- Email: [email protected]
Swine Erysipelas
162
EDITORIAL ARTICLES.
ED I TO RI AL
ART I CLES.
SWINE ERYSIPELAS.
AT a later part of this number there will be found the clinical history of a series of cases of swine erysipelas which were traced by Mr Hedley, of the Veterinary Department of the Irish Privy Council. The history of these cases was traced as part of an investigation conducted by the Departmental Committee which was appointed by the Board of Agriculture in 1895 to inquire into the etiology, pathology, and morbid anatomy of the diseases classed as swine fever. The report is of great interest and value, inasmuch as it furnishes precise information regarding a subject that has hitherto been surrounded by a good deal of obscurity. Since 1891, when a number of cases of the disease were put on record in this Journal,1 it has been known that pigs in this country are not exempt from the disease which is termed Sekweille Rothlauf in Germany and rouget du pore in France. Prior to the date mentioned this disease had not been recognised as a common affection in Great Britain or Ireland, and indeed it was not known that it ever occurred among our pigs. The disease had long been known as a formidable plague of the porcine species in France, Germany, and other Continental States; and as soon as its existence here was proved, the possibility that it was of common occurrence, but overlooked owing to its being confounded with swine fever, naturally suggested itself. As a matter of fact it appeared highly probable that if it existed here at all it could not be a rare disease, since on the Continent it was regarded everywhere as a highly contagious and infectious malady. In the cases which were first detected in England the lesions took the form of endocarditis with luxuriant vegetations on the cardiac valves·, and this is probably the explanation of the fact that even at the present time many veterinary surgeons in this country believe that cardiac lesions are constant in swine erysipelas, and do not recognise the disease by any other mark. That, however, is an erroneous view of the disease, if reliance may be placed on the account of it which is given by all foreign authors. According to these accounts swine erysipelas is in most cases an acute septic~mic disease of a highly fatal character. The duration of the illness usually extends to only a few days, and the mortality is often as high as 50 per cent. In these rapidly fatal cases the only lesions usually encountered at the post-mortem examination are an erysipelatous inflammation of the skin, swelling of the spleen, and gastro-enteritis without ulcerative or diphtheritic changes in the mucous membrane. 1
Vol. IV., p. 316.
EDITORIAL ARTICLES.
Animals that do not succumb within a few days generally make a prompt and apparently complete recovery, but in occasional cases the pig remains unthrifty, develops symptoms of heart disease, and dies suddenly after some weeks or months. These accounts of the disease naturally suggested the thought that the cases of swine erysipelas with heart lesions occasionally detected in this country did not by any means represent the real extent to which the disease prevailed among British pigs, but that pigs so affected were merely a ft;w of the survivors from outbreaks in which most of the animals had died from the acute form of the disease. This possibility was suggested in the article to which reference has already been made, although, as was then pointed out, the history of the cases recorded did not indicate that the disease was of a highly infectious character. When swine fever was taken in hand by the Board of Agriculture the post-mortem examination conducted by the officers of the Board soon showed that at least the chronic form of swine erysipelas was by no means rare, for many cases with cardiac lesions were discovered among pigs that had died from swine fever or been killed as suspected of that disease. The operations of the Board, however, did not suffice to clear up the point of gr~atest interest and importance, since no attempt was made to trace the previous history of these chronic cases in order to find out whether other animals of the same lot had suffered from the acute rapidly fatal form of the disease, or whether there was any evidence that the disease was spreading by contagion. It was to fill up this blank in our knowledge of the disease as it occurs in this country that the investigations recorded in Mr Hedley's report were undertaken. A study of the information given in that report makes it evident that the accounts of swine erysipelas which are given in foreign text-books do not exactly apply to the disease as it occurs with us. If swine erysipelas is a disease that is readily spread by direct or indirect infection-and such is the view of it generally current abroad - one would expect to find it attacking the whole or a considerable number of the pigs kept on the premises where it has obtained a footing; and when the past history of each case of the disease is obtainable, one would also expect to be able' to trace a connection with an antecedent case. This, however, is not the state of affairs disclosed in Mr Hedley's series of cases. Take for example Case R. In this case the owner of the two pigs attacked with the disease had not previously kept animals of that species, and these two pigs had been two months on his premises before the disease showed itself. The two pigs were seized with the acute form of the illness nine weeks after purchase, and one of them promptly died, while the other subsequently developed the symptoms indicative of heart affection, and was found to have vegetations on the cardiac valves when killed six weeks after the onset of the disease.
EDITORIAL ARTICLES.
In this case the disease must have been contracted on the premises where the pigs were attacked, for nine weeks is an impossible period of incubation in swine erysipelas. Besides, four other pigs that had been in contact with the two subsequently attacked remained healthy. Again, take Case S. In this case only two pigs out of a total of twenty on the premises appear to have been attacked. The two affected pigs had been bred on the premises, and three of the same lot remained healthy. There had been no new purchases for nearly two months, and the pigs last bought had never shown any symptom of illness. Case U. is equally opposed to the idea of infection from a previously diseased pig. The owner had only two pigs on his premises, and they had been in his po~sessio:1 for over eight months before the disease showed itself. During that time the two pigs had not been in contact with any others. One died from the disease, and the other escaped. The whole series of cases makes it impossible to believe that the disease is markedly contagious, like swine fever for example. The im. pression which the history of the cases leaves on one's mind is that swine erysipelas and swine fever belong to two perfectly distinct categories of disease. The latter is a strictly contagious and infectious malady, caused by a parasite which, in natural circumstanJ:es, probably has the body of the pig as its exclusive field of propagation-in other words, every case of swine fever has for its starting-point the ingestion (or admission into the body by some other channel) of bacteria that were bred in the body of an antecedent case of the disease. Swine erysipelas, on the other hand, appears to be usually a sporadic disease, caused by a germ which is only a facultative parasite-that is to say, which frequently or generally propagates outside the body of the pig, and is only occasionally the cause of disease. The distinction is of great practical importance. If there were good reasons for supposing that swine erysipelas is a disease mainly spread by contagion, it would have to be combated by just the same measures as are considered necessary for the suppression of swine fever. If on, the other hand, the disease is 'caused by a germ that has a wide distribution in nature, like, for example, the pyogenic organisms or the tetanus bacillus, it would be transparently foolish to endeavour to suppress it by the stamping-out measures now being enforced against swine fever. It does not follow, however, that because swine erysipelas is usually sporadic, and therefore not to be combated by such summary and expensive measures as wholesale slaughter of diseased and suspected, it can be altogether ignored from a prophylactic point of view. As far as can be at present seen there is a certain analogy between swine er-ysipelas and anthrax as regards the origin of outbreaks. In both
EDITORIAL ARTICLES.
cases contagion and infection, in the ordinary sense of these words. have little to do with the origin of cases. The germs of anthrax at the present moment exist in the soil in many places, and perhaps e\'en propagate there, and it is the accidental ingestion of such germs that determines most outbreaks. Very probably cases of swine erysipelas have a similar etiology. But although we do not slaughter animals because they have been in contact with one affected with anthrax, we recognise the necessity of taking steps to prevent further ground contamination, and prudence directs that we should do the same whenever a pig dies from swine erysipelas. A pig dead of that disease contains countless numbers of the specific bacilli, and these are probably also voided in its excretions. These considerations, therefore. suggest such precautionary measures as disinfection and safe disposal of the carcase. Fortunately, however, there appears to be a great difference between anthrax and swine erysipelas in regard to the virulence of their respective microbes, and the facility with which animals may be infected by them. We can with great certainty infect animals belonging to susceptible species by feeding or inoculating them with material containing anthrax germs, but the experiments carried out for the Departmental Committee indicate that swine erysipelas is not very readily transmitted, at least to British pigs, by either of these methods. In these experiments attempts were made to infect pigs of various ages with swine erysipelas, but the attempts were uniformly unsuccessful, whether the material employed was artificial culture. cardiac vegetations from natural cases in the pig, or blood from smaller animals artificially infected, and whether the material was injected under the skin or mixed with food. These results are not such as one would expect to get in dealing with the germs of a virulent contagious or infectious malady, but they are in conformity with clinical experience of the'disease in this country. It might be said that such completely negative results indicate that the disease is never transmitted by the methods employed in the experiments; but such a conclusion is inC!-dmissible. It is impossible to doubt that the disease is caused by the bacillus first identified by Loeffler and Schutz, and it is in the highe?t degree probable that infection takes place by way of ingestion when the disease is naturally contracted; but, either owing to slight virulence on the part of the germ, or a natural insusceptibility on the part of pigs in this country, the disease does not assume epizootic proportions, and rarely affects more than one or two animals, even when a considerable number have been associated with those attacked and presumably exposed to the same risk of infection.
EDITORIAL ARTICLES.
ED I TO RI AL
ART I CLES.
SWINE ERYSIPELAS.
AT a later part of this number there will be found the clinical history of a series of cases of swine erysipelas which were traced by Mr Hedley, of the Veterinary Department of the Irish Privy Council. The history of these cases was traced as part of an investigation conducted by the Departmental Committee which was appointed by the Board of Agriculture in 1895 to inquire into the etiology, pathology, and morbid anatomy of the diseases classed as swine fever. The report is of great interest and value, inasmuch as it furnishes precise information regarding a subject that has hitherto been surrounded by a good deal of obscurity. Since 1891, when a number of cases of the disease were put on record in this Journal,1 it has been known that pigs in this country are not exempt from the disease which is termed Sekweille Rothlauf in Germany and rouget du pore in France. Prior to the date mentioned this disease had not been recognised as a common affection in Great Britain or Ireland, and indeed it was not known that it ever occurred among our pigs. The disease had long been known as a formidable plague of the porcine species in France, Germany, and other Continental States; and as soon as its existence here was proved, the possibility that it was of common occurrence, but overlooked owing to its being confounded with swine fever, naturally suggested itself. As a matter of fact it appeared highly probable that if it existed here at all it could not be a rare disease, since on the Continent it was regarded everywhere as a highly contagious and infectious malady. In the cases which were first detected in England the lesions took the form of endocarditis with luxuriant vegetations on the cardiac valves·, and this is probably the explanation of the fact that even at the present time many veterinary surgeons in this country believe that cardiac lesions are constant in swine erysipelas, and do not recognise the disease by any other mark. That, however, is an erroneous view of the disease, if reliance may be placed on the account of it which is given by all foreign authors. According to these accounts swine erysipelas is in most cases an acute septic~mic disease of a highly fatal character. The duration of the illness usually extends to only a few days, and the mortality is often as high as 50 per cent. In these rapidly fatal cases the only lesions usually encountered at the post-mortem examination are an erysipelatous inflammation of the skin, swelling of the spleen, and gastro-enteritis without ulcerative or diphtheritic changes in the mucous membrane. 1
Vol. IV., p. 316.
EDITORIAL ARTICLES.
Animals that do not succumb within a few days generally make a prompt and apparently complete recovery, but in occasional cases the pig remains unthrifty, develops symptoms of heart disease, and dies suddenly after some weeks or months. These accounts of the disease naturally suggested the thought that the cases of swine erysipelas with heart lesions occasionally detected in this country did not by any means represent the real extent to which the disease prevailed among British pigs, but that pigs so affected were merely a ft;w of the survivors from outbreaks in which most of the animals had died from the acute form of the disease. This possibility was suggested in the article to which reference has already been made, although, as was then pointed out, the history of the cases recorded did not indicate that the disease was of a highly infectious character. When swine fever was taken in hand by the Board of Agriculture the post-mortem examination conducted by the officers of the Board soon showed that at least the chronic form of swine erysipelas was by no means rare, for many cases with cardiac lesions were discovered among pigs that had died from swine fever or been killed as suspected of that disease. The operations of the Board, however, did not suffice to clear up the point of gr~atest interest and importance, since no attempt was made to trace the previous history of these chronic cases in order to find out whether other animals of the same lot had suffered from the acute rapidly fatal form of the disease, or whether there was any evidence that the disease was spreading by contagion. It was to fill up this blank in our knowledge of the disease as it occurs in this country that the investigations recorded in Mr Hedley's report were undertaken. A study of the information given in that report makes it evident that the accounts of swine erysipelas which are given in foreign text-books do not exactly apply to the disease as it occurs with us. If swine erysipelas is a disease that is readily spread by direct or indirect infection-and such is the view of it generally current abroad - one would expect to find it attacking the whole or a considerable number of the pigs kept on the premises where it has obtained a footing; and when the past history of each case of the disease is obtainable, one would also expect to be able' to trace a connection with an antecedent case. This, however, is not the state of affairs disclosed in Mr Hedley's series of cases. Take for example Case R. In this case the owner of the two pigs attacked with the disease had not previously kept animals of that species, and these two pigs had been two months on his premises before the disease showed itself. The two pigs were seized with the acute form of the illness nine weeks after purchase, and one of them promptly died, while the other subsequently developed the symptoms indicative of heart affection, and was found to have vegetations on the cardiac valves when killed six weeks after the onset of the disease.
EDITORIAL ARTICLES.
In this case the disease must have been contracted on the premises where the pigs were attacked, for nine weeks is an impossible period of incubation in swine erysipelas. Besides, four other pigs that had been in contact with the two subsequently attacked remained healthy. Again, take Case S. In this case only two pigs out of a total of twenty on the premises appear to have been attacked. The two affected pigs had been bred on the premises, and three of the same lot remained healthy. There had been no new purchases for nearly two months, and the pigs last bought had never shown any symptom of illness. Case U. is equally opposed to the idea of infection from a previously diseased pig. The owner had only two pigs on his premises, and they had been in his po~sessio:1 for over eight months before the disease showed itself. During that time the two pigs had not been in contact with any others. One died from the disease, and the other escaped. The whole series of cases makes it impossible to believe that the disease is markedly contagious, like swine fever for example. The im. pression which the history of the cases leaves on one's mind is that swine erysipelas and swine fever belong to two perfectly distinct categories of disease. The latter is a strictly contagious and infectious malady, caused by a parasite which, in natural circumstanJ:es, probably has the body of the pig as its exclusive field of propagation-in other words, every case of swine fever has for its starting-point the ingestion (or admission into the body by some other channel) of bacteria that were bred in the body of an antecedent case of the disease. Swine erysipelas, on the other hand, appears to be usually a sporadic disease, caused by a germ which is only a facultative parasite-that is to say, which frequently or generally propagates outside the body of the pig, and is only occasionally the cause of disease. The distinction is of great practical importance. If there were good reasons for supposing that swine erysipelas is a disease mainly spread by contagion, it would have to be combated by just the same measures as are considered necessary for the suppression of swine fever. If on, the other hand, the disease is 'caused by a germ that has a wide distribution in nature, like, for example, the pyogenic organisms or the tetanus bacillus, it would be transparently foolish to endeavour to suppress it by the stamping-out measures now being enforced against swine fever. It does not follow, however, that because swine erysipelas is usually sporadic, and therefore not to be combated by such summary and expensive measures as wholesale slaughter of diseased and suspected, it can be altogether ignored from a prophylactic point of view. As far as can be at present seen there is a certain analogy between swine er-ysipelas and anthrax as regards the origin of outbreaks. In both
EDITORIAL ARTICLES.
cases contagion and infection, in the ordinary sense of these words. have little to do with the origin of cases. The germs of anthrax at the present moment exist in the soil in many places, and perhaps e\'en propagate there, and it is the accidental ingestion of such germs that determines most outbreaks. Very probably cases of swine erysipelas have a similar etiology. But although we do not slaughter animals because they have been in contact with one affected with anthrax, we recognise the necessity of taking steps to prevent further ground contamination, and prudence directs that we should do the same whenever a pig dies from swine erysipelas. A pig dead of that disease contains countless numbers of the specific bacilli, and these are probably also voided in its excretions. These considerations, therefore. suggest such precautionary measures as disinfection and safe disposal of the carcase. Fortunately, however, there appears to be a great difference between anthrax and swine erysipelas in regard to the virulence of their respective microbes, and the facility with which animals may be infected by them. We can with great certainty infect animals belonging to susceptible species by feeding or inoculating them with material containing anthrax germs, but the experiments carried out for the Departmental Committee indicate that swine erysipelas is not very readily transmitted, at least to British pigs, by either of these methods. In these experiments attempts were made to infect pigs of various ages with swine erysipelas, but the attempts were uniformly unsuccessful, whether the material employed was artificial culture. cardiac vegetations from natural cases in the pig, or blood from smaller animals artificially infected, and whether the material was injected under the skin or mixed with food. These results are not such as one would expect to get in dealing with the germs of a virulent contagious or infectious malady, but they are in conformity with clinical experience of the'disease in this country. It might be said that such completely negative results indicate that the disease is never transmitted by the methods employed in the experiments; but such a conclusion is inC!-dmissible. It is impossible to doubt that the disease is caused by the bacillus first identified by Loeffler and Schutz, and it is in the highe?t degree probable that infection takes place by way of ingestion when the disease is naturally contracted; but, either owing to slight virulence on the part of the germ, or a natural insusceptibility on the part of pigs in this country, the disease does not assume epizootic proportions, and rarely affects more than one or two animals, even when a considerable number have been associated with those attacked and presumably exposed to the same risk of infection.