Author, Donkey, Bureaucrats, Administrators
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*'sunburn-like' lesions
*cattle and sheep
*sharply confined to the unpigmented areas of the skin
*occurs as a result of the effect of strong sunlight
**due to the effect of UV light on a photodynamic agent (PDA) present in the skin, such as is '''phylloerythrin''' derived from chlorophyll
**therefore, the disease occurs mostly in those animals consuming large quantities of grass
**the UV light is changed to a longer wavelength which produces the necrosis of the skin
*many unknown/poorly understood causes
**feeding rape, kale, lucerne, alfalfa
**mouldy hay
**lush pasture
**corticosteroid induced
===Primary photosensitisation===
====Causes====
*normal ingestion of growing lush green plants containing PDA
**plants containing such fluorescent pigments
***''Hypericum perforatum'' (St John's Wort) - active principle is hypercin
***''Lolium perenne'' (Perennial Rye Grass) - active principle is perloline
*drugs
**phenothiazine
**thiazides
**tetracyclines
**sulphonamides
*inherited porphyria
===Secondary photosensitisation===
*photosensitisation secondary to liver damage
====Cause====
*hepatogenous photosensitisation
**chlorophyll is metabolised to '''phylloerythrin'''
**when the liver or bile ducts are malfunctioning (eg hepatitis or bile duct obstruction) due to severe toxic damage, '''phylloerythrin''' escapes into the circulation and settles in the tissues including the skin
**the pigment accumulates causing photosensitisation
*hepatotoxic plants
**''Senecio jacobea'' (Ragwort)
**''Lantana camara'' (Lantana)
**''Lupinus angustifolius'' (Lupins)
**Blue-green algae
===Clinical Signs===
*localised to lightly pigmented skin areas
*clear cut demarcation of affected area
*teats, muzzle, ears
*skin only
*skin and liver signs
===Microscopically===
*subepidermal vesicles
**ulcerate
**become secondarily infected
===Treatment===
*remove from sunlight
===Protosensitising Agents===
===Protosensitising Agents===
*Tetracycline - if one injects bitches with tetracycline when pregnant, puppies are born with brown [[Oral Cavity - Teeth & Gingiva - Anatomy & Physiology|teeth]], which fluoresce under UV light.
*Tetracycline - if one injects bitches with tetracycline when pregnant, puppies are born with brown [[Oral Cavity - Teeth & Gingiva - Anatomy & Physiology|teeth]], which fluoresce under UV light.
*Haemosiderin may also produce pinky / brown colour to [[Oral Cavity - Teeth & Gingiva - Anatomy & Physiology|teeth]] usually due to damage and haemorrhage into [[Oral Cavity - Teeth & Gingiva - Anatomy & Physiology|tooth]].[[Category:Teeth_-_Developmental_Pathology]]
*Haemosiderin may also produce pinky / brown colour to [[Oral Cavity - Teeth & Gingiva - Anatomy & Physiology|teeth]] usually due to damage and haemorrhage into [[Oral Cavity - Teeth & Gingiva - Anatomy & Physiology|tooth]].[[Category:Teeth_-_Developmental_Pathology]]
[[Category:Liver_-_General_Pathology]]