DERMATOPHILOSIS (CUTANEOUS STREPTOTHRICOSIS, RAINSCALD, RAIN ROT, LUMPY WOOL OR STRAWBERRY FOOTROT)

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Causative Agent(s)

Dermatophilus congolensis. This is dimorphic in nature, grows as branched filamentous mycelia containing dormant zoospore which are transformed by moisture to the infective stage of motile isolated cocci.

 

Clinical Presentation and Epidemiology

Lesions are commonly obscured by the fleece presenting only as a hard mass at the surface of the skin (lumpy wool disease). The lesions are typically distributed irregularly over the dorsal midline spreading laterally and ventrally. The muzzle, face, ears, and scrotum of rams may also be involved. The health of animal is unaffected unless lesions are widespread. Heavy mortalities can occur in very young lambs. Occasionally secondary pneumonia is seen.

In cattle, the early lesion is a pustule and the hair over the infected site is erect and matted in tuft with greasy exudates (paint brush lesion resembling a wet paint brush) forming crumbly crust which are hard to remove. This eventually develops into a hard scab. The scabs are cream to brown, 2-5cm in diameter, closely apposed giving a mosaic appearance. In early stages the crusts are very tenacious and attempt to lift them causes pain. There is limping when the leg is affected. In young calves, infection commences from the muzzle probably from contact with the infected udder.

Diagnostic Considerations
  • Cytologic examination of fresh crusts and/or impression smears of the underside of freshly avulsed lesions.
  • Indirect fluorescent antibody technique
  • Serology
Management and Treatment

Systemic antibiotics: The causative agent is susceptible to wide range of antibiotics: erythromycin, spiramycin, penicillin G, streptomycin, ampicillin, chloramphenicol, amoxicillin, tetracyclines, novobiocin gentamicin, combination of penicillin and streptomycin, and LA Oxytetracycline.

Topical application: scrubbing of affected areas with Sodium bicarbonate and Sodium chloride and topical application of chlorhexidine, benzoyl peroxide, povidone-iodine or lime-sulphur, povidone iodine. Topical antimicrobial of choice is chlorhexidine.

Acaricides applied externally to control biting insects and ticks.

  • Procaine penicillin - 70,000 unit/kg with streptomycin at 10 mg/kg. IM SID x 5/7
  • Erythromycin at 10 mg/kg SID x 5/7
  • Oxytetracycline LA 20 mg/kg IM SID 2 doses one day apart
  • lincomycin 5 mg/kg + spectinomycin 10 mg/kg IM SID x 5/7
  • Gentamicin 5 mg/kg IM q8h x 5/7
  • Procaine penicillin 2,000,000 IU and streptomycin sulphate 5 g (2ml/50kg) IM SID x 5/7

 

Caution: Infected sheep should be shorn or dipped last. Don’t shear in wet hot weather when transmission is likely.

Close yarding especially after shearing or dipping should be avoided.

In cattle in the tropics, tick control is the most important control measure.