See what damage eating St John’s Wort caused this heifer



Cavan vet Gerard McGovern came across this case of photosensitivity in a Friesian heifer on a farm recently.

This case of chronic photosensitivity in a Friesian heifer, shows the damage to the non-pigmented skin, which is still red and raw, leaving the pigmented areas in tufts of black islands.

He said that in this case the acute phase of the condition occurred a few weeks previously, with the white hair already growing back.

Primary photosensitivity, he said, is caused by compounds in the blood that react with sunlight, causing damage to the skin.

It happens when an animal eats a plant, like St John’s Wort, that contains a photodynamic agent which builds up in the bloodstream and reacts with UV light to release chemicals, damaging the unpigmented skin.

The vet from Derryginney Veterinary Clinic in Ballyconnell said that it’s a very painful condition for animals, especially if it’s affecting a large skin area, and because sunlight triggers the condition a dark house is always helpful in treating the condition.

Secondary photosensitivity happens when an animal has hepatic pathology (liver damage) and the liver cells are unable to mobilise phylloerythrin (breakdown product of chlorophyll), which accumulates in the bloodstream, acting as a photodynamic agent, he said.

The main signs of photosensitivity include:

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·         Twitching, flicking of ears and tail

·         Irritability, stomping and kicking at self

·         Swelling around the eyes, ears, udder and feet

·         Hair loss, reddening, thickening and peeling of affected skin

In the acute stage, steroids and nonsteroidal anti-inflammatory drugs and antibiotics will help, while emollients on the damaged skin will also help, he said.

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