Discuss about the aetiology, epidemiology, symptoms, differential diagnosis, treatment and control of erysipelas of swine.

Aetiology

The causative agent of erysipelas in swine is *Erysipelothrix rhinoscleromatis*. It’s a facultative anaerobic bacterium, meaning it can grow in both aerobic and anaerobic conditions. The bacterium produces several toxins, including ert, which are believed to be major contributors to the pathogenesis of the disease. Genetic variations within *E. rhinoscleromatis* strains can influence virulence and disease severity. The bacterium is relatively fragile and susceptible to drying and disinfectants.

Epidemiology

Erysipelas is prevalent worldwide, affecting pigs of all ages, but particularly prevalent in young piglets. Transmission occurs via several routes:

• Direct Contact: From infected pigs to susceptible pigs.
• Environmental Contamination: Through contaminated feed, water, and surfaces.
• Fomites: Spread via contaminated equipment, vehicles, and personnel.
• Ingestion: Consumption of contaminated feed or water containing the bacteria.
• Vector Transmission: While not definitively proven, certain insects may potentially act as vectors.

Carrier pigs, which shed the bacteria in their tonsils and feces without showing clinical signs, are a significant reservoir and contribute to the spread of the disease. The disease is often seasonal, with increased incidence during periods of stress or poor hygiene.

Symptoms

The clinical signs of erysipelas in swine vary depending on the age of the pig and the virulence of the strain. Common manifestations include:

• Diamond Skin Disease: Characteristic raised, red, diamond-shaped lesions on the skin, particularly around the eyes, ears, and muzzle. This is more common in young pigs.
• Septicemic Erysipelas: High fever, weakness, loss of appetite, and sudden death. Lesions may be internal, affecting the heart, kidneys, and other organs.
• Articular Erysipelas: Swelling and pain in joints, leading to lameness.
• Edema: Swelling of the face and eyelids.
• Respiratory Signs: Coughing and difficulty breathing (less common).

Mortality rates can range from 5% to 50% depending on the severity of the infection and the age of the affected pigs.

Differential Diagnosis

Differentiating erysipelas from other swine diseases is crucial. Important differentials include:

• Foot and Mouth Disease (FMD): FMD causes blisters and lesions, but is highly contagious and notifiable.
• Swine Brucellosis: Can cause systemic illness and reproductive problems.
• Skin Scabies: Causes intense itching and skin lesions.
• Salmonellosis: Can cause similar systemic signs.

Diagnostic tests include bacterial culture and identification from skin lesions or blood samples, serological testing (ELISA or agglutination tests) to detect antibodies against *E. rhinoscleromatis*, and polymerase chain reaction (PCR) for rapid detection of the bacterium.

Treatment

Treatment of erysipelas is primarily supportive and focuses on managing secondary infections.

• Antibiotics: Penicillin, ampicillin, and erythromycin are commonly used, though resistance can be a concern.
• Fluid Therapy: To combat dehydration in septicemic cases.
• Anti-inflammatory Drugs: To reduce fever and inflammation.
• Improved Hygiene: Strict biosecurity measures to prevent further spread.

Treatment success depends on the stage of the disease and the overall health of the pig. Prevention is always better than cure.

Control

Control of erysipelas relies on a multifaceted approach:

• Vaccination: A commercial erysipelas vaccine is available and highly effective in preventing the disease. Regular vaccination of breeding animals and piglets is crucial.
• Biosecurity: Strict biosecurity measures to prevent the introduction and spread of the bacterium. This includes limiting access to the farm, disinfecting vehicles and equipment, and controlling rodents and insects.
• Hygiene: Maintaining a clean and hygienic environment, including proper disposal of manure and carcasses.
• Culling: Culling chronically infected or carrier pigs to eliminate reservoirs of infection.
• Monitoring: Regular monitoring of pigs for signs of the disease and prompt diagnosis and treatment of any outbreaks.

The Indian government's National Livestock Mission promotes disease control programs, including vaccination against major livestock diseases. While a specific scheme for erysipelas control is not available, the mission's principles are applicable.

Disease	Causative Agent	Key Symptoms
Erysipelas	*Erysipelothrix rhinoscleromatis*	Diamond skin lesions, septicemia, arthritis
Foot and Mouth Disease	Picornaviruses	Blisters, lameness, fever
Swine Brucellosis	*Brucella suis*	Systemic illness, reproductive failure

Erysipelas remains a significant threat to swine production worldwide. While the disease is treatable, prevention through vaccination, rigorous biosecurity practices, and improved hygiene is paramount. Continued research into *E. rhinoscleromatis* virulence factors and improved diagnostic tools is essential for better management. A proactive, One Health approach, incorporating veterinary, public health, and environmental considerations, is vital for effectively controlling erysipelas and minimizing its impact on the swine industry and human health.