Definition: Premature expulsion of non-viable fœtus. Synonyms.
Susceptible animals: cows, goats, sows, mares. Accessory causes: Ice
cold drinks at periods of ovulation, frozen aliments, ice cold bath or
rain storm, mechanical injuries, unwholesome fermentescible food,
indigestible foods, close stabling, heavy milking, early breeding,
inbreeding, stagnant water, ergot, smut, vegetable irritants or
ecbolics, constitutional diseases, irritation of generative organs,
death of fœtus, urinary calculi, odor of carcass or carrion,
contagion, experimental infection between cows, between mare and cow,
relation to omphalitis. Nocard’s streptococci and bacilli, Bang’s
bacillus with best growth in two distinct grades of oxygenation,
Galtier’s observations, bacterium of the Colon group in America,
infection of the calves (pneumonia). Various kinds of infectious
abortion. Acquired immunity, variable in different forms. Immunized
cow still infecting. Symptoms. Lesions. Abortion in mares.
Therapeutics. Prevention: Protection of a sound herd, guarantee with
purchase, government control, precautions with male or unimpregnated
female, with pregnant. Extinction in a herd, separation, disinfection,
disposal of abortion, manure, urine, disinfection of animal, of
genital organs, precautions as to service, new born, fields, ewes.
Disinfectants, subcutem or in muscles.
_Definition._ The premature expulsion of the product of conception
before it is viable out of the womb. Strictly speaking, a parturition in
which the offspring is so far matured as to be _viable_ is a _premature
parturition_, while if it is _non-viable_ it is an _abortion_. Vulgarly,
however, as applied to herds, the term is used for any early parting
with the fœtus. In this wider sense infectious abortion is _the
premature expulsion of the fœtus owing to an infectious catarrh of the
womb, transmitted from one animal to another by the transference of the
microbe_.
_Synonyms._ Infectious Abortion, Enzoötic Abortion, Epizoötic Abortion.
_Animals Affected._ Abortion is most common in cows, and less frequent
in ewes, goats, sows and mares.
_Forms and Accessory Causes of Abortion._ It was formerly supposed that
abortion in herds was mainly due to mechanical and chemical agencies
acting injuriously on the system, and in adopting the explanation of a
particulate, transferrable, infectious agent for the habitual widespread
forms of the disease, we should not forget these accessory causes, many
of which by themselves cause sporadic abortions without the intervention
of an infectious element.
The free _consumption of ice cold water_ by the healthy dam causes
active gastro-intestinal peristalsis and vigorous movements of the
advanced fœtus, which can be seen or felt in the right flank, so that
this is often resorted to, to determine whether the animal is pregnant
or not. If this is frequently repeated or carried to excess in
susceptible animals it will at times cause abortions. As in all other
cases of mechanical or physiological disturbance, this is most operative
at those periods of constitutional changes, which if the animal had been
unimpregnated would have brought about ovulation and œstrum.
The greedy ingestion of _cold aliments_, like _frozen roots_, or green
vegetation covered with _hoar frost_, may have a similar action, the
more so that such aliments are extremely fermentescible and liable to
cause tympany and undue pressure on the gravid womb.
Even without ingestion, exposure to _cold rain or snow storms_ or the
_plunging in ice cold water_ tends to produce excessive peristalsis and
fœtal movements and thereby prove injurious.
_Mechanical injuries_ to the abdomen as _crushing by a gate_, _kicks_,
_hooking with horns or tusks_, _hounding with dogs_, _riding of each
other when a cow is in heat_, are liable to produce congestions,
detachment of fœtal membranes, and even death of the fœtus.
Very _fermentescible foods_ like those following a wet season or _bad
harvest_, or those made of the leafy albuminous plants like lucerne
(alfalfa), sainfoin and clover, act injuriously in the way of causing
tympanies and compressions, but it must also be recognized that we are
here dealing with fodders abounding in bacterial ferments, and that some
of their products may act physiologically as ecbolics, even if the
bacteria themselves do not colonize the genital passages as infections.
_Insufficient food_ or very _innutritious forage_, too _close stabling_,
_heavy milking_, _early breeding_ (dam or sire), _inbreeding_, are
liable to lower the general stamina and throw the system more open to
the action of other factors.
_Stagnant_, _corrupt drinking water_ has been charged with causing
abortion, and the trouble has ceased when it has been withdrawn, but it
is difficult to estimate its value in different cases—disturbing
digestion, fermentation, poisoning, or introducing of actual infection.
_Ergoted grasses_ and _smut_ in maize, wheat or oats, have been often
charged with wide spread abortions, and though each has in turn been
administered in large and continuous doses without causing abortion,
this does not invalidate the many cases in which it manifestly had that
effect, nor does it show that obstetricians have been mistaken in their
almost immemorial trust in ergot as an ecbolic. It must be recognized,
however, that grown under different conditions, of sunshine and shade,
and harvested at different stages of its development, ergot varies
greatly in its physiological action, as it does also from having been
overkept and thus one specimen is effective or dangerous while another
is absolutely ineffective. The specific action of the alkaloids in
determining contraction of involuntary muscular fibre, is seen alike
when used medicinally and when acting as an accidental toxic agent in
causing spasms, nervous torpor or paralysis, delirium; gangrene of the
feet, tail or tip of the ear; or contraction of the womb and expulsion
of its contents. Like other agents mentioned ergot is at times an active
ecbolic when coöperating with other similarly operating agencies.
_Irritant vegetables_ of various kinds are to be dreaded. Such as act on
the bowels and kidneys, keeping up a constant diarrhœa and diuresis, are
quite liable to cause abortion in susceptible subjects. _Savin_, _tansy_
and _rue_ have obtained a bad reputation in this sense.
_Cotton root bark_ is an active ecbolic, but is not likely to harm
animals unless deliberately administered.
_Impaction of the rumen or manifolds_, and _obstinate constipation_ with
the resulting straining or compression must be named as an accessory
cause.
Severe _constitutional diseases_, especially the infectious fevers,
_aphthous fever_, _lung plague_, _rinderpest_, etc., are occasional
causes of abortion.
It may be brought about by direct irritation of the womb, as in
_ovariotomy_ or _dilatation of the cervix_, or again by _death of the
fœtus_ through _twisting of the umbilical cord_.
Where cattle are subjected to dry winter feeding, in the absence of
ensilage or roots, on the magnesian limestones, small _calculi in the
kidney_ are almost the rule in winter and the irritation caused by these
conduces to abortion.
Nor must mental influence be altogether ignored. Cows and even mares are
exceedingly sensitive to the smells of _decomposing animal matter_, as
seen every day in the vicinity of _abattoirs_, or in case the _carcass_
of one of their fellows has been opened, and not infrequently in
connection with _carrion_, and the occurrence of abortions after such
excitement has been frequently noticed. Cases are on record of specially
susceptible cows having had active labor pains, from being with another
cow at the time of parturition. Shepherds have noticed that violent
thunder storms have been followed by numerous abortions in the flocks.
_The Contagious Form._ Any of the usual causes of sporadic or accidental
abortion may coöperate with the true infectious element and give unusual
energy to it, yet it is of the utmost importance to recognize the
contagion as the essential cause in all cases in which it is present.
This can usually be done by a careful inquiry into the history of the
outbreak.
When a herd has been continuously healthy up to the date of the
introduction of a cow brought from a herd where abortion has been
prevailing, and when following her arrival, one after another of the
original members of the herd abort, without any apparent cause in the
way of change of feed, water, barn, stalls, or general management, the
evidence of the introduction of contagion by the cow in question is very
circumstantial and forcible. If pregnant cows standing next to the new
cow, or near to her, abort, the argument for contagion is still further
corroborated. If the trouble continues in the herd year after year,
attacking fresh animals some months after their purchase, the case
becomes still stronger.
Or if a cow from a healthy herd is sent to a bull, that has been allowed
to serve an aborting cow, and if the resulting pregnancy in the first
cow is terminated by abortion, and if this is followed by successive
abortions in the previously healthy herd, we may reasonably conclude
that we are dealing with the infectious form. If no other appreciable
cause for the trouble can be found we may reasonably conclude that this
was the channel for infection.
Or a bull is brought from a herd where abortions have taken place, and
some time after his arrival, the cows of the previously sound herd begin
to abort, the first cases being in those that the new bull has served.
The occurrence is manifestly the result of contagion.
Or a newly purchased cow aborts, and is disposed of in consequence, and
another cow, placed in the same stall, in due time aborts also, and
others follow in succession, especially those that stood next or near to
the stall in question. Everything points to an introduced infection.
An indefinite number of other exemplary cases might be adduced, each
varying from the last, but all agreeing in this, that the evidence of
infection stands out prominently and unmistakably. The infecting
material may have been carried by the tail, tongue, soiled stall,
gutter, rubbing post, fence or other object, yet the fact of contagion
can be demonstrated with reasonable certainty.
These conclusions have been repeatedly affirmed by actual experimental
transmission. The Scottish abortion committee found that healthy
pregnant cows often escape, though standing near or even next to an
aborting one, but that when a piece of cotton wool was inserted into the
vagina of an aborting cow for twenty minutes and then transferred to
that of a healthy one, the latter invariably aborted. Galtier found that
when the infecting vaginal mucus of the aborting cow was transferred to
the same passage of the healthy pregnant one, abortion took place in the
latter. He succeeded in conveying the disease in this way from cow to
sow, ewe, goat, rabbit and Guinea pig, and found that growth in the body
of the rodent intensified its virulence, so that it could then be
successfully inoculated on the mare, bitch and cat.
Bang subjected two cows, from healthy herds and three months pregnant,
to repeated injections of the products of the culture of his abortion
bacillus in serum glycerine bouillon. Three injections were made on
April 14, May 23 and June 4, and on June 24 one cow aborted. The other
sickened and when killed was found to carry a dead fœtus. Pure cultures
of the abortion bacillus were found in the fœtal membranes and liquids
of both animals.
_Casual Infections._ In a case which came under the observation of the
present writer, a family cow kept in a barn where no abortion had
previously occurred, was taken for service to a bull in a herd where
abortion was prevailing, and though she was only present at the latter
place for a few minutes, she aborted in the sixth month.
Another cow from the same aborting herd, was taken into another herd at
a distance of two miles, where abortion had been unknown up to that
time, and some months later the cow standing in the stall next to her
aborted. The remainder of this herd was sold soon after, so that the
further progress of the disease was not traced.
Tobiassen quotes the case of a cow from an aborting herd, which calved a
fortnight before the regular time. The calf was at once sent to another
farm where no abortion had occurred, and placed in the same building
with the pregnant cows, all of which later aborted. The outbreak thus
started lasted for several years.
Jansen as quoted by Sand, reports the case of a cow from an aborting
herd having been taken into a herd that had been previously quite free
from the disease. Soon after her arrival she aborted, and later, cows in
the same herd aborted. The owner kept the matter secret and sent his
cows to a neighbor’s bull for service, with the result that for two
years abortion prevailed among the cows served by this bull.
J. R. Jansen reports that a cow brought from an infected farm, for
fattening purposes, proved to be pregnant and finally aborted, and that
24 of the pregnant cows on the same farm aborted in the same year.
Mörck relates how a cow that had aborted a fortnight previously was
taken to a farm where abortions had never been known. She aborted during
her next gestation and so did the rest of the herd, 9 in number.
Christensen records the occurrence of a general abortion in a previously
healthy herd, members of which had been sent for service to the bull of
a neighboring aborting herd.
Nygaard reports that a bull from a healthy herd, but which had been
allowed to serve some cows from a neighboring infected herd, was sold to
go on a previously healthy farm, where he was put to 14 cows only. Of
these 12 aborted, and the complement of the herd, beyond the 14 cows,
put to another bull, remained well.
In each of these cases the environment of the animals and the conditions
remained the same, the one appreciable cause of the outbreak being the
contact with an animal from an aborting herd.
_Experimental Infection._ Braüer led the way by transferring in 11
instances the vaginal mucus of aborting cows to the vagina of healthy
ones. The resulting abortions occurred from the 9th to the 21st day
after inoculation. Lehnert repeated this on two cows, the abortions
taking place on the twelfth and twentieth days respectively. Trinchera
transferred the purulent vaginal mucus of an aborting cow to the vaginæ
of healthy ones, determining in the latter, in 9 to 13 days, abortion
attended by suppurating vaginal catarrh. He secured similar results by
using the material scraped from the surface of the chorion of an
immature fœtus.
The Scottish Commission (Woodhead, McFadyean and Aitkin) placed a
healthy pregnant cow in an aborting herd, and on two successive days
lodged in her vagina for twenty minutes a piece of cotton wool soaked in
the vaginal mucus of a recently aborted cow. Within a month abortion
threatened, and on the seventieth day a seven months calf was dropped.
In a second experiment a cow, six months in calf, was taken from a
healthy herd and placed in an aborting dairy herd and a quantity of
vaginal mucus from a cow that had recently aborted was injected under
the skin of the vagina. She calved prematurely at the end of the eighth
month of gestation.
Williamsen, while treating a herd for abortion, took a piece of the
afterbirth of one of the aborting cows and rubbed it on the vagina of a
healthy cow of his own, which had a habit of carrying her calf fourteen
days over time. Five days after she had premature parturition.
He took a fragment of the fœtal membrane from the cow just named and
rubbed it on the vagina of a pregnant cow condemned for tuberculosis. In
seventeen days the cow aborted.
Though not started as an experiment, the writer may name the general
extension of abortion from one or two cows in a tuberculous herd after
they had been tested with tuberculin. Cases of this kind are doubtless
much more common than has been supposed.
Kilborne and Smith developed suppurating vaginal catarrh in cows and
mares by inoculating them with the artificial cultures of bacilli
obtained from the vaginal secretions of aborting mares.
Turner made cultures from the ovaries of aborting mares, and others from
the genital organs of foals suffering from omphalitis, and produced
abortions in pregnant mares by injecting with the same.
_Pathology._ _Bacteriology._ Franck attributed the disease to
_leptothrix vaginalis_, but subsequent observers failed to substantiate
this.
The Scottish Abortion Commission isolated five different bacteria from
the abortion membranes and vaginal mucus, but failed to identify any one
of these as, by itself, capable of causing the disease.
Nocard found in the fibrino-purulent matter between the chorion and womb
in aborting animals a micrococcus occurring singly or in chains, and a
short, delicate bacillus isolated or in pairs. From the absence of evil
effects between pregnancies he opines that the germs grow in the
membranes only, and do not affect the womb nor the general system. He
recognizes, however, that they survive in the womb from one pregnancy to
another in the complete absence of these membranes.
Galtier, on the contrary, conveyed the disease variously by the
inoculation or feeding of the milk or abortion membranes to sheep, goat,
pig, rabbit and Guinea pig, and accordingly claims that the general
system of the pregnant animal is infected, and that the germs can be
conveyed through the blood to the womb. In deducing this from feeding
experiments he appears to make too little account of the ready infection
through proximity of the anus and vulva.
Chester, of Delaware Agri. Experiment Station, found in the fœtal
membranes of aborting cows a bacillus, which in form and habits of
growth closely resembled the bacillus coli commune. In the fermentation
test, however, it showed a marked difference.
Inoculated on rabbits it did not prove fatal. Injected into the vagina
of a healthy pregnant cow it caused slight catarrhal discharge for four
or five days, but the calf was carried to full time six and a half
months later.
Bang found in aborting cows, between the womb and fœtal membranes, a
considerable odorless, gelatinoid, liquid exudate, and some pus cells.
There was active catarrh of the uterine mucosa which often carried the
disease over into the next pregnancy. In the exudate he found a number
of very minute nonmotile bacilli (1 to 3μ), which stained readily with
aniline colors, excepting in a vacuole or nucleus which was less deeply
pigmented. This bacillus grew well in serum glycerine bouillon, and more
sparingly in serum-gelatine agar. In the latter it showed a remarkable
peculiarity which serves to identify it readily from other microbes, in
two successive zones of luxuriant growth at two different depths, with
an intermediate clear zone, in which little or no growth took place. It
seems to prefer a greater or lesser supply of oxygen (21 or 90:100)
without being able to adapt itself to the intermediate condition. As
already stated it produced abortion in the cow in 21 days after
injection into the vagina. It also induced uterine catarrh and abortion
in ewes, goats, rabbits, Guinea pigs and mares when injected into the
vagina. From the vagina it usually reaches the womb, but not always. In
several cases in which it was injected subcutem or intravenously it
caused hyperthermia, and was later found in abundance in the interior of
the womb and fœtal membranes, and in the bowels of the fœtus. The
microbe is, therefore, capable of living in the blood and affecting the
womb by whatever channel it may enter the system.
V. A. Moore and the present writer made a series of experiments at the
New York State Veterinary College. In the fœtal membranes and uterine
mucus of a number of cows, aborting in different parts of the State and
therefore long distances apart, we found a bacillus that in form and
culture-experiments closely resembles bacillus coli commune. This was
nearly always in pure cultures, and in the few cases showing other
microbes, these were only such as inhabit the healthy vagina. Our
bacillus was never found in the womb nor fœtal membranes of cows that
had calved at the full period in healthy herds. It agreed in most
respects with the bacillus found by Chester, but differed somewhat in
fermentation tests. It differed also in proving fatal to rabbits when
inoculated on these animals. Injected in the form of cultures into the
vagina in three old pregnant cows it continued to live on the mucosa,
producing more or less catarrh and muco-purulent discharge in the
different cases, yet all three carried the calf to full time, one having
calved on the 123d day after injection, the second on the 167th, and the
third on the 190th.
The results obtained at the Delaware College Experiment Station and the
New York State Veterinary College, do not differ so seriously, as either
one does from those obtained in Europe, by Nocard, Bang, and the
Scottish Abortion Committee. The facts that the same germs were found,
either in pure cultures, or exceptionally, along with the normal
microbes of the healthy vagina, in the womb, and fœtal membranes of
every aborting cow, that they were never found in the healthy cow which
had calved at full time, and that the generative passages were the seat
of a catarrh, alike in the cows that aborted and in those that were
inoculated with the abortion discharges, but did not themselves abort,
are all but conclusive that this microbe is the essential cause of the
abortion.
The single objection to this view, namely that the inoculated cows did
not abort is explained by the fact that in the New York abortions it is
the rule that the calf is carried six or seven months from the date of
impregnation (the date of the presumptive infection) to that of
abortion. It is to be further borne in mind that our experimental cows
were old, and may have passed through the disease before and become in
some measure immune, that they were dry during the experiment, and were
subjected to no extraneous excitement that would predispose them to
abort. The presumption is that had the experiments been started earlier
in the gestation, the abortion would have come in due time. The microbe
maintained its hold on the mucosa and continued to advance up to and
beyond parturition.
Another distinction of the European abortions, is in the presence of the
microbe in European form in the digestive organs of the calf, and that
the viable calves of infected cows are liable to die of intestinal
disorders a few days after birth. Galtier, the Marquis de Poncius and
Pry insist strongly on this. On a farm on the estate of the Marquis,
where abortion had prevailed for twenty years, the calves of infected
cows show at birth, or very shortly after, symptoms of broncho-pneumonia
and of a complication of nervous disorders. They are breathless, wheeze,
discharge from the nose, cough, scour, have convulsions or other nervous
trouble. A large proportion of such calves die; and their lungs are
found in part red, consolidated and devoid of air and the bronchia
contain a muco-purulent product. Lesions denoting inflammation of the
serosæ of the lungs, liver and intestines are common. This coincidence
of a fatal disease in many of the surviving calves is exceptional among
the aborting herds of New York.
In noting the evidence of a wide difference between the prevalent
American and European forms of abortion in cows, one should be prepared
to go farther, and accept if need be, still other distinctive forms in
each of the two continents. Any catarrhal condition of the uterine
mucous membrane, is a recognized hindrance to conception, and cause of
abortion, and we must recognize that the forms of invasion of the womb
by pus microbes are as numerous as there are irritant germs capable of
living in the membrane. The question as to how many of these can produce
contagious abortion is to be determined by the susceptibility of the
membrane to irritation by each germ, and whether the latter can retain
all its power of survival and virulence in passing from one animal to
another. The presumption is, therefore, in favor of a variety of forms
of contagious abortion, each due to its own specific microbe or
microbes, rather than of a single unvarying type of the disease. In some
the affection appears to be a purely local one (American), the microbe
being confined to the genital or genito-urinary mucosa, whereas in
others the microbes (Bangs’, Galtier’s, etc.) live also in the blood
producing a general infection.
Two great types at least have been demonstrated in Europe and America.
Whether future investigation shall show the presence in one of these
continents of the types as yet only known in the other, remains to be
seen. If the particular forms should turn out to be limited to different
continents we are at once confronted with the necessity of an
international sanitary quarantine, and inspection. Matters are bad
enough now in our dairying districts, but if we are to be open to the
importation of new types of abortion, which do not mutually immunize
against each other, but which may be taken one after another in
succession through a series of years, they may easily become
incomparably worse.
_Acquired Immunity._ The question of persistent abortion year after
year, in the same animal, is most important. If a first contagious
abortion entails a second, a third, a fourth and a fifth in the same
animal, in as many successive years, then manifestly the preservation of
such animal is a most wasteful economy, altogether independently of the
danger of her transmitting the infection to healthy stock. If, however,
she herself becomes immune after a first or second abortion, it may be
profitable to retain her for milk production or breeding, provided that
she can no longer infect susceptible cows with which she must come in
contact.
_Acquired immunity_ of the individual cow is the rule after one or two
abortions caused by the microbes with which we are at present most
familiar. There are exceptions to this rule due to special nervousness
and excitability of given cows, which tend to an indefinite repetition
of the abortion, under the stimulation of pregnancy, of the continued
presence of the microbe, or of some local disease (tubercle, tumor,
parasite, etc.) of the ovary, womb or peritoneum. Yet statistics show
that this only applies to a small proportion of cows and these the most
nervous and excitable. The tendency toward insusceptibility to the
deleterious action of the germ, which may still be present, is in the
cow as a rule greater than the disposition toward a nervous encrease of
the susceptibility. The difficulty of reaching a conclusion on this
point depends on the fact that stockowners very commonly dispose of
aborting cows, and as the freshly bought cows are usually attacked
sooner or later, it is too confidently assumed that the old cows also
would have continued to abort had they been retained. Many years ago,
however, observant New York dairymen had noticed that the same cow
rarely aborted over three years in succession, and in the great majority
of cases not over two. The owner of a large herd, who has had much
experience with the disease, assures me that the rule has been, that a
cow did not abort with him a second time. The continuous abortion in a
herd was mainly among newly purchased cows and others that had not been
previously attacked, including heifers carrying first calf. The same is
in a measure true of the European abortions.
Nocard says that after three to five years there is an acquired
immunity. Only heifers and the cows that have been recently bought in,
abort.
Penberthy, speaking of England, says that in case of repeated abortion
in the same cow, the calf is carried longer each successive year until
it comes to its full term.
Sand, in his symposium of the experience of Danish veterinarians, says
it is quite exceptional that a cow should continue to abort, but
outbreaks of abortion disappear spontaneously if no new cows are brought
in.
Bang refers to a herd of 200 head of which 83 aborted in their first
pregnancy, and of these only 20 aborted in the second, while 7 failed to
breed. Counting the latter as having aborted, this amounts to less than
one-third, while over two-thirds of the cows that aborted in the first
gestation carried the calf to full time.
Paulsen quotes the case of a herd of 16, 7 of which aborted after
service by a bull in an aborting herd. One of the seven was sold, but
the remaining six all went full time in the following year.
Mörck records the case of a herd of 16 cows, the majority of which
aborted in the same year. All the aborting cows were sold and fresh ones
purchased. Next year the new stock aborted together with some of the
cows that had been held over. He continued this course for eight years
without any improvement, and then decided to keep the aborting cows as
well as the others. In two years the affection disappeared from the
herd.
Such small herds, in which all become early infected, and in which there
is no further opportunity for the infection of susceptible animals (cows
not yet infected, heifers in first gestation, new purchases), furnish a
better opportunity than do large herds, to trace the acquirement of
tolerance.
In a question of this kind, one must allow for variations in the
different types of abortion caused by various microbes, but in the forms
with which we are familiar in Europe and America, the acquired tolerance
of the individual can be counted on with great confidence. It has indeed
been largely traded upon by purveyors of antiabortion nostrums who
promise to cure the individual cow, to which alone their drugs are
administered. Two evils result: the stock owner’s money is paid for that
which unaided, nature would have accomplished for him; and attention is
withdrawn from the real necessity of the case, the prevention of the
infection of freshly introduced animals. The nostrum vender thus secures
for himself a growing market, as the yearly production of fresh cases in
the same herds, appears to demand a constant use of the agent which
appeared to work so well in the earlier ones.
_Immunized animal still infecting._ The cow that no longer aborts is
not, therefore, a safe member of a herd. As an individual animal she has
become resistant to the pathogenic influence of the germ, she is
invulnerable to it to the extent that she no longer aborts, but her
system and generative passages have acquired no such active bactericidal
power over the microbe as to lead to its speedy destruction. The genital
passages, once colonized, continue to be a field of growth of the
bacillus long after its power to cause abortion in that particular
animal has passed. Analogous cases can easily be quoted from the field
of pathology. The horse that has apparently recovered from dourine still
conveys the disease to others with which it has sexual congress; the
recovered syphilitic person is by no means eligible for marriage; the
recovered pig continues to carry the infecting swine plague bacillus in
its air passages. In short, it is the rule that the immunized animal can
with safety to itself carry a germ that readily infects its nonimmunized
fellows.
In the case of infectious abortion this is one of the most dangerous
elements, as the apparently healthy recovered cow receives no attention
in the way of separation and disinfection, but is allowed to spread the
infection through the bull that serves her in common with other cows and
by being sold into new and healthy herds.
_Symptoms._ Contagious abortion sometimes takes the form of temporary
sterility, the animal taking the male at frequent intervals, but failing
to conceive. If conception takes place, the abortion is usually deferred
until the fœtus has attained a considerable development—in cows till the
third or seventh month; in mares till the fourth or ninth month; in ewes
or sows till the tenth week.
Often times premonitory symptoms are entirely unobserved. Usually there
may be detected some heat and enlargement of the mammæ, with a decrease
in the milk yield, or a serous modification of the milk as in colostrum.
Still more striking is a muco-purulent discharge from the vulva—opaque,
white or yellow—in marked contrast with the perfectly clear, transparent
mucus which appears in œstrum. The discharge may be densely white (in
mares) or reddish, and may be accompanied by some swelling of the vulva
and redness of its mucosa, which is dull, rough and granular, or even
the seat of a papillary eruption. There is rarely hyperthermia or other
constitutional disturbance, and in some cases the abortion is only
discovered by the finding of the fœtus and its membranes in the gutter
or pasture. The membranes are, however, not unfrequently retained,
becoming offensively putrid. In other cases a muco-purulent discharge
persists for a length of time, insuring sterility so long as it lasts,
and causing ill health and emaciation. The fœtus is usually born dead.
The _lesions_ are confined to the generative organs. Bang, found an
odorless, dirty yellow, flocculent, slimy and more or less watery
exudate between the chorion and uterine mucosa involving the connective
tissue between the chorion and arachnoid so as to render it thick and
friable. These conditions were well marked in the French and English
cases, and perhaps somewhat less so in the American, which are
habitually slower in reaching the abortion. Bang found the uterine
catarrh with the characteristic bacillus in cases in which the calf had
been carried to full term, exemplifying the local presence and culture
of the bacillus without the usual abortion outcome. The bacilli were
occasionally, though not always, found in the body of the fœtus, and in
some cases the dead and mummified fœtus was found in the womb, which had
not been stimulated to its expulsion. He even found the bacillus in the
mummified fœtus, and still virulent, after an apparent seclusion of
seven months.