Special Veterinary Pathology

RING WORM

Synonym: Dermatomycosis, Dermatophytoses

Definition

• It is a superficial keratinized layers of the skin and its appendages affecting all species of animals and man

Aetiology

• Affects all species of animals
• Microsporum fungi is more common in dogs while Trichophyton is seen in large animals
• Microsporum fungi grow around the root of the hair and form a mosaic pattern of spores (ectothrix) wheras Trichophyton grow both within the shaft of hair follicle (endothrix) as well as outside hair fibre(ectothrix ) and produce spores in long chains
• Micrsporum shows fluorescence in U.V. light while Trichophyton does not

Transmission

• Contact with infected animals

Pathogenesis

Incubation period: one week to one months

• The fungus grows on kerainized tissue and hair follicle, splitting the hair follicle. It causes hyperaemia, oedema, vesiculation and parakeratosis
• Secondary bacterial infection leads to suppuration of hair follicle

Gross lesions

• Raised, round crusty patches and have a diameter of 2-3cm with alopecia
• Cattle: skin of head, neck & Anal region
• Pigs : Trunk region
• Sheep and goats: Head, neck, back, shoulders and chest in the sheep and on the facial region and pinna in goats
• Dogs & Cats: Any part of body
• Horses: Skin of head, neck, chest, shoulder & back
• Camel : Legs and neck

Microscopic lesions

• Histologically, mild to moderate inflammatory reaction associated with momonuclear cells to neutrophils in the stratm corneum

Diagnosis

• Characteristic Lesions
• Demonstration of fungs
• Use of Wood’s lamp