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.