Chapter IX: Part 9

The case of Mayer, who became infected during the course of some
laboratory experiments, is particularly instructive.

During an epidemic of mouse typhoid among his laboratory mice,
evidently spread from some inoculated mice by ants, Mayer[BI] who had
personally handled the infected mice and their cages, became sick July
15, just seven days after the first appearance of the ants and after
the observed rise in virulence of the mouse typhoid among the mice.
His clinical history is as follows:

Footnote BI:

Mayer, Georg: Ueber die Verschleppung typhöser Krankheiten durch
Ameisen und die Pathogenität des Loeffler’schen Mäusetyphusbazillus
für den Menschen. Münch. med. Woch., vol. 52, 1905, p. 2261.

July 15: Weakness, epigastric pain, obstipation, temperature 37.7,
pulse 90.

July 16: Slight diarrhea, increase of pain in region of trans-colon,
temperature 38.3, pulse 98.

July 17: Diarrhea continued, pains increased—severe, chill in evening,
temperature 39.1, pulse 102.

July 18: Obstipation, symptoms worse, chill again in evening,
temperature 39.4, pulse 104.

July 19: Symptoms better, stools from purgative, evening temperature
36.9, pulse 68.

July 20: Left bed. Temperature and pulse normal, but weakness and
slight epigastric pains continued till August 7.

Patient’s serum agglutinated as follows:

──────────────────────────┬──────────────┬──────────────┬────────────── │ Typhoid. │ Paratyphoid. │Mouse-typhoid. ──────────────────────────┼──────────────┼──────────────┼────────────── July 23 │ 1–50+│ 1–50+│ 1–250+ August 7 │ 1–50+│ 1–50+│ [BJ]1–100+ August 16 │ 1–50+│ 1–50+│ 1–50 + ──────────────────────────┴──────────────┴──────────────┴──────────────

Footnote BJ:

Slight

The bacillus of mouse typhoid was isolated from the patient’s stools
July 21 and 23. Negative results thereafter. Examinations continued a
month.

Same organism isolated from urine July 21. Negative thereafter.

The author concludes that the _B. typhi murium_ is able to cause in
man a rather severe acute illness of short duration.

Shibayama[BK] gives the following report of outbreaks of human
infection that have come to his knowledge in Japan, where
mouse-typhoid virus has been used in considerable quantities.

Footnote BK:

Shibayama, G.: Ueber Pathogenität der Mäusetyphusbazillen für den
Menschen. Münch. med. Woch., May, 1907, p. 979.

_Outbreak 1._ In April, 1905, in a village of the Province of Saitama,
30 people became ill and 2 died with severe gastro-intestinal
symptoms. Outbreak investigated by Dr. H. Sezuki, district medical
officer, formerly of the Tokio Institute for Infectious Diseases.

It was found that all the 30 people had partaken of a dish of cooked
vegetables served at a meeting of the town council, and that for
application of sauce to these vegetables (after cooking) a wooden
vessel had been used which two days before had been used for mixing
mouse-typhoid virus with meal, without subsequent cleansing or
sterilization.

The symptoms came on within twelve to forty-eight hours thereafter
(usually twenty hours), chill or chilly sensations, rise of
temperature to 38° or 39° C., or even to 40° C.; face flushed; pulse
accelerated; great weakness; thirst, nausea, colicky pains in abdomen
followed by severe diarrhea and vomiting. In general, the fever and
diarrhea lasted two or three days; but malaise, anorexia, weakness,
and mucous stools persisted for several days. The more severe cases
showed choleraic symptoms of collapse. Two persons died in spite of
medical treatment—a 6-year old boy and a man of 43, on the second and
third day, respectively.

From the intestinal contents of these two cases, from the stools of
several other cases, and from the remnants of the dish of vegetables
in the wooden bowl an organism was isolated, which was demonstrated to
be identical with the bacillus of mouse typhoid.

These results were confirmed at the Tokio Institute for Infectious
Diseases by Shibayama, by biological and immunizing tests.

_Outbreak 2._ On December 7, 1905, a peasant of a village in the
Province of Miyaki brought home some mouse virus mixed with meal in
cakes. This being mistaken for “mochi” was eaten about 2 p. m. the
next day by two little girls, 3 and 8 years old, respectively, and
their grandfather, 61 years old.

The man and the 8-year-old girl became sick at 9 p. m. the same day
and the other child at about 3 p. m. on December 9. The symptoms in
all cases were those of severe gastro-enteritis, as described under
outbreak 1.

The man died December 12, the 8-year-old child died on the 10th; the
3-year-old child recovered after several days’ illness. These three
alone ate of the virus and no other persons in the house became sick.

No bacteriological examination was practicable.

_Outbreak 3._—In a village of the Province of Iskawa, on April 22,
1906, a lot of rat poison was prepared by mixing agar cultures of the
mouse-typhoid bacillus with meal and water in a large wooden bowl.

On April 24 there was a festival in the village at which about 170
persons were served with 240 pounds of rice, which, after being
cooked, was kneaded into cakes in a wooden bowl. About 80 pounds of
this rice was so kneaded in the bowl previously used for preparing the
rat poison. Twenty to twenty-four hours later 120 people who had eaten
of the rice became ill with the already described symptoms of
gastro-enteritis, of mild type among the strong but severe among the
children and old people. Eighty-nine cases came under medical
treatment. There were no deaths, but a number of cases were confined
to bed for a week or more; mild cases recovered in one to three days.

No bacteriological examination was made, but the physicians and town
officials were unanimously of the opinion that the rat virus was the
cause of the outbreak.

_Outbreak 4._—A peasant of the province of Niigata brought home on May
14, 1906, some rat virus (cultures of mouse-typhoid bacilli mixed with
meal) which he laid away. Two of his grandchildren—a boy of 5 and a
girl of 7—together with the 4-year-old daughter of a neighbor, found
and ate the rat virus. The next day all three children became ill with
severe gastro-enteritis, of which the 4-year-old child died on the
third day. The others recovered after several days of medical
treatment.

_Outbreak 5._—On May 16, 1906, a peasant in the province of Jamagata
brought home some rat virus (6 c. c. cultures of mouse-typhoid
bacillus mixed with meal), which was accidentally mixed with the feed
given to a healthy horse next morning. The same evening the horse
showed loss of appetite and appearance of sickness. Within two days he
developed a severe enteritis, of which he died on the seventh day. The
body was buried, but was dug up in the night by a laborer who cut off
the hind quarters, took them home, and distributed the meat among
friends and neighbors.

Within three days 34 persons who had eaten of this meat became ill
with symptoms of severe gastro-enteritis. A 72-year-old man died after
five days; the others recovered in three to eleven days.

This outbreak was investigated by Dr. H. Segawa, a medical officer of
the province and former member of the institute at Tokyo, who isolated
from the remains of the horseflesh by plate cultures and animal
inoculations, an organism identical with the bacillus of mouse
typhoid. A culture was sent to Shibayama, who carefully verified it
(details not given).

Shibayama concludes: In all cases the close relationship between the
bacillus of mouse typhoid and the illness was established; and he
thinks this organism must be accepted as the direct cause of the
outbreaks.

Referring to Loeffler’s uniformly negative human experiments, he calls
attention to known cases where men have taken virulent cultures of
typhoid, diphtheria, etc., without infection. According to many
bacteriological investigations, _B. typhi murium_ is identical with
the bacillus of enteritis. If it is proven that the latter is a cause
of acute gastro-enteritis then the conclusion is likewise justified
that the _B. typhi murium_ is frequently pathogenic for man, causing
an acute gastro-enteritis.

Fleischanderl[BL] a reports six cases of illness—three severe and
three mild—occurring in his practice in the latter part of April,
1908, presenting the following symptoms: Onset with rapidly increasing
body pains, followed in a few hours by diarrhea, rise of temperature,
and general prostration; in the next two or three days aggravation of
the symptoms, fever (39° to 40° C.), copious diarrhea, vomiting (in
one case), severe body pains, vertigo, and considerable prostration.
Symptoms abated quickly in a few days, leaving considerable
prostration, convalescence requiring two weeks in one case. In the
less severe cases there was no fever, and the other symptoms were
generally milder.

Footnote BL:

Fleischanderl, Fritz: Mitteilung über einige Krankheitsfälle,
hervorgerufen durch Mäustyphusbazillen. Munch. med. Woch., vol. 56,
Feb., 1909, p. 392.

The simultaneous appearance of these and other similar rumored mild
cases among the neighbors (about 20 in all) pointed to a common cause.
It was found that three of the six cases were in people who had
handled mouse-typhoid cultures the day before their illness, taking no
precautions to avoid infection.

The other three occurred in a family which, on the day before the
onset of the illness, had drunk raw milk obtained from a house where
the rat virus had been used shortly before, and only three members of
the family who drank the milk became ill.

In order to prove the etiology of these cases Fleischanderl, who had
never suffered any intestinal troubles, had had nothing to do with any
case of typhoid fever for a year, and was in excellent health, took a
culture of the mouse-typhoid bacillus as used in the neighborhood,
rubbed a glass rod over the surface, washed it off in a glass of
water, and drank this before breakfast on the morning of May 3.

In twenty-two hours he experienced mild, increasing body pains,
followed within a few hours by diarrhea, and a few hours later by
slight chill, rise of temperature to 38.2, pulse 106, severe pains in
body, and feeling of great weakness.

May 4, 9 p. m.: Temperature 39.2° C., pulse 120. Height of symptoms.

May 5: Temperature 38.2° to 38.5° C., pulse 106 to 120. Other symptoms
continued.

May 6: Temperature and pulse normal. All symptoms disappeared except
weakness, which lasted two days.

Bacteriological investigations conducted by Herbert Berger in the K.
K. Serotherapeutischen Institut and by Doctor Reichel, assistant in
the Hygienic Institute of the University of Vienna, follow:

From the stools of one of the patients infected from milk an organism
was isolated which, injected into mice (1 c. c. emulsion of
forty-eight-hour culture), killed them in two to five hours. Mice
infected by eating these dead mice died in thirty to forty-eight
hours.

Control mice inoculated similarly with a culture of the market
mouse-typhoid virus died in twenty to thirty hours, while the mice
infected through eating these died after three to four days.

The following strains were used for cultural agglutination tests:

A. From stools of patient infected from milk.

B1. Market virus used in injecting mice.

B2. Market virus taken by author.

C25. From stools of author twenty-five hours after infection.

C55. From stools of author fifty-five hours after infection.

LL. Stock culture of Loeffler’s mouse-typhoid bacillus.

LP. Stock culture of para-typhoid bacillus.

All organisms (A-C55) were demonstrated as motile bacilli, not
liquefying gelatine, not forming lactic acid, and forming gas from
dextrose.

The serum of a rabbit after two injections of LL agglutinated LL and
LP in dilution of 1:1280, did not agglutinate A, B1, B2, C25, and C55.

Serum of rabbit after one injection of B2 agglutinated in 1:320
dilution A, B1, B2, C25, C55, and LL; did not agglutinate LP.

Serum of rabbit after one injection of C25 gave exactly similar
results.

Doctor Reichel considers it proven that the organisms A to C55 are
undoubtedly identical with Loeffler’s bacillus of mouse typhoid, and
distinct from para-typhoid bacilli. The author considers it proven
that this bacillus was the sole cause of the cases of enteritis
observed.

Recently Mallory and Ordway[BM], in a paper read before the American
Association of Pathologists and Bacteriologists held in Boston,
reported that lesions analogous to the early stages of typhoid lesions
may be produced in rats by the use of Danysz virus.

Footnote BM:

Mallory, F. B., & Ordway, T.: Lesions produced in the rat by a
typhoid-like organism (Danysz virus). Journ. Am. med. assn., vol.
52, May 1, 1909, p. 1455.

In view of these facts the statements of some of the advertising
matter of certain rat viruses call for revision.

REFERENCES TO THE LITERATURE.

Loeffler,[BN] 1889, gives an account of two spontaneous outbreaks
among the mice kept at the Hygienic Institute at Griefswald. It was
from these animals that he obtained and described the original _B.
typhi murium_. He determined that the infection was by ingestion and
that the organism was especially virulent for field mice. He described
the organism in detail and also the lesions.

Footnote BN:

Loeffler, F.: Ueber Epidemieen unter den im hygienischen Institute
zu Griefswald gehalten Mäusen und über die Bekämpfung der
Feldmäusplage. Centblt. f. Bakt., Orig., vol. 11, 1898, p. 129.

Laser,[BO] 1892, reports that on the morning of February 6, 1892, 70
of the 76 field mice (_Mus agrarius_) used as experiment animals in
the Hygienic Institut at Königsberg were found dead. A small bacillus
twice as long as broad, displaying a very lively specific motility,
was isolated from the spleen. It was tested upon animals and all the
results compared with Eisenberg’s tables and found to be closely
allied to the bacillus of ferret plague (Ebert-Schummelbusch), to the
bacillus of American swine plague (Billings), and to that of French
swine plague (Chantamesse and Cornil).

Footnote BO:

Laser, Hugo: Ein neuer für Versuchsthiere pathogener Bacillus aus
der Gruppe der Frettschen-Schweinseuche. Centblt. f. Bakt., Orig.,
vol. 11, 1892, p. 184.

Mereshkowsky,[BP] 1893, isolated an organism at the Royal
Bacteriological Institute at St. Petersburg from a stock of Zisel
(_Spermophilus musicus_) among which a spontaneous epizootic had
occurred. The author found this culture to be virulent for domestic
and field mice.

Footnote BP:

Mereshkowsky, S. S.: Ein aus Zieselmäusen ausgeschiedener und zur
Vertilgung von Feld-resp. Mäusen, geeigneter Bacillus. Centblt. f.
Bakt., Orig., vol. 17, 1895, p. 742.

Zupnik,[BQ] 1897, states that Joseph, of the Agricultural Institute of
Breslau, in 1882 originated the use of favus fungus for the
destruction of mice. Zupnik tested _B. typhi murium_ and Danysz virus
upon mice. No experiments with rats.

Footnote BQ:

Zupnik, Leo: Ueber die pratische Verwendbarkeit der Mäuse bacillen
inbesondere des Loeffler’schen _Bacillus typhi murium_. Centblt. f.
Bakt., Orig., vol. 21, 1897, p. 446.

Issatschenko,[BR] in 1898, described briefly a bacillus obtained by
him from gray rats. Recent investigation showed this bacillus to be
very virulent for rats and mice, but harmless for the different
species of domestic animals. Four hundred and forty-three experiments
were made upon rats with pure cultures of the bacillus combined with
dough and fed to the rats. He gives a table showing that the mortality
occurred in 431 rats at an average of ten and one-half days. The
greatest mortality occurred during the first fifteen days (84.2 per
cent), with the greatest number on the seventh day (20.1 per cent).

Footnote BR:

Issatschenko, B.: Untersuchungen mit dem für Ratten pathogenen
Bacillus. Centblt. f. Bakt., Orig., vol. 31, 1902, p. 26.

Danysz,[BS] 1900, isolated a cocco-bacillus during an outbreak of
spontaneous disease amongst field mice which presented the general
characteristics of the colon bacillus and to this extent resembled
Loeffler’s bacillus (_B. typhi murium_), and which from the beginning
exhibited some pathogenicity for gray rats (_M. decumanus_). Of ten
such rats fed upon a culture of this organism, two or three died,
while others that had fallen sick recovered and the same remained
well. This small mortality offered some hope that it would be possible
to increase the virulence of the bacillus by ordinary methods; that
is, passing it from rat to rat. It was found, however, that the
opposite was true; the virulence was always weakened by this process
regardless of the method of administration. Thus in every series the
first culture killed the animals in seven to twelve days; occasionally
after one or two passages five to seven days; but subsequent passages
decreased the virulence so that none died.

Footnote BS:

Danysz, J.: Un microbe pathogène pour les rats (_Mus decumanus_ et
_Mus rattus_) et son application à la destruction de ces animaux.
Ann. Inst. Pasteur, 1900, vol. 14, p. 193.

The general result is that it is difficult to maintain the virulence
of the cocco-bacillus of the rat or to increase it when it is found to
be small. It can only be effected by constantly making a large number
of experiments and frequently testing the virulence of the culture.
Danysz succeeded in keeping up a supply of cultures of sufficient
strength for eight years. In 60 per cent of the operations where this
culture has been used it has been successful in causing the absolute
disappearance of the rats. In 15 per cent the result was entirely
negative, and in the remaining 25 per cent there was a large
diminution.

Oettinger,[BT] in 1903, increased the virulence of the Danysz bacillus
by growth in an egg rendered alkaline after the method previously
introduced by Wiener.

Footnote BT:

Oettinger, M.: Ueber die Wienersche Methode zur Virulenzsteigerung
der Danysz Bazillen. Munch. med. Woch., vol. 1, 1903, p. 324.

Pfreimbtner,[BU] 1904, sees the reason for a partial failure in the
application of Loeffler’s bacillus to the destruction of field mice.
In the use of a solid medium (agar-agar), upon which the bacterial
cultures only grow upon the surface, too few bacteria are transferred
to the pieces of bread, and consequently too few virulent bacteria are
consumed by the mice. An active infection depends not upon the
existence of virulent bacteria, but rather upon the entrance of a
definite number of virulent bacilli.

Footnote BU:

Pfreimbtner, J.: Erfahrung über des Loeffler’schen
Infektionsverfahren zur Bekämpfung der Mäuseplage in einer neuen Art
der Anwendung. Fühlung’s landw. Zeit., 1904, p. 619. Rev. by
Schander in Centblt. f. Bakt., 2. Abt., vol. 15, 1905, p. 502.

The author used skimmed milk as a nutrient medium and describes a
series of 9 experiments and gives an estimate of the cost of the
process with the use of milk instead of agar. The advantage of the use
of milk is in the greater certainty of the results and cheapness as
compared with other methods. The bread cubes impregnated with skimmed
milk were well taken by the mice and desiccation of the cultures,
which not infrequently occurs in the use of more solid media, is
excluded. Notwithstanding the excessive thinning, the liquid still
contains many virulent bacilli. The washing out of bacilli after rain
is slightly less possible as in the use of the more solid media. The
action of light, where the bread cubes contain many bacilli, is
insignificant, and hence the carrying out of the process in the
daytime is made possible. Milk is easily obtained and the thinning and
application less bothersome. Finally the author expresses himself
against the view that the _B. typhi murium_ causes serious diseases in
man.

Teichert,[BV] 1905, speaks of Loeffler’s mice typhus bacillus and
Pfreimbtner’s method of growing it upon sterilized skimmed milk. A
number of experiments carried out at the bacteriological laboratory of
the Vreschen experiment station shows the utility of Loeffler’s
bacillus for the destruction of house and field mice. The long-tailed
field mouse was, on the other hand, not harmed by it.

Footnote BV:

Teichert: Die mechanischen, chemischen und bacteriellen Kampfmittel
gegen Ratten und Mäuse. 2. Teil: Die Bekämpfung der Mäuse. Fühlung’s
landw. Zeit., 1905, No. 16. Rev. by Ehrenberg in Centblt. f. Bakt.,
2. Abt., vol. 15, 1905, p. 503.

Bahr,[BW] 1905, gives a complete and satisfactory summary of the
literature upon the subject of the destruction of rats and mice with
bacteria, including original work of his own.

Footnote BW:

Bahr, L.: Ueber die zur Vertilgung von Ratten und Mäusen benutzten
Bakterien. Centblt. f. Bakt., Orig., vol. 39, 1905, p. 263.

Zielander,[BX] 1908, obtained fairly good results with Danysz virus in
the laboratory, also with ratin. No fixed tests were recorded.

Footnote BX:

Zielander: Der Rattenbacillus als Rattenvertilgungsmittel. Arb. a.
d. k. Gesndhtsmte., Berl., vol. 28, 1908, p. 145.

RÉSUMÉ.

Rats are notoriously resistant to bacterial infection. Even plague
usually fails markedly to diminish their prevalence. An epizootic of
bacterial nature, therefore, can not be classed with the natural
enemies of the rat. We are not surprised, then, to learn that the
bacterial viruses have signally failed to accomplish their mission.

These bacterial viruses belong to the colon-typhoid group of
organisms. They are either identical with or closely related to the
original bacillus of mouse typhoid discovered by Loeffler, or the
para-typhoid bacillus type B, which is frequently the cause of meat
poisoning, or the _Bacillus enteritidis_ of Gærtner, which has been
associated with gastro-intestinal disorders.

The claim that these rat viruses are harmless to man needs revision,
in view of the instances of sickness and death reported by various
observers. The pathogenicity for man depends upon the virulence of the
culture, the amount ingested, the nature of the medium in which it
grows, and many other factors.

Danysz virus is pathogenic for rats under laboratory conditions, but
has feeble powers of propagating itself from rat to rat. It rapidly
loses its virulence, especially when exposed to light and air. The
result depends largely upon the amount ingested. The other viruses
have proven even less satisfactory.

Under natural conditions these rat viruses may be likened to a
chemical poison, with the great disadvantage that they rapidly lose
their virulence and are comparatively expensive. They also have the
further disadvantage that chemical poisons do not possess of rendering
animals immune by the ingestion of amounts that are insufficient to
kill or by the ingestion of cultures that have lost their virulence.

PLAGUE ERADICATION IN CITIES BY SECTIONAL EXTERMINATION OF RATS AND
GENERAL RAT PROOFING.

By VICTOR G. HEISER,

_Passed assistant surgeon, U. S. Public Health and Marine-Hospital
Service, chief quarantine officer and director of health for the
Philippine Islands_.

The health officials of the city of Manila, P. I., for the five-year
period from 1900 to 1905 made most valiant efforts to destroy the rats
of the city; approximately $15,000 were paid in rat bounties and
$325,000 in salaries and wages and other expenses for rat catching,
but at the end of that time the rats were apparently as plentiful as
before and the plague was still present. The experience in Tokio and
Osaka had been practically the same. Professor Kitasato expressed the
opinion that a given city could only have up to a certain number
anyhow, because further increase was limited by the amount of
available food, and when the limit had been reached the rats commenced
to eat one another, which prevented more than a certain number ever
being present, and that the increase by breeding was about as rapid as
any method of destruction which had yet been tried.

The following plan was then tried, and the plague among human beings
soon disappeared, there being no cases since April, 1906; and it has
been eradicated among rats each time that it has made its appearance.

A list of the places at which plague-infected rats were found was
made. Each was regarded as a center of infection. Radiating lines,
usually five in number, were prolonged from this center, evenly spaced
like the spokes of a wheel. Rats were caught along these lines and
examined. Plague rats were seldom found more than a few blocks away.
The furthermost points at which infected rats were found were then
connected with a line, as is roughly shown in the diagram on page 206
(Fig. 59.)

The space inclosed by the dotted line was regarded as the section of
infection. The entire rat-catching force, which had heretofore been
employed throughout the city, was then concentrated along the border
of the infected section; that is, along the dotted line. They then
commenced to move toward the center, catching the rats as they closed
in. Behind them thorough rat proofing was carried out. One section
after another was treated in this way until they had all been wiped
out. Once weekly thereafter rats were caught in the previously
infected sections and at other places which were insanitary and which
had been infected in years gone by. This was continued for one year.

The city was then divided as is shown in the diagram facing this page,
and rats are caught once weekly at each point at which the lines
intersect and sent to the laboratory for examination.

FIG. 59.—Isolated plague-infested center, Manila, P. I.
]

In addition, sanitary inspectors are instructed to bring in dead rats
which have evidently died of disease, and more detailed rat catchings
are made along the water front.

It is understood of course that rat proofing of the entire city should
be thoroughly carried out and constantly maintained.

CONCLUSIONS.

1. Since the above system was adopted plague has disappeared in the
city of Manila; among human beings in 1906; among rats in 1907, and it
has not reappeared since.

2. That the cost is only a small fraction of that of general rat
extermination.

3. That the plan is thoroughly practical for any kind of a city.

FIG. 60.—General Scheme for testing plague rat infection, City of Manila.
Sanitary Map Bureau of Health. _Escala 1:38,500_
]

THE RAT IN RELATION TO SHIPPING.

By WILLIAM C. HOBDY,

_Passed Assistant Surgeon, Public Health and Marine-Hospital Service_.

Since men first went down to the sea in ships the rat’s voyage-making
tendencies have been known, and their fecundity is as well established
as their fondness for travel. The record does not state that there
were more than a pair on the ark at the beginning of her voyage, but
the chances are better than even that her skipper began that voyage
with more rats than his manifest showed; but whether he did or not, we
can be sure he had more at the end of the voyage than at the
beginning. Whether or not succeeding generations inherited from their
forbears on the ark this well-known wanderlust is undetermined, but it
is a fact that the intimacy and companionship established and begun
then have been persistently maintained by the rat ever since. His
travels have been coextensive with man’s, until to-day there is not a
port on earth where the rat is not present. Any exception to this
statement simply proves the rule. The rat is cute; he knows when he is
well off and his absence from a port does not prove that he has not
been there, but that he has been too intelligent to follow man ashore.
In establishing this shipboard intimacy there has been no “by your
leave” courtesy on his part either; he goes without consent—against
orders, even—and man’s ingenuity has as yet discovered no effective
means of keeping him off. This is not surprising when the rat’s
ability as a rope walker is considered. I have seen a rat gallop with
all appearance of enjoyment along an inclined electric cable from a
church steeple on one side of a street into the second story of a
hotel on the other. Others have been seen traveling along the
telephone wires from house to house, and on shipboard they frequently
have runways on small pipes along which they scurry in perfect
security. When a ship is fended off 6 feet from the dock and her gang
plank is lifted or guarded she is still freely accessible, because all
her mooring lines are only so many highways along which rats can and
do pass with ease and in perfect safety.

This fondness for ships and sea travel is shared by the various
species of the rat family, but the _Mus norvegicus_ has earned the
reputation of being the greatest traveler of them all. He almost
invariably predominated among those killed by fumigation on shipboard.
That he finds life on shipboard easy and the conditions satisfactory
is proved by the numbers that are destroyed from time to time by
fumigation. While in charge of the outgoing quarantine work in San
Francisco the chief engineer of a small lumber carrier called to book
his vessel for fumigation. The vessel was small, only 260 tons, and
carried nothing but lumber and her own ship’s stores, but the chief
declared she was overrun with rats, and to prove it showed where they
had eaten the patches from his shoes. He declared they robbed him of
his sandwich when he came off watch, and requested me to give her a
thorough fumigation. This was done. The next morning the agent of the
vessel phoned to ask how I measured rats, stating that on this vessel
they had collected “a barrelful and seven.” Three hundred and ten on a
little vessel of only 260 tons burthen.

On another vessel after one fumigation 100 were collected immediately
after fumigation, but a few days later, when the vessel was undergoing
extensive repairs, 425 others were found—a total of 525 on one small
vessel. These numbers are small, however, when compared with the
results obtained on others, i. e., on grain-carrying vessels. For
instance, a vessel was fumigated some years since in Bombay where
1,300 were destroyed at one time, and the _Minnehaha_, a new vessel
only nine months in commission, on fumigation in London, England, in
May, 1901, yielded a bag of 1,700 rats.

ADAPTABILITY OF THE RAT TO HIS SURROUNDINGS.

In addition to his qualities as a sailor and tight-rope walker, the
rat has the power of adapting himself to most unusual conditions and
surroundings. At the beginning of the outgoing work in San Francisco
it was urged that rats either could not or would not live on any part
of tank ships engaged exclusively in carrying oil, owing to the fumes
and vapors that permeated the entire vessel. This statement was
unquestionably correct for those compartments in which the oil itself
was stored or carried. It was not true, however, for the
superstructure of these vessels, for on one of the oil carriers 60
rats were found after one fumigation, and of the thirty or more
vessels of this class that were regularly fumigated in San Francisco,
although the odors of oil or gasoline were quite strong in the living
compartments, not one was found that did not harbor rats. Still more
remarkable, as illustrating the rat’s adaptability, was the fact that
from the large refrigerating plants which some vessels carried and in
which fumigation had not been practiced for a long time rats were
obtained that had grown a fur an inch and a half long to protect
themselves from the cold.

DAMAGE TO CARGO.

That rats on shipboard in any such numbers as mentioned above must do
much damage to cargo can not be doubted.

Inquiry as to the extent of this damage showed that there were no data
on the subject. That such damage was common and considerable, however,
was revealed by the fact, elicited by these inquiries, that nearly
every steamship company on both the Atlantic and Pacific took
precautions both to keep rats from getting on board and to destroy
them after they did. One example will show what damage may occur. The
British steamer _Gadsby_, on a voyage from India to Antwerp, covering
a period of twenty-nine days, had 44,000 out of 46,000 bags of wheat
cut by rats, with an estimated damage of $2,200.

The constant and almost universal presence, then, of rats on shipboard
can not be doubted, and if it could the results of fumigation,
wherever practiced with SO_{2}, would serve to settle the question,
for they are found under all conditions, even on the most unlikely
vessels.

How do these rodents gain access to a vessel? It has been the custom
to assume that they came on board from the docks over the side when
this was possible, and when it was not, as when the vessel was fended
off or stood too high out of the water, that they made use of the
gangways, mooring lines, hawsers, etc., as avenues of communication.
It is still the practice, therefore, in enforcing antirat precautions,
to compel the ship to fend off 6 feet from the dock, to wear fat
funnels on all lines, and to raise the gangway from the dock at night.
Just a word as to these precautions. The most practical fender is a
floating one made of heavy timbers either bolted together into a solid
frame, with the necessary cross braces bolted in, or made up of logs
or spars chained together. They should be long enough to distribute
the pressure of the vessel as the tide moves over a number of piers or
piles so that the weight does not bear, through the medium of these
fenders, on just one or two of the wharf foundations. Such a fender
will stay in position, will do no damage to the vessel, and no matter
how great the amplitude of the tide may be, will always remain below
the ship’s gunwale and can not therefore be utilized by rats as a
means to get on board. Large vessels require at least two. Small ones
need but one, and it was found in San Francisco, in the case of those
vessels changing their mooring several times daily, that this one
could be carried from wharf to wharf by the vessel without trouble or
delay simply by lashing it edgewise outside on top of the guard.

Funnels should be of heavy galvanized iron, circular in shape, and not
less than 36 inches in diameter. The spout of the funnel should be 3
inches in diameter and should be at least 18 inches long. The flange
of the funnel should be soldered to this 18-inch pipe at its middle so
that the spout projects 9 inches out of the funnel and 9 inches into
it. When the two halves of the funnel are brought together this spout
or tube is occupied by the line or hawser to be protected, and by
lashing this tube to the hawser the funnel is held in position and
prevented from lying down. Such a funnel should be put on every line
from the vessel to the dock, and when the tube does not fit the line
the latter should be parceled before the tube is lashed to it.

These, together with raising the gang plank from the dock at night,
make up the precautions ordinarily taken to prevent the rats from
getting on ships. As stated above, they are based on the assumption
that these are the common avenues of entrance. That these precautions
do much good can not be doubted, but in the writer’s opinion they do
not entirely cover the case, for there remains one other road of
ingress, one of the important, if not the most important, which these
precautions do not and can not block and through which rats constantly
get on board, and that is through the medium of the cargo itself.
There is at present nothing to prevent access in this manner to a
vessel and the route is so easy that there can be no doubt that whole
families of rats are carried on board in this way. In fact some
articles of cargo offer inviting harbors and homes to rats,
particularly when these articles have been stored for a time in
rat-infested warehouses. Among such articles of cargo may be mentioned
crockery or china packed in hay or straw or excelsior and loosely
crated; various articles of furniture packed in excelsior, wrapped in
gunny, and loosely crated; wheat, corn, oats, peanuts, or barley when
shipped in bags; and matting in hollow rolls when sewed up in gunny.
Any of these articles could easily become the home of even an entire
rat family after having been stored for a time prior to shipment in a
rat-infested warehouse. As a matter of fact, the last plague rat
discovered in San Francisco was found in a bag of peanuts on the third
floor of a warehouse.

That rats are thus carried on board is absolutely certain in my
opinion. In the recent antiplague campaign at San Francisco there were
ample opportunities for observations along this line, and in no other
way can the presence of rats in troublesome numbers on board certain
vessels be explained. These vessels were new, were freed from rats by
careful and repeated fumigation, and between these acts touched at no
wharves save in Honolulu and San Francisco, where constant antirat
precautions were observed. And yet on their second trip (about five
months after the fumigation had been discontinued) they were badly
rat-infested. Of course, by no means had all these rats been carried
on board in cargo, but the original patriarchs of the colony had,
after which, as is probably the case in all rat-infested ships, their
natural prolific characteristics did the rest.

In the same way, too, rats are carried from ship to shore and the
truth of Kitasatso’s aphorism that “wherever ships go, plague will
go,” at once becomes apparent, and any regulations to prevent the
introduction of such vermin and the plague which they may carry to be
effective must include the inspection of cargo to insure its freedom
from rats, this inspection to be made just before it goes on board.

The relation these rodents bear to plague and the part they play in
its transmission have been thoroughly discussed and set forth in
another article in this work. The work of Ashburton Thompson in
Australia and of the British Medical Commission in India was a
scientific demonstration that plague was primarily a rat disease
transmitted by fleas, while McCoy in the United States has gone
further probably than anyone else in demonstrating the manner in which
the flea does this work. The importance of this relation is emphasized
and the difficulty of ridding a port of pest infection is explained by
a fact, first observed so far as I know by Klein, of London, that rats
suffer from a chronic form of pest, not fatal, at least for a long
time, and during the course of which the rat may exhibit practically
his normal activity. This fact then, that plague is primarily a rat
disease and that it may occur in the rat in a chronic form, shows how
great the danger may be from their presence on shipboard, explains why
it is that where ships go plague will go, and emphasizes the
importance of destroying them on shipboard apart from the damage and
loss which their presence entails.

So important is this and so preeminent is the rôle played by the rat
in plague transmission and propagation that I believe regulations
should demand that all ships be disinfected at least three times, and
better still, four times, a year, for the destruction of rats. If this
precaution were taken, and if to it were added an inspection of cargo
at the port of embarkation to insure its freedom from rats, I believe
the disinfection of cargo could be entirely dispensed with. It is
infectious only in so far as it harbors rats, and if these are not
present disinfection, in my opinion, does as little good in preventing
plague as dipping ballast did in preventing yellow fever.

FUMIGATION.

Once the rat has gained access to a vessel, what is the best method of
getting rid of him?

There are several methods, all of which are effective if properly
used, and all of which depend on sulphur dioxide as the destructive
agent. The following are mentioned: Pot and pan, sulphur furnace,
Clayton system, and Marot system. A choice of one of these methods
will be determined by the cost, the rapidity of fumigation desired,
and the condition of the vessel, whether empty or loaded. No matter
which method is selected, to be effective the sulphur dioxide must be
simultaneously delivered to or generated in every compartment on the
vessel.

For an empty vessel nothing is so satisfactory as the pot and pan
method of generating the gas. It has the following advantages; is more
rapid than any other, is cheaper, is more effective, and is equally
applicable to the largest and the smallest vessel afloat. With a
sufficient number of pots and pans 3,500 pounds of sulphur can be
burned just as quickly as 100. Ten pounds of sulphur in each of 350
pots will be consumed just as quickly as will 10 pounds in any one of
that number, namely, in less than five hours, a fact which was
demonstrated over and over in the outgoing work in San Francisco.

At the beginning of this work it was thought a 2½ per cent gas with
three hours’ exposure would be sufficient. Practice proved, however,
that this was not effective and the strength of gas was increased to 3
per cent and the exposure to five hours which a test, extending over
twelve months and embracing over 3,000 vessels, proved to be ample.

The best pot in which to burn sulphur is 6 inches deep, has a flare of
6 inches—that is, the diameter at the top exceeds the diameter at the
bottom by that much, is from 16 inches to 24 inches in diameter at the
top and has four hemispherical legs about the size of half a billiard
ball. These pots when in use are set in a galvanized iron tub. These
tubs contain a little water, and are of a diameter 6 inches greater
than the top of the pot. The hemispherical legs of these pots will not
punch holes into the tub. The pots are filled with sulphur, which is
hollowed out into a little crater at the top, into which crater from 4
to 6 ounces of alcohol are poured and when all are ready a lighted
match is dropped into each little crater and the compartment is
closed.

In actual practice it was found that an exposure of five hours to a 3
per cent gas would not destroy all the rats in absolutely every case.
Some ships afford better hiding places than others, and on these an
occasional rat would escape. It was the custom, however, to fumigate
all vessels every thirty days and after the third fumigation, on
vessels that did not carry general cargo, no more rats were obtained,
though the fumigations were continued for a number of months.

On those vessels that carried miscellaneous general cargoes a few rats
were found after almost every fumigation. These vessels touched no
wharf from the time they left San Francisco until their return, except
for a short time in Honolulu, where adequate precautions were
observed, and it is difficult to understand how these rats got on
board if they were not carried on in cargo.

For vessels with cargo in their holds the pot and pan method is
dangerous owing to the possibility of fire. For these vessels one of
the other methods of generating the sulphur gas must be used. This
involves the use of an expensive plant consisting of a furnace,
cooling chamber, blower, or fan, and a system of mains and delivery
pipes by means of which the gas is delivered to the various holds and
compartments of the vessel. To be at all effective the gas must be 4½
per cent strength, with at least twenty-four hours exposure. The one
recommendation of such a system is its freedom from danger by fire. It
is too slow; the pipes, even where 6 inches in diameter, are liable to
clogging with sublimed sulphur, an inevitable result if the fans are
driven too rapidly, and it is not possible to do more than one or at
most two ships at a time. The inadequacy of such a method when
compared to the work done in San Francisco where we averaged over nine
vessels every day for almost fourteen months is at once apparent. Many
ships now carry their own disinfecting plants, by means of which not
only is sulphur dioxide generated and pumped into a compartment, but
at the same time also the air of this space is sucked out. This
principle is excellent, but in its application the machines used are
wholly inadequate, having a very limited sulphur capacity per hour and
equipped with delivery pipes in many instances only 2 or 3 inches in
diameter. It would be a matter of days to disinfect some of these
ships with the machines they carry. In San Francisco we again and
again used pots and pans to fumigate these vessels, including the very
compartments in which their own machines sat doing nothing.

The Marot system of generating the gas from compressed liquid sulphur
dioxide has in this country been found too expensive to apply to
vessels. Probably no system will effectually destroy all the rats on a
cargo-laden vessel.

SUMMARY.

To summarize then:

1. The rat is found on all vessels, sometimes in enormous numbers, and
is able to adapt himself to all sorts of conditions. He either gets on
board himself or is carried on in cargo. Owing to his seagoing
tendency, his distribution is world-wide.

2. On shipboard, to live he must do damage to either cargo or stores,
or both.

3. Plague is primarily a rat disease; it may exist in the rat in a
chronic form. Hence where ships go plague will go sooner or later.

4. To prevent the ingress of rats and the consequent spread of plague,
ships should observe antirat precautions, and cargo inspection should
be included in these.

5. At stated intervals, three or, better still, four times a year, all
vessels should be fumigated for the destruction of rats.

6. On empty vessels this can best be done by generating sulphur by the
pot and pan method.

7. On laden vessels some special apparatus must be used to generate
the gas. A longer exposure is required, at least twenty-four hours,
and the gas should be 4½ per cent strength instead of 3 percent. It is
extremely difficult by any method to kill all the rats on a
cargo-laden vessel.

THE RAT AS AN ECONOMIC FACTOR.

By DAVID E. LANTZ,

_Assistant Biologist, United States Department of Agriculture_.

INTRODUCTION.

The world has rightly learned to dread rats as disseminators of
disease, and recent efforts to rid cities of the pests have resulted
chiefly from sanitary considerations. Yet the material losses due to
depredations of rats are now, and always have been, a sufficient
argument for their destruction. The requirements of sanitation and
public health are slowly bringing to pass what economic interests
failed to accomplish, namely, a general recognition of the fact that
the rat is a standing menace to prosperity. To point out some of the
many ways in which rats inflict injury and the extent to which they
drain the resources of the people is the object of the present
chapter.

UTILITY OF THE RAT.

Do rats serve any useful purpose? With very slight reservation, the
question may be answered in the negative. There have been times and
places in which the rat’s work as a scavenger accomplished good, but
modern methods of garbage disposal are superseding the feeding it to
rats.

It was Robert Southey, the poet, who, nearly a century ago, humorously
suggested as the first three steps to eradicate rats—first,
introducing them as a table delicacy; second, utilizing the skins; and
third, inoculating them with a contagious disease.[BY] The last of
these plans is now receiving considerable attention from
bacteriologists, but the others, for obvious reasons, have been
neglected.

Footnote BY:

Omniana, vol. 1, p. 25, 1812.

It is true that under exceptional circumstances the rat has been a
source of human food. The principal instances on record were during
the siege of Paris in 1870, and during the siege of the French
garrison at Malta, 1798–1800, when food was so scarce that rat
carcasses brought high prices. Another was on board the ship _Advance_
during an arctic winter, when Doctor Kane attributed his entire
immunity from scurvy to his diet of fresh rats, of which none of the
other members of the party would partake.[BZ]

Footnote BZ:

Second Grinnell Expedition, vol. 1, p. 393, 1856.

The statement is often made in newspapers, and even in encyclopedias,
that in Europe, and especially in France, rat skins are extensively
used in the manufacture of gloves. The late Frank T. Buckland, about a
half century ago, made diligent inquiry in London, and through friends
in Paris and other places on the Continent, but found no confirmation
of such statement. He concluded that either rat skins were not used
for making gloves or the manufacturers were unwilling to acknowledge
such a use.[CA] Personally, the writer has been unable to learn of any
demand or market for rat skins at the present time. They are not
strong, and the fur is of inferior quality. The occasional finding of
one or more rat skins in the fur lining of coats is probably to be
explained by the fact that they are sometimes included in lots of
small muskrat skins (“kitts”) and overlooked by the buyer.

Footnote CA:

Curiosities of Natural History, first series, p. 83, 1857 (Reprint
1900).

DESTRUCTIVENESS OF THE RAT.

Rats inflict injury in a surprising number of ways, and before an
attempt is made to consider the magnitude of the losses due to these
animals a statement of the nature of their depredations should be
made.

DAMAGE TO GRAINS.

Cultivated grains are the favorite food of rats. The animals begin
their depredations by digging up the newly-sown seed. They eat the
tender sprouts when they first appear, and continue destroying the
plants until the crop matures. They then attack the grain itself, and
after harvest take toll from shock, stack, mow, crib, granary,
elevator, mill, and warehouse. When rats are abundant their
depredations amount to an appreciable percentage of the entire yield
of grain, and in exceptional cases whole crops have been ruined.

INDIAN CORN.

Probably this crop suffers greater injury from rats than any other in
the United States. To some extent the animals dig up newly planted
corn, but their injury to the maturing grain is far greater. They are
especially fond of corn in the milk stage, and often climb the upright
stalks and strip the cobs bare. In this way sometimes whole fields are
destroyed.

Corn in the shock is often attacked by rats, especially in parts of
fields adjacent to hedges, drains, or embankments that afford shelter
for the animals. A pair of rats often make a corn shock their home,
and soon destroy both grain and fodder.

Corn in cribs is often damaged by rats. Many cribs are built close to
the ground, and rats take up their abode under the floor. They soon
gnaw through the wooden barrier and have free access to the grain.
They shell the corn and eat the soft part of the kernels, wasting much
more than they eat. They carry the grain into underground burrows and
bring up moist soil from below, which in contact with the grain makes
it moldy and unfit for market or for feeding to stock. A number of
farmers have reported the loss by rat depredations of from a fifth to
a half of the contents of a large corn crib during a single winter.

An Iowa farmer, writing to an agricultural journal, relates the
following experience:

We had about 2,000 bushels of corn in three cribs to which rats ran,
and they ate and destroyed about one-fourth of the corn. Much of it
was too dirty to put through the grinder until it had been cleaned
an ear at a time. All the time we were poisoning and trapping the
rats. We killed as high as 300 rats in two days and could hardly
miss them. They destroyed more than enough corn to pay taxes on 400
acres of land.[CB]

Footnote CB:

Missouri Valley Farmer, April, 1907.

Throughout the United States, but especially in the West and South,
corn is often stored for months in rail or other open pens, to which
rats have free access. Often the loss in a single season would pay for
the construction of rat-proof cribs, or at least for wire netting,
that would fully protect the crop.

SMALL GRAINS.

Much has been written about the rat as a house and barn pest, but its
depredations in the fields have usually been overlooked. In some
localities the common rat, as well as the house mouse, swarms in the
fields, especially in summer, and subsists entirely upon the farmers’
crops.

Stacked grain is peculiarly exposed to rat depredations. In the United
States, although the cost of protection is small, rats are seldom
fenced away from stacks, and, if threshing is delayed, serious loss
results. Often, at the removal of a stack, large numbers of rats are
discovered, which have been living at the expense of the farmer. As
early as 1832 a farmer in Frederick County, Md., with the help of men
and dogs, killed 217 large brown rats from one stack of rye.[CC] In
England instances are on record of the killing of over a thousand rats
from one stack of wheat.

Footnote CC:

Am. Turf. Register, vol. 3, p. 632, August, 1832.

The destruction of feed by rats is a serious loss not only on the farm
but also in city and village. The feed bin or barrel is often left
uncovered and rats swarm to the banquet thus exposed. Small feeders
suffer greater proportional losses, for managers of larger barns
recognize the enormous drain and usually provide rat-proof bins, if
not rat-proof stables. When rats have access to a stable they take a
good share of the feed directly from the mangers, but the loss is
seldom noticed.