CHAPTER XVIII
Salmonellal Infections
Dwight M. Kuhns, M. D.1
HISTORICAL NOTE
The early history of salmonella food poisoning isnot directly related to the military; however, itis briefly presented here to orient the reader as to the status of theproblem in past years. In 1888,an epidemic of food poisoning occurred in Frankenhausen, Germany, thatwas traced tocontaminated meat.2 From the fecesof a fatal case of the disease,Gärtner isolated an organismwhich he called Bacillus enteritidis, because of the enteritisproduced. The organism wasrenamed Salmonella, to honor Dr. Daniel E. Salmon inrecognition of his research on hogcholera. Dr. Salmon was the first to describe a member of this group.In 1885, Dr. Salmon andDr. Theobald Smith isolated Bacillus choleraesuis from casesof hog cholera (Salmonellacholeraesuis in modern terminology). 3Although itwas excellent work, Dorset and deSchweinitz, in 1903, demonstrated that hog cholera is actually causedby a filterable virus, thebacteria being secondary invaders and not always present.
The rod-shaped motile bacterium (implicated at Frankenhausen) was subsequently discovered in other cases of food poisoning, although many other types of food poisoning were not found to be caused by Salmonella organisms nor were all the newly discovered related species first found in food-poisoning cases. Staphylococci were implicated in cases of food poisoning several years before the discovery of the genus Salmonella. Furthermore, many of the Salmonella species were not first discovered in connection with food poisoning. Thus, Salmonella aertrycke, today known as Salmonella typhimurium, was first isolated from mice by Lofller in 1890, while Sal. choleraesuis, as has already been noted, was first found in swine. Still others, such as Salmonella oranienburg, were first isolated from the feces of healthy humans.
Numerous cases of food poisoning are mentioned inthe older literature such as those describedby van Ermengem in which sausages were suspected of having causedillness .4ABelgianinspector of meat, reputed to have been an expert in his field,examined the meat and declaredthe sausages to be fit for human consumption. The inspector developedsevere diarrhea 10 hours
1 Acknowledgmentis hereby made to Martin Roth, M. A., for his faithful assistance. inthe research for historicalmaterial for this section and in the final preparation of the manuscript.
2 Gartner, A.: Ueber die Fleischvergiftung in Frankenhausen a. k. and den Erreger derselben. Cor.-Bl. d. allg. ärztl. Ver. v. Thüringen, Weimar, 1888, xvii, 573-600.
3 Salmon, D. E.: Investigations in Swine Plague. U. S. Bur. Anim. Indus. 2d Ann. Report, 1885, pp. 184-246.
4 Dack, G. M.: Food Poisoning. Chicago: The University of Chicago Press, 1949.
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later, on 26 October 1895. This was followed by fever, high pulse, and abdominal distress. Six days later, he died. Necropsy revealed viscera laden with Salmonella enteritidis. This account is mentioned here not to cite the fact that some inspectors may lack competence but rather to point out that food, highly contaminated with pathogenic organisms, can appear quite satisfactory in gross appearance as well as in smell and taste.
Many organisms similar to Sal. enteritidis were discovered even before the First World War. However, up to and including the period of World War 1, there is no substantial literature on either Salmonella or food poisoning. Scattered reports are available on what were then designated as the paratyphoid fevers. This group consisted of a variety of gastroenteric conditions similar, though not identical, to typhoid fever. It is generally believed that the paratyphoid fevers were by no means a major problem to the United States Army during World War I but what might be more accurately described as a nuisance. During 1916 and 1917, there were sporadic and epidemic occurrences of the disease in United States Army personnel along the Texas-Mexico border and in Mexico itself. Soon after, it was learned that outbreaks were occurring in France among British and French troops. In July 1917, the United States Army incorporated paratyphoid A and paratyphoid B organisms in its regular typhoid vaccine.
Table 71 shows the incidence and deaths for paratyphoid fever, most of which resulted from contaminated food or water, among officers and enlisted personnel from 1 April 1917 to 31 December 1919, inclusive. It is necessary to view the statistics with caution. First, a wide variety of conditions in the World War I period were consigned to the ill-defined categories paratyphoid A and paratyphoid B. They were milder than classical typhoid fever, with diarrhea a more characteristic feature. Secondly, an individual who died in an Army hospital was listed as a paratyphoid (or typhoid) death if that was the condition for which he had been admitted. It was the practice of the Surgeon General's Office, at the time, to list for statistical purposes the disease for which a patient was initially admitted to the hospital as the cause of death if the patient died.5 Thus, while many paratyphoid deaths were, in fact, ascribed to paratyphoid fever, others were not. Further, the concept of food poisoning had not yet been clearly defined, many cases being considered examples of ptomaine poisoning, a meaningless classification. 6
During the interval between World War I and World War II, little of note occurred in the history of salmonellal food poisoning, at least insofar as the Army was concerned. One development of great significance, however, was the classification schemata that were gradually devised through biochemical
5 (1) The MedicalDepartment of the United States Army in the World War. Communicable andOther Diseases. Washington: U. S. Government Printing Office, 1928,vol. IX. p. 15. (2) The Medical Department of the UnitedStates Army in the World War. Statistics. Washington: GovernmentPrinting Office, 1925, vol. XV, pt. 2, p. 12. (3)Annual Reports of The Surgeon General, U. S. Army, to the Secretary ofWar. Washington: Government PrintingOffice, 1921. pp. 20-21; 1934,pp. 5-6; 1936, p. 7.
6 (1) Morgan, 11. R.:The Salmonella. In Bacterialand Mycotic Infections of 6an.2d ed.Philadelphia: J. B.Lippincott Co., 1952, ch. 17, pp. 420-436. (2) Savage, W. G.: BacterialFood Poisoning. In A System of Bacteriologyin Relation to Medicine. London: II. M. Stationery Office, 1929. vol.III, ch. 12, pp. 407-413.
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study of the organisms, not only asrelating to the cultural characteristics but also their antigeniccomposition. Progress in this area was largely due to the excellentwork of Kauffmann (1937)and White (1926) who first studied the Salmonella species in greatdetail and showed how theycould be classified on the basis of their antigenic structure.
TYPINGAND CLASSIFICATION
At the beginningof World War II,there was at Copenhagen, Denmark, an internationalSalmonella typing center of which Dr. Fritz Kauffmann was director. Inthe United States, therewere two large Salmonellacenters, one at Beth Israel Hospital, NewYork, N. Y., under thesupervision of Dr. E. Seligmann and one at the Kentucky AgriculturalExperiment Station,Lexington, Ky., supervised by Dr. P. R. Edwards. Some of the work atLexington was, as a resultof the war, sponsored and paid for by the Army Medical Service GraduateSchool, then knownas the Medical Department Professional Service School, Army MedicalCenter, Washington, D.C.
The main role of the Army Medical Service Graduate School was that of preparing and supplying typing serums for Army laboratories, Army service command medical laboratories, medical general laboratories, other general hospital laboratories, and station hospital laboratories. A great part of the Army's knowledge of the species of Salmonella causing food poisoning is due to the fine work of such laboratories as the 15th Medical General Laboratory, which was located at Naples, Italy, from 21 November 1943 to 25 October 1945. Salmonella typing and identification had become a new field, with new skills for the bacteriologist and technician to learn and master.7 Military and
7(1) Edwards, P. R., and Bruner, D. W.:Serological Identification of Salmonella Cultures. Kentucky Agr. ExpSta.Cir. 54: 3-35,1942. (2) Kauffmann, Fritz: Enterobacteriaceae: CollectedStudies on Salmonella, Arizona, Ballerup-Bethesda, Escherichia,Alkalescens-Dispar, Klebsiella, Shigella,Providence and Proteus. Copenhagen: EjnarMunksgaard, 1951.
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civilian bacteriologistsdistinguished themselves in that field. Never before in the history ofmedicine and bacteriology had so much concentrated attention beencentered upon the species ofone bacterial genus. It should be noted that during this period ofintensive research, two schoolsof thought on Salmonela classification arose. Some believedthat the division of this genusinto species and strains had been carried to hair-splitting extremes,where minute, differenceswere deemed sufficient reason for such subdivision. Others maintainedthat the differences,regardless of how minute they might be, had taxonomic and epidemiologicsignificance, if theyremained constant.
The following is a list of those Salmonella species discovered during the World War II period and is included here for reference purposes: 8
Species: | Source | Species: | Source |
| Sal. kaposvar | Human | Sal. heves | Human |
| Sal. kaapstad | Do | Sal. florida | Do |
| Sal. hartford | Rat . | Sal. madelia | Human, chick. |
| Sal. manhattan | Human, turkey, chick, reptile, hog | Sal. sundsvall | Human |
Sal. szentes | Do. | ||
| Sal. narashino | Human | Sal. schwarzengrund | Do. |
| Sal. sendai | Do. | Sal. concord | Human, turkey, chick |
| Sal. durban | Do. | Sal. orientalis | Human |
| Sal. vejle | Do. | Sal. gorgia | Human |
Sal. meleagridis | Human, reptile | Sal. claibornei | Do. |
Sal. illinois | Human, hog, turkey, partridge | Sal. loma linda | Do. |
Sal. mississippi | Human, hog | Sal. New York | Do. |
Sal. oregon | Human, turkey, chick, hog, reptile | Sal. butantan | Human, (child) |
Sal. pretoria | Hog | Sal. grumpensis | Guinea pig |
| Sal. havana | Human | Sal. adelaide | Do. |
| Sal. urbana | Human, hog, chick | Sal. inverness | Do. |
| Sal. salinatis | Human, rat | Sal. papauna | Do. |
| Sal. tennessee | Human, turkey, fowl, egg | Sal. cardiff | Do. |
| Sal. bonariensis | Human, hog | Sal. virginia | Do. |
Sal. amherstiana | Chicken | Sal. pensacola | Do. |
| Sal. javiana | Human | Sal. miami | Human, chimpanzee |
| Sal. weltevreden | Do. | Sal. canastel | Human |
| Sal. simsbury | Human, turkey | Sal. italiana | Do |
| Sal. kohn | Human | Sal. napoli | Do. |
| Sal. infantalis | Human, (child) | Sal. orion | Do. |
Sal. pueros | Human | Sal. veneziana | Do. |
Sal. taksony | Do. | Sal. pamona | Human, fowl |
Sal. solt | Do. | Sal. champaign | Chicken |
8 Breed, Robert S., Murray, E. G. D., and Hitchens, A. Parker: Bergey's Manual of Determinative Bacteriology. 6th ed. Baltimore. The Williams & Wilkins Co., 1948.
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The names of the species indicate, in some instances, where they, were first isolated.Chickens became an important source, and rodents and hogs were often found to be infected. Spray-dried egg powder was the source of a number of Salmonella strains. They, were found in 10 percent of over 6,000 samples of spray-dried egg powder. The commonest types were Sal. oranienbury, Sal. montevidio, Sal. meleagridis, Sal. bareilly, and Sal. anatum, but several others were encountered. One of the outstanding epidemiologic contributions of this experiment of infected egg powder was that it revealed the cause of a cluster of outbreaks around holiday seasons. Although dogs are not mentioned as an original source in this group, they were found to have a significant carrier role.
Table 72 is a brief summary of the outstanding salmonellal food-poisoning outbreaks during World War II. Most of the recorded outbreaks are those of the European and the Mediterranean Theaters of Operations. Salmonellal infections in these two theaters were the subject of special field study. The data which appear in table 72 represent only those cases of food poisoning which were reported on individual medical records and will grossly understate the total experience with this disease group. Several facts become apparent from a study of this table. Very often it was possible to trace the outbreak to the food responsible for it. Sometimes this was not possible as the foods had been discarded before being suspected of contamination. Certain types of foods seem to be responsible for salmonellal food-poisoning outbreaks more frequently than do others, in particular, desserts (especially puddings) and meats (especially poultry). Of the various types of poultry, turkey seems often to be responsible for outbreaks. This may be significant since turkey is not frequently served. In most outbreaks, the cause was traced to a single Salmonella species; however, two or three species were found to be simultaneously involved in some cases. 9 Most of the cases ran the typical course for food poisoning with nausea, diarrhea, vomiting, and cramps as the salient symptoms, and these lasted only a few days.
An analysis ofnational statistics made by Dr. Milton Feig, a district health officerin Wisconsin,revealed that meat and meat products were involved in 27.8 percent ofsalmonellal food-poisoning cases; poultry, 18.5 percent; bakeryproducts, 14.8 percent; milk and milk products,14.8 percent; vegetables, 13 percent; and other and unknown foods, 29.6percent. These add to approximately 119 percent because more than onefood item was responsible in some of theoutbreaks.10
9 (1) Bruner, D. W., and Joyce, B. J.:Salmonella Types Encountered by the 15th Medical General Laboratory.Am.J. Hyg. 45:19-24, January 1947. (2) Anderson, D. T., Johnson, L. M.,Wetherbee, D. G., and Kuhns, D. M.: Isolationof Three Salmonella Species of Group C in One Case of Salmonellosis. U.S. Armed Forces M. J. 1: 1511-1515,December 1950. (3) Edwards, P. R., and Bruner, D. W.: The Occurrence ofMultiple Types of Paratyphoid Bacilli inInfections of Fowls; With Special Reference to Two New SalmonellaSpecies. J. Infect. Dis. 66: 218-221, May-June1940. (4) Randall, C. C., and Marks, L. M.: A Salmonella OutbreakInvolving Three Types of Genus. Mil. Surgeon97:144-146, August 1945.
10 Feig, M.: Diarrhea, Dysentery, FoodPoisoning, and Gastroenteritis; A Study of 926 Outbreaks and 49,879CasesReported to the United States Public Health Service (1945-1947). Am. J.Pub. Health 40: 1372-1394, November1950.
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TABLE72.–Chronologicallist ofsalmonellal outbreaks in World War II
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TABLE 72.–Chronological list of salmonellal outbreaks in World War II -continued
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CONTROL OF SALMONELLOSIS
During World War11, the approach taken to the problem of salmonellosis was largelypreventive. Most of the methods employed were not new, as they had beenused, though not withthe same thoroughness, in previous wars.11Troops were thoroughly indoctrinated in thefundamentals of hygiene, with emphasis on personal cleanliness as wellas cleanliness of themessgear that a soldier carries in the field.
At those installations where dishes were used, the dishes were air dried following washing and sterilization; no dish towels were used. Frequent dish culturing was carried out to determine the thoroughness of washing and sterilization.12 Dish culturing was introduced in the Fourth Service Command early in the war and was found invaluable in maintaining good mess sanitation for a million and a half troops in training.
High standards were maintained in the processing of foods. Milk samples were sent to laboratories to determine how well pasteurization had been carried out. For meat products, cattle and poultry were inspected before being sent to slaughter as well as after slaughter, for determining fitness for consumption. Since the epidemiology of salmonellal food poisoning in animals and birds is essentially the same as for humans, the possibility of chlorinating water to be used for animals and poultry was considered. However, such measures are largely out of the control of the Army. Foods were carefully refrigerated to prevent bacterial growth during storage and in the preparation of meats; no meats were to be used for consumption if undercooked.
The need for control of fly breeding and prevention of flies from contacting excreta (for example, by screening latrines) and contacting food supplies was on the whole appreciated. Rodents, stray dogs, and stray cats were also recognized as a potential danger and were not permitted to come in contact with food supplies and human excreta.
One of the great achievements of military medicine in World War II was the accommodation of all Army installations throughout the world with laboratory facilities. Specimens of milk, foods, and feces were forwarded to the appropriate laboratories for bacteriologic examination. The fecal specimens were often those of permanent foodhandlers, and when a carrier was discovered his unit commander was to be notified and instrusted that carriers were not permitted to be permanent handlers of food.
In addition to these procedures, TAB (typhoid, paratyphoid A, and paratyphoid B) vaccine continued to be routinely administered to all Army personnel.
11 Dunham, George C.: Military PreventiveMedicine. 3d ed. Harrisburg: Military Service. Publishing Co., 1940.
12 War Department Field Manual 21-10,MilitarySanitation. Washington: U. S. Government Printing Office, July1945.
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RESEARCH
In the UnitedStates, pioneer work in the development of agglutination serums for Salmonellaidentification was done by Edwards, of the University of Kentucky,Lexington, Ky. This work,as already noted, was adopted by the Army Medical Service GraduateSchool where theproduction of typing serums was expanded for Army-wide usage (p.419).The purpose of thiswas to carry out applied research and investigation whenever anoutbreak of salmonellosisoccurred; thus, a considerable amount of information was obtainedconcerning the species ofSalmonella involved in an outbreak. Many epidemiologicinvestigations were carried out, andvery often it was possible to trace the origins of an epidemic. If anoutbreak was traceable to asample of powdered dehydrated eggs, it was necessary to trace that eggpowder to determinewhere and flow it had become contaminated originally: whether it leadbecome contaminatedfrom the poultry or the foodhandlers, whether flies had contaminatedit, or whether it was thefault of improperly cleaned mess equipment. Many outbreaks were neversuccessfully traced,and often the causative Salmonella was not found.
EPIDEMIOLOGIC ASPECTS OF SALMONELLOSIS
Under wartime conditions, the diarrheal diseases areespecially important, and many factorscontribute to their occurrence.13 For example, early inWorld War II, as the Armed Forcesincreased in size and large numbers of men from all parts of the Nationwere required to livetogether in centers of basic military training, the various proposedmethods of prevention andcontrol were due for the acid test. The men lived together in maneuverareas and in closequarters, often at hastily constructed camps and bivouacs in which itis impossible to achieve thehighest sanitary standards.Active immunity, developed from exposure tothe commonSalmonella organisms, had not as yet been established, and a fertilefield was afforded foroutbreaks of salmonellosis. There was epidemiologic significance in thefact that the Armyconsisted of men who had been quickly brought together from all walksof life, from all parts ofthe country, and from all levels of sanitary habits and education.
Among other factors of epidemiologic importance is the fact that animals and birds as well as human beings furnish an ever-present reservoir of the Salmonella organisms. Among the possible carriers of Salmonellae are rats, mice, rooks, turkeys, pigs, ducks, and chickens. Rats, flies, mosquitoes, and even ticks have been shown to be capable of acting as vectors.14 The matter is further complicated by the fact that carriers play a vital role in the spread of
13 Rubenstein, A. D., Feemster, R. F., andSmith, H. M.: Salmonellosis as a Public Health Problem in Wartime. Am.J. Pub. Health 34: 841-853, August 1944.
14 (1) Ostrolenk, AL; and Welch, H.: The HouseFly as a Vector of Food Poisoning Organisms in Food ProducingEstablishments. Am. J. Pub. Health 32: 487-494, May 1942. (2) Smith, H.W., and Buxton, A.: An Outbreak ofSalmonella schwartzengrund Infection in Poultry. J. Path. &Baet. 63: 459-463, July 1951. (3) Weleh, H., Ostrolenk,and Bartram, M. T.: Role of Rats in the Spread of Food PoisoningBacteria of the Salmonella Group.Am. J. Pub.Health 31: 332-340, April 1941.
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salmonellosis. Some of these carriers are of the convalescent type since they continue to excrete the bacteria during the time they are recovering from their illness.Others are asymptomatic and therefore represent a far greater danger than those exhibiting symptoms, since the former may be the origin of many an outbreak of undetermined origin before being apprehended. Some Salmonella carriers are intermittent since periods of time during which Salmonella organisms are excreted alternate with periods of time in which they are apparently absent. Most individuals continue to be carriers for relatively short periods of time, while a few retain the organisms for longer periods. In civilian life, the laws and facilities in some areas are inadequate for dealing with the carrier problem, while in the Army close followups are maintained on known carriers.
ATypical Outbreak
Greifinger andSilberstein describe a completely investigated outbreak of Salmonellafoodinfection in military personnel.15 Theplaces ofoccurrence perhaps for reasons of militarysecurity are not mentioned.The outbreak was first recognized on 25 July1943 when 28individuals, all males, between 21 and 50 years of age werehospitalized mainly for thesymptoms of nausea and abdominal cramps. These symptoms subsided in 24to 48 hours. Bowelmovements numbered 8 to 15 per day and were loose, watery, and brownishgreen in color.Fourteen of the patients had occult blood in their stools, ten had pus,and three showed pus andmucus. Temperatures ranged from 1010 to 1040 F. Fried fish, tartar sauce, and rice puddinghadbeen served at the evening mess.The fish was suspected, since it wasnoticed that the ice,refrigerating it, had melted.More individuals developed the usualsymptoms until a total of 115persons were incapacitated; 93 percent had diarrhea, 72.2 percent hadcramps, and only 21.7percent complained of nausea.
An interesting followup study was conducted to determine how long the individuals would continue to harbor the organisms. This is one of the greatest contributions to historical literature on salmonellosis. The results are summarized in table 73.
From the figuresin table 73, it is apparent that as long as 3 monthsafter the initial infection onemay remain a carrier of Salmonella. Of the 115 individuals whowere infected, 5.2 percentcontinued to harbor Sal. oranienburg into the 13th week. Thepatients were retained in thehospital until three consecutive stools were negative. The differentialmedia employed weredesoxycholate citrate, eosine methylene blue, and S.-S. (Shigella-Salmonellathiosulfatecitrate-bile) agar. Of these differential media, S.-S.agar was found to yield the largest incidence ofpositives. If the 5.2 percent infected individuals were carriers ratherthan reinfected individuals,it would indicate that individuals who have had salmonellosis should bepotential carriers forthat period of time.
15Greifinger, W., and Silberstein, J. K.:Salmonella Food Infection in Military Personnel; An Outbreak Caused by S.oranienburg, S. typhimurium, S. anatum. J. Lab. & Clin. Med.29: 1042-1053, October 1944.
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TABLE 73.-Persistenceof salmonellal infectionas determined bypositivefecal cultures in 115patients
RELATIVEINCIDENCE OF SALMONELLA SPECIES
Several Salmonellaspecieswere cited as the one most frequently occurring. Thus, according toSeligmann, in 1946, Salmonella schottmülleri was the mostcommon Salmonella in the UnitedStates. Dack, in 1949, considered Sal. typhimurium as the Salmonellaspecies found in moreoutbreaks of food poisoning than any other type. Edwardsand Bruner 16 studied 225culturesisolated from the feces of patients who had gastroenteritis.In order offrequency, the first ninespecies were: Sal. typhimurium, Sal. newport, Sal. paratyphi B. var.java, Sal. panama, Sal.oranienbury, Sal. san diego, Sal. bareilly, Sal. montevideo, and Sal.enteritidis. Undoubtedly,the original source of some of these species was eggs. During World WarII, dried eggs wereshipped to United States troops in all theaters of operations.According to Dack, of 7,584 amplesthat were sent from the United States, Canada, and Argentina, 754 (9.9percent) were found tocontain Salmonella. In all, 33 species were found.
A thorough study on the relative occurrence of Salmonella species was made by Brunet in the Mediterranean theater during World War II.17 It is
16 Edwards. P. R., and Bruner, D. W.: The Occurrence and Distribution ofSalmonella Types inthe United States. J. Infect. Dis. 72: 58-67, January-February1943.
17 Bruner, D. W.: Salmonella Infections of World War II,[Officialrecord.]
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probably the most comprehensive analysis as to species and group occurrence on Salmonella conducted in any theater of operations. The study not only covers the incidence among United States Army troops in the Mediterranean theater but also includes valuable data on incidence among civilians, prisoners of war, French Army personnel, and carriers. The group C Salmonellae apparently were the most frequent cause of salmonellal food poisoning. Salmonella sp. (Type Oranienburg) was the most common Salmonella species causing gastroenteritis in United States Army personnel in the Mediterranean. Also, there were more carriers of Salmonella sp. (Type Oranienburg) in the United States Army than any other Salmonella species. Salmonella sp. (Type Montevideo) remained a close second. The increased number of carriers in each species were in proportion to the number of cases of gastroenteritis reported and cultured.
The occurrence of salmonellosis in the Pacific area was recorded by the 19th Medical General Laboratory, the laboratory research center for New Guinea and the Philippines.The species of Salmonella that were isolated on New Guinea in order of the number of bacteriologic isolations is shown in table 74. On New Guinea, as in other areas of the Pacific, the Salmonellae were not as common a cause of food poisoning as the Shigellae.
It is to be notedthat while Sal. enteritidis was the number one disease inoccurrence, Salmonellatyphosa was responsible for the greatest number of outbreaks. Thedistinction made here is ofepidemiologic significance particularly in food-poisoning outbreaks.Eventually, it is presumedthat bacteriologists will no longer refer to infections with Salmonellacontracted through food asfood poisoning but simply as Salmonella infections.
The species of Salmonella that were isolated in the Philippines, in descending number of isolations, is shown in table 75. The outstanding causes of salmonellal food poisoning in the Philippines were, according to these data, Sal. enteritidis and Sal. paratyphi.
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LABORATORYADVANCES IN DIAGNOSIS OF SALMONELLOSIS
The laboratory diagnosis of salmonellal food poisoning is basically not different from what it has always been. It depends upon the recovery of the organism, usually from the stools, based on a principle dating back to Koch's postulates. Yet, considering the incidence of salmonellal food poisoning, it is a fact that in many cases the organism is never demonstrated. In the field, it was often impossible to transport biological specimens under proper conditions. Another and perhaps more important point is the fact that Salmonellae will often be present only during the brief period of acute symptoms. According to Verder and Sutton,18 there is an inverse relationship between the number of ingested organisms and the incubation period. The smaller the number of organisms taken in, the more prolonged will be the period of incubation. Thus, there is a strong lilkelihood that a stool specimen taken even 1 day following the subsidence of symptoms will be void of Salmonellae. As for the contaminated food, it is often. discarded before an examination can be conducted.
There are several differential media in use, including Shigella-Salmonella medium, tetrathionate broth base, and selinite-F enrichment medium. Occasionally, one encounters a Salmonella species that will not grow on S.-S. agar.For this reason it is a prudent policy to use a less inhibiting medium in addition. Most often in salmonella. outbreaks, only one species is found. Occasionally, two or even three species are present simultaneously, and it would be a moot question to inquire as to which species is producing which symptoms.19 A procedure of great value in diagnosing salmonella. food
18 Verder, E., and Sutton, C.: Is SalmonellaFood Poisoning Caused by Living Bacilli or by Thermostabile ToxicProduct?. J. Infect. Dis. 53: 262-271, September-October 1933.
19 See footnote 9 (2), p. 421,
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poisoning was the anal-swab technique introduced by Hardy. Its mainadvantage lay in the factthat it was not necessary to wait until stool specimens were collectedfrom those who were to betested. Anal swabs could be taken from a number of individuals in avery short time and culturesmade on a large scale.
EVALUATIONOF THE ARMY'S EXPERIENCE
Carriers.-In evaluating the Army's experience withsalmonellosis, several conclusions can beelicited. First, it was never among the most serious of themedicomilitary problems. Thehistory of salmonellal food poisoning shows that the preventive aspectshave always been givenmore attention than the therapeutic aspects. In typical cases, thesymptoms are striking and soondisappear completely leaving the victim little cause for alarm. As aresult, many of the patientsrecover, only to become carriers for a greater or shorter period oftime. Although the Army'streatment of the carrier problem compares favorably with that of thebest civilian healthdepartments, it is also true that the Army especially during the timeof war places major stress onreturning to duty as many men as possible as soon as they appearcapable of resuming work.However, in cases of salmonellal infection, it is not safe to return aman to duty in the messmerely because of the subsidence of acute symptoms. In connection withthe carrier problem, itshould be noted that surprisingly few outbreaks during World War IIwere found traceable to acarrier origin.
Foodhandlers.-The most important military consideration in the carrier problem is that of the career foodhandler as developed during World War II..20 A foodhandler may without his or anyone else's knowledge dispense Salmonellae systematically to large numbers of troops throughout his career. Of lesser significance is the temporary foodhandler, especially in basic training units where it is accepted procedure to utilize kitchen police in the handling and distribution of food.
Vectors and reservoirs of salmonellal infection.-The role ofvectors and reservoirs insalmonellal food poisoning has already been mentioned in theliterature.Flies are of primeimportance.The problem is more than one of using insecticides; alsorequired is the rigorousapplication of the basic well-known principles of hygiene and theexecution of such measures asthe screening of messhalls and latrines whenever possible. Even then,there exists the problem ofanimal and bird reservoirs, perhaps more challenging than the flies andsurely a far moredifficult problem under field conditions. It must be stressed, however,that even though hygienicprinciples were sometimes abandoned during World War II fieldconditions, the sanitary levelachieved in the field during the war was higher than that of anyprevious war.
The military problem.-Salmonellosis is of special interest to the Army for more than the theoretic reasons that have been discussed. Although it
_
20 Stone, W. S.: Food Handlers in the Army andTheir Relationship to Salmonella Food Poisoning.Am. J. Pub.Health 33: 706-708, June 1943.
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rarely caused serious infection, itcan with dramatic suddenness temporarily incapacitate largenumbers of troops. In time of war, this can lead to catastrophicresults. During World War II, asin World War I, most of the Army's outbreaks were sporadic, and realepidemics were theexception rather than the rule. There are two explanations for this.The first explanation is thatover a period of half a century the Army had attained and on the wholemaintained a high standard of sanitation. The second explanation is thepreventive role of the Army's TABvaccine which is routinely administered to all military personnel. Thevalidity of the first point isgenerally accepted. There is, however, divided opinion as to the valueof the vaccine. Whilesome consider it effective in preventing salmonellal infection, manybelieve it has little value.The truth may be between the two extremes, and while TAB vaccine mightnot be effective inpreventing salmonellosis it may have some effect on mitigating thesymptoms, therebymodifying the course of the disease.
