FOOD-BORNE PATHOGENIC BACTERIA (_Continued_)
PARATYPHOID INFECTION
The most characteristic examples of "food poisoning," popularly
speaking, are those in which the symptoms appear shortly after eating
and in which gastro-intestinal disturbances predominate. In the typical
group-outbreaks of this sort all grades of severity are manifested, but
as a rule recovery takes place. The great majority of such cases that
have been investigated by modern bacteriological methods show the
presence of bacilli belonging to the so-called paratyphoid group (_B.
paratyphosus_ or _B. enteritidis_). Especially is it true of meat
poisoning epidemics that paratyphoid bacilli are found in causal
relation with them. Huebener[62] enumerates forty-two meat poisoning
outbreaks in Germany in which bacilli of this group were shown to be
implicated, and Savage[63] gives a list of twenty-seven similar
outbreaks in Great Britain. In the United States relatively few
outbreaks of this character have been placed on record, but it cannot be
assumed that this is due to their rarity, since no adequate
investigation of food poisoning cases is generally carried out in our
American communities.
_Typical paratyphoid outbreaks._--Kaensche[64] describes an outbreak at
Breslau involving over eighty persons in which chopped beef was
apparently the bearer of infection. The animal from which the meat came
had been ill with severe diarrhea and high fever and was slaughtered as
an emergency measure (_notgeschlachtet_). On examination a pathological
condition of the liver and other organs was noted by a veterinarian who
declared the meat unfit for use and ordered it destroyed. It was,
however, stolen, carried secretly to Breslau, and portions of it were
distributed to different sausage-makers, who sold it for the most part
as hamburger steak (_Hackfleisch_). The meat itself presented nothing
abnormal in color, odor, or consistency. Nevertheless, illness followed
in some cases after the use of very small portions. With some of those
affected the symptoms were very severe, but there were no deaths.
Bacilli of the _Bacillus enteritidis_ type were isolated from the meat.
A large and unusually severe outbreak reported by McWeeney[65] occurred
in November, 1908, among the inmates of an industrial school for girls
at Limerick, Ireland. There were 73 cases with 9 deaths out of the total
number of 197 pupils. The brunt of the attack fell on the first or
Senior class comprising 67 girls between the ages of thirteen and
seventeen. Out of 55 girls belonging to this class who partook of beef
stew for dinner 53 sickened, and 8 of these died. One of the two who
were not affected ate the gravy and potatoes but not the beef. Some of
the implicated beef was also eaten as cold meat by girls in some of the
other classes, and also caused illness. Part of the meat had been eaten
previously without producing any ill effects. "The escape of those who
partook of portions of the same carcass on October 27 and 29 [five days
earlier] may be accounted for either by unequal distribution of the
virus, or by thorough cooking which destroyed it. Some of the infective
material must, however, have escaped the roasting of the 29th, and,
multiplying rapidly, have rendered the whole piece intensely toxic and
infective during the five days that elapsed before the fatal Tuesday
when it was finally consumed." The animal from which the fore quarter of
the beef was taken had been privately slaughtered by a local butcher. No
reliable information could be obtained about the condition of the calf
at, or slightly prior to, slaughter. The meat, however, was sold at so
low a price that it was evidently not regarded as of prime quality. In
this outbreak the agglutination reactions of the blood of the patients
and the characteristics of the bacilli isolated showed the infection to
be due to a typical strain of _Bacillus enteritidis_.
An epidemic of food poisoning occurred in July, 1915, at and near
Westerly, Rhode Island.[66] The outbreak was characterized by the usual
symptoms of acute gastro-enteritis, and followed the eating of pie which
was obtained at a restaurant in Westerly. All the circumstances of the
outbreak showed that a particular batch of pies was responsible. About
sixty persons were made seriously ill and four died. There was no
unusual taste or odor to the pies to excite suspicion. The symptoms
followed the eating of various kinds of pie: custard, squash, lemon,
chocolate, apple, etc., that had been made with the same pie-crust
mixture. _Bacillus paratyphosus_ B was isolated from samples of pie
that were examined. No definite clue was obtained as to the exact source
of infection of the pie mixture. It is possible that the pie became
infected in the restaurant through the agency of a paratyphoid-carrier,
but since there had been no change in the personnel of the restaurant
for several months, this explanation is largely conjectural. Possibly
some ingredient of animal origin was primarily infected.
_General characters of paratyphoid infection._--The symptoms of
paratyphoid food infection are varied. As a rule the first signs of
trouble appear within six to twelve hours after eating, but sometimes
they may come on within half an hour, or they may not appear until after
twenty-four to forty-eight hours. Gastro-intestinal irritation is
practically always present, and may take the form of a mild
"indigestion" or slight diarrhea or may be of great severity accompanied
with agonizing abdominal pain. Fever is usual, but is generally not very
high. Recovery may occur quickly, so that within two or three days the
patient regains his normal state, or it may be very slow, so that the
effects of the attack linger for weeks or months.
Investigators have noted the occurrence of at least two clinical types
of paratyphoid infection, the commoner gastro-intestinal type just
described and a second type resembling typhoid fever very closely, and
occasionally not to be distinguished from it except by careful bacterial
examination. It is not yet clear how these two clinical varieties are
related to the amount and nature of the infecting food material. No
difference in the type of paratyphoid bacillus has been observed to be
associated with the difference in clinical manifestation. Possibly the
amount of toxin present in the food eaten as well as the number of
bacilli may exercise some influence. The individual idiosyncrasy of the
patient doubtless plays a part.
While there is still some uncertainty about particular features of
paratyphoid infection, a few significant facts have been clearly
established: (1) Certain articles of diet are much more commonly
associated than others with this type of food poisoning. The majority of
recorded outbreaks are connected with the use of meat, milk, fish, and
other protein foods. Vegetables and cereals have been less commonly
implicated, fruits rarely. (2) In many, though not all, of the cases of
paratyphoid meat poisoning it has been demonstrated that the meat
concerned has been derived from an animal slaughtered while ailing
(_notgeschlachtet_, to use the expressive German term). There seems
reason to believe that in such an animal, "killed to save its life," the
specific paratyphoid germ is present as an infection before death. Milk
also has caused paratyphoid poisoning and in certain of these cases has
been found to be derived from a cow suffering from enteritis or some
other disorder. (3) There is evidence that originally wholesome food may
become infected with paratyphoid bacilli during the process of
preparation or serving in precisely the same way that it may become
infected with typhoid bacilli; the handling of the food by a
paratyphoid-carrier is commonly responsible for this. In a few instances
the disease is passed on from case to case, but this mode of infection
seems exceedingly rare and is not nearly so frequent as "contact"
infection in typhoid. (4) The majority of paratyphoid outbreaks are
associated with the use of uncooked or partly cooked food. A selective
action is often manifested, those persons who have eaten the
incriminated food substance raw or imperfectly cooked being most
seriously affected, while those who have partaken of the same food after
cooking remain exempt.
[Illustration: FIG. 6.--_Bacillus enteritidis_, Gaertner; pure culture;
Van Ermengem preparation. (Kolle and Wassermann.)]
The discovery of the connection of paratyphoid bacilli with meat
poisoning dates from the investigation by Gaertner,[67] in 1888, of a
meat poisoning outbreak in Frankenhausen, a small town in Germany. This
epidemic was traced to the use of meat from a cow that was slaughtered
because she was ill with a severe enteritis. Fifty-eight persons were
affected in varying grades of severity; the attack resulted fatally in
one young workman who ate about eight hundred grams of raw meat. Gaertner
isolated from the spleen of the fatal case and also from the flesh and
intestines of the cow a bacillus to which he gave the name _B.
enteritidis_. Inoculation experiments showed it to be pathogenic for a
number of animal species. Bacilli with similar characters have since
been isolated in a number of other meat poisoning epidemics in Germany,
Belgium, France, and England. One well-studied instance of food
poisoning due to the paratyphoid bacillus has been reported in the
United States.[68]
The bacteria of the paratyphoid group are closely related to the true
typhoid bacillus, but differ from the latter organism in being able to
ferment glucose with gas production. They are more highly pathogenic for
the lower animals than is the typhoid bacillus, but apparently somewhat
less pathogenic for man. Most types of paratyphoid bacilli found in food
poisoning produce more or less rapidly a considerable amount of alkali,
and, if they are inoculated into milk containing a few drops of litmus,
the milk after a time becomes a deep blue color. Several distinct
varieties of paratyphoid bacilli have been discovered. The main
differences shown by these varieties are agglutinative differences. That
is, the blood serum of an animal that has been inoculated with a
particular culture or strain will agglutinate that strain and also other
strains isolated from certain other meat poisoning epidemics, but will
not agglutinate certain culturally similar paratyphoid bacteria found in
connection with yet other outbreaks. Except in this single matter of
agglutination reaction, no constant distinction between these varieties
has been demonstrated. The clinical features of the infections produced
in man and in the higher animals by the different varieties seem to be
very similar if not identical.
The bacillus discovered by Gaertner (_loc. cit._) and known as _B.
enteritidis_ or Gaertner's bacillus is commonly taken as the type of one
of the agglutinative varieties. Bacilli with all the characters of
Gaertner's bacillus have been found in meat poisoning epidemics in
various places in Belgium and Germany. Mayer[69] has compiled a list of
forty-eight food poisoning outbreaks occurring between 1888 and 1911 and
attributed to _B. enteritidis_ Gaertner. These outbreaks comprised
approximately two thousand cases and twenty deaths. In twenty-three of
the forty-eight outbreaks the meat was derived from animals known to be
ill at the time, or shortly before, they were slaughtered. Sausage and
chopped meat of undetermined origin were responsible for eleven of the
remaining twenty-five outbreaks. Two of the _B. enteritidis_ outbreaks
were attributed to _Vanille Pudding_; one, to potato salad.
In other food poisoning outbreaks a bacillus is found which is
culturally similar to the Gaertner bacillus, but refuses to agglutinate
with the Gaertner bacillus serum. Its cultural and agglutination
reactions are almost, if not quite, identical with those of the bacilli
found in human cases of paratyphoid fever which have no known connection
with food poisoning. Mayer[70] gives a list of seventy-seven outbreaks
of food poisoning (1893-1911) in which organisms variously designated as
"_B. paratyphosus_ B" or as "_B. suipestifer_" were held to be
responsible. The total number of cases (two thousand) and deaths
(twenty) is about the same as ascribed to _B. enteritidis_. According to
Mayer's tabulation meat from animals definitely known to be ailing is
less commonly implicated in this type (ten in seventy-seven) than in _B.
enteritidis_ outbreaks (twenty-three in forty-eight). Sausage and
chopped meat of unknown origin, however, were connected with eighteen
outbreaks.
The bacillus named _B. suipestifer_ was formerly believed to be the
cause of hog cholera, but it is now thought to be merely a secondary
invader in this disease; it is identical with the bacillus called _B.
paratyphosus_ B in its cultural and to a large extent in its
agglutinative behavior, but is regarded by some investigators as
separable from the latter on the basis of particularly delicate
discriminatory tests. Bainbridge, Savage, and other English
investigators consider indeed that the true food poisoning cases should
be ascribed to _B. suipestifer_ and would restrict the term _B.
paratyphosus_ to those bacteria causing "an illness clinically
indistinguishable from typhoid fever." German investigators, on the
other hand, regard _B. suipestifer_ and _B. paratyphosus_ B as
identical. My own investigations[71] indicate that there is a real
distinction between these two types.
Bearing directly on this question is the discussion concerning the
distribution of the food poisoning bacilli in nature. Most investigators
in Germany, where the majority of food poisoning outbreaks have
occurred, or at least have been bacteriologically studied, are of the
opinion that _B. suipestifer_ (the same in their opinion as _B.
paratyphosus_ B) is much more widely distributed than _B. enteritidis_
and that it occurs, especially in certain regions, as in the southern
part of the German Empire, quite commonly in the intestinal tract of
healthy human beings. Such paratyphoid-carriers, it is supposed, may
contaminate food through handling or preparation just as
typhoid-carriers are known to do. A number of outbreaks in which
contamination of food during preparation is thought to have occurred
have been reported by Jacobitz and Kayser[72] (vermicelli),
Reinhold[73] (fish), and others. Reinhold notes that in one outbreak
several persons who had nursed those who were ill became ill themselves,
indicating possible contact infection. In another outbreak also reported
by Reinhold it was observed that those who partook of the infected food,
in this case dried codfish, on the first day were not so severely
affected as those who ate what was left over on the second day. A
bacillus belonging to the paratyphoid group was isolated from the stools
of patients, but not from the dried codfish. These facts were
interpreted as signifying that the fish had become infected in the
process of preparation and that the bacilli multiplied in the food while
it was standing.
There seems no doubt that certain cases of paratyphoid food poisoning
are caused by contamination of the food during preparation and are,
sometimes at least, due to infection by human carriers. The bacilli in
such cases are usually (according to many German investigators) or
always (according to most English bacteriologists) of the _B.
suipestifer_ type. Other cases are due to pathogenic bacteria derived
from diseased animals, and these bacteria are often, possibly always, of
a slightly different character (_B. enteritidis_ Gaertner). It is still
unsettled whether both types of food poisoning bacteria are always
associated with disease processes of man or animals, or whether they are
organisms of wide distribution which may at times acquire pathogenic
properties. In certain regions, as in North Germany and England, such
bacteria are rarely, if ever, found except in connection with definite
cases of disease. In parts of Southwest Germany, on the other hand, they
are said to occur with extraordinary frequency in the intestines of
healthy men and animals. Savage[74] believes that there is some
confusion on this subject owing to the existence of saprophytic bacteria
which he calls "Paragaertner" forms and which bear a close resemblance
to the "true" Gaertner bacilli. They can be distinguished from the latter
only by an extended series of tests. The bacilli of this group show
remarkable variability, and in the opinion of some investigators
"mutations" sometimes occur which lead to the transformation of one type
into another.[75]
In spite of the present uncertainty regarding the relationship and
significance of the varieties observed, a few facts emerge plainly from
the confusion: (1) The majority of meat poisoning outbreaks that have
been bacterially studied in recent years have been traceable to one or
another member of this group and not to "ptomain poisoning." (2)
Bacteria of the _paratyphoid enteritidis_ group that are culturally
alike but agglutinatively dissimilar can, when taken in with the food,
give rise to identical clinical symptoms in man. (3) Food poisoning
bacteria of this group, when derived directly from diseased animals,
seem more likely to be of the Gaertner type (_B. enteritidis_) than of
the _B. suipestifer_ type.
_Toxin production._--The problem of the production of toxin by the
bacteria of this group and the possible relation of the toxin to food
poisoning has been much discussed. Broth cultures in which the living
bacilli have been destroyed by heat or from which they have been removed
by filtration contain a soluble poison. When this germ-free broth is
injected into mice, guinea-pigs, or rabbits, the animals die from the
effects. Practically nothing is known about the nature of the poisonous
substances concerned, except that they are heat-resistant. They are
probably not to be classed with the so-called true toxins generated by
the diphtheria and tetanus bacilli, since there is no evidence that they
give rise to antibodies when injected into susceptible animals. In the
opinion of some investigators the formation of these toxic bodies by the
_paratyphoid-enteritidis_ bacilli in meat and other protein foodstuffs
is responsible for certain outbreaks and also for some of the phenomena
of food poisoning, the rapid development of symptoms being regarded as
due to the ingested poisons, whereas the later manifestations are
considered those of a true infection. Opposed to this view is the fact
that well-cooked food has proved distinctly less liable to cause food
poisoning than raw or imperfectly cooked food.
A large proportion of the recorded meat poisoning outbreaks are
significantly due to sausages made from raw meat and to meat pies,
puddings, and jellies. This is most likely because the heat used in
cooking such foods is insufficient to produce germicidal results. In
milk-borne epidemics also it is noteworthy that the users of raw milk
are the ones affected. For example, respecting an extensive _B.
enteritidis_ outbreak in and about Newcastle, England, it is stated:
In no instance was a person who had used only boiled milk known to
have been affected. Thus in one family, consisting of husband,
wife, and wife's mother, the two women drank a small quantity of raw
milk from the farm, at the most a tumblerful, and both were taken
ill about twelve hours later. The husband, on the other hand,
habitually drank a pint a day, but always boiled. He followed his
usual custom on this occasion, and was unaffected.[76]
When in addition it is taken into consideration that the ordinary
roasting or broiling of a piece of meat is often not sufficient to
produce a germicidal temperature throughout, the argument that a
heat-resistant toxin is present in such cases is not conclusive. It must
be remembered also that in some outbreaks those persons consuming raw or
partly cooked meat have been affected while at the same time others
eating well-cooked meat from the same animal have remained exempt; this
would seem to indicate the destruction of living bacilli by heat, since
the toxic substances formed by these organisms are heat-resistant. The
view that a definite infection occurs, is favored, too, by the fact that
the blood-serum of affected persons so frequently has an agglutinative
action upon the paratyphoid bacillus. This would not be the case if the
symptoms were due to toxic substances alone. Altogether the role of
toxins formed by _B. enteritidis_ and its allies in food outside the
body cannot be said to be established. The available evidence points to
infection as the main, if not the sole, way in which the bacilli of this
group are harmful.
_Sources of infection._--The main sources of _enteritidis-suipestifer_
infection are: (1) diseased domestic animals, the infected flesh or milk
of which is used for food; (2) infection of food by human carriers
during the process of preparation or serving. To these may be added a
third possibility: (3) contamination of food with bacteria of this group
which are inhabitants of the normal animal intestine. Considering these
in order:
1. Diseased animals: The majority of the meat poisoning outbreaks are
caused by meat derived from pigs or cattle. Table III gives the figures
for a number of British[77] and German[78] epidemics.
TABLE III[79]
====================================================================
| | | BELONGING TO
| B. ENTERITIDIS | B. SUIPESTIFER | THIS GROUP BUT
| | |UNDIFFERENTIATED
|--------------------+--------------------+----------------
|British|German|Total|British|German|Total| British
---------+-------+------+-----+-------+------+-----+----------------
Pig | 1 | 1 | 2 | 3 | 5 | 8 | 4
Ox or cow| 3 | 9 | 12 | 2 | 3 | 5 | 5
Calf | 0 | 7 | 7 | 2 | 2 | 4 | 0
Horse | 0 | 1 | 1 | 0 | 1 | 1 | ...
Chickens | 1 | 0 | 1 | 0 | 1 | 1 | ...
--------------------------------------------------------------------
Occasional outbreaks have also been attributed to infection through
eating rabbit, sheep, goose, fish, shrimp, and oysters. Especially
noteworthy is the relative rarity of infection from the meat of the
sheep.
More definite information is needed respecting the pathological
conditions caused by these bacteria in animals and the relation of such
conditions to subsequent human infection. A rather remarkable problem
is presented by the relation of _B. suipestifer_ to hog cholera. This
bacillus, although not now considered the causal agent of hog cholera,
is very commonly associated with the disease as an accessory or
secondary invader, and is frequently found in the internal organs of
swine after death. It might be supposed that in regions where hog
cholera is prevalent human infections would be more common than in
other districts, but this seems not to be the case. No connection
has ever been demonstrated between outbreaks of hog cholera--in which
_B. suipestifer_ is known to be abundantly distributed--and so-called
_B. suipestifer_ infections in man.
Suppurative processes in cattle, and especially in calves, have
given rise to poisoning from the use of the meat or milk of the
infected animals. It has been often demonstrated that bacteria of
the _enteritidis-suipestifer_ group are associated with inflammation
of the udder in cows and with a variety of septicemic conditions in
cattle and other domestic animals as well as with manifestations of
intestinal disturbances ("calf diarrhea," etc.).[80] The frequency
with which poisoning has occurred through the use of the meat of
"emergency-slaughtered" animals has been already mentioned. K. F.
Meyer[81] has reported an instance of accidental infection in a
laboratory worker caused by handling a bottle of sterilized milk
that had been artificially contaminated with a pure culture of
_B. enteritidis_ for experimental purposes. The strain responsible
for the infection had been isolated from the heart blood of a calf
that had succumbed to infectious diarrhea.
2. Human contamination: In a certain number of paratyphoid food
infections there is some evidence that the food was originally derived
from a healthy animal and became infected from human sources during the
process of preparation. In addition to the instances already mentioned
(Reinhold _et al._, p. 67) the Wareham (England, 1910) epidemic[82] was
considered by the investigators to be due to infection of meat pies by a
cook who was later proved to be a carrier of paratyphoid bacilli. The
evidence in this case, however, is not altogether conclusive.
Soederbaum[83] mentions a milk-borne paratyphoid epidemic occurring in
Kristiania which was ascribed to infection of the milk by a woman
milker. Sacquepee and Bellot[84] report an interesting paratyphoid
outbreak involving nineteen out of two hundred and fifty men in a
military corps. The patients fell ill on different dates between June 14
and June 21.
It was found that an assistant cook who had been in the kitchen for
several months had been attacked a little before the epidemic
explosion by some slight malady which was not definitely diagnosed.
He had been admitted to the hospital and was discharged
convalescent. The cook, on being recalled and quarantined, stated
that some days before June 10 he was indisposed with headache and
anorexia. He had nevertheless continued his service in the
kitchen.... _B. paratyphosus_ B (_B. suipestifer_) was repeatedly
found in his stools in August, September, and October.... In all
probability, therefore, the outbreak was due to food contaminated
by a paratyphoid-carrier who had passed through an abortive attack
of the fever.[85]
Bainbridge and Dudfield[86] describe an outbreak of acute
gastro-enteritis occurring in a boarding-house; it was found that no one
article of food had been eaten by all the persons affected, and there
were other reasons for supposing the outbreak to be due to miscellaneous
food contamination by a servant who was a carrier.
There is, therefore, ground for believing that occasional contamination
of food may be brought about by bacteria of this group derived from
human sources. It is not clear, however, how frequent this source of
infection is, compared to infection originating in diseased animals. It
must be admitted, too, that English investigators are disposed to look
upon outbreaks similar to those just described as infections with _B.
paratyphosus_ B, an organism which they would distinguish from the
"true" food poisoning bacilli, _B. enteritidis_ and _B. suipestifer_.
3. Miscellaneous contaminations: Some investigators, especially certain
German writers, regard the bacilli of the paratyphoid group as so widely
distributed in nature that any attempt to control the spread of
infection is like fighting windmills. According to this view the bacilli
occur commonly in our everyday surroundings and thence make their way
rather frequently into a variety of foodstuffs. Various German
investigators have reported the presence of paratyphoid bacilli in the
intestinal contents of apparently normal swine, cattle, rats, and mice
and more rarely of other animals, in water and ice, in German sausage
and chopped meat, and in the bodies of apparently healthy men. To what
extent their alleged ubiquity is due to mistaken bacterial
identification, as claimed by some English investigators, remains to be
proved. There is no doubt that in some quarters exaggerated notions have
prevailed respecting a wide distribution of the true paratyphoid
bacteria. Savage and others believe that the hypothesis that food
poisoning outbreaks are derived from ordinary fecal infection of food is
quite unfounded. It is pointed out that there is good evidence of the
frequent occurrence of intestinal bacteria in such food as sausages and
chopped meat, and that consequently, if paratyphoid infections could
occur through ordinary contamination with intestinal bacteria not
connected with any specific animal infection, food poisoning outbreaks
should be exceedingly common instead of--as is the case--comparatively
rare.
At the present time even those who maintain that these bacilli are of
common occurrence admit that their abundance is more marked in some
regions than in others. Southwest Germany, for example, seems to harbor
paratyphoid bacilli in relatively large numbers. Possibly local
differences in distribution may account for the discrepancies in the
published findings of German and British investigators.
A special case is presented by the relation of these bacilli to rats and
mice. Among the large number of bacteria of the paratyphoid group is the
so-called Danysz bacillus, an organism quite pathogenic for rodents, and
now and again used in various forms as a "rat virus" for purposes of
rodent extermination. Several outbreaks of food poisoning in man have
been attributed on more or less cogent evidence to food contamination
by one of these viruses either directly by accident, as in the case
described by Shibayama,[87] in which cakes prepared for rats were eaten
by men, or indirectly through food contaminated by mice or rats that had
been infected with the virus.[88] The use of such viruses has not proved
of very great practical value in the destruction of rodents, and is open
to serious sanitary objections, since the animals after apparent
recovery can continue to carry the bacilli of the virus and to
distribute them on or near food substances.
It seems possible that rats and mice may become infected with certain
bacteria of this group without human intervention, and that these
infected animals may be the means of contaminating foodstuffs and so
causing outbreaks of food poisoning. Proof of the frequency with which
this actually occurs is naturally difficult to obtain.
There is no escape from the conclusion that in any given case of food
poisoning the exact source of infection is often largely conjectural.
Even when suspicion falls strongly on a particular article of food, it
may not be possible to establish beyond a reasonable doubt whether the
material (meat or milk) came from a diseased animal or whether it was
infected from other sources (man or other animals) at some stage during
the process of preparation and serving. The most definitely attested
cases yet put on record are those in which it is possible to trace the
infection to food derived from an ailing animal.
_Means of prevention._--The most obvious and probably the most important
method of preventing infection with paratyphoid bacilli is the adoption
of a system of inspection which will exclude from the market as far as
possible material from infected animals. To be most effective such
inspection must be directed to examination of the living animal. The
milk or the meat from diseased animals may give no visible sign of
abnormality. In the Ghent outbreak of 1895 the slaughter-house
inspector, a veterinary surgeon, was so firmly convinced that the meat
which he had passed could have had no connection with the outbreak, that
he ate several pieces to demonstrate its wholesomeness. The experiment
had a tragic ending, as the inspector was shortly attacked with severe
choleraic symptoms and died five days later, paratyphoid bacilli being
found at the autopsy. Mueller[89] also has described a case in which
paratyphoid bacilli were found in meat that had given rise to a meat
poisoning outbreak although the meat was normal in appearance and the
organs of the animal showed no evidence of disease to the naked eye. It
is evident that inspection of the live animal will often reveal evidence
of disease which might be missed in the ordinary examination of
slaughter-house products.
Although inspection of cows used for milking and of food animals before
slaughter is highly important, it does not constitute an absolute
protection. Emphasis must be repeatedly laid on the fact that meat, and
especially milk that is derived from seemingly healthy animals, may
nevertheless contain paratyphoid bacilli. To meet this difficulty in
part the direct bacterial examination of the carcasses of slaughtered
food animals has been proposed, but this seems hardly practicable as a
general measure. In spite of all precautions taken at the time of
slaughtering it seems probable that occasionally paratyphoid-infected
meat will pass the first line of defense and be placed on the market.
This danger, which is probably not a very grave one under a reasonably
good system of inspection of live animals, may be met by thoroughly
cooking all foods of animal origin. It is worth noting that some of the
internal organs, as the liver and kidneys, are more likely to contain
bacteria than the masses of muscle commonly eaten as "meat." Sausages,
from their composition and mode of preparation, and chopped meat
("hamburger steak") are also to be treated with especial care.
Consumption of such foods as raw sausage or diseased goose liver (pate
de foie gras) involves a relatively high risk. It is true of paratyphoid
infection as of most other forms of food poisoning that thorough cooking
of food greatly diminishes the likelihood of trouble.
Whatever be the precise degree of danger from food infection by healthy
paratyphoid-carriers (man or domestic animals), it is obvious that
general measures of care and cleanliness will be more or less of a
safeguard. As with typhoid fever so all outbreaks of paratyphoid should
be thoroughly investigated in order that the sources of infection may be
found and eliminated. The possible connection of rats and mice with
these outbreaks should furnish an additional incentive to lessen the
number of such vermin as well as to adopt measures of protecting food
against their visits.
FOOTNOTES:
[62] _Fleischvergiftungen u. Paratyphusinfektionen_ (Jena, 1910).
[63] _Rept. to Local Govt. Board_, N.S. No. 77 (London, 1913).
[64] _Zeit. f. Hyg._, XXII (1896), 53.
[65] _Brit. Med. Jour._, I (1909), 1171.
[66] Bernstein and Fish, _Jour. Amer. Med. Assoc._, LXVI (1916), 167.
[67] _Breslau aerztl. Ztschr._, X (1888), 249.
[68] Bernstein and Fish, _Jour. Amer. Med. Assoc._, LXVI (1916), 167.
[69] _Deutsche Viertelj. f. oeffentl. Ges._, XLV (1913), 58-59.
[70] _Op. cit._, pp. 60-62.
[71] _Jour. Infect. Dis._, XX (1917), 457.
[72] _Centralbl. f. Bakt._, I Orig., LIII (1910), 377.
[73] _Cor.-Bl. f. schweiz. Aerzte_, XLII (1912), 281 and 332.
[74] _Jour. Hyg._, XII (1912), 1.
[75] See Sobernheim and Seligmann, _Centralbl. f. Bakt._, Ref., Beilage,
L (1911), 134.
[76] _Report Med. Officer of Health_ (Newcastle-upon-Tyne, 1913).
[77] Compiled from Savage, _Report of Local Gov't Board_, 1913.
[78] Mayer, _Deutsche Viertelj. f. oeffentl. Ges._, XLV (1913), 8.
[79] It must be noted that origin of the food from a diseased animal was
not definitely proved in all the cases cited. Some of these cases should
possibly be classed under human contamination (2).
[80] Although not directly connected with the question of food
poisoning, it is of interest to note that certain diseases of birds have
been traced to infection with members of this group of bacteria. In a
few cases, as in several epidemics among parrots in Paris and elsewhere,
the infection has been communicated to man by contact.
[81] _Jour. Infect. Dis._, XIX (1916), 700.
[82] R. Trommsdorff, L. Rajchman, and A. E. Porter, _Jour. Hyg._, XI
(1911), 89.
[83] _Hygiea_, LXXV (1913), 1.
[84] _Progres med._, 3d series, XXVI (1910), 25.
[85] Ledingham and Arkwright, _The Carrier Problem in Infectious
Diseases_, pp. 152-53.
[86] _Jour. Hyg._, XI (1911), 24.
[87] _Muench. med. Wchnschr._, LIV (1907), 979.
[88] See, for example, H. Langer and Thomann, _Deutsche med. Wchnschr._,
XL (1914), 493.
[89] _Ztschr. f. Infektionsk. ... d. Haustiere_, VIII (1910), 237.