Dermatophilosis

The bacteria  dermatophilus congolensis is responsible for causing dermatophilosis.
Dermatophilosis occurs mainly in winter, during wet weather conditions, on animals living out in muddy fields, or on horses working on damp ground.

Dermatophilosis mainly affects the lower limbs, particularly around the pasterns, but can also affect the top line (back and rump) when horses live outside.
The affected area becomes inflammed with pus-filled sores and scabs, it can be painful (on horses with socks, the skin becomes red), and hair loss is noted, but there is not necessarily any itchiness. When the pasterns are affected, the legs can become « filled » (swollen).
As a general rule the horse does not go lame, but movement can be impeded due to local pain.

The symptoms and the environmental context are fairly characteristic. However dematophilosis should not be mistaken for other skin complaints :

• Foot mange, due to an acarid : Chorioptes equi, which is less frequent ;
• Chronic dermatosis on the legs of draught horses (« dew poisoning » or « greasy heels » are some of the common names given to the condition) : weepy eczema which is not related to the presence of mud. There is a genetic predispostion in some breeds or breeding lines. In the long term the skin thickens in the affected areas. .
• Ringworm : there are small round bald patches on different parts of the body ;
• Lice : generally all over the body, the hair is rough and raised, intense ithciness.

Diagnosis can be established with certainty following laboratory examinations of a skin scrape from the affected areas, or from a sample of hair from around the lesions.
When the legs become swollen, or if movement is impeded, a circulation problem may be involved, or an affliction of the locomotor system (tendonitis, sprain….).

Local treatment

To be effective, treatment should first consist in eliminating the cause, i.e permanent humidity on the bottom of the legs (when horses are affected, do not use stable bandages after hosing down). Then the bacteria ccan be addressed.

• Bring the horse in if he lives permanently outside ;
• Clip the lower part of the limb to prevent the long hair from retaining moisture;
• After work, carefully clean the affected areas with an antisceptic soap, rince and dry thoroughly (with a hair dryer) and apply an antisceptic barrier cream (sulphur vaseline or other ointments found on the market);
• Protect the pastern folds from the damp during work, by applying a vaseline containing sulphate for example.  

General treatment

In addition to essential local treatment, a general anti-biotic based treatment can sometimes become necessary. Your veterinarian will decide on what is appropriate.
Both treatment and prevention aim to avoid humidity on the lower limbs.

Limit exposure of the lower limbs to the damp :

•  Avoid as much as possible any build up of mud in the places where horses are stationed (e.g stabilise the ground of the paddocks, move the feed buckets or augers around in the fields to avoid trampled areas…);
• Carefully dry the legs after work.