655

RECENT WORK ON UNDULANT FEVER AND BRUCELLA ABORTUS.

B y ALAN THOMPSON.

D URING the past decade considerable attention has been directed to the occurrence of an irregular fever in man due to infection with Br. abortus. Such infections are

n o w generally known as undulant fever, a term which was formerly regarded as synonymous with Malta or Mediterranean fever. The whole question is so intimately associated with the pioneer work on this latter condition that I will commence with a brief survey of its historical aspect.

During the Crimean War the attention of medical men was drawn to the occurrence of an irregular feSrile condition amongst the troops which differed in many respects from enteric fever. This disease became known as Mediterranean, Malta or gastric remittent fever, and by the middle of the 19th century was a recognised clinical entity. Nearly 30 years later Bruce discovered an organism in the spleen of a fatal case, and subsequently he was able to obtain the same organism by culture from the splenic blood during the course of the disease. This organism was estab- lished by him as the cause of Mediterranean fever, and was named the Micrococcus Melitensis. Further study showed it ~o be a minute pleomorphic bacillus, and it was subsequently called Bacillus Melitensis.

Investigation of the epidemiology of the disease revealed the fact that infection was almost invariably incurred by drinking the raw milk of goats; these animals are widely distributed in Mediterranean countries and harbour the organism in the udder while showing no symptoms of disease. An order to the troops in 1906 prohibiting the use of raw goats' milk was followed by a dramatic fall in the incidence of Melitensis fever. This condition, which from the peculiarity of its course became known as undulant fever, was generally regarded as being confined to the countries bordering the Mediterranean Sea. Isolated cases seen in England and elsewhere were traced to infections incurred abroad.

In 1897, Bang of Copenhagen isolated an organism from cases of bovine contagious abortion and definitely incriminated it as the cause of that disease. For over twenty years this organism was considered to be non-pathogenic for man. In 1918 Alice Evans described the close resemblance between Bacillus melitensis and Bang's bacillus, and shortly afterwards reports came from Rhodesia of cases of clinical undulant fever in a district where no goats were raised. Contagious abortion was rife in the country, and it was suggested that human infection with Bang's bacillus was possibly responsible for the fever. Conclusive evidence of the pathogenicity of this organism for man was furnished the following year by the report of a case of undulant fever in America from which Bang's bacillus was isolated.

656 IRISH JOURNAL OF MEDICAL SCIENCE

Further cases of this infection were rapidly forthcoming, and the condition soon became widely recognised and as eagerly sought. Up to the present day the chief incidence of the disease has been in America, Denmark and Rhodesia, in all of which countries bovine contagious abortion is rife.

To avoid confusion of terminology, it is convenient to summarise here the various names which have been applied to these organisms and the diseases they produce. Following the work of Alice Evans on the resemblances between the causative organisms of Melitensis fever and bovine contagious abortion, the generic name Brucella was adopted for the group; Bacillus Melitensis was now called Brucella Melitensis, and Bang's bacillus became Brucella abortus; of this latter organism two varieties have been described, the bovine and the porcine. Irregular fever due to Br. Melitensis was originally termed Mediterranean or Malta fever. This slur on their country's name was resented by the Maltese, and the term undulant fever was eventually introduced to designate the con- dition. Following the recognition of human infections with Br. abortus, undulant fever was used to denote all Brucella infections showing the characteristic pyrexia.

Those who investigated cases of suspected undulant fever soon found that the agglutinating power of the patient's serum was a very variable factor, and considerable difficulty was ex- perienced in assessing the significance of the titres observed. This was further complicated by the discovery that many apparently healthy persons carried agglutinins for Br. abortus in their blood. Investigations were made to determine the frequency with which such agglutinins occurred, and to this end some thousands of sera were set up in the usual dilutions against suspensions of Br. abortus. The results obtained sh,owed .considerable variation. This is no doubt due in part to variations in the technique of the agglutination tests as performed in different laboratories, but it also represents a genuine difference in the average range of serum titres in these areas. This table shows some of the results obtMned in the British Isles, America and Denmark�9 In most laboratories the opportunity was taken of testing the sera submitted for the routine Wassermann reaction, but sera from other sources have also been examined.

S E R A O N A P P A R E N T L Y H E A L T H Y P E R S O N S T E S T E D A G A I N S T B R . A B O R T U S S U S P E N S I O N S .

S o u r c e of sera . x / i o - - I / 5 O i / 5 o C o n d i t i o n of m i l k

IOWa . . . . S y r a c u s e . . . . N. Y . C i t y . . . . E h i c a g o . . . . D e n m a r k I r e l a n d : (J.W.B.i" I r e l a n d : ( J . W . B . )

[ r e l a n d : (A .H.T . ) M a n c h e s t e r . .

z e r o

�9 . 7 7 % �9 . 9I% . . 9 7 . 6 % �9 . 9 6 % � 9 9 ~ % � 9 8 o %

� 9 80 %

. . 4 2 % �9 �9 9 0 %

22% 7.5%

2 . 4 % 4 %

i o % x o % 1 6 %

(I ~ I"50) 4 7 % x o %

1% x.5%

4%

z o %

c h i e f l y r a w

p a s t e u r i s e d

'i c h i e f l y r a w

J,

RECENT WORK ON UNDULANT FEVER 657

The condition of the major part of milk supply is recorded in the right-hand column of the table. I t will be noticed that those districts of America showing the lower ranges of positive sera are supplied mainly with pasteurised milk. In Iowa and Syracuse, where the milk is consumed chiefly in the raw state, the number of positive sera is greater and the maximum titres are higher. The figures recorded for Ireland are consistently in advance of those from other sources. The first series of figures was recorded by Dr. Bigger in 1930. The second series is based on sera examined by me during 1931. The discrepancy between the two series is probably due entirely to differences in technique; the tests in 1930 were performed with heated sera at a minimum dilution of 1/20, while in the 1931 series unheated sera were used and the minimum dilution was 1/10. Though the same strain was used as antigen in both series, slight variations were introduced in preparing the later suspensions. Finally, the personal factor can- not be excluded in recording the results.

When it was generally recognised that many individuals showed agglutinins for Br. abortus in their blood, attempts were made to explain this occurrence without assuming an infection. I t was suggested that the agglutinins commonly present in the milk of infected cows were absorbed through the intestinal wall, and so appeared in the blood of those who had drunk the milk, though no infection had occurred. Experiments carried out in America with raw and pasteurised milks from infected cows de- monstrated conclusively that such absorption of ingested agglutinins did mot oc, cur. I t was further suggested that the low titre agglutinations observed with many sera were due to the presence of agglutinins not specific for Br. abortus, and could not therefore be regarded as evidence of infection or invasion by that organism. There is little to be said in support of such an assumption, and considerable evidence can be brought against it. For example, the sera of nearly 700 sanatorium patients in Massachusetts were tested for the presence of abortus agglutinins, but were in all cases negative. The milk supply to these sanatoria was carefully pasteurised, and there can be no doubt that this pre- caution was responsible for the uniformly negative results observed.

I t is now generally considered that agglutinins in the sera of apparently healthy persons have been developed in response to the presence of Br. abortus in the tissues. I t is assumed that, in its mildest form~ this invasion is localised, probably in the lymph nodes of the intestine or in the mesenteric glands, where the presence of the organisms stimulates the formation of anti- bodies. This is presumably the condition obtaining in the vast majority of those whose sera agglutinate the organism.

Attention must now be directed to the paths by which Br. abortus can invade the human body. The obvious reservoir for the organism is the infected tissues of livestock in districts where contagious abortion is widespread. In this disease the pathological changes are confined to the pregnant uterus, the animal being

658 IRISH JOURNAL OF MEDICAL SCIENCE

otherwise apparently in good health. Though the uterine con- tents are infected, abortion does not necessarily result, and the disease may pass unnoticed. Furthermore, a proportion of in- fected cows abort once only, though they may continue to harbour the infect ion for some months or years after. The organism does not remain localised to the uterus, but almost invariably gains access to the udder, without, however, causing a mastitis. The milk from such cows is likely to contain BruceUa, the excretion of the organism being usually intermittent.

Milk so contaminated is the commonest vehicle by which Br. abortus gains access to the human body, but other dairy products, such as cream and cheese, may also carry the infection. The organism is destroyed by efficient pasteurisation, and milk is dangerous only when consumed in the raw state. Brucella organisms frequently survive exposure to a temperature somewhat below the degree required for pasteurisation, and hence some " pasteurised " milks may still be contaminated if the heating has been inadequate.

I t has been shown that invasion can also follow inoculation through the skin, and cases of infection by this route have been observed amongst those who handle contaminated material, such as the milk or the uterine contents of infected animals, or even their carcasses after slaughter. Many of the more serious in- fections in America were incurred in this manner. Cases of undulant fever following experimental skin inoculation have also been recorded.

It is obviously of importance to estimate the extent to which the milk supply of a country is contaminated with Br. abortus. There are few figures showing the degree to which this occurs in the British Isles, but it is believed to be considerable. An examination of the Manchester milk supply showed Brucella organisms present in 5.7 per cent. of single milks and 8.8 per cent. of mixed milks, out of a total of 488 samples. Norris, in this country, found 18 per cent. of 100 samples of mixed milk to contain Br. abortus. No other figures are available for Irish milk.

The results obtained by different observers in America show wide variation. Brucella organisms have been found in as many as 66 per cent. of some market milks, but this is unusually high. Examination of samples representing 95 per cent. of the raw milk supply of New York City showed that 20 per cent. were con- taminated with Brucella. Average results show that about 10 to 20 per cent. of market milks are contaminated, while lower figures are given by samples from certified herds. Since the cow excretes the organism intermittently in her milk, considerable discrepancy in these results is inevitable.

Pasteurisation of milk is not employed to any great extent in Ireland. Certainly it is of no importance outside the cities of Dublin and Belfast. As a liberal estimate we may assume that 25 per cent. of the Dublin milk is pasteurised more or less efficiently, the remaining 75 per cent. being consumed raw. A

RECENT WORK ON UNDULANT FEVER 659

considerable proportion of the population is therefore ingesting living Brucella organisms. This exposure to infection is not, however, followed by the appearance of undulant fever. Hence we must assume either that the Irish people are unduly resistant to Brucella infection, or that the strains which contaminate our milk supply are of such low virulence for humans that infection does not occur. The latter alternative seems the more reasonable. I t is supported by the fact that the more virulent strains of Brucella, notably those which infect hogs, have never been isolated by the Veterinary Department of the Irish Free State.

We have seen that localised invasion by Brucella abortus occurs in apparently healthy persons, following the ingestion of organisms of low virulence. Such invasion gives rise to agglutinins in the serum,~but produces no symptoms of disease..Infection, us distinct from invasion, can be considered to have occurred only when the symptoms characteristic of undulant fever are definitely mani- fested. Terms such as " sub-clinical " or " latent " undulant fever are misleading and should not be employed. They have been applied to certain cases presenting no symptoms, where the accidental recognition of a high agglutinating titre suggested the advisability of blood culture, which in at least two instances was positive. The invasion of the blood stream in such cases is probably of transient duration, and is certainly distinct from the infection which is associated with undulant pyrexia.

True infection with Br. abortus results in undulant fever. I t is obvious, however, that prolonged irregular fever due to other causes may occur in persons having agglutinins for Brucella already present in their blood, and there is a lamentable readiness on the part of some clinicians to presume on this coincidence, and label such cases " lmdulant fever " without more ado. In view of this difficulty the criteria for the diagnosis of undulant fever must of necessity be strict. No case should be labelled " undulant f e v e r " in the absence of definite bacteriological confirmation, but what constitutes " definite bacteriological confirmation " is often difficult to decide. The one unequivocal method by which the diagnosis may be established is, of course, the isolation of the causative organism from the blood stream or the urine. This desirable degree of certainty is, however, not often achieved, for several reasons. Firstly, Brucella organisms are difficult to isolate from the body, many strains requiring an atmosphere of increased carbon dioxide tension for primary culture. Even under optimum eonditions growth is slow, and culture is therefore of limited value a s a diagnostic procedure. I t should never be neglected, however, and in sllggestive cases repeated efforts should be made to isolate the organism from the blood stream during the periods of fever. Various media are recommended by different authorities, but glucose broth or glycerine broth is probably as satisfactory as any of the more elaborate media, at least for blood culture. Cultures should be made in duplicate and incubated at body temperature, one in air, the other in a 10 per cent. carbon dioxide atmosphere,

660 IRISH JOURNAL OF MEDICAL SCIENCE

A method sometimes employed is that of intraperitoneal inoculation of a guinea pig with the suspected blood. Culture of the urine is occasionally successful even when blood cultures remain sterile. An attempt should also be made to isolate the organism from the supposed source of infection, whenever possible. When this is milk or other dairy product the method of choice is that of guinea pig inoculation.

When cultures are persistently negative a presumptive diagnosis is often justified on other grounds. In such a case repeated examinations of the serum should be made for the presence of specific agglutinins. We have seen that such agglutinins may be very misleading, and their interpretation is often a matter of difficulty. Their presence cannot of itself establish the diagnosis, since they may represent a past infection or merely a localised invasion, and no one titre can be regarded as definite evidence of active infection. Indeed the titres in established cases of undulant fever vary over a very wide range, being in some cases zero and in others as high as 1/32,000. A marked increase in t i tre on repeating the test is of more significance, but it must be regarded as presumptive evidence only, as the titre occasionally shows a rapid rise in apparently healthy persons.

The frequency with which cultures are sterile and the wide variations in the serum titre in suspected cases allow considerable diagnostic licence to the clinician, and it is not surprising to find that many cases of " undulant fever " have been so labelled on rather inadequate grounds. No doubt this is due in part to the enthusiasm with which any new complaint is greeted, and it may be expected to cure itself in time.

A brief consideration of the incidence of undulant fever as reported in various countries is instructive. In America, a Public Health Report for 1930 records 442 cases in the Northern States. 1,305 cases were reported in 1929. In one group of 200 eases, investigated by a team of workers, positive cultures were obtained from 48 patients, or 24 per cent. In Rhodesia 35 cases were reported in 1925, and the annual number is steadily increasing. Between three and four hundred cases are diagnosed in Denmark every year : Kristensen, in a series of 500 cases, obtained positive cultures from 34 patients.

I t is obvious from a consideration of these figures that positive cultures are infrequent, and the majority of these eases have therefore been diagnosed on presumptive grounds. While this is legitimate in countries where the disease is of relatively common occurrence stricter criteria should be enforced in countries such as the British Isles where undulant fever is apparently a rarity. In the most recent repor t for Great Britain 39 cases are reported as authentic, but the number of positive cultures is not stated.

A consideration of some of these cases shows that they have been very inadequately established, the diagnosis often depending solely on irregular fever with one agglutination test and a very dubious history of exposure to infection. It should be emphasised

RECENT WORK ON UNDULANT F E V E R 661

that the criteria for the diagnosis of undulant fever must be more strict in these countries than in America or Denmark where many established cases occur every year. We should be loath to diagnose undulant fever in Ireland in the absence of a positive culture from the blood or urine.

Whether undulant fever has ever occurred in Ireland is a moot point. Since May, 1930, every serum sent to Trinity College laboratory for the Widal reaction has been tested against a suspen- sion of Br. abortus, in the expectation of recognising a case. During this period sera were received from 64 patients. Nine of these were apparently from cases of enteric fever : fifty sera failed to agglutinate any of the suspensions used; the remaining five scra agglutinated the Br. suspension. Of these five, two caused slight agglutination at titres of 1/25 and 1/125 respectively, and were not investigated further. One serum agglutinated strongly at a titre of 1/125 : a blood culture was sterile, and no additional evidence was forthcoming to suggest Brucella infection. The serum of the fourth case agglutinated to a titre of 1/1,000. Although blood cultures were sterile on two occasions when incubated in 10 per cent. carbon dioxide atmosphere, the clinical features of the case and a history of exposure to infection seemed to justify the diagnosis of undulant fever. This case, reported by Dr. Abrahamson and Dr. Dockeray in 1930, appears to have incurred the infection in England, and cannot therefore be regarded as an Irish case, at least in the epidemiological sense.

The fifth serum was from a man who had made a prolonged stay abroad and who developed an irregular fever on his return to Ireland. His serum did not agglutinate the enteric organisms but caused definite agglutination of Br. abortus at a titre of 1/250. Four days later the titre against this organism was 1/1,000, with ground-glass turbidity at 1/2,500. A blood culture taken at this time was sterile, and a suggestion of further investi- gation was resented by the patient.

Fur ther efforts were made to establish possible cases by blood cultures in 10 per cent. carbon dioxide atmosphere from cases of obscure pyrexia not showing specific agglutinins. These cultures were uniformly negative. Several cases were investigated whose sera on routine examination were found to agglutinate Br. abortus at a titre of 1/125 or more. Cultures and repeated agglutination tests were performed, but no conclusive evidence of Brucella infection was obtained, and in none of these patients was a typica! undulant pyrexia observed. One of the cases, however, deserves special mention, as it indicates a possible pitfall for the unwary clinician. The man in question returned from Canada two years ago. His serum was submitted for the Wassermann reaction en three occasions within the past nine months. The titres against Brucella abortus on these three occasions were respectively 1/25, 1/50 and 1/1,000. The man was apparently in good health at the time of the third test, and his Wassermann reaction had been reduced to negative. A blood culture taken at the same time

662 IRISH JOURNAL OF MEDICAL SCIENCE

remained sterile. There was nothing in his past history to suggest an attack of undulant fever. Presumably the rapid increase in his serum titre was due to a local invasion which stimulated the formation of antibodies.

Some attempt must be made to explain the absence of undulant fever in Ireland, where bovine contagious abortion is second in importance only to bovine tuberculosis. Presumably it is due to the low virulence of the Irish strains of Brucella. At least two varieties of Br. abortus are described, the bovine and the porcine. The former variety is commonly isolated from milk and infected cattle, is of low virulence for guinea-pigs and apparently also for man. The porcine type, as isolated from cases of hog abortion and occasionally also from cattle, shows slight cultural and meta- bolic differences from the bovine variety, and produces more severe lesions in guinea-pigs, often with multiple abscess formation. The more serious cases of human infection appear to be due to the porcine strain. It is questionable whether there are justifiable grounds for describing two varieties of Br. abortus, and it would appear more sensible to assume different degrees of virulence in one variety, only the more virulent strains being capable of infecting hogs and man.

All the Brucella strains isolated in the Irish Free State by the Veterinary Research Laboratory are of low virulence for guinea pigs, the so-called porcine variety never having been isolated. In view of this and of the persistently negative results obtained in the investigation of cases, one is forced to conclude that undulant fever is as yet unknown in Ireland.

MEDICAL HOBBIES AND COLLECTIONS.

It is proposed to hold, at some time in the near future, an exhibition of the Hobbies and Collections of Medical P:'actitioners, provided there is a satisfactory response to this appeal. We wvuld be ~bliged if medical men who have hobbies or collections of any kind would kindly send their names and particulars t~ any of the undermentioned : - -

T. G. Wilson, M.B., F.R.C.S.I., 26 Upper Fitzwilli, am Street. C. L. MacDon~gh, M.D., 37 Fitzwilliam Place. F. S. Bourke, L.R.C.P. & S.I., 25 Lower Lceson Street.