Erysipelas is an infectious disease mostly of growing or adult swine. It may be clinically inapparent, may cause acute illness involving many animals, or be a chronic disease characterized by enlarged joints, lameness, and endocarditis. Rhomboid skin (diamond-skin) lesions are an inconsistent feature only associated with acute cases.
Occurrence
Erysipelas occurs in swine, lambs and turkeys. It occurs occasionally in other poultry and many kinds of wild birds. Seasonal distribution has not been documented but losses may be greater during warm summer months. Sporadic outbreaks are seen in most kinds of livestock, wild mammals (including rodents), reptiles and amphibians. Erysipeloid, a localized skin infection, occasionally occurs in people who work with infected animals or process meats, poultry, fish or animal by-products. In humans, the disease referred to as “erysipelas” is actually caused by a streptococcal infection.
Epidemiology
Erysipelothrix rhusiopathiae is thought to be spread among swine by carriers in the herd. Many healthy swine are carriers of pathogenic and/or nonpathogenic Erysipelothrix and disseminate the organism in their feces and oronasal secretions. Pigs affected with erysipelas also shed large numbers that contaminate feed, water, soil and bedding. Contaminated soil probably does not remain infective for more than 35 days. The resistant organisms can flow in surface water to adjacent premises. A wide range of wild mammals, poultry, wild birds and pets can disseminate the bacteria. There is empirical evidence that biting flies and ticks can sometimes transmit E. rhusiopathiae between swine. The many carriers of E. rhusiopathiae make eradication of SE unlikely
Pathogenesis
Ingestion of contaminated feed and water usually allows E. rhusiopathiae to gain access to the body, probably through the tonsils or other lymphoid tissue of the digestive tract (the organism often can be cultured from tonsils of normal swine). Less often, contaminated skin wounds may permit entry. In acute erysipelas, and perhaps in other forms of the disease, a bacteremia develops and leads to spread of organisms throughout the body.
Clinical signs
Many acute outbreaks of SE occur in animals approaching market weight. Acute outbreaks often begin with the sudden and unexpected death of one or a few thrifty pigs. Careful observation then reveals other sick pigs with very high temperatures (104-108°F), usually without respiratory signs or diarrhea. Sick pigs often have reddened or cyanotic skin, especially about the ears, snout, jowls, throat and ventral abdomen. On a few of the animals there may be discrete, raised, and red to purple areas of skin. These often have a rhomboid or diamond shape and are more obvious on white pigs. On dark skinned pigs, the lesions may be visible or palpable as slightly raised patches of hair. Leg joints are painful but may or may not be swollen. Affected pigs resist getting on their feet but are alert. When forced to arise, they often have to be assisted, squeal with pain, stand with their feet close together and soon lie down again. Pregnant sows may abort.
Control
Acute outbreaks of SE usually can be controlled by administering penicillin and/or erysipelas antiserum to affected pigs along with antimicrobials added to the drinking water until no sick pigs have been observed for at least three days. Vaccination in the face of an outbreak is warranted
A vaccination program is advisable for premises on which outbreaks have occurred or where exposure is expected. Attenuated vaccines and bacterins are available with recent products improved, having duration of immunity of 26 weeks and efficacy across a broad spectrum of serotypes. Killed vaccines may be given by injection and attenuated live vaccines via injection or in drinking water. Two doses of most bacterins usually will protect growing pigs to market weight but may have to be boostered later in grow-finish stages in some herds, especially those with a history of repeated exposure to the organism. Booster vaccination at least 1-2 times per year is recommended for breeding stock.
A combination of regular vaccination, good sanitation, the elimination of carriers with skin and joint lesions, and appropriate quarantine measures for purchased stock usually will aid control of SE.
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