Changes

==Introduction==

==Introduction==

Photosensitisation is an abnormal reaction of the skin to sunlight due to the presence of a photodynamic agent in the dermis. It is

Photosensitisation is an abnormal reaction of the skin to sunlight due to the presence of a photodynamic agent in the dermis. It is

primarily a condition of sheep, cattle and horses but other species may also be susceptible.  

primarily a condition of sheep, cattle and horses but other species may also be susceptible.  

The condition can be divided into two categories; primary and secondary. '''Primary photosensitisation''' occurs due to the ingestion of lush green plants containing photodynamic agents, such as St John's Wort or clover. '''Secondary (hepatogenous) photosensitisation''' is the most commmon type of photosensitivity seen in animals and occurs due to liver or bile duct damage, most often as a result of ingestion of hepatotoxic plants such as [[Ragwort Toxicity|Ragwort]]. The normal conjugation and excretion of phylloerythrin (a breakdown product of chlorophyll) is prevented leading to its accumulation in the blood and body tissues. In the skin this leads to the absorption and release of UV light, resulting in a phototoxic reaction.

The condition can be divided into two categories; primary and secondary. '''Primary photosensitisation''' occurs due to the ingestion of lush green plants containing photodynamic agents, such as St John's Wort or clover. '''Secondary (hepatogenous) photosensitisation''' is the most commmon type of photosensitivity seen in animals and occurs due to liver or bile duct damage, most often as a result of ingestion of hepatotoxic plants such as ''Senecio jacobea'' ([[Ragwort Toxicity|ragwort]]), ''Lantana camara'' (Lantana), ''Lupinus angustifolius'' (Lupins) and [[Blue-Green Algae Toxicity|Blue-green algae]]. The normal conjugation and excretion of phylloerythrin (a breakdown product of chlorophyll) is prevented leading to its accumulation in the blood and body tissues. In the skin this leads to the absorption and release of UV light, resulting in a phototoxic reaction.

==Clinical signs==

==Clinical signs==

Animals should not be grazed on pasture known to contain photodynamic agents and contaminated hay and grain should also be avoided. In the case of farm livestock, less valuable or older animals may be used to 'pre-graze' affected pastures before other animals are introduced.  

Animals should not be grazed on pasture known to contain photodynamic agents and contaminated hay and grain should also be avoided. In the case of farm livestock, less valuable or older animals may be used to 'pre-graze' affected pastures before other animals are introduced.  

==Test yourself with the Liver Pathology Flashcards==

 

|flashcards = [[Liver_Flashcards_-_Pathology|Liver Pathology Flashcards]]

[[Liver_Flashcards_-_Pathology|Liver Pathology Flashcards]]

 

[[File:CABI logo.jpg|left|90px]]

 

|literature search = [http://www.cabdirect.org/search.html?it=any&q2=photosenzitivity&q1=photosensitivity&calendarInput=yyyy-mm-dd&q4=photosensitization&q3=photosensitisation&occuring1=title&show=all&rowId=1&rowId=2&rowId=3&rowId=4&options1=AND&options2=OR&occuring4=title&options3=OR&options4=OR&occuring3=title&occuring2=title&publishedend=yyyy&la=any&publishedstart=yyyy&fq=sc%3A%22ve%22&y=11&x=55 Photosensitisation publications]

[http://www.cabdirect.org/search.html?it=any&q2=photosenzitivity&q1=photosensitivity&calendarInput=yyyy-mm-dd&q4=photosensitization&q3=photosensitisation&occuring1=title&show=all&rowId=1&rowId=2&rowId=3&rowId=4&options1=AND&options2=OR&occuring4=title&options3=OR&options4=OR&occuring3=title&occuring2=title&publishedend=yyyy&la=any&publishedstart=yyyy&fq=sc%3A%22ve%22&y=11&x=55 Photosensitisation publications]

==References==

==References==

{{review}}

{{review}}

[[Category:Liver_-_General_Pathology]]

[[Category:Liver_-_General_Pathology]]

[[Category:Brian Aldridge reviewing]]

[[Category:Expert Review]]

[[Category:Dermatological Diseases - Cattle]]

[[Category:Dermatological Diseases - Cattle]]

[[Category:Dermatological Diseases - Sheep]]

[[Category:Dermatological Diseases - Sheep]]