zoonoses and communicable diseases common to ... - PAHO/WHO

18 BACTERIOSESHarrington, 1978). Alkaline soil is particularly favorable to the agent’s survival. Agreat variety of serotypes may be isolated from apparently healthy swine. In experimentaltests, some serotypes prove to be highly virulent, others moderately pathogenic(producing only localized urticaria), and others avirulent (Takahashi, 1987).Fish, mollusks, and crustaceans are an important source of infection. The etiologicagent has been isolated from fish skin. In the former Soviet Union, an epidemicof erysipeloid was caused by handling fish brought in by several differentboats; on the Baltic coast there was another outbreak of 40 cases. In Argentina,where swine erysipelas has not been confirmed but where cases of humanerysipeloid have been described, the agent was isolated from 2 out of 9 water samplesfrom the Atlantic coast, and from 1 out of 40 samples of external integument offish (de Diego and Lavalle, 1977). Subsequently, these strains were identified asbelonging to serotypes 21 and 22.In meat and poultry processing plants, rodents can be important reservoirs anddisseminators of the infection. Fourteen different serotypes of E. rhusiopathiae wereisolated from 38 samples (33.9%) obtained from pork in 112 shops in Tokyo. Somesamples contained more than one serotype (Shiono et al., 1990).E. rhusiopathiae can survive a long time outside the animal organism, both in theenvironment and in animal products, which contributes to its perpetuation.Man is infected through wounds and skin abrasions, but is very resistant to otherentry routes. The infection is contracted by handling animals and animal products,including fish. Veterinarians have contracted the infection when they pricked themselveswhile administering the simultaneous vaccination (virulent culture andserum). This procedure is no longer in use. In Chile, a case of human endocarditiswas attributed to the ingestion of smoked fish sold on the street (Gilabert, 1968).The agent can multiply in an apparently healthy carrier under stress, and cancause disease and contaminate the environment. A pig with the acute form oferysipelas sheds an enormous amount of the bacteria in its feces, urine, saliva, andvomit, thus becoming a source of infection for the other pigs on the farm (Timoneyet al., 1988).The routes of infection are believed to be digestive and cutaneous, through abrasionsand wounds. The long survival of the agent in the environment ensuresendemism in affected areas. Other animals and fowl may also contribute to maintainingthe infection or to causing outbreaks.Role of Animals in the Epidemiology of the Disease: Man is an accidental hostwho contracts the infection from sick animals, carriers, animal products, or objectscontaminated by animals.Diagnosis: Clinical diagnosis, based on the patient’s occupation and on the characteristicsof the cutaneous lesion, can be confirmed by isolation and identificationof the etiologic agent. E. rhusiopathiae can be isolated from biopsies of the lesion.The sample is cultured in trypticase soy broth and incubated at 35°C for seven days;if there is growth, the culture is repeated in blood agar. The blood of septicemicpatients can be cultured directly in blood agar (Bille and Doyle, 1991).In septicemic cases in animals, the etiologic agent can be isolated from the bloodand internal organs. In cases of arthritis or skin infections, cultures are made fromlocalized lesions. Isolations from contaminated materials are accomplished throughinoculation of mice, which are very susceptible.