Swine Erysipelas

SWINE ERYSIPELAS, swine redwater, bacillary swine erysipelas, an infectious disease affecting primarily pigs between 3 months and 1 year of age. The causative agent is Bacillus erysipelatis suis, or Bacillus rhusiopathiae suis, discovered by Löffler in 1882; it is one of the most delicate bacteria. It occurs in the form of elongated rods or threads and is classified by some authors as streptotrichs or trichomycetes; it is easily stained with aqueous aniline dyes. It does not decolorize by Gram's method. It grows aerobically and anaerobically on ordinary artificial nutrient media except potato. It has a characteristic puncture growth on gelatin in the form of a test tube brush. It is non-motile, does not possess flagella, and does not form spores. It differs from other non-spore-forming pathogenic bacteria by its somewhat increased resistance to drying, heating to 70°, salting, smoking, putrefactive processes, and the action of scattered and direct sunlight. The bacillus in its morphological and biological properties is so close to the causative agent of mouse septicemia discovered by Koch (Bacillus murisepticus) that many authors identify it with it. Swine erysipelas is found in all European countries and in North America, mainly in enzootic or epizootic form, rarely in the form of sporadic cases (England, USA). According to official statistical data of 1925, swine erysipelas was registered in all pig-breeding areas of the RSFSR. However, surveys showed that it does not have a pandemic nature in all localities and that in some areas, swine plague (see Animal Plague) was mistaken for it. At present, there is still no precise map of the geographical distribution of swine erysipelas in the USSR. The causative agent of swine erysipelas is pathogenic not only for pigs but also for gray and white mice, pigeons, rabbits, to a lesser extent for sheep, horses, cattle, chickens, and finally for humans. Its virulence varies within very wide limits depending on the affected animal as well as on the conditions of the external natural or artificial environment. Hot and humid weather favors the development of epizootics in pigs, weakening their resistance and promoting the multiplication of the causative agent in soil, manure, and water. Purebred pigs are more susceptible than common pigs; suckling piglets as a rule do not get sick; pigs older than one year are rarely infected - apparently due to acquired immunity after the disease in apparent or latent form. Infection of pigs under natural conditions occurs mainly through the digestive tract, especially if its mucous membranes are irritated by some inflammatory process or injured by intestinal parasites. The slightest skin injuries, scratches, can also serve as the gateway for the virus. Artificial infection is most easily achieved through the skin or intravenously. Having entered the body by one way or another, the swine erysipelas bacteria reach the bloodstream, in which they multiply more or less abundantly and rapidly, and after an incubation period lasting on average 3-5 days, they cause a disease picture manifested in one of three forms: cutaneous, septicemic, and chronic. The cutaneous form, the mildest, occurs in the form of urticaria. After 1-2 days of general malaise with elevated temperature, red spots, several centimeters in size, single or confluent, sharply defined, swollen, hot, painful, quadrangular (square, rhombic), sometimes round in shape, appear on the skin of the back, sides, and outer surface of the thighs. The color of the spots gradually darkens at the edges, taking on a purple hue, while their central part pales. With the appearance of urticaria, the body temperature decreases. In uncomplicated cases, after 2-3 days the spots begin to disappear, and after 8-12 days complete recovery occurs. The septicemic form, more severe, is characterized by high fever (with corresponding signs of general disturbance), digestive disorders (vomiting, constipation, sometimes replaced by diarrhea), conjunctivitis, and mainly the appearance of light red but then darkening spots on hairless areas of the skin, painless, diffusely variable in shape, blanching under pressure. The usual outcome is death after 3-4 (rarely 8-9) days with signs of paralysis of the hind limbs, general cyanosis, and pulmonary edema. In exceptional cases, an apparent improvement occurs 2-3 days after the disease, which subsequently passes into the chronic form. Some authors also distinguish a 'white' septicemic form, which runs so rapidly that the characteristic symptoms of swine erysipelas do not have time to develop. The chronic form develops in most cases in animals that have apparently recovered after one of the described acute forms. It always ends in death after a more or less prolonged time (up to six months), most often due to the development of verrucous endocarditis. Of the other manifestations of this form, necrosis of the skin and arthritis are distinguished as the most characteristic. Human diseases caused by swine erysipelas have been known since 1884, when Rosenbach described them under the name 'erysipeloid'. Infection occurs almost exclusively in people dealing with sick pigs, their carcasses, or cultures of the causative agent, with skin wounds (scratches, punctures) of the hands serving as the gateway. At the site of infection, a dark red, painful, itchy, sharply defined swelling appears after 1-3 days, which soon turns into a raised purple spot of rhombic shape with a red border; in rare cases, lymphangitis and painful swelling of the lymph glands are added, even more rarely - swelling of the nearest joints. The usual outcome is recovery, sometimes already after several days, but usually after 2-4 weeks, rarely later. However, individual cases of chronic course and even death are also described. Reliable cases of human infection through the digestive tract have not been described. Specific therapy consists in the use of serum from hyperimmunized animals, first proposed by Lorenz in Germany and currently usually obtained from horses. For prevention, in addition to veterinary-sanitary measures, preventive vaccinations are given to pigs in affected or threatened farms. Vaccines were first developed in 1882 by Pasteur, who partially weakened the virus isolated from sick pigs (although not yet in the form of pure cultures) by passages through rabbits, and partially intensified by passing through pigeons, and thus created 2 vaccines of different virulence, used sequentially with an interval of 12 days. With these or other changes, this active immunization is still carried out. Along with this, serovaccination is also used, introduced into practice by Lorenz and Leclainche and consisting in the simultaneous or sequential single injection of immune serum and virulent culture.