Alleged identity with ague. Geographical distribution. Points of
difference from ague. Causes: low, damp, undrained, inundated
localities, hot seasons; inoculation, congenital. Symptoms: restless,
drowsy, stiff, shivering, hyperthermia, tremors, cough, frothy, rusty
expectoration, excited breathing and pulse, anorexia; puffy,
petechiated eyelids; epiphora; dyspnœa: albuminous, yellow or red
urine with casts: hæmoglobinæmia: colics, constipation, fœtid
diarrhœa. Death in a few hours to 6 days, or months. Lesions:
reduction in blood globules, crenation, watery blood: petechiæ:
enlarged, blood-gorged liver and spleen; congested, swollen, softened,
kidneys; congested lungs with extravasations: in chronic—anæmia,
dropsies, lung hepatization and suppuration. Prevention: keep
susceptible horses from low, infected lands from June to November and
from their water: protect from insect enemies. Treatment: quinia
sulphate or bromide, hot baths, etc.
Cadeac and others describe an intermittent or remittent febrile
affection of the horse, as identical with ague, and due, they allege, to
the presence in the blood of the _plasmodium malariæ_ of Laveran.
_Geographical Distribution._ It has been observed on the low marshy
grounds of Sicily, the Danube bottom lands, Algiers, Tonkin, Madagascar,
Soudan, Senegal and Cochin China (Dupuy, Lenoir, Pierre, Colin). Dr.
Gelston informs me that in the American cavalry in the Philippines
extensive losses are sustained from this disease.
_Microbiology._ The causation of the disease is attributed to the
_plasmodium malariæ_, which is carried by the Anopheles and inoculated
in the skin of man, in malarious regions at night, but we are confronted
with the difficulty, that accepting the alleged identity, the disease in
the horse should be coextensive with that occurring in man. Yet we have
in the New World many areas characterized by the all but universal
prevalence of intermittent fever in man, and at the same time by its
entire absence in the case of the equine races. It may further be
considered that protozoa, found in the red globules of birds, were at
one time considered identical with those of malarious fever, but have
been demonstrated to be entirely different so far as pathogenesis is
concerned. There is every presumption that the protozoa of the red
globules found in the horse in this disease are also distinct
pathogenically.
Laveran has sought in vain for his plasmodium in the blood of the
affected horses, while Pierre found in the blood globules of the Soudan
victims refrangent, crescent shaped bodies, thickened and staining
deeply in the centre, which in his opinion represented the growing
hæmatozoa of Laveran. Gelston found the rounded and crescent shaped
forms abundant in the red globules. The disease in the horse is said to
be conveyed by direct contact, which would again distinguish it from
intermittent fever of man. If the protozoön is the cause, and not a mere
sequel or attendant on the disease of the horse, the indications are
that it is peculiar to the equine race and distinct from the germ of
human malaria.
_Causes._ Like malarial diseases in man, it is confined to low, damp,
undrained or inundated localities, and shows in the hot seasons when the
surface dries out. The elevated plains and tablelands which are
habitually dry or well drained are exempt. Cadeac alleges that infection
is usually inhaled in the floating dust. The mortality of Algerian
horses taken to the Soudan is 90 per cent., while but 25 to 35 per cent.
of the native horses in the Soudan or in Senegal suffer. This difference
is manifestly the result of the survival of a comparatively immune
strain of blood, or of immunity resulting from a previous invasion.
Subcutaneous inoculation on a soliped failed, while transfusion of blood
from the affected horse to a sound mule produced the disease. It is also
claimed that it is transmitted from the affected mare to the fœtus in
utero, which showed characteristic visceral lesions after birth.
_Symptoms._ Premonitory symptoms of restlessness, drowsiness, or
stiffness, are followed by violent shivering, elevation of temperature
(104° or 106° F.), muscular tremors, rapid breathing, hacking cough with
expectoration of frothy mucus, tumultuous heart beats, and small
irritable pulse. There is complete anorexia, an opaque, infiltrated,
petechiated, mahogany colored, conjunctiva, epiphora, and sometimes
blood extravasations into the vitreous. The lungs may become intensely
congested, with rapid, panting breathing, dyspnœa, a frothy, rusty
expectoration, and extended head and limbs. This may prove fatal in a
few hours. Otherwise there may be remissions of the fever and dyspnœa at
somewhat irregular intervals. Sooner or later are observed urinary
changes, the liquid becomes albuminous, yellow, or red, or it shows
distinct casts. These indicate the destruction of the red globules and
the escape of hæmoglobin. In other cases there are slight colics and
constipation alternating with a greenish yellow fœtid diarrhœa. The
early nervous prostration and drowsiness may merge into vertigo, or
paralysis. Vertigo is a very prominent feature in the Philippine cases
(Gelston). The skin which, at first, may often be pricked without
response, sometimes becomes tender, itchy and congested, with erection
of the hairs and the formation of pustules, or small abscesses like
hazelnuts.
_Course. Duration._ In very acute cases death may take place in a few
hours. More commonly illness lasts from three to six days. In certain
instances it becomes chronic and may last two or even three months, the
early congestion of the mucosæ giving place to pallor and anæmia with
advancing emaciation, dropsies and finally marasmus and death.
_Lesions._ These are mainly in the blood, red globules being distorted,
crenated, massed in clusters and greatly diminished in numbers so that
the liquid appears thin and watery. The mucosæ, internal organs and
serosæ are petechiated and the serous cavities contain a yellowish
serum. A yellowish tint pervades the white tissues generally. The liver
is congested, virtually gorged with blood, enlarged and yellow or
yellowish brown. The spleen is greatly enlarged, blood gorged, and shows
irregular, rounded swellings indicating the seats of extravasation of
blood. In some instances rupture has taken place. The kidneys are
congested, enlarged, softened and of a brownish red or black color, with
circumscribed extravasations especially in the cortical area. The lungs
are violently congested, with many areas of blood extravasation, and
they do not collapse when the chest is opened. The heart is petechiated,
with a parboiled aspect and shows areas of commencing necrosis or fatty
degeneration.
In the chronic form the watery condition of the blood is remarkable, the
serous cavities (peritoneum, pleuræ, pericardium, arachnoid) contain
considerable effusion, dropsical conditions of the limbs and dependent
parts of the body are common, the lungs show hepatization and minute
centres of suppuration, and other viscera may show fibroid degeneration.
_Prevention._ It is advisable to keep susceptible horses from the low
marshy infected lands from June to November and to avoid especially
water that is drawn from such lands. It is not needful to take the stock
to any very marked elevation provided the land is dry and free from wet
or swampy areas. The native horses or those that have been long in the
marshy district and have thus secured a partial immunity may profitably
replace the more recently imported and susceptible horses during the
dangerous summer months.
The habit of the paludal protozoa of securing their transfer from one of
the higher animals to another through the intermediation of insects in
which they undergo developmental changes essential to their survival,
would further suggest the adoption of especial precautions against such
invertebrate enemies in the affected district.
_Treatment._ Pierre employed quinia sulphate or bromide 45 grs. in
distilled water 1 oz., intravenously, Gelston, creolin, subcutem. Hot
baths, 95° to 100° F. are claimed to lower the temperature and
contribute to the arrest of an attack. Other complications are treated
according to indications.