incubation which may extend from ten days to one and one-half months, at
the end of which time the onset of the disease is manifested by a rise
of temperature. If uncomplicated, the infection runs a chronic course,
terminating in death in from two months to one and one-half years, or
even longer. The probability of the virus being spread by an
intermediate host, such as flies, mosquitoes, internal parasites, etc.,
is now receiving careful investigation.
From experiments already conducted it appears that this disease,
formerly supposed to be confined to Manitoba and Minnesota, is more or
less prevalent in Kansas, Nebraska, Colorado, Wyoming, Montana, North
Dakota, Virginia, Texas, and New York. It also occurs in Europe, having
been reported in Germany under the name of infectious anemia and in
France as infectious typho-anemia.
_Symptoms._--The disease is characterized by a progressive pernicious
anemia, remittent fever, polyuria, and gradual emaciation in spite of a
voracious appetite. It begins to manifest itself by a dull, listless
appearance and by general weakness, the animal tiring very easily. This
stage is followed closely by a staggering, swaying, uncertain gait, the
hind legs being mostly affected. There is also noted a weakness and
tenderness in the region of the loins, and at the same time the pulse,
though weak, stringy, and intermittent, increases in rapidity and may
run as high as 70. The temperature may rise to 103 deg. F. or higher,
remaining high for several days, and then dropping to rise again
irregularly. Toward the end of the disease the temperature occasionally
remains persistently high. The horse may improve for a time, but usually
this improvement is followed by a more severe attack than the first.
Venous regurgitation is sometimes noticed in the jugular before death.
The quantity of urine passed is enormous in some cases. Death finally
occurs from exhaustion or syncope.
The blood shows a slight decrease in the number of white blood cells,
while there is a gradual but marked diminution of red corpuscles, the
count running as low as 2,000,000 per cubic millimeter, the normal count
being 7,000,000. If the blood is drawn from such an animal, the
resulting red clot will be about one-fifth of the amount drawn.
Occasionally a slow dripping of blood-tinged serum from the nostrils is
observed as a result of this very thin blood oozing from the mucous
membranes. Petechiae, or small hemorrhagic points, are sometimes noticed
on the nictitating membrane and conjunctiva, while paleness of the
visible mucous membranes of the nose and mouth is usually in evidence,
although they may have a yellow or mahogany tinge. Often a fluctuating,
pendulous swelling may appear on the lower lip, point of elbow, sheath,
legs, under the belly, or on some other pendent portion, especially late
in the disease, which is indicative of poor circulation, thinning of the
blood, and consequent loss of capillary action.
_Lesions._--After death the carcass is found to be very much emaciated
and anemic, the visible mucosa being very pale. This marked absence of
adipose tissue makes the skinning of the animal a difficult task.
Subcutaneous and intermuscular edema and hemorrhages are frequently
observed, although in many cases it is remarkable to see how few
macroscopic lesions may be present. The predominating and most constant
lesion is probably the petechiae, so often observed in the muscle or on
the serous membranes of the heart. The heart is generally enlarged and
may be the only organ to show evidence of disease. In other cases the
lungs may be studded with petechiae, with a serous exudate present in the
thoracic cavity. In addition to the petechiae already noted, the
pericardial sac generally contains an increased quantity of fluid. The
abdominal cavity may show peritonitis and a hemorrhagic condition of the
intestines, which probably result from overfeeding in consequence of the
ravenous appetite. The liver, although usually normal, sometimes
presents a few areas of degeneration. The spleen is at times found to be
enlarged and covered with petechiae. The kidneys may appear normal or
anemic and flaccid, but microscopically they usually show a chronic
parenchymatous degeneration. The lymph glands may be enlarged and
hemorrhagic.
_Diagnosis._--The diagnosis of the disease is not difficult, especially
in advanced stages. The insidious onset, remittent fever, progressive
emaciation and anemia, unimpaired or ravenous appetite, staggering gait
and polyuria are a train of symptoms which make the disease sufficiently
characteristic to differentiate it from other diseases affecting horses
in this country. The peculiar relapsing type of fever, the great
reduction in the number of red blood cells, and the absence of
eosinophila are sufficient to differentiate it from the anemias produced
by internal parasites, while it may be readily distinguished from surra
by the nonsusceptibility of cattle and by the great ease with which the
trypanosoma may be found in the latter affection.
_Prognosis._--The prognosis of the disease is very unfavorable.
Veterinarians in different sections of the country where it is prevalent
report a mortality of 75 per cent or even higher. Recovery takes place
only when treatment is begun early or when the animal has a long
convalescent period.
_Treatment._--The treatment of the disease has so far been far from
satisfactory. The iodid, permanganate, and carbonate of potash have been
used. Arsenic, axytol, quinin, and silver preparations have been
suggested, but all have been uniformly without success. Intestinal
antiseptics have been resorted to, and the results are encouraging but
not altogether satisfactory. Symptomatic treatment seems to be the most
dependable. For instance, Davison, of this bureau, was able to reduce
greatly the mortality from this affection by giving an antipyretic of 40
grains of quinin, 2 drams of acetanilid, and 30 grains of powdered nux
vomica four times daily. In the late stages, with weak heart action,
alcohol should be substituted for acetanilid. Cold-water sponge baths
may be given, and in addition frequent copious injections of cold water
per rectum, which has a beneficial effect in reducing the temperature
and in stimulating peristalsis of the bowels, which, as a result of the
disease, show a tendency to become torpid during the fever. Purgatives,
on account of their debilitating effect, should not be given unless
absolutely necessary, but laxatives and easily digested feeds should be
given instead. Not infrequently a dirty yellowish tinge of the visible
mucous membranes has been observed, in which cases 20 grains of calomel
in from 2 to 4 drams of aloes in a ball, or 2-dram doses of fluid
extract of podophyllin, may be given. Following the subsidence of the
fever, a tonic should be administered, composed of the following drugs
in combination:
Arsenious acid grams 2
Powdered nux vomica do 28
Powdered cinchona bark do 85
Powdered gentian root do 110
These should be well mixed and one-half teaspoonful given to the
affected animal at each feed.
As in the case of all other infectious diseases, the healthy should be
separated from the sick horses and thorough disinfection of the infected
stables, stalls, litter, and stable utensils should be carried out in
order to prevent the recurrence of the disease. As a disinfectant the
compound solution of cresol, carbolic acid, or chlorid of lime may be
used, by mixing 6 ounces of any one of these chemicals with 1 gallon of
water. One of the approved coal-tar sheep dips may also be used to
advantage in a 5 per cent solution (6 ounces of dip to 1 gallon of
water). The disinfectant solution should be applied liberally to all
parts of the stable, and sufficient lime may be added to the solution to
make the disinfected area conspicious.
Investigations are now in progress with a view of producing a vaccine or
serum that will protect horses that have been exposed to the disease.
SURRA.
By CH. WARDELL STILES, PH. D.
_Professor of Zoology, United States Public Health Service._
Surra is not known to occur in the United States, but it is more or less
common in the Philippine Islands and India. It is caused by a
microscopic, flagellate animal parasite, known as _Trypanosoma evansi_,
20 to 34 mu long by 1 to 2 mu broad, which lives in the blood and destroys
the red blood corpuscles. In general the disease is very similar to and
belongs in the same general class with tsetse-fly disease, or nagana, of
Africa and mal de caderas, of South America.
Surra is a wet-weather disease, occurring chiefly during or immediately
after heavy rainfalls, floods, or inundations.
Surra attacks especially horses, asses, and mules, but it may occur in
carabao, camels, elephants, cats, and dogs, and has been transmitted to
cattle, buffaloes, sheep, goats, rabbits, guinea pigs, rats, and
monkeys. No birds, reptiles, amphibia (frogs, etc.), or fish are known
to suffer from it. It attacks both male and female animals, young and
old. Australian breeds of horses and white and gray mules are said to be
more susceptible than animals of other breeds and color.
Surra in equines and camels is said to be an invariably fatal disease,
but cattle occasionally recover from it. There is no history of a
definite onset of the disease, and the condition is progressive, usually
with a number of relapses. The period of incubation may vary somewhat;
in experimental cases it is from 2 to 75 (usually 6 to 8) days,
according to conditions. The duration varies with the species of animal
attacked, their age, and general condition. The average duration in the
horse is reported at less than two months, though some cases may
terminate fatally in less than one to two weeks.
_Method of infection._--All evidence now available seems to indicate
that surra is strictly a wound disease, namely, that the parasite may
enter the body only through a wound of some kind. Apparently by far the
most common method is through wounds produced by biting flies whose
mouth parts are moist with the infected blood of some animal bitten by
the same flies immediately before biting the healthy animal. Crows may
also transmit the infection by pecking at sores on a diseased animal,
soiling their beaks with blood, and transferring this infected blood to
a healthy animal. Likewise, if a scratch is made on a horse and then
infected blood is rubbed on the scratch, the horse will become diseased.
If, in experiment, infected blood is fed to a healthy animal, the latter
may contract surra in case it has an abraded or wounded spot in the
mouth; but if no part of the lining of the alimentary canal is wounded,
infection does not take place. Thus dogs and cats may contract the
disease by wounding the lining of the mouth (as with splinters of bone)
while feeding on the carcasses of surra subjects. All available evidence
indicates that under normal conditions of pregnancy the disease is not
transmitted from mother to fetus.
There is a popular view that surra may be contracted by drinking
stagnant water and by eating grass and other vegetation grown upon land
subject to inundation, but there is no good experimental evidence to
support this view: Probably the correct interpretation of the facts
cited in support of this theory is that biting flies are numerous around
stagnant water and in inundated pastures; hence, that a great number of
possible transmitters of the disease are present in these places.
_Symptoms._[7]--The invasion of this disease when contracted naturally
is usually marked by symptoms of a trivial character; the skin feels
hot, and there may be more or less fever; there is also slight loss of
appetite, and the animal appears dull and stumbles during action; early
a symptom sometimes appears which may be the first intimation of the
animal's indisposition, and which, as a guide to diagnosis, is of great
importance; it is the presence of a general or localized urticarial
eruption. If the blood is examined microscopically, it may be found to
present a normal appearance; but in the majority of cases a few small,
rapidly moving organisms will be observed, giving to the blood, as it
passes among the corpuscles, a peculiar, vibrating movement, which if
once observed will not easily be forgotten. If the parasite has not been
discovered in the blood for several days, the symptoms mentioned above
may be the only ones noticed, and, as a rule, when treated with
febrifuges, the horse quickly improves in health and the appetite
returns. This condition does not last for more than a few days, when the
animal is again observed to present a dull and dejected appearance, and
on examination well-marked symptoms are found; the skin is hot, the
temperature more or less elevated--101.7 deg. to 104 deg. F.; the pulse full and
frequent--56 to 64 beats a minute; the visible mucous membranes may
appear clean, but the conjunctival membranes, especially those covering
the membrana nictitans, are usually the seat of dark-red patches of
ecchymosis, varying in size in different animals. There is more or less
thirst and slight loss of appetite; the animal eats its grain and green
grass, but leaves all or a portion of the hay with which it has been
supplied. At the same time there are slight catarrhal symptoms present,
including lacrimation and a little mucous discharge from the nostrils.
Occasionally at this period of the disease the submaxillary glands may
be found enlarged and perhaps somewhat tender on manipulation. One
symptom is markedly absent, namely, the presence of rigors or the
objective sign of chilliness. In addition, it will be noted that there
is some swelling and edema of the legs, generally between the fetlock
and the hock, which pits but is not painful on pressure, and in case of
horses there may be also some swelling of the sheath at this stage of
the disease. When the fever and concomitant symptoms have declared
themselves for a short period, one thing becomes especially noticeable
in every animal attacked, namely, the rapidity with which it loses
flesh. If the blood has been examined microscopically during the second
period of fever, at first a few parasites will have been observed in it,
which day by day increase in number and reach a maximum, where they
remain for a varying period, or at once suddenly or gradually disappear
during the period of apyrexia. After the fever and the accompanying
symptoms have for the second time been present for a few days--the
period varying from one to six--the animal is found to have lost the
dull, dejected appearance and to look bright. The temperature has fallen
and, in some cases, has attained normal or even subnormal limits. The
visible mucous membranes are clean, and the conjunctival petechiae begin
to fade; the pulse, however, will be found to be weak and thready in
character, but the appetite excellent, and, in fact, if it were not for
the loss of flesh and slight edema of the legs, there would be little to
show that the animal was sick. Unfortunately, however, this condition
does not continue for any great length of time, for again the
temperature is elevated; in the course of a few hours the thermometer
registers a still higher degree, the animal is dull and dejected, and by
the following day the visible mucous membranes present a yellow tinge;
large ecchymoses, dark in color, appear on the conjunctival membranes,
the action of the heart is irritable, the pulse full and quick, or at
times intermittent, and regurgitation may be observed in the jugulars,
the breathing is quickened, and the individual respirations are shallow.
On watching an animal in this condition it may be noticed that it takes
seven or eight very short inspirations, followed by a much more
prolonged and sonorous one; at the same time the breathing is more
abdominal than thoracic in character. On examination of the legs it will
be found that the swelling and edema have increased considerably, and
that on the under surface of the abdomen, where previously it was
confined to the sheath, it has now commenced to spread forward along the
subcutaneous tissue between the skin and the muscles. During the whole
of this time the appetite will have varied little, and the evacuations
will be only slightly, if at all, altered in character. In the blood a
repetition of the previous events takes place, the parasites make their
appearance and increase to a maximum and again suddenly or gradually
disappear, according to the length of the fever period. These periods,
alternating with and without fever, may go on for a considerable time.
The progress of the disease is variable and greatly depends upon the
condition of the animal attacked, the weak one succumbing very rapidly,
but each return of the fever brings with it, as a rule, an increase in
the severity of the symptoms. There is increased yellowness of the
membranes, fresh crops of petechiae on the conjunctiva, a collection of
gelatinous material at the inner angle, which at times becomes red in
color from an admixture of blood, and which on microscopic examination
is found to contain a varying number of the surra parasites; increased
swelling and edema of the extremities and abdomen, which now extends
between the fore limbs and up the chest. During this time the wasting
has been steadily progressive, especially of the muscles of the back and
those surrounding the hip joint and the glutei.
Toward the termination of the disease it will be noticed that an animal
is disinclined to move, and when made to do so there is manifest loss of
power over the hind quarters, somewhat simulating a slight partial
paralysis, and the hind quarters of the animal reel from side to side.
In connection with this it may be noted that frequently there is
paralysis of the sphincter ani and a dilated condition of the anus.
These symptoms taken together point to some interference with the normal
functions of the spinal cord in the lower dorsal and lumbar regions, and
are probably owing to pressure caused by an exudation within the spinal
membranes. In many cases shortly before death the heart's action becomes
exceedingly violent, shaking the whole frame at each beat, so that the
sound can be heard at some distance from the animal. In some of these
cases the animal may suddenly drop dead; in others the emaciation and
weakness become so pronounced that it falls to the ground, and, after a
short struggle, succumbs to the disease. In other cases, again, the
animal falls to the ground and appears to be suffering from acute pain,
struggles violently, sweat covers the body, and respiration is very
hurried. The struggles soon exhaust the patient's strength, and for a
time it lies quiet; soon, however, the struggles commence again,
continuing until death occurs. In some cases the appetite is voracious.
The symptoms of the disease as observed in experimentally inoculated
animals are as follows: Twenty-four hours after the subcutaneous
injection of a small quantity of surra blood, in the great majority of
cases, a small circumscribed and somewhat raised swelling is noticed at
the seat of the inoculation. After forty-eight hours the tumor has
increased in size and is accompanied with some edema; it presents a
certain amount of tension of the parts involved, and is generally tender
on manipulation. These conditions continue to increase, until by the
fourth day the tumor may measure 3 or 4 inches in; one direction by 2 or
3 in the other, and raised to the extent of an inch or an inch and a
half above the surrounding tissues, or in some cases the tumor presents
an almost circular form throughout. It will be also found that, if the
tumor is firmly grasped, it is not fixed, but can be lifted up from the
subcutaneous tissue. According to the nature and quantity of the
inoculated blood, these symptoms rapidly present themselves, and either
attain a maximum or are retarded until, varying from the fourth to the
thirteenth day, the tumor at the seat of inoculation will be found to
have lost a certain amount of its tension and tenderness. From this date
the swelling and edema gradually begin to grow less, until finally,
after a period of 10 to 14 days, the only sign left of the former
swelling is a slight thickening of the skin over the point of the
injection; but at the moment when the tension and tenderness of the
parts at the seat of inoculation become suddenly decreased a symptom of
the utmost clinical importance takes place, namely, at that moment the
parasite of surra enters the blood of the general circulation.
The temperature on the day of inoculation, and, in fact, for several
days afterwards, may remain normal in character, there being only a few
degrees difference between the morning and evening observations. In
other cases there may be a slight rise from the first evening, and a
gradual progressive rise until the swelling at the seat of inoculation
shows signs of reduction in size, when the temperature generally takes a
decided rise again, and may attain 104 deg. or 105.8 deg. F. This elevation will
last a varying period of from two to six days, and on the day following
its onset the ordinary symptoms of fever will be noticed, and in
addition there will be petechiae on the conjunctival membranes,
lacrimation, a slight mucous discharge from the nose, and in severe
cases some edema of the lower portion of the legs, and perhaps of the
sheath in horses. At the termination of the period of fever the
temperature will be found to have fallen to normal or nearly so; the
animal will present a brighter aspect, and there is every appearance of
its return to health; in a few days, however, the animal again appears
dull and half asleep; the temperature is elevated, a relapse takes
place, and a repetition of all the symptoms in the primary paroxysm,
including the reappearance of the parasite, is observed.
_Diagnosis._--A diagnosis may also be established by the
complement-fixation or agglutination tests with the sera from suspected
animals. This, however, can be carried out only in laboratories and
requires special facilities for its execution.
_Treatment._--No satisfactory treatment is known. Intravenous injections
of Fowler's solution of arsenic give temporary relief, but relapses
occur. In view of the great economic importance of this disease, it
would not be advisable to attempt to treat any sporadic cases should
they occur in this country. On the contrary, the animals should be
slaughtered immediately and their carcasses promptly burned.
OSTEOPOROSIS OR BIGHEAD.
By JOHN R. MOHLER, V. M. D., _Assistant Chief, Bureau of Animal
Industry_.