are very resistant to adverse 
 conditions. It is the spores which infect the soil, where they will 
 remain alive for j^ears. When they infect a susceptible animal, they 
 must gain entrance through a comparatively slight wound of a pene- 
 trating nature which does not tear open the skin or mucous membrane 
 and allow oxygen of the air to come in contact with the underlying 
 tissue. Such injuries to the skin may be made by briers, sharp sticks, 
 barbed wire, etc., through which wounds the bacteria enter. The 
 disease is practically confined to cattle, although very rarely sheep, 
 goats, and even hogs have been known to contract it. 
 
 Seasons have a marked influence on the disease. It is most liable 
 to make its appearance in the late summer and fall, following which 
 it is most prevalent in the spring, but it has been found in California 
 at all times of the year. 
 
SYMPTOMS 
 
 In many cases the first evidence of the disease is the finding- of one 
 or more dead animals with a local swelling nnder the skin. The time 
 between which the organism gains access to the body and the first 
 symptoms appear, known as the period of incubation, is from one to 
 three days. The symptoms are both local and general. There is a 
 marked rise of temperature, with loss of appetite and dullness, and 
 the animal fails to keep up with the herd. This is accompanied with 
 or soon followed by a characteristic local swelling on some part of 
 the body. The swelling appears suddenly and contains gas formed 
 by the bacteria which gives it a peculiar crackling feeling. It varies 
 in size in different cases often beginning as a small area and spreading 
 rapidly in extent until the animal dies. It never occurs below the 
 knees or hocks but, with these exceptions, may be found in any part 
 of the body. The frequent appearance of the swelling on one of the 
 legs has given the disease its name of blackleg or black quarter. The 
 quarter on which the swelling occurs is usually stiff and the animal 
 goes lame. On incising the area the animal evinces little or no pain, 
 and a dark-colored fluid is exuded, consisting of blood and broken- 
 down muscle tissue mixed with gas bubbles having a sweetish-sour 
 odor and frothy appearance. The area should be incised with caution 
 as the discharges resulting are teeming with organisms and if allowed 
 to drop on the ground will add further infection to the soil. Atypical 
 cases of blackleg occur with no local swelling. The absence of swell- 
 ing, therefore, is not alone sufficient evidence to exclude the disease — 
 but in the vast majority of cases, careful examination will reveal a 
 local affected area. So, also, while the age incidence is clearly marked, 
 cases frequently occur up to three years of age and at times even in 
 much older animals. The symptoms develop rapidly, accompanied by 
 great weakness and depression, rapid breathing, and occasionally con- 
 vulsions and death in from twenty-four to seventy-two hours. 
 
 POST-MORTEM APPEARANCE 
 
 The important things to observe in an animal dead of suspected 
 blackleg are its age, the local swelling, and the practically normal 
 spleen. On examining the carcass, the first step is to examine for the 
 local swelling above described. On removing the skin over the area, 
 a large, dark swelling involving the muscle will be observed. The 
 muscle affection may be present in any degree from slight darkening 
 of the normal muscle tissue with gas bubbles in its substance, to com- 
 plete degeneration of the muscle in the center of the area to a semi- 
 solid mass filled with gas bubbles. The peculiar, somewhat character- 
 istic odor of the disease can be best obtained from the local swelling. 
 Internally, there is a general congested condition of the organs as is 
 seen in most all acute infectious diseases. The spleen, however, is 
 not enlarged. The liver is congested and may show a mottled colora- 
 tion on its surface. There may be present ecchymoses or small 
 
hemorrhagic spots in the serous membranes, such as the pericardium 
 or heart sack, pleura or lining of the chest wall and covering of the 
 lungs and peritoneum, or covering of the intestine and lining the 
 abdominal walls. The lungs are congested but show nothing char- 
 acteristic. 
 
 Biological preparations used in prevention and treatment of blackleg. 
 
In making post-mortem examinations of carcasses, care must be 
 taken not to infect the soil further. Therefore, the work is to be 
 done at the point of disposal of the animal. The carcass should be 
 burned or buried deeply after covering with quicklime and the con- 
 taminated surface soil thrown on the fire or into the burial hole. 
 
 DIFFERENTIAL DIAGNOSIS 
 
 There are other diseases with which blackleg may be confounded, 
 chief of which is anthrax. The latter is differentiated from blackleg 
 by the fact that it attacks animals of all ages with equal frequency, 
 as well as all species of domestic animals and man. In some cases a 
 local swelling is present, but this is evidence of localization and is 
 always slower in development. Animals with this form of anthrax 
 will live longer than blackleg cases. On palpation of the local anthrax 
 swelling, no crackling sound is noticed and, on cutting into same, no 
 gas bubbles are present and the blackleg odor is absent. On post- 
 mortem the spleen is found much enlarged and softened and the blood 
 is black and tarry, clotting imperfectly or not at all. On account 
 of the danger of further soil infection in opening anthrax carcasses 
 as well as of human infection, it is better to have veterinary or labora- 
 tory assistance in making a diagnosis. (See circular from this station 
 on anthrax, by Haring). 
 
 The laboratory diagnosis of blackleg from specimens received is 
 unsatisfactory, as a rule, due in many instances to the character of 
 the tissues sent and to more or less decomposition which usually occurs 
 during transit. Under these conditions the isolation of the causative 
 organism, which is difficult at best, is rendered almost impossible. 
 Greater dependence should therefore be placed on the field examin- 
 ation, which is usually sufficient to make a positive diagnosis. 
 
 Another disease, quite common in California, which so closely 
 simulates hemorrhagic septicaemia that it cannot be positively differ- 
 entiated from it, may be mistaken for blackleg. This disease, however, 
 affects animals of all ages. Local swellings are not usually present 
 and on post-mortem examination extensive hemorrhagic blotches and 
 small blood spots are present on the lining and covering membranes 
 of the body cavities and organs. 
 
 TREATMENT AND PREVENTION 
 
 Powdered, Pellet, and String Vaccine. — Until recently no remedy 
 of any real value was known and even now nearly all affected animals 
 die. The method therefore has been to prevent the spread of the dis- 
 ease by vaccinating all susceptible animals as soon as the disease was 
 found or in a great many cases to make vaccination the procedure on 
 all infected lands without waiting for the disease to make its appear- 
 ance. This vaccine was made by drying the affected muscle tissue 
 from animals dead of blackleg. It was then ground in a mill, 
 
moistened, spread out on thin trays and subjected to heat at about 
 95° C. for six hours, which weakens or attenuates the organisms. 
 When the resulting material containing the powdered muscle tissue 
 and spores is injected into an animal, it produces a mild form of the 
 disease which renders the animal immune from natural infection. As 
 originally made by Arloing, who devised the method, two vaccines 
 were used, the first being subjected to a higher degree of attenuation 
 than the second. No. 1 vaccine was used to prepare the animal to 
 be immunized for the second stronger vaccine given ten days to two 
 weeks later. As generally used at present, only one injection is given. 
 After heating and regrinding the vaccine is always tested on guinea 
 pigs to see that the contained organisms have been properly attenuated 
 by the heat before sending it out. 
 
 This vaccine in powdered form has been put out by the U. S. 
 Bureau of Animal Industry free of charge to cattlemen for twenty 
 years, at the rate of from one to several million doses yearly. Com- 
 mercial biological firms have been making the same vaccine in pellet 
 as well as string form, which is easier to administer, and are selling- 
 it in large quantities as a preventive of the disease. Many stockmen 
 have used this vaccine and statistics covering millions of animals so 
 treated as a whole show most satisfactory results. 
 
 The fact remained, however, that the vaccine could not be properly 
 standardized. Its activity depended on the presence of spores of 
 the blackleg organism. To give proper immunity it was necessary 
 for these spores to germinate in the body of the injected animal. There 
 was no way of ascertaining the number of these spores and one vac- 
 cine might contain few while another would contain many. In spite 
 of the guinea-pig test batches of vaccine have been sent out which 
 were not sufficiently attenuated by the heating process, and resulted 
 in the production of the disease in the less resistant of the injected 
 animals and in some very severe losses. At other times sufficient 
 spores would not be present or they had been too highly attenuated 
 by heat, so that no immunity was produced and injected animals 
 woulel continue to die from natural infection. Also the vaccine had 
 no curative effect and some time was required after injection before 
 immunity was established, during which time losses from natural 
 infection would continue. It was these facts so well known to all 
 workers with blackleg vaccine, both in the laboratory and in the 
 field, that leel to the development of what may be called the new 
 methods of treating and preventing this disease. 
 
 Blackleg Serum. — In the treatment of this disease there is now 
 being produced a blackleg serum, originated in Europe by Kitt, 
 Vallee, Leclainche and others. This is prepared in the usual way 
 of making serum for other infectious diseases. Horses or cattle are 
 gradually infected with blackleg organisms of increasing virulence 
 and numbers until they can withstand enormous doses of the most 
 virulent strain of the organisms injected directly into the circulating 
 blood. These animals are then bled from the jugular vein under 
 asceptic precautions and the serum allowed to separate from the 
 
G 
 
 clotted blood. This serum contains immune bodies against the black- 
 leg organism and when injected into an affected animal in sufficient 
 doses has distinct curative properties. In smaller doses it will also 
 protect healthy animals against the disease immediately. The effect 
 produced by the injection of such a serum is termed passive immunity, 
 as distinct from active immunity, which is produced by an attack of 
 the disease or by causing the animal to pass through a mild form 
 of the disease such as is caused by vaccination. Passive immunity in 
 this disease is of short duration and cannot be depended on for a 
 longer period than ten days. Unless a supply of serum is close at 
 hand, blackleg-affected animals will be dead before they can be treated. 
 
 The great field of usefulness of the serum is -in its application to 
 all susceptible animals in a valuable herd where animals have already 
 died, to produce an immediate immunity and cessation of further 
 cases developing. For this purpose 25 to 30 cubic centimeters are 
 given each animal with a hypodermic syringe under the skin. As a 
 curative in animals already affected several injections may be neces- 
 sary with much larger doses of from 100 to 200 cubic centimeters. In 
 herds where serum is being administered it is well to take tempera- 
 tures of the animals and any with a high temperature (104° S\ or 
 above) should be considered as infected with the disease even if show- 
 ing no other physical signs. Such animals should be given 100 cubic 
 centimeters or more of serum as a curative. After this has been done 
 and the disease stopped, it must be followed in a week by a vaccination 
 of the animals to produce an active immunity, which is much more 
 lasting. The cost of such a procedure at the present time probably 
 justifies its use only in suddenly appearing severe outbreaks and in 
 valuable pure-bred animals. Commercial houses are charging from 
 3 to 4 cents per cubic centimeter for the serum, depending on the 
 quantity purchased. The difficulty with the serum is that at the 
 present time no definite means of standardizing it have been perfected 
 and no degree of potency is required. If further field trials prove 
 its value this will no doubt be given consideration. 
 
 Tissue Filtrate and Culture Filtrate. — In the prevention of the 
 disease two new products are now being prepared. These are both 
 free from the causative organism in either vegetative or spore form 
 and therefore cannot produce the disease. One of these is made 
 directly from the muscle juices of affected animals, which are extracted 
 by pressure, and is known as tissue filtrate, and the other is made 
 by growing the blackleg organism under anaerobic condition in the 
 laboratory in a special medium containing meat, and the product is 
 known as culture filtrate. The term filtrate is applied because the 
 finished products are filtered through specially constructed clay filters 
 of such fine porosity that no bacteria are allowed to pass. The tissue 
 filtrate or extract is also called aggressin in the literature put out 
 by the commercial laboratories which have the products for sale. 
 
 The tissue filtrate or aggressin was developed by veterinarians at 
 the Kansas Agricultural College, and the culture filtrate, by Nitta, 
 of the University of Tokio, in Japan. The first product requires the 
 
actual production of the disease in animals to obtain the affected 
 muscle tissue and juices. A great amount of the material cannot be 
 obtained from one animal. It can be readily seen, therefore, that its 
 production on a large scale would involve the sacrifice of a good many 
 young cattle and its cost thereby be greatly enhanced over that of the 
 culture nitrate. Even though experiments may prove the protective 
 value of the tissue filtrate to be greater than that of the culture 
 filtrate, this difference may not be sufficiently great to warrant the 
 increased cost of the former. Further experimentation, backed up 
 by field trials, is required on this point. In the final stages of manu- 
 facture the culture filtrate is partially evaporated to reduce its volume 
 and preserved by the addition of glycerin. The present cost of the 
 culture filtrate is from 15c to 20c per dose, depending on the quantity 
 purchased. The material is put up to inject in 1 cubic centimeter or 
 5 cubic centimeter doses, depending on the degree of concentration. 
 The tissue filtrate costs 30 to 35 cents per dose of 5 cubic centimeters. 
 Both kinds of vaccine are in liquid form. The freedom of these 
 products from the blackleg organism is greatly in their favor as this 
 precludes the setting up of a virulent form of the disease through 
 their use. A considerable number of laboratory experiments have 
 clearly demonstrated that these products have distinct immunizing 
 value and these have been backed up by many field trials on a con- 
 siderable number of animals. In Japan the culture filtrate is the 
 only means of immunization at present in general use. The product 
 is tested in the laboratory on guinea pigs before it is ready for distri- 
 bution. Further standardization would, however, be desirable, which 
 would include toxicity tests. 
 
 Rather extravagant claims have been made for these products with 
 the desire to get them into general use against the competition of the 
 older and cheaper powdered muscle vaccine. Chief of these may be 
 mentioned the claim that they will produce permanent immunity or 
 at least immunity until the animal has passed the susceptible age with 
 one injection. At the present time there does not seem to be sufficient 
 evidence to justify such claims. Where these results have appeared 
 to be obtained under field trials unusually favorable conditions may 
 have prevailed. The degree of infection of ranges undoubtedly differs 
 in this disease as it does in anthrax. Where animals have passed 
 through the susceptible age period with one treatment they may have 
 been on very slightly infected ranges. Also, animals treated as year- 
 lings or older might pass through safely with one treatment, whereas 
 animals treated at six months of age under the same conditions might 
 break with the disease as short two-year-olds. Further evidence is 
 necessary before any conclusive statements can be made on this sub- 
 ject. This station is very anxious to obtain such evidence and to 
 make it available for stockmen. Any data along this line which are 
 obtained, therefore, from the use of either blackleg serum or culture 
 or tissue filtrate would be gratefully received and tabulated by this 
 experiment station if sent to the Division of Veterinary Science, 
 University of California, Berkeley. 
 
WHEN TO VACCINATE 
 
 On known infected ranges cattle owners should not wait for the 
 disease to appear before vaccinating susceptible animals. As there 
 are two principal seasons for the disease there should be two vacci- 
 nation periods, one in the spring and the other in the fall. The vac- 
 cination should be done fifteen to thirty days before the time when 
 cases have usually appeared in the past. As a general practice, the 
 period between February 15 and March 1 is a good time for the spring 
 vaccination and from August 15 to September 1 for the fall vaccina- 
 tion. This may, of course, have to be varied depending on local 
 conditions. Young animals being turned out on unknown ranges 
 or pastures should be vaccinated as a precautionary measure. It is 
 not necessary to vaccinate young animals on dairies or in small valley 
 communities where no cases of the disease have been reported. One 
 should not brand, castrate, or ear-mark and vaccinate at the same 
 time. With our present knowledge it is safer to vaccinate all animals 
 of susceptible age at each vaccination period. It may save the life of 
 an animal at times, when the muscle vaccine is used, to give them 
 the double vaccination. In this case No. 1 vaccine should be given ten 
 days to two weeks before No. 2 vaccine. 
 
 SUMMARY 
 
 Blackleg is quite generally prevalent in California. Stock owners 
 should suspect the disease in all cases where animals from six months 
 to two years of age die suddenly with a local swelling. 
 
 The old single or double muscle vaccine for blackleg in either 
 powdered, pellet, or string form, has given such satisfactory results 
 for so many years that its continued use is justified. 
 
 Blackleg serum has immediate immunizing and curative properties. 
 Its use is to be recommended in affected animals and in the hope of 
 immediately stopping losses in already infected herds where animals 
 are dying of the disease. Its immunizing effects in healthy animals 
 are not permanent and it must be followed by vaccine or filtrate within 
 a week to ten days. 
 
 Both culture filtrate and tissue filtrate have well-marked im- 
 munizing effects on cattle against blackleg. Their freedom from the 
 causative organism is greatly in their favor. 
 
 The routine use of either of these preparations by cattlemen is 
 justified under our present knowledge. In time, they may largely 
 replace the old method of vaccination. 
 
 Culture filtrate of sufficient potency is of equal value and has 
 advantages in manufacture and cost over tissue filtrate. 
 
 There are not sufficient data available to substantiate the general 
 statement that one treatment with either of the filtrate vaccines will 
 confer life immunity.