_Definition_: Structure of lesion. Nomenclature. History, smallpox,
sheeppox, cowpox, horsepox. Animals susceptible: Man, sheep, cow,
goat, horse, pig, dog, buffalo, camel, monkey. Microbiology: A pure
contagium, particulate contagium, cocci, sporidium vaccinale.
_Horsepox_: Early history, means of infection. Symptoms: Vesicles on
lips, on heels, concretions, treatment. _Cowpox_: Relation to
horsepox. Causes. Relation to smallpox. Observations of Ceely,
Fletcher, Thiele, Klein, Martin, Reiter, Chauveau, influence of
vaccination, of spring parturitions, of infected stables. Symptoms:
Incubation, seat and nature of vesicle, inoculations for vaccine.
Diagnosis from aphthous fever, rinderpest, eruption of mastfeeding,
false cowpox, streptococcus eruption. Duration. Course. Prognosis.
Treatment. _Sheeppox_: Synonyms. Definition. Pathogenesis: Sheep,
goat, ox, dog, pig, horse. Forms: Discrete, confluent, hæmorrhagic.
Distribution. Causes. Contagion; extends on air; experiments on blood;
wool, hides, litter, buildings, yard, parks, railway cars, boats,
clothes, manure, wine, milk, men, dogs, cats, birds, vermin, flies.
Receptivity. Overcrowding, filth, starvation, neglect, wars, commerce.
Recovered sheep. Disinfectants. Incubation 4 to 7 days; conditions
affecting. Symptoms: Hyperthermia, general disorders, rigors,
anorexia, skin blush on parts devoid of wool, red points, papules,
vesicles, pustules, desiccation. Successive crops. On eye, nasal
mucosa, mouth, pharynx, intestines, lungs. Confluent cases. Lesions.
Prognosis. Mortality. Depreciation. Treatment. Prevention: By
segregation, slaughter and disinfection; by ovination. Technique of
ovination. Resulting immunity. _Sheeppox in Goat_: Danger of infection
to sheep. _Goatpox._ _Swinepox_: From man, sheep, goat. Symptoms.
Forms: Discrete, confluent. Susceptibility of young. Treatment.
Prevention. _Dogpox_: From man; from sheep. Other eruptions in dog.
Symptoms: Fever, flushed skin, red points, papules, vesicles,
pustules. Discrete. Confluent. Treatment. Prevention of infection of
man and sheep.
By the generic name _Variola_ is understood a febrile malady attended by
a characteristic eruption on the skin, at first papular, then becoming
vesicular and finally pustular. The structure of the vesicle is so
characteristic that it may be taken to indicate the variolous eruption
as found in man and a variety of the domestic animals. The first
indication of the lesion is the appearance on the skin of fine points of
congestion like fleabites. This is followed by active diapedesis and
proliferation of cells in the papillary layer and rete mucosum,
constituting the nodule or pimple stage. In smallpox this is so firm and
definitely outlined that it has been compared to the presence of a shot
in the skin. As the proliferation of cells increases these form in
separate clusters or groups, isolated from each other by septa or walls
largely made up of the epidermic cells. In the next stage, therefore,
when exudation takes place the lymph accumulates in the spaces occupied
by the clusters of growing cells, and is found in a series of chambers
more or less perfectly separated from each other, so that to evacuate
the whole vesicle, each minute sac must be punctured independently. The
vesicles thus differ from others caused by ordinary irritants in that
each is chambered, instead of forming one common undivided sac, which
may be emptied by a single puncture. In the next stage, when suppuration
ensues, the septa usually undergo liquefaction, so that the liquid
occupies one individed cavity in each pustule. For this reason the
central depression seen in the larger vesicles (cowpox) in their early
stage tends to disappear in the pustule. It may reappear later in the
resulting scab. Desiccation, scabbing and desquamation complete the
course of the affection, a distinct _pit_ being left as a result of the
destruction of the superficial layer of the dermis.
_Nomenclature._ The term _variola_ is believed to come from the Latin
varius (variegated, spotted) and _pox_ from the Saxon pock (pouch). The
specific names, drawn from these tongues sustain this view: As, _variolæ
vaccinæ_, _cowpox_, _kine-pox_; _variolæ equinæ_, _horsepox_; _variolæ
ovinæ_, _sheeppox_; _variolæ caprinæ_, _goatpox_; _variolæ suillæ_,
_swine pox_; _variolæ caninæ_, _dog pox_. The term _smallpox_, (_petite
verole_) is deduced from the small size of the vesicle as compared with
that of cowpox, just as the same has originated the term _smallpox_ in
sheep.
_History._ Variola has undoubtedly existed from very ancient times.
Moore found it referred to in Chinese records of 1122 years before
Christ, but it was only clearly described early in the tenth century by
Rhazes an Arabian physician. Gregory, however, found the name _variola_
in Latin manuscripts in the British Museum of a much earlier date. The
early epidemics of small pox have usually extended from the east, and
the disposition has been to refer its origin to the crowded communities
of central Asia, but nothing is certainly known as to such origin and
the lack of definite recognition and description cannot be taken as
implying that the disease did not exist. The extension of small pox to
America in 1520 was distinctly traced to a sick negro slave landed in
Mexico, and the way in which it swept the continent killing the Indians
by tens of thousands, speaks strongly for its prior absence and the
extraordinary susceptibility of the hitherto unaffected Indian races.
The variolæ of animals are not recorded until later, the mildness of the
forms attacking cattle and horses, and the lack of close observation of
the diseases of sheep furnishing a reasonable explanation. We must pass
over as uncertain the _lues ovium_ of Thomas Wallsingham, (Historia
Anglicana), imported in a _rotten_ Spanish ewe in 1274, and which
prevailed for 25 years destroying nearly all the sheep of the kingdom,
also the reference to the “pockes” of sheep in Chaucer’s “Pardoners’
tale” as highly uncertain. Laurent Joubert in his work on the “_peste_”
mentions _sheep pox_ as prevailing in 1567, and Rabelais speaks of it as
prevailing in France in 1578. It prevailed in Padua in 1649, in Venice
in 1664, 1672, and 1674 (Bottani), in Italy in 1690 (Ramazini), in
Germany in 1687–8 (Stegman), in England in 1711, in Hungary in 1712, in
France, Italy, etc., in 1714 (Kanold), in Venice and Bohemia in 1719
(Bottani), in Saxony in 1720, in Venice and France in 1723–24 (Bottani,
Astruc), in Thuringia in 1725, in Siberia in 1771 (Pallas), and in
Persia generally at the beginning of the 19th century (Bruce). Great
Britian, long protected by her insular position, was infected by sheep
from Germany in 1847 and again in 1862. Under ovination the first
invasion prevailed for four years causing wide spread destruction; under
strict separation based on thermometry, the second lasted but four
months.
_Cowpox_ has existed in England for centuries, but it has only attracted
general attention since the introduction of vaccination by Jenner in
1796. _Horsepox_ has existed concurrently with cowpox, the infection
being habitually transferred by the hands of the milkers from horse to
cow and vice versa. Jenner found it so common in the Valley of
Gloucester, that he considered it as the habitual source of cowpox.
Sacco recognized it at the beginning of the 19th century, Hertwig in
Berlin in 1830, Röll in Vienna in 1855, and Bouley and others later in
different parts of Europe.
_Animals Susceptible._ Variola in some form affects man, sheep, cattle,
horses, goats, pigs, dogs, buffaloes, camels and monkeys.
_Microbiology and Infection._ It has long been well established that
variola is due to contagion alone. The habitual dread of contact with a
smallpox patient, shows the general appreciation of the danger of
contagion, and the many epidemics, started by the introduction of a
smallpox patient and thereafter spreading from that as a centre,
together with the long continued immunity of certain insular or
trans-oceanic countries illustrate this. One of the most striking
examples is the immemorial immunity of the New World until the landing
of the variolous slave in Mexico in 1520, and the immediate, rapid and
destructive spread of the disease among the native tribes. Sheeppox
offers a no less striking example. Prevailing for centuries in Asia and
Europe, its extension to a new district was always the manifest result
of the movement of infected sheep; England remained immune until her
first invasion in 1847, and the second in 1862, in both cases the source
was easily traced, and the disease completely extinguished by the
destruction of the infection in its circumscribed area; the more distant
sheep raising countries, America, North and South, Australia, Tasmania,
New Zealand, South Africa, in the absence of importation of infected
sheep remain free to the present time. For horsepox and cowpox the
demonstration is more difficult as limited outbreaks, have occurred at
intervals in different localities, traceable more or less clearly to
infection from vaccinated persons, yet often mistakenly attributed to
spontaneous developments of the disease. Before the days of Jenner
however it prevailed habitually in certain dairying districts
(Gloucestershire), and I can point to localities in New York, in which
the infection is manifestly laid up in the stables, and the disease
develops yearly in the heifers coming into milk for the first time and
in newly purchased cows, that have not been previously exposed.
The contagion varies greatly in force in the different forms of variola,
the milder horsepox or cowpox, requiring actual contact (inoculation)
while in smallpox and sheeppox, infection may take place at some
distance from the patient (in sheep over 200 yards).
A particulate infecting material was demonstrated by Chauveau, who
filtered the virus and inoculated the filtered liquid without effect,
while the solids retained on the filter invariably produced the disease.
The identity of the microbe of variola has been much discussed. Guttmann
and Grigorjew found in the lymph a coccus (Staphylococcus albus
variolæ), Ruete a very motile diplococcus, and others streptococcus, but
in cutaneous lesions it is very difficult to exclude such elements.
Pfeiffer, Guarnieri, Van der Loeff, Wasielewski and others have drawn
attention to small protoplasmic bodies (manifestly protozoa) found in
the vaccine lymph, and which appear to be the infecting agents.
Wasielewski cultivated these on a rabbit’s cornea to the 48th
generation, and from the last successfully inoculated a calf and several
children.
Funck finds this _sporidium vaccinale_ constantly in the vaccine lymph
and surrounding tissue, as a refractile, amœboid, spherical organism
(spore) 1 to 3μ in diameter, and, less abundantly, a round or ovoid
spore cyst 25μ. These cysts are either smooth or uneven like a
raspberry, and have a single or double contoured membrane. They are
easily stained with Sudan III. Examined in hanging drops they are seen
just under the cover glass, not on the surface of the drops. Larger
flattened bodies found in the lymph, with many included spores are
manifestly epithelial cells. Copiman cultivated the organism in
glycerinated collodion capsules in the peritoneal cavity of rabbits and
dogs, producing zoöglœea masses staining peripherically with methylene
blue, and which caused typical vaccinia in calves. He found the same
elements in variola of man.