Synonyms. Definition. Geographical distribution, Argentina, France,
etc. Causes: bacillus; intravenously, etc., youth, verminous
affections, low condition. Bacteriology: ovoid bacillus with polar
stain, bleached by Gram’s solution, ærobic, nonmotile. Symptoms:
Chronic form in summer, diarrhœa, arched back, stiffness, emaciation,
flattened wool, segregation, impaired or depraved appetite, shedding
wool, anæmic skin, dependent dropsies, sunken eyes, weak small pulse,
temperature variable—elevated, nasal and buccal discharge, weakness,
paresis, dulness, torpor, lung symptoms, arthritis. Diagnosis: from
distomatosis and strongylosis. Acute form with high fever,
constitutional disorder, colics, diarrhœa, death in 24 to 36 hours,
subacute form. Lesions: black blood, congestions, and general
petechiæ. Lungs, liver, kidneys and spleen, congested, swollen.
Subacute cases have lighter blood, and lesions. Chronic cases anæmic,
blood diffluent, lymph glands enlarged, congested; connective tissues
and serous cavities dropsical, gastric, intestinal and hepatic worms,
spleen shrunken. Mortality: great in acute, less in chronic.
Prevention: segregation, exclusion of all sheep from unknown or
suspected flocks, antiseptic dip and quarantine for new purchases,
expose a few as a test; cleanliness, disinfectants, avoid watershed
from infected lands, wide range, outdoor life, generous diet, remove
weak, emaciated, anæmic. Immunization. Treatment.
_Synonyms._ Pasteurellosis Ovina. Infectious Pneumo-Enteritis.
_Definition._ An infectious febrile affection of the sheep, chronic or
acute, characterized by dulness, stiffness, or paresis, anorexia,
thirst, disorder of the breathing and digestive organs, black diffluent
blood, petechiæ, reddish effusions in the serosæ or connective tissue,
and congestive or inflammatory lesions of the lungs, liver, kidneys and
intestines. The presence of a cocco-bacillus (diplococcus,
strepto-cocco-bacillus, pasteurellosa) in the lesions is especially
characteristic.
_Geographical Distribution._ Though Lignieres first demonstrated this as
a bacteridian disease in the Argentine Republic, he was, after his
return, able to identify the same affection in the flocks of almost
every department of France, in newly imported English Lincolns and
German Merinos, so that there can be little doubt that the malady exists
in all or nearly all countries engaged in sheep husbandry, though it has
been usually attributed to parasitisms of the lungs, liver or alimentary
canal alone.
_Causes._ The essential cause is manifestly the bacillus, which
Lignieres has isolated, cultivated in vitro, and successfully inoculated
intravenously in the sheep, which he also infected by feeding the pure
cultures. Intravenously it proved fatal to Guinea pig, rabbit, pigeon,
chicken, rat, mouse, horse, ass and ox. Yet many other accessory causes
must be admitted as operating in different cases.
_Youth_ shows the greatest susceptibility whether the victim be mammal
or bird. So marked is this influence that the principle sufferers are
lambs just weaned or yearlings. Yet mature animals, that are debilitated
from any cause, also fall victims. The measure of immunity usually
noticed in mature sheep may well be attributed to a previous mild and
non-fatal attack of the bacillus.
_Verminous affections_ are undoubtedly predisposing causes, hence, the
common practice of attributing the malady to the worms alone. This again
in part explains the susceptibility of the young which so often harbor
worms to a dangerous extent. It seems to matter less what worms are
present than, that they are in sufficient numbers to greatly deteriorate
the health. It is noticeable, however, that those worms that make
breaches in the mucosæ, have been noted as infesting the victims of this
malady. In the stomach worms sent from Argentina, Railliet identified
Strongylus Contortus, S. circumcentus, and S. instabilis and in the
duodenum S. filicollis and S. Curticei. These, like the distomata often
found in the liver, are blood suckers and not only render the animal
anæmic, but make numerous perforations to act as infection-atria. The
various lung worms, encysting themselves in the air sacs and determining
local congestions may act in the same way, opening channels for the
entrance of the microbe.
_Low condition_ or a _low tone_ of health from any cause predisposes.
Old, worn out animals, ewes in lamb, or those just lambed, sheep that
have been shut up and denied proper exercise in winter, those on poor
feeding and perhaps nursing twins, those that have suffered from any
debilitating disease of any kind are especially obnoxious to a dangerous
attack.
_Microbiology._ The microbe, which Lignieres found in the pulmonary
lesions, is one of the colon group of pathogenic bacteria that have been
classed together as _pasteurella_. It usually appears as a very minute
ovoid bacillus which stains promptly and deeply at the poles in fuchsine
or gentian violet, leaving a clear median part, so that it seems a
_diplococcus_. It bleaches readily in Gram’s solution. Its form varies
in different culture media sometimes showing long _bacilli_, and
sometimes _streptococco-bacilli_, but the usual and characteristic
appearance is that of a _cocco-bacillus_, and to this it constantly
returns. The microbe is ærobic and nonmotile (the slow zig-zag motion
sometimes seen does not seem to be automatic). In peptonised bouillon it
produces opacity in 18 hours, or in simple bouillon in 24 to 48 hours,
the best temperature being 100° F. Gelatine plate cultures are slow
because of the compulsory low temperature, yet in 36 to 48 hours it
forms pale blue, translucent, round colonies the size of a pin head. It
never liquefies. In coagulated blood serum it forms only a thin
transparent pellicle hardly visible, and there is no growth on potato.
_Symptoms: Chronic Form._ In Argentina, Lignieres observed the disease
especially during the hot summer months (December to May), and after
weaning in the lambs. This may be from the marked change of food, from
the greater activity of microbian life at this season, from the
exhausting effect of the heat, or from a combination of two or more of
these conditions. It appears alike in the sheepfold, and on the open
prairie. In considerable flocks the symptoms may be at first overlooked,
so that the death of several sheep may be the first thing to draw
attention. Then a certain number are found to scour, arch the back, walk
stiffly, lose condition, and have the wool flattened and devoid of yolk
(_clapped_ wool). The sheep may be dull, lagging behind its fellows, or
lying apart by itself, ruminating infrequently and for shorter periods
than natural, and there may be inappetence, or depraved appetite (eating
earth), though some eat well to the end. Irregular and at intervals
capricious appetite is a frequent condition. When caught and examined,
the wool is easily torn out, the muscles are soft and wasted, (the leg
muscles may have practically disappeared), the bones stand out at all
points, the skin is pale, thin, bloodless and devoid of its subcutaneous
fat, (paper skin), there may be œdemas along the ventral aspect of the
body, pitting on pressure, and between the branches of the lower jaw
(poked), the eyes are sunken, the conjunctiva may be puffy and
œdematous, but like the muzzle and mouth they are pale and anæmic and
the pulse is small, though the excitement may have roused cardiac
palpitations. The temperature varies from time to time often reaching
105° or 106° F. There is liable to be a muco-purulent discharge from
nose and mouth especially noticeable during drinking. As the disease
advances the subject becomes weak, paretic, dull and stupid, it remains
down without interest enough to seek food, though still eating if it is
brought to it. The head is usually rested on the flank, and the animal
often lies so for days in a state of semi-stupor without disposition or
ability to rise, paretic or paraplegic. Auscultation may sometimes
detect a mucous râle or crepitus, and percussion a flatness of sound
over some part of the lung. Chronic arthritis is an occasional symptom.
_Diagnosis._ The symptoms closely resemble those of distomatosis or
strongylosis, and the disease is often complicated with one or more of
these, so that it may become difficult to judge how much is due to the
microbian infection and how much to the helminthiasis. The presence,
continuously or intermittently, of the hyperthermia is almost
pathognomonic of the operation of the microbe.
_Acute Form._ This has been particularly observed in the ewe just after
lambing, when the system is especially susceptible to microbian
invasion, and little able to cope with it. There are hot ears, nose and
feet, temperature of 104° to 106° F., accelerated pulse and breathing,
anorexia, ardent thirst, deeply congested mucosæ, colicy pains, pawing
the ground, frothy or bloody diarrhœa, arched back, pendent head, ears
and eyelids, muscular trembling, albuminous urine, plaintive cries, dark
red vaginal discharge, muco-purulent or glairy nasal discharge, and
death in 24 to 36 hours. Such animals may be in fair condition or even
fat, no time having been allowed for emaciation.
In other cases death may be delayed for three or four weeks, with the
same general symptoms, only less marked. In such cases, pregnant ewes
are likely to abort, and the lambs are born dead, or prove weak and
listless, and die when a few days old. Some have too little energy to
suck; others suck heartily but perish all the same on the second or
third day, after diarrhœa, thirst, hyperthermia, prostration, and
stupor.
_Lesions._ These vary according to the type. In the _rapidly fatal
cases_ there is dark colored blood, with congestion of the serous and
mucous membranes, which, together with the skin and often the solid
tissues, are covered with petechiæ, and even circumscribed hæmorrhages.
The lungs, liver, kidneys, spleen, and many of the lymph glands are
congested and swollen, seeming at times of a black hue as if
blood-saturated. The lesions, indeed, indicate an acute septicæmia.
In _cases that have survived three or four weeks_, the morbid changes
are slighter, the blood is brighter in tint, and the congestions less
deep in color, ecchymoses may be especially confined to the heart,
abomasum and small intestines, which may also show hæmorrhages.
Enlargement and congestion of the lymph glands are the rule, while
pulmonary consolidation and gastro-intestinal mucous inflammations are
frequently found. As in the more acute types the urine is albuminous.
In _chronic cases_ the anæmia is prominent. The clot is soft, relatively
small, elastic and black, the serum is relatively very abundant and
pale. The red globules are greatly reduced in numbers, and there are a
number of giant cells which stain deeply as in chlorosis. The lymph
glands are usually enlarged, softened and slightly congested but rarely
the seat of blood extravasation. The tissues generally are pallid, soft
and shrunken. There is a marked absence of subcutaneous and
intermuscular fat, while the connective tissue is more or less
infiltrated with a transparent, watery lymph. The serous cavities
usually contain more than the normal amount of fluid, transparent or
straw-colored, and with few globules or granules. Congestions and even
shreds of false membrane are sometimes present on the serosa. In some
cases the lungs and bronchia are the seat of inflammatory exudates,
causing nodular consolidations of from one-half to one inch in diameter.
Not unfrequently the lungs show strongylosis as the fourth stomach shows
strongylus contortus, the small intestines strongylus filicollis, tæniae
(expansa, fimbriata, etc.), the large intestines æsophagostoma
Columbiana, and tricocephalus affinis, and the gall ducts distoma
hepaticum and distoma lanceolatum. In these chronic cases the spleen is
usually shrunken, and the liver firm, sometimes even cirrhotic.
_Mortality._ The acute cases are usually fatal. Those that assume a
chronic form, if free from local lesions in important organs, well-fed,
and, above all, kept in the open air, and changed to a different
pasture, tend largely to recovery.
_Prevention._ The propagation of the infection from animal to animal is
slow and somewhat uncertain, and when introduced by the purchase of a
new ram or other animal, it may take a considerable time to affect the
stock extensively, but for this reason, and because an apparently sound
sheep may harbor the germ, it is difficult to oppose it successfully by
segregation. All the same, it is desirable to take all possible
precautions against its advent, and among these, the exclusion of
strange sheep from noninfected pastures and flocks. When the time comes
to make an outcross from the home strain, the ram must be selected not
only for his pedigree and individual qualities, but no less for the
soundness of the flock from which he is taken. If the lambs of that
flock have been decimated by disease, the best blue blood, and most
faultless form should not tempt the flockmaster. He should be rejected
in favor of one taken from a flock that is above suspicion. It matters
little if it can be plausibly argued that the mortality came from worms
of the lungs, liver, or digestive organs; these in themselves may soon
ruin any flock, but they, too, often coexist with the microbe of
infectious septicæmia, and, when this is the case, they prepare the
system and open a way for its invasion.
New purchases should not only be selected from apparently sound and
guaranteed stock, but they should be passed through an antiseptic dip on
arrival, and then if possible quarantined in a special enclosure until
they shall have proved their freedom from infection. A valuable ram may
be placed with some lambs or yearlings in close quarters to ascertain
whether he has brought the infecting matter with him. If all escape
after some months the presumption is that he is sound. Perfect
cleanliness of the fold should be maintained, and disinfectants may be
freely used in it.
The water supplies should be watched, rejecting streams that have
drained sheep-pastures where there have been marked losses of lambs and
ewes. Water from deep wells without any surface leakage is to be
preferred.
When new stock (ram, ewes, lambs) are of necessity mixed with the sound
herd, a wide range, an open air life, and abundant dietary must be
secured. The system that is full of strength and vigor can better resist
the microbe and even throw it off entirely, whereas the weak, confined
subject succumbs. For the same reason, the weak, emaciated and
debilitated subjects should be at once separated from the sound flock,
and kept in a special enclosure, in the open air, on a rich diet. Should
they harbor worms, this seclusion is even more imperative. (See
parasites of lungs, liver, stomach and bowels).
Lignieres advocates immunization by serum prepared on the Pasteur
method, but, as he has not divulged the exact technique of its
preparation, it is impossible as yet, to give this an unqualified
endorsement. It has this in its favor that the mature sheep, in full
vigor of middle life, though in an infected area, usually resist the
infection, while the young, old, debilitated and verminous suffer.
Opposed to it are these considerations that are recognized by Lignieres
himself;—1st, The acquired immunity is not perfect, as shown by
occasional relapses in sheep that have survived a first attack; 2d, The
serum inoculation is not only useless, but dangerous in animals that
already harbor the germ; I may, add 3d, Any acquired parasitism or
debilitating disease may tend to break down the immunity and prostrate
the system under the infection. Lignieres advises that the serum
treatment should be restricted to the new born lambs in infected herds,
or herds in infected areas. The first three or four weeks after birth
are to be preferred for the operation, though failing this it may still
be ventured on, up to a few days before weaning. The longer it is
delayed the greater the danger of a preëxisting infection, and of
untoward results from the new access of infecting material, on the back
of an infection which varies so extremely in its pathogenic potency.
Even among the new born lambs, Lignieres would restrict the serum
therapy to the strong, robust and healthy, and, if they survive the
resulting fever, would repeat the _treatment_ after the hyperthermia has
ceased. No satisfactory treatment of the disease has been made. An open
air life, a generous diet, and a course of iron, and bitters will,
however, be of use in serving to improve health, digestion and vigor, to
solicit a better production of red globules, and to enable the patient
to survive the period of anæmia, prostration and debility. Antiseptics
like quinia, the sulphites and the iodides might be used as adjuncts.