Non-pruriginous, exudative, pustular dermatitis common to several animal species. Transmissible but of a low degree of contagion, it is caused by a ubiquitous bacteria (Dermatophilus congolensis) which, in association with other risk factors, causes symptoms to appear.
Despite a low death rate, dermatophilosis leads to economic loss in terms of a fall in production, inability of pack animals to work and leather depreciation.
It is frequent in tropical and sub-tropical countries and especially where the Amblyomma variegatum tick, an aggravating factor of the disease, is present.
Declaration to the OIE by the following countries (2004): Canada, USA, Argentina, Brasil, Chile, Dominica, Guadeloupe, Martinique, St Kitts and Nevis, Trinidad and Tobago, Uruguay.
Bovines, ovines, caprines, equids, camelids
Rarely: pigs, dogs, cats, man (minor zoonosis)
Wild species: mammals and reptiles
Dermatophilosis lesions in a goat in Guadeloupe (N. Barré).
In tropical regions: bovines are particularly susceptible. Local breeds are more resistant (eg: Creole bovines from Guadeloupe) than imported or improved breeds.
In temperate regions: sheep and horses are susceptible.
Dermatophilus congolensis is a polymorphic gram positive bacteria from the Actynomyces group. It exists in two forms:
• Filamentous (0.5 – 1 micrometre Ø): branching and multiplying in the living epidermis forming characteristic chains.
• Coccoid (1 micrometre Ø): mobile form (with flagella), responsible for infection.
The bacteria resists in the outside environment. Scabs falling to the ground remain infectious for several months.
Culture: by aerobiosis, optimum T° = 37°C, on blood or serum-enriched agar.
Symptoms appear when both the bacteria and risk factors are present.
This is the most frequent form with an incubation period of 2 to 4 weeks. Non-pruriginous lesions appear on the upper part of the body (neck, withers, back) followed by the lower part (ends of the legs). Atypical lesions may also appear (smooth areas: perineum, teats, scrotum).
Progressive weight loss, bacterial secondary infections. Death in 10 to 20% of cases, often through reactivation of intercurrent disease.
At the end of the wet season, the lesions disappear only to reappear the following season.
Less frequent. Exudative form, occurring in humid, tropical areas in predisposed subjects:
• imported susceptible breeds (taurines)
• young animals
Significant erythema followed by hair loss, skin thickening - the skin forms pleats in which serous exudate accumulates. Rapid spreading of lesions to the whole body.
Overall health is affected: inappetence, weight loss, reduction in milk production.
In the absence of treatment, the animal dies within 10-12 days following general deterioration of health.
Antibiotherapy via general route
• Injectable Penicillin (75000 UI/kg) + dihydrostreptomycin (75 mg/kg).
• Oxytetracyclin (20 mg/kg), in a single intramuscular injection.
Above all, de-tick all animals!
Anti-tick pulverisation treatment (CIRAD EMVT)