Erysipelothrix rhusiopathiae is a nonsporulating, facultative anaerobe, gram-positive, rod-shaped bacterium which causes erysipelas. Domestic swine (pigs) are believed to be the most important animal reservoir of E. rhusiopathiae. The organism is shed by infected animals in feces, urine, saliva, and nasal secretions, which can contaminate food, water, soil, and bedding. Maintenance of the organism in nature appears to result from asymptomatic carriage in animals and subsequent dissemination of the organism to the environment.
The second significant source of E. rhusiopathiae is marine animals, such as freshwater fish, molluscs, and crustaceans. The organism survives and grows on the exterior mucoid slime of fish, without causing disease in the fish themselves. Therefore, any boxes used for transport of fish also play a vital role in the transmission of E. rhusiopathiae., and many human cases resulted from contact with these objects.
Humans can also become infected, and is prevalent in those working in association with farm animals, especially pigs. Occupations most at risk are those with the most frequent animal contact, such as butchers, abattoir workers, farmers fisherman, fish-handlers, veterinarians, and house wives are the most commonly infected.
Survival in environment: : E. rhusiopathiae is ubiquitous and able to persist for a long period of time in the environment (up to 5 years). Best growth is favored by an alkaline pH. The optimum pH range is 7.2-7.8. Has been recovered from sewage effluent from abattoirs, streams, drains, and fertilizer, survival in drinking water for 4-5 days and sewage for 10-14 days. Can also survive in decaying tissue, and will remain viable in a carcass for 12 days in direct sunlight, for 4 months in putrefied flesh, for 9 months in a buried carcass and at least 10 months in refrigerated tissue.