Rain scald

Rain scald (also known as rain rot or streptothricosis) is a common skin disease in horses, caused by the bacterium Dermatophilus congolensis. This condition is characterized by scabby and crusty lesions that typically appear on parts of the body where rain or moisture is likely to accumulate, such as the back, rump, and lower limbs. Rain scald is most prevalent in regions with high rainfall and humidity, where conditions are conducive for the bacteria to thrive.

Causes and Transmission

Rain scald is caused by the bacterium Dermatophilus congolensis, which can lie dormant in the skin until activated by prolonged wetness, high humidity, or skin damage. The bacteria require a compromised skin barrier to establish infection. Transmission occurs through direct contact with infected animals or indirectly through contaminated objects such as grooming tools, tack, or even through biting insects.

Symptoms

The primary symptoms of rain scald include:

• Patchy hair loss
• Scabby, crusty lesions
• Skin redness and irritation
• In severe cases, lameness or discomfort if lesions are located on the legs

The lesions are distinctive, often appearing as matted tufts of hair with scabs that, when removed, reveal a moist, pink surface underneath.

Diagnosis

Diagnosis of rain scald is primarily based on clinical signs and the presence of characteristic lesions. Laboratory tests, including culture and microscopic examination of the scabs, can confirm the presence of Dermatophilus congolensis and rule out other conditions with similar symptoms, such as ringworm or lice infestation.

Treatment

Treatment involves:

• Removing the horse from wet conditions and allowing the skin to dry
• Gently removing scabs to expose the bacteria to air, which is detrimental to their survival
• Applying topical antiseptic or antibiotic treatments as recommended by a veterinarian
• In severe cases, systemic antibiotics may be necessary

Preventive measures include providing adequate shelter, regular grooming to identify and address skin issues early, and avoiding sharing of grooming tools and tack between horses.

Prevention

Preventive strategies focus on minimizing the risk factors that contribute to the disease:

• Providing adequate shelter to horses during wet weather
• Ensuring good hygiene and regular grooming
• Avoiding sharing of grooming tools and tack between horses
• Controlling insect populations that can spread the bacteria

See Also

• Dermatitis
• Horse care
• Infectious diseases in horses

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